// Package config provides configuration loading and validation for the proxy server.
//
// Configuration can be provided via:
//   - Command line flags (highest priority)
//   - Environment variables (PROXY_ prefix)
//   - Configuration file (YAML or JSON)
//
// Storage Configuration:
//
// The proxy supports multiple storage backends via gocloud.dev/blob:
//
// Local filesystem (default):
//
//	storage:
//	  url: "file:///var/cache/proxy"
//
// Amazon S3:
//
//	storage:
//	  url: "s3://bucket-name"
//
// S3-compatible (MinIO, etc.):
//
//	storage:
//	  url: "s3://bucket?endpoint=http://localhost:9000"
//
// Google Cloud Storage:
//
//	storage:
//	  url: "gs://bucket-name"
//
// For S3, configure credentials via AWS environment variables:
//
//	AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION
//
// For GCS, authentication uses Application Default Credentials. This supports
// GKE Workload Identity, attached service accounts on GCE and Cloud Run, and
// local credentials created by `gcloud auth application-default login`.
// When direct_serve is enabled without a private key, the GCS backend uses the
// IAM Credentials signBlob API. The service account must hold
// roles/iam.serviceAccountTokenCreator on itself.
//
// Database Configuration:
//
// The proxy supports two database backends:
//
// SQLite (default):
//
//	database:
//	  driver: "sqlite"
//	  path: "/var/lib/proxy/cache.db"
//
// PostgreSQL:
//
//	database:
//	  driver: "postgres"
//	  url: "postgres://user:password@localhost:5432/proxy?sslmode=disable"
//
// See config.example.yaml in the repository root for a complete example.
package config

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/git-pkgs/proxy/internal/denylist"
	"github.com/git-pkgs/proxy/internal/retention"
	"github.com/git-pkgs/purl"
	"gopkg.in/yaml.v3"
)

// DefaultSwiftUpstream is the Swift Package Registry used when none is configured.
const DefaultSwiftUpstream = "https://tuist.dev/api/registry/swift"

// Config holds all configuration for the proxy server.
type Config struct {
	// Listen is the address to listen on (e.g., ":8080", "127.0.0.1:8080").
	Listen string `json:"listen" yaml:"listen"`

	// BaseURL is the public URL where package endpoints are reachable.
	// Used for rewriting package metadata URLs and shown to humans on the
	// install guide so they know what to point their package manager at.
	// Example: "https://proxy.example.com" or "http://localhost:8080"
	BaseURL string `json:"base_url" yaml:"base_url"`

	// UIBaseURL is the public URL where the web UI is reachable. Defaults to
	// BaseURL when unset. Set this separately when the UI is served on a
	// different hostname than the package endpoints — for example, the UI on a
	// public domain behind auth while build machines hit a Docker network alias
	// for the package endpoints.
	// Example: "https://proxy.example.com/ui"
	UIBaseURL string `json:"ui_base_url" yaml:"ui_base_url"`

	// TrustForwardedFor attributes requests to the leftmost X-Forwarded-For
	// entry instead of the TCP peer address, in the structured log, the access
	// log and the request-source table on /ui/analytics.
	//
	// Enable this only when the proxy sits behind a load balancer or ingress
	// that sets the header, because any client can send it: behind one it is
	// the only way to see past the hop, in front of one it lets a caller choose
	// what address it is attributed to.
	TrustForwardedFor bool `json:"trust_forwarded_for" yaml:"trust_forwarded_for"`

	// UIRequestSources shows the request-source table on /ui/analytics, which
	// reports caller addresses, the tool each ran and how much each pulled.
	//
	// Off by default. The proxy has no authentication of its own, so until this
	// is enabled /ui exposes what is cached rather than who called.
	UIRequestSources bool `json:"ui_request_sources" yaml:"ui_request_sources"`

	// UIFailureDetails lists the latest failures behind each failure counter on
	// /ui/analytics: the package, its upstream URL or storage path, and the
	// error. URLs are shown without credentials or query strings.
	//
	// Off by default, for the same reason as UIRequestSources: package names and
	// upstream hosts say what the proxy's users depend on.
	UIFailureDetails bool `json:"ui_failure_details" yaml:"ui_failure_details"`

	// Storage configures artifact storage.
	Storage StorageConfig `json:"storage" yaml:"storage"`

	// Database configures the cache database.
	Database DatabaseConfig `json:"database" yaml:"database"`

	// Log configures logging.
	Log LogConfig `json:"log" yaml:"log"`

	// AccessLog configures the JSONL activity log.
	AccessLog AccessLogConfig `json:"access_log" yaml:"access_log"`

	// Upstream configures upstream registry URLs (optional overrides).
	Upstream UpstreamConfig `json:"upstream" yaml:"upstream"`

	// Cooldown configures version age filtering to mitigate supply chain attacks.
	Cooldown CooldownConfig `json:"cooldown" yaml:"cooldown"`

	// Denylist blocks explicitly configured package versions.
	Denylist DenylistConfig `json:"denylist" yaml:"denylist"`

	// Scanning configures pre-cache artifact scanning (trivy, ClamAV, Wiz,
	// or a custom service) to mitigate supply chain attacks.
	Scanning ScanningConfig `json:"scanning" yaml:"scanning"`

	// CacheMetadata enables caching of upstream metadata responses for offline fallback.
	// When enabled, metadata is stored in the database and storage backend.
	// The mirror command always enables this regardless of this setting.
	CacheMetadata bool `json:"cache_metadata" yaml:"cache_metadata"`

	// MetadataTTL is how long cached metadata is considered fresh before
	// revalidating with upstream. Uses Go duration syntax (e.g. "5m", "1h").
	// Default: "5m". Set to "0" to always revalidate.
	MetadataTTL string `json:"metadata_ttl" yaml:"metadata_ttl"`

	// MetadataMaxSize is the maximum size of an upstream metadata response
	// the proxy will buffer (e.g. "100MB", "250MB"). Responses over this
	// size return ErrMetadataTooLarge. Default: "100MB".
	MetadataMaxSize string `json:"metadata_max_size" yaml:"metadata_max_size"`

	// ArtifactMaxSize is the largest upstream artifact the proxy will fetch
	// (e.g. "2GB"). Larger artifacts are refused and not cached. Default: ""
	// (unlimited). "0" is also unlimited.
	ArtifactMaxSize string `json:"artifact_max_size" yaml:"artifact_max_size"`

	// MetadataRewriteCacheSize is how much rewritten npm and Composer
	// metadata to keep in memory, so a document is rewritten once rather than
	// on every request (e.g. "256MB", "1GB"). Default: "256MB". Set to "0" to
	// rewrite on every request.
	MetadataRewriteCacheSize string `json:"metadata_rewrite_cache_size" yaml:"metadata_rewrite_cache_size"`

	// HTTPTimeout is the timeout for individual upstream HTTP requests made
	// by protocol handlers (metadata fetches, pass-through file requests).
	// Uses Go duration syntax (e.g. "30s", "2m"). Default: "30s".
	// Set to "0" to disable the timeout entirely. Independently of this
	// setting, the shared transport gives up on an upstream that has not sent
	// response headers within 60 seconds.
	HTTPTimeout string `json:"http_timeout" yaml:"http_timeout"`

	// MirrorAPI enables the /api/mirror endpoints for starting mirror jobs via HTTP.
	// Disabled by default to prevent unauthenticated users from triggering downloads.
	MirrorAPI bool `json:"mirror_api" yaml:"mirror_api"`

	// Hosted configures pushing packages to the proxy (/api/hosted).
	Hosted HostedConfig `json:"hosted" yaml:"hosted"`

	// Gradle configures Gradle HttpBuildCache behavior.
	Gradle GradleConfig `json:"gradle" yaml:"gradle"`

	// Health configures the /health endpoint behavior.
	Health HealthConfig `json:"health" yaml:"health"`
}

// CooldownConfig configures version cooldown periods.
// Versions published more recently than the cooldown are hidden from metadata responses.
type CooldownConfig struct {
	// Default is the global default cooldown (e.g., "3d", "48h", "0" to disable).
	Default string `json:"default" yaml:"default"`

	// Ecosystems overrides the default for specific ecosystems.
	Ecosystems map[string]string `json:"ecosystems" yaml:"ecosystems"`

	// Packages overrides the cooldown for specific packages (keyed by PURL).
	// Valid PURL keys are normalized to canonical form before use.
	Packages map[string]string `json:"packages" yaml:"packages"`

	// PackagePatterns overrides the cooldown for packages whose PURLs match a glob.
	// Exact package overrides take precedence over matching patterns.
	PackagePatterns map[string]string `json:"package_patterns" yaml:"package_patterns"`
}

// NormalizedPackages returns a copy of the package overrides with valid PURL
// keys in canonical form. An explicitly canonical key wins over an equivalent
// noncanonical key, and invalid keys are preserved unchanged.
func (c *CooldownConfig) NormalizedPackages() map[string]string {
	if c == nil || c.Packages == nil {
		return nil
	}

	keys := make([]string, 0, len(c.Packages))
	for key := range c.Packages {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	normalized := make(map[string]string, len(c.Packages))
	for _, key := range keys {
		canonical := key
		if parsed, err := purl.Parse(key); err == nil {
			canonical = parsed.String()
		}
		if _, exists := normalized[canonical]; exists && key != canonical {
			continue
		}
		normalized[canonical] = c.Packages[key]
	}
	return normalized
}

// ScanningConfig configures pre-cache artifact scanning (e.g. trivy,
// ClamAV, Wiz, or a custom service) to mitigate supply chain attacks.
// Unlike Cooldown, which only looks at a version's publish timestamp,
// scanning inspects the actual artifact bytes before they become
// servable from cache.
type ScanningConfig struct {
	// Enabled turns on the scan gate. When false (default), artifacts are
	// cached exactly as if scanning didn't exist.
	Enabled bool `json:"enabled" yaml:"enabled"`

	// FailOpen treats scanner errors and timeouts as an allow verdict
	// instead of a block. Default is fail-closed, since the default
	// posture for a security gate should block on infrastructure failure.
	FailOpen bool `json:"fail_open" yaml:"fail_open"`

	// Timeout bounds each scan call. Uses Go duration syntax (e.g. "30s").
	// Default: "30s".
	Timeout string `json:"timeout" yaml:"timeout"`

	// SigningKey authenticates pull requests to the internal scan-fetch
	// route used by every storage backend. Required whenever Enabled is
	// true. Supports ${VAR_NAME} expansion like AuthConfig fields.
	SigningKey string `json:"signing_key" yaml:"signing_key"`

	// FetchBaseURL is the address scanners use to reach this proxy to pull
	// staged artifacts. Defaults to BaseURL. Set this separately when
	// scanners reach the proxy over an internal address different from the
	// public-facing BaseURL (mirrors DirectServeBaseURL/UIBaseURL).
	FetchBaseURL string `json:"fetch_base_url" yaml:"fetch_base_url"`

	// Scanners is the list of external scanning services to call.
	Scanners []ScannerConfig `json:"scanners" yaml:"scanners"`
}

// ScannerConfig configures a single external scanning service.
type ScannerConfig struct {
	// Name identifies this scanner in logs and metrics.
	Name string `json:"name" yaml:"name"`

	// URL is the endpoint the proxy POSTs scan notifications to.
	URL string `json:"url" yaml:"url"`

	// Mode is "block" (default) or "monitor". A "block" scanner's verdict
	// can prevent caching; a "monitor" scanner's findings are logged but
	// never gate caching.
	Mode string `json:"mode" yaml:"mode"`

	// Ecosystems restricts this scanner to specific ecosystems (e.g.
	// "npm", "pypi"). Empty means all ecosystems.
	Ecosystems []string `json:"ecosystems" yaml:"ecosystems"`

	// Headers are additional HTTP headers sent with every scan request
	// (e.g. for authenticating to the scanner service). Values support
	// ${VAR_NAME} expansion like AuthConfig fields.
	Headers map[string]string `json:"headers" yaml:"headers"`
}

// SigningKeyExpanded returns SigningKey with ${VAR_NAME} references expanded.
func (s *ScanningConfig) SigningKeyExpanded() string {
	return expandEnv(s.SigningKey)
}

// HeadersExpanded returns Headers with ${VAR_NAME} references expanded in
// each value.
func (s *ScannerConfig) HeadersExpanded() map[string]string {
	if len(s.Headers) == 0 {
		return nil
	}
	expanded := make(map[string]string, len(s.Headers))
	for k, v := range s.Headers {
		expanded[k] = expandEnv(v)
	}
	return expanded
}

// Validate checks the scanning configuration for errors, applying the
// default timeout if unset.
func (s *ScanningConfig) Validate() error {
	if !s.Enabled {
		return nil
	}

	if s.SigningKeyExpanded() == "" {
		return fmt.Errorf("scanning.signing_key is required when scanning.enabled is true")
	}

	if len(s.Scanners) == 0 {
		return fmt.Errorf("scanning.scanners must not be empty when scanning.enabled is true")
	}

	if s.FetchBaseURL != "" {
		if err := validateAbsoluteURL("scanning.fetch_base_url", s.FetchBaseURL); err != nil {
			return err
		}
	}

	if s.Timeout == "" {
		s.Timeout = defaultScanningTimeoutStr
	}
	if d, err := time.ParseDuration(s.Timeout); err != nil {
		return fmt.Errorf("invalid scanning.timeout %q: %w", s.Timeout, err)
	} else if d <= 0 {
		return fmt.Errorf("invalid scanning.timeout %q: must be > 0", s.Timeout)
	}

	for i := range s.Scanners {
		if err := s.Scanners[i].Validate(); err != nil {
			return fmt.Errorf("scanning.scanners[%d]: %w", i, err)
		}
	}

	return nil
}

// Validate checks a single scanner's configuration, applying the default
// mode ("block") if unset.
func (s *ScannerConfig) Validate() error {
	if s.Name == "" {
		return fmt.Errorf("name is required")
	}
	if err := validateAbsoluteURL("url", s.URL); err != nil {
		return err
	}
	if s.Mode == "" {
		s.Mode = "block"
	}
	switch s.Mode {
	case "block", "monitor":
	default:
		return fmt.Errorf("invalid mode %q (must be block or monitor)", s.Mode)
	}
	return nil
}

// StorageConfig configures artifact storage.
type StorageConfig struct {
	// URL is the storage backend URL.
	// Supported schemes:
	//   - file:///path/to/dir - Local filesystem (default)
	//   - s3://bucket-name - Amazon S3
	//   - s3://bucket?endpoint=http://localhost:9000 - S3-compatible (MinIO)
	//   - gs://bucket-name - Google Cloud Storage (Workload Identity supported)
	//   - azblob://container-name - Azure Blob Storage
	// If empty, defaults to file:// with the Path value.
	URL string `json:"url" yaml:"url"`

	// Path is the directory where cached artifacts are stored.
	// If URL is empty, this is used as file://{Path}.
	//
	// Deprecated: Use URL with file:// scheme instead.
	Path string `json:"path" yaml:"path"`

	// MaxSize is the maximum cache size (e.g., "10GB", "500MB").
	// When exceeded, least recently used artifacts are evicted.
	// Empty or "0" means unlimited.
	MaxSize string `json:"max_size" yaml:"max_size"`

	// DirectServe enables redirecting cached artifact downloads to presigned
	// storage URLs (HTTP 302) instead of streaming bytes through the proxy.
	// Only effective for backends that support URL signing (S3, GCS, Azure).
	DirectServe bool `json:"direct_serve" yaml:"direct_serve"`

	// DirectServeTTL is how long presigned URLs remain valid.
	// Uses Go duration syntax (e.g. "5m", "1h"). Default: "15m".
	DirectServeTTL string `json:"direct_serve_ttl" yaml:"direct_serve_ttl"`

	// DirectServeBaseURL overrides the scheme and host of presigned URLs
	// before returning them to clients. Useful when the proxy reaches
	// storage at an internal address (e.g. 127.0.0.1 or a Docker hostname)
	// but clients must use a public one.
	DirectServeBaseURL string `json:"direct_serve_base_url" yaml:"direct_serve_base_url"`

	// CacheArtifacts stores fetched artifacts so later downloads are served
	// from storage. When false, every download streams from upstream and
	// nothing is stored; metadata is still cached, and cooldown and the
	// denylist still apply. Useful when another caching layer sits in front
	// of the proxy. False is incompatible with scanning, direct_serve and
	// mirror_api, which all depend on stored artifacts. Default: true.
	CacheArtifacts bool `json:"cache_artifacts" yaml:"cache_artifacts"`

	// Retention evicts cached artifacts that have not been accessed for a
	// configured time, per ecosystem and per package.
	Retention RetentionConfig `json:"retention" yaml:"retention"`
}

// RetentionConfig configures age-based eviction of cached artifacts. An
// artifact's age is the time since it was last served, or since it was
// fetched when it has not been served since. Durations accept a "d" suffix
// for days; "0" or empty means never evict by age.
type RetentionConfig struct {
	// Default applies to every ecosystem that supports retention and has no
	// rule of its own.
	Default string `json:"default" yaml:"default"`

	// Ecosystems overrides the default per ecosystem key (e.g. "npm", "oci").
	// Configuring an ecosystem whose retention is not supported yet is an
	// error.
	Ecosystems map[string]string `json:"ecosystems" yaml:"ecosystems"`

	// Packages overrides the ecosystem rule for single packages, keyed by
	// package PURL.
	Packages map[string]string `json:"packages" yaml:"packages"`

	// SweepInterval is how often expired artifacts are looked for, at least
	// one minute. Default: "10m".
	SweepInterval string `json:"sweep_interval" yaml:"sweep_interval"`
}

// GradleConfig configures Gradle-specific features.
type GradleConfig struct {
	// BuildCache configures the /gradle HttpBuildCache endpoint.
	BuildCache GradleBuildCacheConfig `json:"build_cache" yaml:"build_cache"`
}

// GradleBuildCacheConfig configures Gradle HttpBuildCache safeguards.
type GradleBuildCacheConfig struct {
	// ReadOnly disables PUT uploads and keeps cache reads (GET/HEAD) enabled.
	ReadOnly bool `json:"read_only" yaml:"read_only"`

	// MaxUploadSize caps a single PUT body size (e.g., "100MB"). Must be > 0.
	// Default: "100MB".
	MaxUploadSize string `json:"max_upload_size" yaml:"max_upload_size"`

	// MaxAge evicts entries older than this duration (e.g., "24h", "7d").
	// Empty or "0" disables age-based eviction.
	MaxAge string `json:"max_age" yaml:"max_age"`

	// MaxSize evicts oldest entries until total Gradle cache size is <= MaxSize.
	// Empty or "0" disables size-based eviction.
	MaxSize string `json:"max_size" yaml:"max_size"`

	// SweepInterval controls periodic eviction frequency.
	// Default: "10m".
	SweepInterval string `json:"sweep_interval" yaml:"sweep_interval"`
}

// HealthConfig configures the /health endpoint.
type HealthConfig struct {
	// StorageProbeInterval is the minimum time between storage backend probes.
	// Uses Go duration syntax (e.g. "30s", "1m"). Default: "30s".
	// Set to "0" to probe on every /health request (useful for low-traffic deployments).
	StorageProbeInterval string `json:"storage_probe_interval" yaml:"storage_probe_interval"`
}

// DatabaseConfig configures the cache database.
type DatabaseConfig struct {
	// Driver is the database driver: "sqlite" or "postgres".
	Driver string `json:"driver" yaml:"driver"`

	// Path is the path to the SQLite database file.
	Path string `json:"path" yaml:"path"`

	// URL is the PostgreSQL connection string.
	URL string `json:"url" yaml:"url"`

	// HitFlushInterval is how often cache hit counts and last-access times
	// are written, batched in one transaction. Uses Go duration syntax
	// (e.g. "1s", "10s"). Default: "1s". Set to "0" to write each hit as it
	// happens.
	HitFlushInterval string `json:"hit_flush_interval" yaml:"hit_flush_interval"`
}

// String returns a human-readable description of the configured database
// suitable for logging. For postgres the password in the connection URL is
// redacted; if the URL cannot be parsed only the driver name is returned to
// avoid leaking credentials.
func (d DatabaseConfig) String() string {
	if d.Driver == "postgres" {
		u, err := url.Parse(d.URL)
		if err != nil || u.Host == "" {
			return "postgres"
		}
		return u.Redacted()
	}
	return d.Path
}

// LogConfig configures logging.
type LogConfig struct {
	// Level is the minimum log level: "debug", "info", "warn", "error".
	Level string `json:"level" yaml:"level"`

	// Format is the log format: "text" or "json".
	Format string `json:"format" yaml:"format"`
}

// AccessLogConfig configures the JSONL activity log.
type AccessLogConfig struct {
	// Path is the file to append activity records to. Empty disables the access log.
	Path string `json:"path" yaml:"path"`
}

// UpstreamConfig configures upstream URLs for built-in routes and authentication.
// Leave empty to use defaults.
type UpstreamConfig struct {
	// AllowPrivateHosts permits listed upstream hosts to resolve to private addresses.
	AllowPrivateHosts []string `json:"allow_private_hosts" yaml:"allow_private_hosts"`

	// AllowLoopback permits upstream requests and redirects to loopback addresses.
	AllowLoopback bool `json:"allow_loopback" yaml:"allow_loopback"`

	// NPM is the upstream npm registry URL.
	// Default: https://registry.npmjs.org
	NPM string `json:"npm" yaml:"npm"`

	// NPMFullMetadata always requests the full packument (application/json)
	// from the npm upstream, so served metadata carries the "time" map even
	// when cooldown is disabled. Clients that gate on publish age (for
	// example Yarn's npmMinimalAgeGate) need this.
	// Default: false (the abbreviated format is preferred).
	NPMFullMetadata bool `json:"npm_full_metadata" yaml:"npm_full_metadata"`

	// NPMRoutes maps package name patterns to npm registry URLs. A package
	// whose name matches a pattern is fetched only from that registry, never
	// from upstream.npm, so a public package cannot stand in for it. Patterns
	// use path.Match syntax, e.g. "@example/*"; the longest matching pattern
	// wins.
	NPMRoutes map[string]string `json:"npm_routes" yaml:"npm_routes"`

	// Cargo is the upstream cargo index URL.
	// Default: https://index.crates.io
	Cargo string `json:"cargo" yaml:"cargo"`

	// CargoDownload is the upstream cargo download URL.
	// Default: https://static.crates.io/crates
	CargoDownload string `json:"cargo_download" yaml:"cargo_download"`

	// Gem is the upstream RubyGems registry URL.
	// Default: https://rubygems.org
	Gem string `json:"gem" yaml:"gem"`

	// Go is the upstream Go module proxy URL.
	// Default: https://proxy.golang.org
	Go string `json:"go" yaml:"go"`

	// GoSumDBs maps Go checksum database names to their base URLs, served at
	// /go/sumdb/{name}/ so the go command reaches the database through
	// GOPROXY. Unknown names get 404, which makes the go command contact the
	// database directly.
	// Default when empty: {"sum.golang.org": "https://sum.golang.org"}.
	GoSumDBs map[string]string `json:"go_sumdbs" yaml:"go_sumdbs"`

	// GoSumDBsOffline keeps answering for a checksum database from its
	// cached signed tree, however old, when the database cannot be reached.
	// Set this when clients have no route to the database of their own;
	// otherwise the proxy stops answering once the cached tree is older than
	// metadata_ttl, and the go command contacts the database directly.
	// Requires cache_metadata. Default: false.
	GoSumDBsOffline bool `json:"go_sumdbs_offline" yaml:"go_sumdbs_offline"`

	// Hex is the upstream Hex repository URL.
	// Default: https://repo.hex.pm
	Hex string `json:"hex" yaml:"hex"`

	// HexAPI is the upstream Hex API URL used for package timestamps.
	// Default: https://hex.pm
	HexAPI string `json:"hex_api" yaml:"hex_api"`

	// Pub is the upstream pub registry URL.
	// Default: https://pub.dev
	Pub string `json:"pub" yaml:"pub"`

	// PyPI is the upstream PyPI index and API URL.
	// Default: https://pypi.org
	PyPI string `json:"pypi" yaml:"pypi"`

	// PyPIDownload is the upstream PyPI package download URL.
	// Default: https://files.pythonhosted.org
	PyPIDownload string `json:"pypi_download" yaml:"pypi_download"`

	// Maven is the upstream Maven repository URL.
	// Default: https://repo1.maven.org/maven2
	Maven string `json:"maven" yaml:"maven"`

	// GradlePluginPortal is the upstream Gradle Plugin Portal Maven URL.
	// Used to resolve Gradle plugin marker artifacts.
	// Default: https://plugins.gradle.org/m2
	GradlePluginPortal string `json:"gradle_plugin_portal" yaml:"gradle_plugin_portal"`

	// NuGet is the upstream NuGet API URL.
	// Default: https://api.nuget.org
	NuGet string `json:"nuget" yaml:"nuget"`

	// NuGetSearch is the upstream NuGet search API URL.
	// Default: https://azuresearch-usnc.nuget.org
	NuGetSearch string `json:"nuget_search" yaml:"nuget_search"`

	// Composer is the upstream Packagist API URL.
	// Default: https://packagist.org
	Composer string `json:"composer" yaml:"composer"`

	// ComposerRepository is the upstream Packagist repository URL.
	// Default: https://repo.packagist.org
	ComposerRepository string `json:"composer_repository" yaml:"composer_repository"`

	// ComposerRoutes maps package name patterns to Composer repository URLs
	// (the base that serves /p2/{vendor}/{package}.json). A package whose
	// name matches a pattern is fetched only from that repository, never
	// from upstream.composer_repository, so a public package cannot stand in
	// for it. Patterns use path.Match syntax, e.g. "example/*"; the longest
	// matching pattern wins.
	ComposerRoutes map[string]string `json:"composer_routes" yaml:"composer_routes"`

	// Conan is the upstream Conan registry URL.
	// Default: https://center.conan.io
	Conan string `json:"conan" yaml:"conan"`

	// Conda is the upstream Conda channel base URL.
	// Default: https://conda.anaconda.org
	Conda string `json:"conda" yaml:"conda"`

	// CRAN is the upstream CRAN mirror URL.
	// Default: https://cloud.r-project.org
	CRAN string `json:"cran" yaml:"cran"`

	// Julia is the upstream Julia package server URL.
	// Default: https://pkg.julialang.org
	Julia string `json:"julia" yaml:"julia"`

	// OCIDefault is the default upstream OCI registry URL.
	// Default: https://registry-1.docker.io
	OCIDefault string `json:"oci_default" yaml:"oci_default"`

	// Swift is the upstream Swift Package Registry URL.
	// Default: https://tuist.dev/api/registry/swift
	Swift string `json:"swift" yaml:"swift"`

	// Debian is the upstream APT repository base URL, served at /debian/.
	// Example: http://archive.ubuntu.com/ubuntu would get Ubuntu.
	// Default: http://deb.debian.org/debian
	Debian string `json:"debian" yaml:"debian"`

	// DebianRepositories maps repository names to additional APT repository
	// base URLs, served at /debian/{name}/.
	// Example: {"security": "https://security.debian.org/debian-security"}.
	DebianRepositories map[string]string `json:"debian_repositories" yaml:"debian_repositories"`

	// RPM is the upstream RPM repository base URL.
	// Default: https://dl.fedoraproject.org/pub/fedora/linux
	RPM string `json:"rpm" yaml:"rpm"`

	// HomebrewAPI is the upstream Homebrew JSON API URL.
	// Default: https://formulae.brew.sh/api
	HomebrewAPI string `json:"homebrew_api" yaml:"homebrew_api"`

	// HomebrewArtifact is the upstream registry URL for Homebrew artifacts.
	// Default: https://ghcr.io
	HomebrewArtifact string `json:"homebrew_artifact" yaml:"homebrew_artifact"`

	// Helm maps repository names to HTTP Helm chart repository URLs.
	// Requests use /helm/{name}/index.yaml and chart URLs in the index are
	// rewritten to the same named proxy endpoint.
	Helm map[string]string `json:"helm" yaml:"helm"`

	// APK maps repository names to Alpine APK repository base URLs, served
	// at /apk/{name}/. The remaining request path mirrors the upstream
	// layout, e.g. /apk/alpine/v3.22/main/x86_64/APKINDEX.tar.gz.
	// Default when empty: {"alpine": "https://dl-cdn.alpinelinux.org/alpine"}.
	APK map[string]string `json:"apk" yaml:"apk"`

	// Arch maps repository names to Arch Linux pacman mirror base URLs,
	// served at /arch/{name}/. The remaining request path mirrors the
	// upstream layout, e.g. /arch/archlinux/core/os/x86_64/core.db.
	// Default when empty: {"archlinux": "https://geo.mirror.pkgbuild.com"}.
	Arch map[string]string `json:"arch" yaml:"arch"`

	// OCI maps names to OCI registry URLs. Requests to a named registry use
	// the repository prefix upstream/{name}/, for example
	// oci://proxy.example.com/upstream/ghcr/owner/chart.
	OCI map[string]string `json:"oci" yaml:"oci"`

	// OCIMirrors lists, per upstream.oci name, the registry hosts that
	// upstream mirrors, for example {"ghcr": ["ghcr.io"]} for an Artifactory
	// remote of ghcr.io. containerd requests whose ns query parameter names
	// one of these hosts are served by that upstream.
	OCIMirrors map[string][]string `json:"oci_mirrors" yaml:"oci_mirrors"`

	// Generic maps names to plain HTTP upstream base URLs, served at
	// /generic/{name}/. The remaining request path and query string are
	// appended to the upstream URL. GitHub release asset paths
	// ({owner}/{repo}/releases/download/{tag}/{asset}) and paths matching
	// GenericArtifacts are cached in the artifact cache; everything else
	// goes through the metadata cache.
	// Example: {"github": "https://github.com", "github-api": "https://api.github.com"}.
	Generic map[string]string `json:"generic" yaml:"generic"`

	// GenericArtifacts maps a Generic upstream name to regular expressions for
	// its version-pinned download paths. A request path after
	// /generic/{name}/ that one of them matches in full is cached in the
	// artifact cache like a GitHub release asset. Each pattern needs `version`
	// and `file` named groups; an optional `name` group names the package,
	// which otherwise is the upstream name.
	// Example: {"apache": ["dist/(?P<name>maven)/maven-3/(?P<version>[^/]+)/binaries/(?P<file>[^/]+)"]}.
	GenericArtifacts map[string][]string `json:"generic_artifacts" yaml:"generic_artifacts"`

	// Auth configures authentication for upstream registries.
	// Keys are absolute URL scopes matched by scheme, host, effective port,
	// and path-segment prefix.
	// Example: "https://npm.pkg.github.com" matches all requests to that host.
	Auth map[string]AuthConfig `json:"auth" yaml:"auth"`
}

// AuthForURL returns the auth config that matches the given URL.
// The longest matching URL scope wins.
func (u *UpstreamConfig) AuthForURL(url string) *AuthConfig {
	if u.Auth == nil {
		return nil
	}
	target, err := parseAuthURL(url)
	if err != nil {
		return nil
	}

	var bestMatch *AuthConfig
	var bestLen int

	for pattern, auth := range u.Auth {
		configured, err := parseAuthURL(pattern)
		if err == nil && authURLMatches(configured, target) && len(pattern) > bestLen {
			a := auth // copy to avoid loop variable capture
			bestMatch = &a
			bestLen = len(pattern)
		}
	}

	return bestMatch
}

// Validate checks upstream authentication URL scopes.
func (u *UpstreamConfig) Validate() error {
	for pattern := range u.Auth {
		if _, err := parseAuthURL(pattern); err != nil {
			return fmt.Errorf("invalid upstream.auth URL %q: %w", pattern, err)
		}
	}
	if err := validateNamedUpstreams("upstream.helm", u.Helm); err != nil {
		return err
	}
	if err := validatePackageRoutes("upstream.composer_routes", u.ComposerRoutes); err != nil {
		return err
	}
	if err := validatePackageRoutes("upstream.npm_routes", u.NPMRoutes); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.apk", u.APK); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.arch", u.Arch); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.go_sumdbs", u.GoSumDBs); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.oci", u.OCI); err != nil {
		return err
	}
	if err := validateOCIMirrors(u.OCIMirrors, u.OCI); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.generic", u.Generic); err != nil {
		return err
	}
	if err := u.validateGenericArtifacts(); err != nil {
		return err
	}
	if err := validateNamedUpstreams("upstream.debian_repositories", u.DebianRepositories); err != nil {
		return err
	}
	for _, name := range debianReservedRepositoryNames {
		if _, found := u.DebianRepositories[name]; found {
			return fmt.Errorf(
				"invalid upstream.debian_repositories name %q: reserved for the upstream.debian archive",
				name,
			)
		}
	}
	return nil
}

func (u *UpstreamConfig) validateGenericArtifacts() error {
	for name, patterns := range u.GenericArtifacts {
		if _, found := u.Generic[name]; !found {
			return fmt.Errorf("invalid upstream.generic_artifacts name %q: no upstream.generic entry", name)
		}
		for _, pattern := range patterns {
			if _, err := CompileGenericArtifactPattern(pattern); err != nil {
				return fmt.Errorf("invalid upstream.generic_artifacts.%s pattern %q: %w", name, pattern, err)
			}
		}
	}
	return nil
}

// validateUpstream checks the upstream block, including the one setting in
// it that depends on a top-level option.
func (c *Config) validateUpstream() error {
	if err := c.Upstream.Validate(); err != nil {
		return err
	}
	if c.Upstream.GoSumDBsOffline && !c.CacheMetadata {
		return fmt.Errorf("upstream.go_sumdbs_offline requires cache_metadata")
	}
	return nil
}

// CompileGenericArtifactPattern compiles an upstream.generic_artifacts pattern
// so that it only matches a whole path, and checks it has the `version` and
// `file` groups.
func CompileGenericArtifactPattern(pattern string) (*regexp.Regexp, error) {
	re, err := regexp.Compile(`^(?:` + pattern + `)$`)
	if err != nil {
		return nil, err
	}
	for _, group := range []string{"version", "file"} {
		if re.SubexpIndex(group) < 0 {
			return nil, fmt.Errorf("missing (?P<%s>...) group", group)
		}
	}
	return re, nil
}

// debianReservedRepositoryNames are the upstream.debian archive's own root
// paths, which a repository of the same name would shadow.
var debianReservedRepositoryNames = []string{"pool", "dists"}

// validateOCIMirrors checks that every upstream.oci_mirrors entry belongs to
// an upstream.oci name and lists bare registry hosts, the form containerd
// sends in the ns query parameter. A host may belong to one upstream only;
// otherwise both prefixes would take it while unprefixed requests silently
// went to one of them.
func validateOCIMirrors(mirrors map[string][]string, upstreams map[string]string) error {
	names := make([]string, 0, len(mirrors))
	for name := range mirrors {
		names = append(names, name)
	}
	sort.Strings(names)
	owners := make(map[string]string)
	for _, name := range names {
		if _, ok := upstreams[name]; !ok {
			return fmt.Errorf("invalid upstream.oci_mirrors name %q: no upstream.oci entry of that name", name)
		}
		for _, host := range mirrors[name] {
			parsed, err := url.Parse("https://" + host)
			if host == "" || err != nil || parsed.Host != host {
				return fmt.Errorf("invalid upstream.oci_mirrors.%s host %q: must be a registry host such as ghcr.io or registry.example:5000", name, host)
			}
			key := ociMirrorHostKey(host)
			if owner, taken := owners[key]; taken && owner != name {
				return fmt.Errorf("invalid upstream.oci_mirrors.%s host %q: already listed for %s", name, host, owner)
			}
			owners[key] = name
		}
	}
	return nil
}

// ociMirrorHostKey normalizes an upstream.oci_mirrors host the way the
// container handler builds its ns lookup keys: lowercase, IPv6 literals in
// brackets, an empty or default https port dropped. Two entries with the same
// key would select the same route.
func ociMirrorHostKey(host string) string {
	name, port, err := net.SplitHostPort(host)
	if err != nil {
		name, port = strings.TrimSuffix(strings.TrimPrefix(host, "["), "]"), ""
	}
	name = strings.ToLower(name)
	if strings.Contains(name, ":") {
		name = "[" + name + "]"
	}
	if port == "" || port == "443" {
		return name
	}
	return name + ":" + port
}

func validateNamedUpstreams(field string, upstreams map[string]string) error {
	for name, upstreamURL := range upstreams {
		if name == "" || name == "." || name == ".." || strings.ContainsAny(name, `/\\`) {
			return fmt.Errorf("invalid %s name %q", field, name)
		}
		if err := validateAbsoluteURL(field+"."+name, upstreamURL); err != nil {
			return err
		}
	}
	return nil
}

func validatePackageRoutes(field string, routes map[string]string) error {
	for pattern, upstreamURL := range routes {
		if _, err := path.Match(pattern, ""); pattern == "" || err != nil {
			return fmt.Errorf("invalid %s pattern %q", field, pattern)
		}
		if err := validateAbsoluteURL(field+"."+pattern, upstreamURL); err != nil {
			return err
		}
	}
	return nil
}

func parseAuthURL(value string) (*url.URL, error) {
	parsed, err := url.Parse(value)
	if err != nil || !parsed.IsAbs() || parsed.Hostname() == "" || parsed.Opaque != "" {
		return nil, fmt.Errorf("invalid authentication URL")
	}
	return parsed, nil
}

func authURLMatches(configured, target *url.URL) bool {
	if !strings.EqualFold(configured.Scheme, target.Scheme) ||
		!strings.EqualFold(configured.Hostname(), target.Hostname()) ||
		authURLPort(configured) != authURLPort(target) {
		return false
	}
	if configured.RawQuery != "" && configured.RawQuery != target.RawQuery {
		return false
	}

	configuredPath := strings.TrimSuffix(configured.EscapedPath(), "/")
	if configuredPath == "" {
		return true
	}
	targetPath := strings.TrimSuffix(target.EscapedPath(), "/")
	return targetPath == configuredPath || strings.HasPrefix(targetPath, configuredPath+"/")
}

func authURLPort(value *url.URL) string {
	if port := value.Port(); port != "" {
		return port
	}
	if strings.EqualFold(value.Scheme, "https") {
		return "443"
	}
	if strings.EqualFold(value.Scheme, "http") {
		return "80"
	}
	return ""
}

// AuthConfig configures authentication for an upstream registry.
type AuthConfig struct {
	// Type is the authentication type: "bearer", "basic", "header", or "ecr".
	Type string `json:"type" yaml:"type"`

	// Token is used for bearer authentication.
	// Can reference environment variables with ${VAR_NAME} syntax.
	Token string `json:"token" yaml:"token"`

	// Username is used for basic authentication.
	Username string `json:"username" yaml:"username"`

	// Password is used for basic authentication.
	// Can reference environment variables with ${VAR_NAME} syntax.
	Password string `json:"password" yaml:"password"`

	// HeaderName is the custom header name (for type "header").
	HeaderName string `json:"header_name" yaml:"header_name"`

	// HeaderValue is the custom header value (for type "header").
	// Can reference environment variables with ${VAR_NAME} syntax.
	HeaderValue string `json:"header_value" yaml:"header_value"`

	// Region is the AWS region for ECR authentication (for type "ecr").
	// If empty, the region is inferred from private ECR registry URLs before
	// falling back to the AWS SDK default region chain.
	Region string `json:"region" yaml:"region"`
}

// Default returns a Config with sensible defaults.
func Default() *Config {
	return &Config{
		Listen:  ":8080",
		BaseURL: "http://localhost:8080",
		Storage: StorageConfig{
			Path:           "./cache/artifacts",
			MaxSize:        "",
			CacheArtifacts: true,
			Retention: RetentionConfig{
				SweepInterval: defaultRetentionSweepIntervalStr,
			},
		},
		Database: DatabaseConfig{
			Driver: "sqlite",
			Path:   "./cache/proxy.db",
		},
		Log: LogConfig{
			Level:  "info",
			Format: "text",
		},
		Upstream: UpstreamConfig{
			NPM:                "https://registry.npmjs.org",
			Cargo:              "https://index.crates.io",
			CargoDownload:      "https://static.crates.io/crates",
			Gem:                "https://rubygems.org",
			Go:                 "https://proxy.golang.org",
			Hex:                "https://repo.hex.pm",
			HexAPI:             "https://hex.pm",
			Pub:                "https://pub.dev",
			PyPI:               "https://pypi.org",
			PyPIDownload:       "https://files.pythonhosted.org",
			Maven:              "https://repo1.maven.org/maven2",
			GradlePluginPortal: "https://plugins.gradle.org/m2",
			NuGet:              "https://api.nuget.org",
			NuGetSearch:        "https://azuresearch-usnc.nuget.org",
			Composer:           "https://packagist.org",
			ComposerRepository: "https://repo.packagist.org",
			Conan:              "https://center.conan.io",
			Conda:              "https://conda.anaconda.org",
			CRAN:               "https://cloud.r-project.org",
			Julia:              "https://pkg.julialang.org",
			Swift:              DefaultSwiftUpstream,
			OCIDefault:         "https://registry-1.docker.io",
			Debian:             "http://deb.debian.org/debian",
			RPM:                "https://dl.fedoraproject.org/pub/fedora/linux",
			HomebrewAPI:        "https://formulae.brew.sh/api",
			HomebrewArtifact:   "https://ghcr.io",
		},
		Gradle: GradleConfig{
			BuildCache: GradleBuildCacheConfig{
				ReadOnly:      false,
				MaxUploadSize: defaultGradleMaxUploadSizeStr,
				MaxAge:        "168h",
				MaxSize:       "",
				SweepInterval: defaultGradleSweepIntervalStr,
			},
		},
	}
}

// Load reads configuration from a file (YAML or JSON).
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config file: %w", err)
	}

	cfg := Default()

	ext := strings.ToLower(filepath.Ext(path))
	switch ext {
	case ".yaml", ".yml":
		if err := yaml.Unmarshal(data, cfg); err != nil {
			return nil, fmt.Errorf("parsing YAML config: %w", err)
		}
	case ".json":
		if err := json.Unmarshal(data, cfg); err != nil {
			return nil, fmt.Errorf("parsing JSON config: %w", err)
		}
	default:
		// Try YAML first, then JSON
		if err := yaml.Unmarshal(data, cfg); err != nil {
			if err := json.Unmarshal(data, cfg); err != nil {
				return nil, fmt.Errorf("parsing config (tried YAML and JSON): %w", err)
			}
		}
	}

	return cfg, nil
}

// setEnvString sets *dst from the named environment variable, leaving it
// untouched if the variable is unset or empty.
func setEnvString(dst *string, key string) {
	if v := os.Getenv(key); v != "" {
		*dst = v
	}
}

// setEnvBool is setEnvString for boolean fields, parsed via envBool.
func setEnvBool(dst *bool, key string) {
	if v := os.Getenv(key); v != "" {
		*dst = envBool(v)
	}
}

func setEnvStringSlice(dst *[]string, key string) {
	value := os.Getenv(key)
	if value == "" {
		return
	}
	var items []string
	for item := range strings.SplitSeq(value, ",") {
		if item = strings.TrimSpace(item); item != "" {
			items = append(items, item)
		}
	}
	if len(items) > 0 {
		*dst = items
	}
}

// LoadFromEnv applies environment variable overrides to a Config.
// Environment variables use the PROXY_ prefix:
//   - PROXY_LISTEN
//   - PROXY_BASE_URL
//   - PROXY_UI_URL
//   - PROXY_STORAGE_PATH
//   - PROXY_STORAGE_MAX_SIZE
//   - PROXY_DATABASE_PATH
//   - PROXY_LOG_LEVEL
//   - PROXY_LOG_FORMAT
//   - PROXY_ACCESS_LOG_PATH
//   - PROXY_TRUST_FORWARDED_FOR
//   - PROXY_UI_REQUEST_SOURCES
//   - PROXY_UPSTREAM_SWIFT
//   - PROXY_HEALTH_STORAGE_PROBE_INTERVAL
func (c *Config) LoadFromEnv() {
	setEnvString(&c.Listen, "PROXY_LISTEN")
	setEnvString(&c.BaseURL, "PROXY_BASE_URL")
	setEnvString(&c.UIBaseURL, "PROXY_UI_URL")
	setEnvBool(&c.TrustForwardedFor, "PROXY_TRUST_FORWARDED_FOR")
	setEnvBool(&c.UIRequestSources, "PROXY_UI_REQUEST_SOURCES")
	setEnvBool(&c.UIFailureDetails, "PROXY_UI_FAILURE_DETAILS")
	setEnvString(&c.Storage.URL, "PROXY_STORAGE_URL")
	setEnvString(&c.Storage.Path, "PROXY_STORAGE_PATH")
	setEnvString(&c.Storage.MaxSize, "PROXY_STORAGE_MAX_SIZE")
	setEnvBool(&c.Storage.DirectServe, "PROXY_STORAGE_DIRECT_SERVE")
	setEnvString(&c.Storage.DirectServeTTL, "PROXY_STORAGE_DIRECT_SERVE_TTL")
	setEnvString(&c.Storage.DirectServeBaseURL, "PROXY_STORAGE_DIRECT_SERVE_BASE_URL")
	setEnvBool(&c.Storage.CacheArtifacts, "PROXY_STORAGE_CACHE_ARTIFACTS")
	setEnvString(&c.Storage.Retention.Default, "PROXY_STORAGE_RETENTION_DEFAULT")
	setEnvString(&c.Storage.Retention.SweepInterval, "PROXY_STORAGE_RETENTION_SWEEP_INTERVAL")
	setEnvString(&c.Database.Driver, "PROXY_DATABASE_DRIVER")
	setEnvString(&c.Database.Path, "PROXY_DATABASE_PATH")
	setEnvString(&c.Database.URL, "PROXY_DATABASE_URL")
	setEnvString(&c.Database.HitFlushInterval, "PROXY_DATABASE_HIT_FLUSH_INTERVAL")
	setEnvString(&c.Log.Level, "PROXY_LOG_LEVEL")
	setEnvString(&c.Log.Format, "PROXY_LOG_FORMAT")
	setEnvString(&c.AccessLog.Path, "PROXY_ACCESS_LOG_PATH")
	setEnvStringSlice(&c.Upstream.AllowPrivateHosts, "PROXY_UPSTREAM_ALLOW_PRIVATE_HOSTS")
	setEnvBool(&c.Upstream.AllowLoopback, "PROXY_UPSTREAM_ALLOW_LOOPBACK")
	setEnvString(&c.Upstream.NPM, "PROXY_UPSTREAM_NPM")
	setEnvBool(&c.Upstream.NPMFullMetadata, "PROXY_UPSTREAM_NPM_FULL_METADATA")
	setEnvBool(&c.Upstream.GoSumDBsOffline, "PROXY_UPSTREAM_GO_SUMDBS_OFFLINE")
	setEnvString(&c.Upstream.Cargo, "PROXY_UPSTREAM_CARGO")
	setEnvString(&c.Upstream.CargoDownload, "PROXY_UPSTREAM_CARGO_DOWNLOAD")
	setEnvString(&c.Upstream.Gem, "PROXY_UPSTREAM_GEM")
	setEnvString(&c.Upstream.Go, "PROXY_UPSTREAM_GO")
	setEnvString(&c.Upstream.Hex, "PROXY_UPSTREAM_HEX")
	setEnvString(&c.Upstream.HexAPI, "PROXY_UPSTREAM_HEX_API")
	setEnvString(&c.Upstream.Pub, "PROXY_UPSTREAM_PUB")
	setEnvString(&c.Upstream.PyPI, "PROXY_UPSTREAM_PYPI")
	setEnvString(&c.Upstream.PyPIDownload, "PROXY_UPSTREAM_PYPI_DOWNLOAD")
	setEnvString(&c.Upstream.Maven, "PROXY_UPSTREAM_MAVEN")
	setEnvString(&c.Upstream.GradlePluginPortal, "PROXY_UPSTREAM_GRADLE_PLUGIN_PORTAL")
	setEnvString(&c.Upstream.NuGet, "PROXY_UPSTREAM_NUGET")
	setEnvString(&c.Upstream.NuGetSearch, "PROXY_UPSTREAM_NUGET_SEARCH")
	setEnvString(&c.Upstream.Composer, "PROXY_UPSTREAM_COMPOSER")
	setEnvString(&c.Upstream.ComposerRepository, "PROXY_UPSTREAM_COMPOSER_REPOSITORY")
	setEnvString(&c.Upstream.Conan, "PROXY_UPSTREAM_CONAN")
	setEnvString(&c.Upstream.Conda, "PROXY_UPSTREAM_CONDA")
	setEnvString(&c.Upstream.CRAN, "PROXY_UPSTREAM_CRAN")
	setEnvString(&c.Upstream.Julia, "PROXY_UPSTREAM_JULIA")
	setEnvString(&c.Upstream.Swift, "PROXY_UPSTREAM_SWIFT")
	setEnvString(&c.Upstream.OCIDefault, "PROXY_UPSTREAM_OCI_DEFAULT")
	setEnvString(&c.Upstream.Debian, "PROXY_UPSTREAM_DEBIAN")
	setEnvString(&c.Upstream.RPM, "PROXY_UPSTREAM_RPM")
	setEnvString(&c.Upstream.HomebrewAPI, "PROXY_UPSTREAM_HOMEBREW_API")
	setEnvString(&c.Upstream.HomebrewArtifact, "PROXY_UPSTREAM_HOMEBREW_ARTIFACT")
	setEnvString(&c.Cooldown.Default, "PROXY_COOLDOWN_DEFAULT")
	setEnvBool(&c.Scanning.Enabled, "PROXY_SCANNING_ENABLED")
	setEnvBool(&c.Scanning.FailOpen, "PROXY_SCANNING_FAIL_OPEN")
	setEnvString(&c.Scanning.Timeout, "PROXY_SCANNING_TIMEOUT")
	setEnvString(&c.Scanning.SigningKey, "PROXY_SCANNING_SIGNING_KEY")
	setEnvString(&c.Scanning.FetchBaseURL, "PROXY_SCANNING_FETCH_BASE_URL")
	setEnvBool(&c.CacheMetadata, "PROXY_CACHE_METADATA")
	setEnvBool(&c.MirrorAPI, "PROXY_MIRROR_API")
	setEnvBool(&c.Hosted.Enabled, "PROXY_HOSTED_ENABLED")
	setEnvString(&c.Hosted.Token, "PROXY_HOSTED_TOKEN")
	setEnvString(&c.Hosted.MaxUploadSize, "PROXY_HOSTED_MAX_UPLOAD_SIZE")
	setEnvStringSlice(&c.Hosted.NPMScopes, "PROXY_HOSTED_NPM_SCOPES")
	setEnvStringSlice(&c.Hosted.ComposerVendors, "PROXY_HOSTED_COMPOSER_VENDORS")
	setEnvString(&c.MetadataTTL, "PROXY_METADATA_TTL")
	setEnvString(&c.MetadataMaxSize, "PROXY_METADATA_MAX_SIZE")
	setEnvString(&c.ArtifactMaxSize, "PROXY_ARTIFACT_MAX_SIZE")
	setEnvString(&c.MetadataRewriteCacheSize, "PROXY_METADATA_REWRITE_CACHE_SIZE")
	setEnvString(&c.HTTPTimeout, "PROXY_HTTP_TIMEOUT")
	setEnvBool(&c.Gradle.BuildCache.ReadOnly, "PROXY_GRADLE_BUILD_CACHE_READ_ONLY")
	setEnvString(&c.Gradle.BuildCache.MaxUploadSize, "PROXY_GRADLE_BUILD_CACHE_MAX_UPLOAD_SIZE")
	setEnvString(&c.Gradle.BuildCache.MaxAge, "PROXY_GRADLE_BUILD_CACHE_MAX_AGE")
	setEnvString(&c.Gradle.BuildCache.MaxSize, "PROXY_GRADLE_BUILD_CACHE_MAX_SIZE")
	setEnvString(&c.Gradle.BuildCache.SweepInterval, "PROXY_GRADLE_BUILD_CACHE_SWEEP_INTERVAL")
	setEnvString(&c.Health.StorageProbeInterval, "PROXY_HEALTH_STORAGE_PROBE_INTERVAL")
}

// validateAbsoluteURL returns an error if value is not a parseable URL with
// both a scheme and host. fieldName is used in the error message.
func validateAbsoluteURL(fieldName, value string) error {
	u, err := url.Parse(value)
	if err != nil || u.Scheme == "" || u.Host == "" {
		return fmt.Errorf("invalid %s %q: must be an absolute URL", fieldName, value)
	}
	return nil
}

// Validate checks the configuration for errors.
func (c *Config) Validate() error {
	if c.Listen == "" {
		return fmt.Errorf("listen address is required")
	}
	if c.BaseURL == "" {
		return fmt.Errorf("base_url is required")
	}
	if c.UIBaseURL == "" {
		c.UIBaseURL = c.BaseURL
	} else if err := validateAbsoluteURL("ui_base_url", c.UIBaseURL); err != nil {
		return err
	}
	if c.Storage.URL == "" && c.Storage.Path == "" {
		return fmt.Errorf("storage.url or storage.path is required")
	}
	switch c.Database.Driver {
	case "sqlite":
		if c.Database.Path == "" {
			return fmt.Errorf("database.path is required for sqlite driver")
		}
	case "postgres":
		if c.Database.URL == "" {
			return fmt.Errorf("database.url is required for postgres driver")
		}
	default:
		return fmt.Errorf("invalid database.driver %q (must be sqlite or postgres)", c.Database.Driver)
	}

	// Validate log level
	switch strings.ToLower(c.Log.Level) {
	case "debug", "info", "warn", "error":
		// OK
	default:
		return fmt.Errorf("invalid log level %q (must be debug, info, warn, or error)", c.Log.Level)
	}

	// Validate log format
	switch strings.ToLower(c.Log.Format) {
	case "text", "json":
		// OK
	default:
		return fmt.Errorf("invalid log format %q (must be text or json)", c.Log.Format)
	}

	// Validate max size if specified
	if c.Storage.MaxSize != "" {
		if _, err := ParseSize(c.Storage.MaxSize); err != nil {
			return fmt.Errorf("invalid storage.max_size: %w", err)
		}
	}

	// Validate direct serve TTL if specified
	if c.Storage.DirectServeTTL != "" {
		if _, err := time.ParseDuration(c.Storage.DirectServeTTL); err != nil {
			return fmt.Errorf("invalid storage.direct_serve_ttl %q: %w", c.Storage.DirectServeTTL, err)
		}
	}

	// Validate direct serve base URL if specified
	if c.Storage.DirectServeBaseURL != "" {
		if err := validateAbsoluteURL("storage.direct_serve_base_url", c.Storage.DirectServeBaseURL); err != nil {
			return err
		}
	}

	if err := c.validateCacheArtifacts(); err != nil {
		return err
	}

	// Validate metadata TTL if specified
	if c.MetadataTTL != "" && c.MetadataTTL != "0" {
		if _, err := time.ParseDuration(c.MetadataTTL); err != nil {
			return fmt.Errorf("invalid metadata_ttl %q: %w", c.MetadataTTL, err)
		}
	}

	if err := c.validateDownloadSizeLimits(); err != nil {
		return err
	}

	if err := validateHTTPTimeout(c.HTTPTimeout); err != nil {
		return err
	}

	if err := validateHitFlushInterval(c.Database.HitFlushInterval); err != nil {
		return err
	}

	return c.validateComponents()
}

func (c *Config) validateCacheArtifacts() error {
	if c.Storage.CacheArtifacts {
		return nil
	}
	switch {
	case c.Scanning.Enabled:
		return fmt.Errorf("storage.cache_artifacts: false cannot be combined with scanning.enabled: scanning needs stored artifacts")
	case c.Storage.DirectServe:
		return fmt.Errorf("storage.cache_artifacts: false cannot be combined with storage.direct_serve: no artifacts are stored to redirect to")
	case c.MirrorAPI:
		return fmt.Errorf("storage.cache_artifacts: false cannot be combined with mirror_api: mirrored artifacts would never be served")
	case c.Hosted.Enabled:
		return fmt.Errorf("storage.cache_artifacts: false cannot be combined with hosted.enabled: pushed packages would never be served")
	}
	return nil
}

func (c *Config) validateComponents() error {
	if err := validateMetadataRewriteCacheSize(c.MetadataRewriteCacheSize); err != nil {
		return err
	}

	if _, err := c.RetentionRules(retention.Default); err != nil {
		return err
	}

	if _, err := denylist.New(c.Denylist.Packages); err != nil {
		return err
	}

	if err := c.validateUpstream(); err != nil {
		return err
	}

	if err := c.Health.Validate(); err != nil {
		return err
	}

	if err := c.Scanning.Validate(); err != nil {
		return err
	}

	if err := c.Hosted.Validate(); err != nil {
		return err
	}

	return c.Gradle.BuildCache.Validate()
}

// Validate checks the /health configuration. An unset interval is allowed
// (the cache uses its default); explicit values must parse and be non-negative.
func (h *HealthConfig) Validate() error {
	if h.StorageProbeInterval == "" || h.StorageProbeInterval == "0" {
		return nil
	}
	d, err := time.ParseDuration(h.StorageProbeInterval)
	if err != nil {
		return fmt.Errorf("invalid health.storage_probe_interval %q: %w", h.StorageProbeInterval, err)
	}
	if d < 0 {
		return fmt.Errorf("invalid health.storage_probe_interval %q: must be non-negative", h.StorageProbeInterval)
	}
	return nil
}

// Validate checks Gradle build cache settings, applying the default upload
// size if unset.
func (g *GradleBuildCacheConfig) Validate() error {
	if g.MaxUploadSize == "" {
		g.MaxUploadSize = defaultGradleMaxUploadSizeStr
	}
	uploadSize, err := ParseSize(g.MaxUploadSize)
	if err != nil {
		return fmt.Errorf("invalid gradle.build_cache.max_upload_size: %w", err)
	}
	if uploadSize <= 0 {
		return fmt.Errorf("invalid gradle.build_cache.max_upload_size %q: must be > 0", g.MaxUploadSize)
	}

	if g.MaxAge != "" && g.MaxAge != "0" {
		if _, err := parseDayDuration(g.MaxAge); err != nil {
			return fmt.Errorf("invalid gradle.build_cache.max_age %q: %w", g.MaxAge, err)
		}
	}

	if g.MaxSize != "" {
		if _, err := ParseSize(g.MaxSize); err != nil {
			return fmt.Errorf("invalid gradle.build_cache.max_size: %w", err)
		}
	}

	if g.SweepInterval != "" {
		d, err := time.ParseDuration(g.SweepInterval)
		if err != nil {
			return fmt.Errorf("invalid gradle.build_cache.sweep_interval %q: %w", g.SweepInterval, err)
		}
		if d <= 0 {
			return fmt.Errorf("invalid gradle.build_cache.sweep_interval %q: must be > 0", g.SweepInterval)
		}
	}

	return nil
}

const (
	defaultMetadataTTL                   = 5 * time.Minute  //nolint:mnd // sensible default
	defaultDirectServeTTL                = 15 * time.Minute //nolint:mnd // sensible default
	defaultHTTPTimeout                   = 30 * time.Second //nolint:mnd // sensible default
	defaultHitFlushInterval              = time.Second
	defaultMetadataMaxSize               = 100 << 20
	defaultMetadataRewriteCacheSize      = 256 << 20
	defaultGradleBuildCacheMaxUploadSize = 100 << 20
	defaultGradleBuildCacheSweepInterval = 10 * time.Minute
	defaultGradleMaxUploadSizeStr        = "100MB"
	defaultGradleSweepIntervalStr        = "10m"
	defaultRetentionSweepInterval        = 10 * time.Minute
	defaultRetentionSweepIntervalStr     = "10m"
	minRetentionSweepInterval            = time.Minute
	maxDurationDays                      = 36500
	defaultScanningTimeoutStr            = "30s"
)

// ParseMaxSize returns the maximum cache size in bytes.
// Returns 0 if unset or explicitly disabled (meaning unlimited).
func (c *Config) ParseMaxSize() int64 {
	if c.Storage.MaxSize == "" || c.Storage.MaxSize == "0" {
		return 0
	}
	size, err := ParseSize(c.Storage.MaxSize)
	if err != nil {
		return 0
	}
	return size
}

func validateHTTPTimeout(s string) error {
	if s == "" || s == "0" {
		return nil
	}
	d, err := time.ParseDuration(s)
	if err != nil {
		return fmt.Errorf("invalid http_timeout %q: %w", s, err)
	}
	if d < 0 {
		return fmt.Errorf("invalid http_timeout %q: must be non-negative", s)
	}
	return nil
}

func validateMetadataMaxSize(s string) error {
	if s == "" {
		return nil
	}
	size, err := ParseSize(s)
	if err != nil {
		return fmt.Errorf("invalid metadata_max_size: %w", err)
	}
	if size <= 0 {
		return fmt.Errorf("invalid metadata_max_size %q: must be positive", s)
	}
	return nil
}

func (c *Config) validateDownloadSizeLimits() error {
	if err := validateMetadataMaxSize(c.MetadataMaxSize); err != nil {
		return err
	}
	return validateArtifactMaxSize(c.ArtifactMaxSize)
}

func validateArtifactMaxSize(s string) error {
	if s == "" {
		return nil
	}
	size, err := ParseSize(s)
	if err != nil {
		return fmt.Errorf("invalid artifact_max_size: %w", err)
	}
	if size < 0 {
		return fmt.Errorf("invalid artifact_max_size %q: must not be negative", s)
	}
	return nil
}

func validateMetadataRewriteCacheSize(s string) error {
	if s == "" || s == "0" {
		return nil
	}
	size, err := ParseSize(s)
	if err != nil {
		return fmt.Errorf("invalid metadata_rewrite_cache_size: %w", err)
	}
	if size < 0 {
		return fmt.Errorf("invalid metadata_rewrite_cache_size %q: must not be negative", s)
	}
	return nil
}

// ParseMetadataRewriteCacheSize returns how many bytes of rewritten metadata
// to keep in memory. Returns 256MB if unset or invalid, 0 if disabled.
func (c *Config) ParseMetadataRewriteCacheSize() int64 {
	if c.MetadataRewriteCacheSize == "" {
		return defaultMetadataRewriteCacheSize
	}
	if c.MetadataRewriteCacheSize == "0" {
		return 0
	}
	size, err := ParseSize(c.MetadataRewriteCacheSize)
	if err != nil || size < 0 {
		return defaultMetadataRewriteCacheSize
	}
	return size
}

// ParseMetadataMaxSize returns the maximum metadata response size in bytes.
// Returns 100MB if unset or invalid.
func (c *Config) ParseMetadataMaxSize() int64 {
	if c.MetadataMaxSize == "" {
		return defaultMetadataMaxSize
	}
	size, err := ParseSize(c.MetadataMaxSize)
	if err != nil || size <= 0 {
		return defaultMetadataMaxSize
	}
	return size
}

// ParseArtifactMaxSize returns the artifact size limit in bytes, or 0 for
// no limit.
func (c *Config) ParseArtifactMaxSize() int64 {
	if c.ArtifactMaxSize == "" {
		return 0
	}
	size, err := ParseSize(c.ArtifactMaxSize)
	if err != nil || size < 0 {
		return 0
	}
	return size
}

// ParseHTTPTimeout returns the upstream HTTP client timeout.
// Returns 30s if unset, 0 (no timeout) if explicitly set to "0".
func (c *Config) ParseHTTPTimeout() time.Duration {
	if c.HTTPTimeout == "" {
		return defaultHTTPTimeout
	}
	if c.HTTPTimeout == "0" {
		return 0
	}
	d, err := time.ParseDuration(c.HTTPTimeout)
	if err != nil || d < 0 {
		return defaultHTTPTimeout
	}
	return d
}

func validateHitFlushInterval(s string) error {
	if s == "" || s == "0" {
		return nil
	}
	d, err := time.ParseDuration(s)
	if err != nil {
		return fmt.Errorf("invalid database.hit_flush_interval %q: %w", s, err)
	}
	if d < 0 {
		return fmt.Errorf("invalid database.hit_flush_interval %q: must be non-negative", s)
	}
	return nil
}

// ParseHitFlushInterval returns how often batched cache hits are written.
// Returns 1 second if unset or invalid, 0 if explicitly disabled.
func (c *Config) ParseHitFlushInterval() time.Duration {
	if c.Database.HitFlushInterval == "" {
		return defaultHitFlushInterval
	}
	if c.Database.HitFlushInterval == "0" {
		return 0
	}
	d, err := time.ParseDuration(c.Database.HitFlushInterval)
	if err != nil || d < 0 {
		return defaultHitFlushInterval
	}
	return d
}

// ParseMetadataTTL returns the metadata TTL duration.
// Returns 5 minutes if unset, 0 if explicitly disabled.
func (c *Config) ParseMetadataTTL() time.Duration {
	if c.MetadataTTL == "" {
		return defaultMetadataTTL
	}
	if c.MetadataTTL == "0" {
		return 0
	}
	d, err := time.ParseDuration(c.MetadataTTL)
	if err != nil {
		return defaultMetadataTTL
	}
	return d
}

// ParseGradleBuildCacheMaxUploadSize returns the max accepted PUT body size.
// Defaults to 100MB if unset or invalid.
func (c *Config) ParseGradleBuildCacheMaxUploadSize() int64 {
	if c.Gradle.BuildCache.MaxUploadSize == "" {
		return defaultGradleBuildCacheMaxUploadSize
	}
	size, err := ParseSize(c.Gradle.BuildCache.MaxUploadSize)
	if err != nil || size <= 0 {
		return defaultGradleBuildCacheMaxUploadSize
	}
	return size
}

// ParseGradleBuildCacheMaxAge returns age-based eviction threshold.
// Returns 0 when disabled or invalid.
func (c *Config) ParseGradleBuildCacheMaxAge() time.Duration {
	if c.Gradle.BuildCache.MaxAge == "" || c.Gradle.BuildCache.MaxAge == "0" {
		return 0
	}
	d, err := parseDayDuration(c.Gradle.BuildCache.MaxAge)
	if err != nil || d <= 0 {
		return 0
	}
	return d
}

// ParseGradleBuildCacheMaxSize returns total-size cap in bytes.
// Returns 0 when disabled or invalid.
func (c *Config) ParseGradleBuildCacheMaxSize() int64 {
	if c.Gradle.BuildCache.MaxSize == "" || c.Gradle.BuildCache.MaxSize == "0" {
		return 0
	}
	size, err := ParseSize(c.Gradle.BuildCache.MaxSize)
	if err != nil || size <= 0 {
		return 0
	}
	return size
}

// ParseGradleBuildCacheSweepInterval returns eviction sweep cadence.
// Defaults to 10m if unset or invalid.
func (c *Config) ParseGradleBuildCacheSweepInterval() time.Duration {
	if c.Gradle.BuildCache.SweepInterval == "" {
		return defaultGradleBuildCacheSweepInterval
	}
	d, err := time.ParseDuration(c.Gradle.BuildCache.SweepInterval)
	if err != nil || d <= 0 {
		return defaultGradleBuildCacheSweepInterval
	}
	return d
}

// ParseDirectServeTTL returns the presigned URL expiry duration.
// Returns 15 minutes if unset.
func (c *Config) ParseDirectServeTTL() time.Duration {
	if c.Storage.DirectServeTTL == "" {
		return defaultDirectServeTTL
	}
	d, err := time.ParseDuration(c.Storage.DirectServeTTL)
	if err != nil {
		return defaultDirectServeTTL
	}
	return d
}

// ParseSize parses a human-readable size string (e.g., "10GB", "500MB").
// Returns the size in bytes.
func ParseSize(s string) (int64, error) {
	s = strings.TrimSpace(strings.ToUpper(s))
	if s == "" || s == "0" {
		return 0, nil
	}

	// Check suffixes in order of length (longest first) to avoid partial matches
	suffixes := []struct {
		suffix string
		mult   int64
	}{
		{"TB", 1024 * 1024 * 1024 * 1024},
		{"GB", 1024 * 1024 * 1024},
		{"MB", 1024 * 1024},
		{"KB", 1024},
		{"T", 1024 * 1024 * 1024 * 1024},
		{"G", 1024 * 1024 * 1024},
		{"M", 1024 * 1024},
		{"K", 1024},
		{"B", 1},
	}

	for _, s2 := range suffixes {
		if numStr, ok := strings.CutSuffix(s, s2.suffix); ok {
			num, err := strconv.ParseFloat(numStr, 64)
			if err != nil {
				return 0, fmt.Errorf("invalid number %q", numStr)
			}
			return int64(num * float64(s2.mult)), nil
		}
	}

	// Try parsing as plain number (bytes)
	num, err := strconv.ParseInt(s, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("invalid size %q", s)
	}
	return num, nil
}

// Header returns the HTTP header name and value for this auth config.
// Returns empty strings if the config is invalid or incomplete.
func (a *AuthConfig) Header() (name, value string) {
	switch strings.ToLower(a.Type) {
	case "bearer":
		token := expandEnv(a.Token)
		if token == "" {
			return "", ""
		}
		return "Authorization", "Bearer " + token

	case "basic":
		username := expandEnv(a.Username)
		password := expandEnv(a.Password)
		if username == "" {
			return "", ""
		}
		encoded := base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
		return "Authorization", "Basic " + encoded

	case "header":
		name := a.HeaderName
		value := expandEnv(a.HeaderValue)
		if name == "" {
			return "", ""
		}
		return name, value

	default:
		return "", ""
	}
}

// expandEnv expands ${VAR_NAME} references in a string.
func expandEnv(s string) string {
	return os.Expand(s, os.Getenv)
}

func envBool(v string) bool {
	return v == "true" || v == "1"
}