package server

import (
	"context"
	"database/sql"
	"io"
	"log/slog"
	"slices"
	"strings"
	"testing"
	"time"

	"github.com/git-pkgs/proxy/internal/database"
	"github.com/git-pkgs/proxy/internal/storage"
)

// seedMetadata caches a 500-byte metadata document last used at
// accessedAt and returns its storage path.
func seedMetadata(t *testing.T, ctx context.Context, db *database.DB, store storage.Storage, key string, accessedAt time.Time) string {
	t.Helper()
	path := "_metadata/golang/" + key + "/metadata"
	size, _, err := store.Store(ctx, path, strings.NewReader(strings.Repeat("m", 500)))
	if err != nil {
		t.Fatalf("storing metadata: %v", err)
	}
	if err := db.UpsertMetadataCache(&database.MetadataCacheEntry{
		Ecosystem:   "golang",
		Name:        key,
		StoragePath: path,
		Size:        sql.NullInt64{Int64: size, Valid: true},
		FetchedAt:   sql.NullTime{Time: time.Now(), Valid: true},
	}); err != nil {
		t.Fatalf("upserting metadata: %v", err)
	}
	query := db.Rebind(`UPDATE metadata_cache SET last_accessed_at = ? WHERE ecosystem = ? AND name = ?`)
	if _, err := db.Exec(query, accessedAt.UTC(), "golang", key); err != nil {
		t.Fatalf("setting last access: %v", err)
	}
	return path
}

func TestEvictLRU_CountsAndEvictsMetadata(t *testing.T) {
	db, store := setupEvictionTest(t)
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	now := time.Now()

	oldTile := seedMetadata(t, ctx, db, store, "tile-old", now.Add(-3*time.Hour))
	seedArtifact(t, ctx, db, store, "mid-pkg", 500, now.Add(-2*time.Hour))
	newTile := seedMetadata(t, ctx, db, store, "tile-new", now)

	// Artifacts alone are within the limit; with metadata the cache is
	// 1500 bytes, so the least recently used entry has to go, and that is
	// the old metadata document.
	evictLRU(ctx, db, store, logger, 1100)

	if entry, _ := db.GetMetadataCache("golang", "tile-old"); entry != nil {
		t.Error("least recently used metadata row was kept")
	}
	if ok, _ := store.Exists(ctx, oldTile); ok {
		t.Error("least recently used metadata blob was kept")
	}
	if entry, _ := db.GetMetadataCache("golang", "tile-new"); entry == nil {
		t.Error("recently used metadata row was evicted")
	}
	if ok, _ := store.Exists(ctx, newTile); !ok {
		t.Error("recently used metadata blob was deleted")
	}
	art, err := db.GetArtifact("pkg:npm/mid-pkg@1.0.0", "mid-pkg-1.0.0.tgz")
	if err != nil || art == nil || !art.StoragePath.Valid {
		t.Errorf("artifact used after the old metadata was evicted: %+v, %v", art, err)
	}
}

func TestEvictLRU_EvictsArtifactBeforeNewerMetadata(t *testing.T) {
	db, store := setupEvictionTest(t)
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	now := time.Now()

	seedArtifact(t, ctx, db, store, "old-pkg", 500, now.Add(-3*time.Hour))
	seedMetadata(t, ctx, db, store, "tile", now)

	evictLRU(ctx, db, store, logger, 600)

	art, err := db.GetArtifact("pkg:npm/old-pkg@1.0.0", "old-pkg-1.0.0.tgz")
	if err != nil || art == nil || art.StoragePath.Valid {
		t.Errorf("older artifact kept: %+v, %v", art, err)
	}
	if entry, _ := db.GetMetadataCache("golang", "tile"); entry == nil {
		t.Error("newer metadata evicted although evicting the artifact was enough")
	}
}

// TestEvictBatch_KeepsMetadataUsedSinceRead evicts from a row read before a
// request served the document again. The row and its blob stay, and nothing
// is counted as freed.
func TestEvictBatch_KeepsMetadataUsedSinceRead(t *testing.T) {
	db, store := setupEvictionTest(t)
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	path := seedMetadata(t, ctx, db, store, "tile", time.Now().Add(-time.Hour))

	stale, err := db.GetLeastRecentlyUsedCacheEntries(evictionBatch)
	if err != nil || len(stale) != 1 {
		t.Fatalf("reading LRU rows: %v, %v", stale, err)
	}
	if err := db.RecordMetadataHit("golang", "tile"); err != nil {
		t.Fatalf("recording hit: %v", err)
	}

	cleared, freed := evictBatch(ctx, db, store, logger, stale, 0, 500)
	if cleared != 0 || freed != 0 {
		t.Errorf("cleared %d records freeing %d bytes, want nothing", cleared, freed)
	}
	if entry, _ := db.GetMetadataCache("golang", "tile"); entry == nil {
		t.Error("metadata row served since it was read was evicted")
	}
	if ok, _ := store.Exists(ctx, path); !ok {
		t.Error("metadata blob served since it was read was deleted")
	}
}

// TestEvictLRU_MetadataLeavesNothingQueued checks that a completed eviction
// takes the path it queued with the row's delete off the queue again.
func TestEvictLRU_MetadataLeavesNothingQueued(t *testing.T) {
	db, store := setupEvictionTest(t)
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	path := seedMetadata(t, ctx, db, store, "tile", time.Now().Add(-time.Hour))

	evictLRU(ctx, db, store, logger, 0)

	if ok, _ := store.Exists(ctx, path); ok {
		t.Error("metadata blob kept")
	}
	if got := queuedPaths(t, db); len(got) != 0 {
		t.Errorf("queue = %v, want it empty after the delete", got)
	}
}

// TestEvictMetadata_InterruptedBeforeDeleteIsReclaimed stops an eviction
// after the row is gone but before the blob is deleted, as a crash would. The
// path is queued, so reclaim still deletes the blob.
func TestEvictMetadata_InterruptedBeforeDeleteIsReclaimed(t *testing.T) {
	db, store := setupEvictionTest(t)
	ctx := context.Background()
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	path := seedMetadata(t, ctx, db, store, "tile", time.Now().Add(-time.Hour))

	entries, err := db.GetLeastRecentlyUsedCacheEntries(evictionBatch)
	if err != nil || len(entries) != 1 {
		t.Fatalf("reading LRU rows: %v, %v", entries, err)
	}
	e := entries[0]
	if ok, err := db.EvictMetadataCache(e.Key, e.Name, path, e.LastAccessedAt); err != nil || !ok {
		t.Fatalf("EvictMetadataCache = %v, %v", ok, err)
	}
	if got := queuedPaths(t, db); !slices.Equal(got, []string{path}) {
		t.Fatalf("queue = %v, want the evicted path", got)
	}

	// Nothing left for a restarted eviction pass to retry; reclaim takes it.
	if again, _ := db.GetLeastRecentlyUsedCacheEntries(evictionBatch); len(again) != 0 {
		t.Errorf("LRU after interruption = %+v, want nothing", again)
	}
	reclaimDue(ctx, db, store, logger, time.Now().Add(time.Hour), time.Minute)
	if objectExists(t, store, path) {
		t.Error("blob still stored after reclaim")
	}
	if got := queuedPaths(t, db); len(got) != 0 {
		t.Errorf("queue = %v, want it drained", got)
	}
}

func TestBackfillMetadataAccessDrainsInBatches(t *testing.T) {
	db, _ := setupEvictionTest(t)
	for _, name := range []string{"a", "b", "c", "d", "e"} {
		query := db.Rebind(`INSERT INTO metadata_cache (ecosystem, name, storage_path, size, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?)`)
		if _, err := db.Exec(query, "npm", name, "_metadata/npm/"+name+"/metadata", 1, time.Now(), time.Now()); err != nil {
			t.Fatalf("inserting: %v", err)
		}
	}

	backfillMetadataAccess(context.Background(), db, slog.New(slog.NewTextHandler(io.Discard, nil)), 2)

	var left int
	if err := db.Get(&left, `SELECT COUNT(*) FROM metadata_cache WHERE last_accessed_at IS NULL`); err != nil {
		t.Fatalf("counting: %v", err)
	}
	if left != 0 {
		t.Errorf("%d rows left without an access time", left)
	}
}