package compaction

import (
	"context"
	"encoding/json"
	"testing"
	"time"

	"chat-switchboard/database"
	"chat-switchboard/models"
	postgres "chat-switchboard/store/postgres"
)

// ── Helpers ─────────────────────────────────

func requireDB(t *testing.T) {
	t.Helper()
	database.RequireTestDB(t)
	database.TruncateAll(t)
}

func seedChannel(t *testing.T, userID, title string, msgCount, contentSize int) (channelID string, msgIDs []string) {
	t.Helper()
	channelID = database.SeedTestChannel(t, userID, title)
	msgIDs = database.SeedTestMessages(t, channelID, msgCount, contentSize)
	if len(msgIDs) > 0 {
		database.SeedTestCursor(t, channelID, userID, msgIDs[len(msgIDs)-1])
	}
	return
}

// setGlobalSetting writes a global_settings key for scanner config tests.
func setGlobalSetting(t *testing.T, key string, value interface{}) {
	t.Helper()
	valMap := models.JSONMap{"value": value}
	valJSON, _ := json.Marshal(valMap)
	_, err := database.DB.Exec(`
		INSERT INTO global_settings (key, value) VALUES ($1, $2)
		ON CONFLICT (key) DO UPDATE SET value = $2
	`, key, string(valJSON))
	if err != nil {
		t.Fatalf("setGlobalSetting(%s): %v", key, err)
	}
}

// seedChannelBackdated creates a channel with updated_at set to (now - age).
// Uses INSERT with an explicit timestamp so the BEFORE UPDATE trigger on
// channels (which overwrites updated_at = NOW()) never fires.
func seedChannelBackdated(t *testing.T, userID, title string, age time.Duration, msgCount, contentSize int) (channelID string, msgIDs []string) {
	t.Helper()
	target := time.Now().Add(-age)
	err := database.DB.QueryRow(`
		INSERT INTO channels (user_id, title, type, updated_at)
		VALUES ($1, $2, 'direct', $3)
		RETURNING id
	`, userID, title, target).Scan(&channelID)
	if err != nil {
		t.Fatalf("seedChannelBackdated: %v", err)
	}
	msgIDs = database.SeedTestMessages(t, channelID, msgCount, contentSize)
	if len(msgIDs) > 0 {
		database.SeedTestCursor(t, channelID, userID, msgIDs[len(msgIDs)-1])
	}
	return
}

// setChannelSettings sets the channel.settings JSONB.
func setChannelSettings(t *testing.T, channelID string, settings models.JSONMap) {
	t.Helper()
	sJSON, _ := json.Marshal(settings)
	_, err := database.DB.Exec(`UPDATE channels SET settings = $1 WHERE id = $2`, string(sJSON), channelID)
	if err != nil {
		t.Fatalf("setChannelSettings: %v", err)
	}
}

// ═══════════════════════════════════════════
// Estimator Tests (no DB — duplicated here for package-level access)
// ═══════════════════════════════════════════
// Note: estimator_test.go covers the unit tests more thoroughly.
// These are here to verify the package compiles with DB tests.

func TestEstimateTokens_Basic(t *testing.T) {
	if got := EstimateTokens("hello world!"); got != 3 { // 12 chars → 3
		t.Errorf("EstimateTokens = %d, want 3", got)
	}
}

// ═══════════════════════════════════════════
// Scanner: Candidate Query
// ═══════════════════════════════════════════

func TestScanner_FindCandidates_ReturnsQualifying(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil) // no resolver needed for this test
	sc := NewScanner(svc, stores, ScannerConfig{})

	userID := database.SeedTestUser(t, "scanuser1", "scan1@test.com")

	// Create a channel with enough messages to qualify
	// 20 messages × 2000 chars = 40K chars (> candidateMinChars=20K)
	// Backdated 5min so it passes activity gap (>2min) and recency (<7 days)
	channelID, _ := seedChannelBackdated(t, userID, "Big Chat", 5*time.Minute, 20, 2000)

	ctx := context.Background()
	candidates := sc.findCandidates(ctx)

	if len(candidates) == 0 {
		t.Fatal("expected at least 1 candidate, got 0")
	}

	found := false
	for _, c := range candidates {
		if c.ID == channelID {
			found = true
			break
		}
	}
	if !found {
		t.Fatalf("channel %s not in candidates (got %d candidates)", channelID, len(candidates))
	}
}

func TestScanner_FindCandidates_ExcludesTooFewMessages(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	userID := database.SeedTestUser(t, "scanuser2", "scan2@test.com")

	// Only 4 messages — below candidateMinMessages=10
	channelID, _ := seedChannelBackdated(t, userID, "Small Chat", 5*time.Minute, 4, 2000)

	ctx := context.Background()
	candidates := sc.findCandidates(ctx)

	for _, c := range candidates {
		if c.ID == channelID {
			t.Fatal("channel with <10 messages should not be a candidate")
		}
	}
}

func TestScanner_FindCandidates_ExcludesTooRecent(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	userID := database.SeedTestUser(t, "scanuser3", "scan3@test.com")

	// Enough messages but updated just now (< candidateActivityGap=2min)
	seedChannel(t, userID, "Fresh Chat", 20, 2000)
	// Don't backdate — should be excluded

	ctx := context.Background()
	candidates := sc.findCandidates(ctx)

	for _, c := range candidates {
		if c.UserID == userID {
			t.Fatal("channel updated just now should not be a candidate (activity gap)")
		}
	}
}

func TestScanner_FindCandidates_ExcludesArchived(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	userID := database.SeedTestUser(t, "scanuser4", "scan4@test.com")
	channelID, _ := seedChannelBackdated(t, userID, "Archived Chat", 5*time.Minute, 20, 2000)

	// Archive the channel
	database.DB.Exec(`UPDATE channels SET is_archived = true WHERE id = $1`, channelID)

	ctx := context.Background()
	candidates := sc.findCandidates(ctx)

	for _, c := range candidates {
		if c.ID == channelID {
			t.Fatal("archived channel should not be a candidate")
		}
	}
}

// ═══════════════════════════════════════════
// Scanner: Cooldown + Dedup
// ═══════════════════════════════════════════

func TestScanner_Cooldown(t *testing.T) {
	sc := &Scanner{
		lastCompacted: make(map[string]time.Time),
	}

	channelID := "test-cooldown-channel"

	// No cooldown initially
	sc.mu.Lock()
	_, inCooldown := sc.lastCompacted[channelID]
	sc.mu.Unlock()
	if inCooldown {
		t.Fatal("should not be in cooldown initially")
	}

	// Record compaction
	sc.mu.Lock()
	sc.lastCompacted[channelID] = time.Now()
	sc.mu.Unlock()

	// Now it's in cooldown
	sc.mu.Lock()
	last, ok := sc.lastCompacted[channelID]
	sc.mu.Unlock()
	if !ok {
		t.Fatal("should be in cooldown after recording")
	}
	if time.Since(last) > time.Second {
		t.Fatal("cooldown timestamp should be recent")
	}
}

func TestScanner_InFlightDedup(t *testing.T) {
	sc := &Scanner{}
	// sync.Map zero value is ready to use

	channelID := "test-dedup-channel"

	// First load — not in flight
	_, loaded := sc.inFlight.LoadOrStore(channelID, struct{}{})
	if loaded {
		t.Fatal("should not be loaded on first attempt")
	}

	// Second load — already in flight
	_, loaded = sc.inFlight.LoadOrStore(channelID, struct{}{})
	if !loaded {
		t.Fatal("should be loaded on second attempt (dedup)")
	}

	// Clean up
	sc.inFlight.Delete(channelID)
	_, loaded = sc.inFlight.LoadOrStore(channelID, struct{}{})
	if loaded {
		t.Fatal("should not be loaded after delete")
	}
}

// ═══════════════════════════════════════════
// Scanner: Channel Opt-Out
// ═══════════════════════════════════════════

func TestScanner_ShouldCompact_ChannelOptOut(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil) // no resolver → IsConfigured returns false
	sc := NewScanner(svc, stores, ScannerConfig{})

	userID := database.SeedTestUser(t, "optout_user", "optout@test.com")
	channelID, _ := seedChannel(t, userID, "Opt-Out Chat", 20, 2000)

	// Opt out via channel settings
	setChannelSettings(t, channelID, models.JSONMap{"auto_compaction": false})

	ch := models.Channel{Settings: models.JSONMap{"auto_compaction": false}}
	ch.ID = channelID
	ch.UserID = userID

	ctx := context.Background()
	if sc.shouldCompact(ctx, &ch) {
		t.Fatal("shouldCompact should return false for opted-out channel")
	}
}

// ═══════════════════════════════════════════
// Scanner: Settings Helpers
// ═══════════════════════════════════════════

func TestScanner_IsEnabled(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})
	ctx := context.Background()

	// Default: disabled
	if sc.isEnabled(ctx) {
		t.Fatal("should be disabled by default")
	}

	// Enable
	setGlobalSetting(t, "auto_compaction_enabled", true)
	if !sc.isEnabled(ctx) {
		t.Fatal("should be enabled after setting to true")
	}

	// Disable again
	setGlobalSetting(t, "auto_compaction_enabled", false)
	if sc.isEnabled(ctx) {
		t.Fatal("should be disabled after setting to false")
	}
}

func TestScanner_GetThreshold_Default(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	ch := &models.Channel{}
	got := sc.getThreshold(ch)
	if got != DefaultThreshold {
		t.Errorf("default threshold = %f, want %f", got, DefaultThreshold)
	}
}

func TestScanner_GetThreshold_GlobalOverride(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	setGlobalSetting(t, "auto_compaction_threshold", 0.85)

	ch := &models.Channel{}
	got := sc.getThreshold(ch)
	if got != 0.85 {
		t.Errorf("global threshold = %f, want 0.85", got)
	}
}

func TestScanner_GetThreshold_ChannelOverride(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})

	setGlobalSetting(t, "auto_compaction_threshold", 0.85)

	ch := &models.Channel{
		Settings: models.JSONMap{"compaction_threshold": 0.60},
	}
	got := sc.getThreshold(ch)
	if got != 0.60 {
		t.Errorf("channel threshold = %f, want 0.60", got)
	}
}

func TestScanner_GetCooldownDuration_Default(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})
	ctx := context.Background()

	got := sc.getCooldownDuration(ctx)
	if got != DefaultCooldown {
		t.Errorf("default cooldown = %s, want %s", got, DefaultCooldown)
	}
}

func TestScanner_GetCooldownDuration_Override(t *testing.T) {
	requireDB(t)
	stores := postgres.NewStores(database.TestDB)
	svc := NewService(stores, nil)
	sc := NewScanner(svc, stores, ScannerConfig{})
	ctx := context.Background()

	setGlobalSetting(t, "auto_compaction_cooldown_minutes", float64(15))

	got := sc.getCooldownDuration(ctx)
	want := 15 * time.Minute
	if got != want {
		t.Errorf("cooldown = %s, want %s", got, want)
	}
}

// ═══════════════════════════════════════════
// Context Budget Guard Rail
// ═══════════════════════════════════════════

func TestEstimateTokens_GuardRailMath(t *testing.T) {
	// Simulate a large conversation that exceeds a 32K utility model
	// 120K chars ≈ 30K tokens of conversation + system prompt overhead
	// inputCeiling = 32K * 0.80 = 25.6K → 30K exceeds it
	largeContent := make([]byte, 120000)
	contentTokens := EstimateTokens(string(largeContent))
	systemTokens := EstimateTokens("You are a conversation summarizer...") + 8 // +overhead

	totalPrompt := contentTokens + systemTokens
	utilityBudget := 32000 // 32K model
	inputCeiling := int(float64(utilityBudget) * 0.80)

	if totalPrompt <= inputCeiling {
		t.Errorf("120K chars (%d tokens) should exceed 32K model ceiling (%d tokens)",
			totalPrompt, inputCeiling)
	}

	// Smaller conversation should fit
	smallContent := make([]byte, 50000)
	smallTokens := EstimateTokens(string(smallContent)) + systemTokens
	if smallTokens > inputCeiling {
		t.Errorf("50K chars (%d tokens) should fit in 32K model ceiling (%d tokens)",
			smallTokens, inputCeiling)
	}
}