package lane

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"
)

// fakeStore is an in-memory PersistenceStore used by persistence
// tests. Records every method call so tests can assert ordering.
type fakeStore struct {
	mu      sync.Mutex
	rows    map[string]*storeRow
	enqErr  error
	updErr  error
	purgeFn func(time.Time) (int64, error)
}

type storeRow struct {
	jobID, lane, callerID string
	priority              int
	metadata              []byte
	state                 string
	enqueuedAt            time.Time
	startedAt             *time.Time
	finishedAt            *time.Time
}

func newFakeStore() *fakeStore { return &fakeStore{rows: map[string]*storeRow{}} }

func (f *fakeStore) EnqueueJob(_ context.Context, jobID, lane, callerID string, priority int, metadata []byte) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	if f.enqErr != nil {
		return f.enqErr
	}
	if _, exists := f.rows[jobID]; exists {
		return errors.New("duplicate enqueue")
	}
	f.rows[jobID] = &storeRow{
		jobID: jobID, lane: lane, callerID: callerID,
		priority: priority, metadata: metadata,
		state: "queued", enqueuedAt: time.Now(),
	}
	return nil
}

func (f *fakeStore) UpdateJobState(_ context.Context, jobID, state string, at time.Time) error {
	f.mu.Lock()
	defer f.mu.Unlock()
	if f.updErr != nil {
		return f.updErr
	}
	r, ok := f.rows[jobID]
	if !ok {
		return errors.New("not found")
	}
	r.state = state
	t := at
	switch state {
	case "running":
		r.startedAt = &t
	case "finished", "cancelled", "failed":
		r.finishedAt = &t
	}
	return nil
}

func (f *fakeStore) ListQueuedJobs(_ context.Context, lane string) ([]QueuedJobRef, error) {
	return f.list(lane, "queued"), nil
}

func (f *fakeStore) ListRunningJobs(_ context.Context, lane string) ([]QueuedJobRef, error) {
	return f.list(lane, "running"), nil
}

func (f *fakeStore) list(lane, state string) []QueuedJobRef {
	f.mu.Lock()
	defer f.mu.Unlock()
	var out []QueuedJobRef
	for _, r := range f.rows {
		if r.lane == lane && r.state == state {
			out = append(out, QueuedJobRef{
				JobID: r.jobID, Lane: r.lane,
				CallerID: r.callerID, Priority: r.priority,
				Metadata: r.metadata, EnqueuedAt: r.enqueuedAt,
			})
		}
	}
	return out
}

func (f *fakeStore) PurgeFinishedJobs(_ context.Context, olderThan time.Time) (int64, error) {
	if f.purgeFn != nil {
		return f.purgeFn(olderThan)
	}
	f.mu.Lock()
	defer f.mu.Unlock()
	var deleted int64
	for id, r := range f.rows {
		if (r.state == "finished" || r.state == "cancelled" || r.state == "failed") &&
			r.finishedAt != nil && r.finishedAt.Before(olderThan) {
			delete(f.rows, id)
			deleted++
		}
	}
	return deleted, nil
}

func (f *fakeStore) state(jobID string) string {
	f.mu.Lock()
	defer f.mu.Unlock()
	if r, ok := f.rows[jobID]; ok {
		return r.state
	}
	return ""
}

// metaJob is a Job impl that exposes Metadata. Used in persistence
// tests that assert metadata round-trip.
type metaJob struct {
	id, caller string
	priority   int
	meta       []byte
	run        func(ctx context.Context) error
}

func (m *metaJob) ID() string                    { return m.id }
func (m *metaJob) CallerID() string              { return m.caller }
func (m *metaJob) Priority() int                 { return m.priority }
func (m *metaJob) Metadata() []byte              { return m.meta }
func (m *metaJob) Run(ctx context.Context) error { return m.run(ctx) }

// TestPersistedLane_Submit_WritesRow verifies Submit writes a queued
// row with the right fields, then on Run completes transitions to
// finished.
func TestPersistedLane_Submit_WritesRow(t *testing.T) {
	store := newFakeStore()
	inner := New("ollama", 1)
	pl := NewPersistedLane(inner, store)

	done := make(chan struct{})
	job := &metaJob{
		id: "j1", caller: "alice", priority: 3,
		meta: []byte(`{"prompt":"hi"}`),
		run: func(ctx context.Context) error {
			close(done)
			return nil
		},
	}
	if _, _, err := pl.Submit(context.Background(), job); err != nil {
		t.Fatal(err)
	}
	<-done

	// Wait for state-update goroutine to land "finished".
	waitFor(t, func() bool { return store.state("j1") == "finished" })

	r := store.rows["j1"]
	if r.lane != "ollama" || r.callerID != "alice" || r.priority != 3 {
		t.Fatalf("row identity mismatch: %+v", r)
	}
	if string(r.metadata) != `{"prompt":"hi"}` {
		t.Fatalf("metadata mismatch: %s", r.metadata)
	}
	if r.startedAt == nil || r.finishedAt == nil {
		t.Fatalf("expected started_at + finished_at set; row=%+v", r)
	}
}

// TestPersistedLane_Submit_RunErrorMarksFailed verifies a failing Run
// transitions to state=failed.
func TestPersistedLane_Submit_RunErrorMarksFailed(t *testing.T) {
	store := newFakeStore()
	inner := New("test", 1)
	pl := NewPersistedLane(inner, store)

	job := &metaJob{
		id: "j1", caller: "alice",
		run: func(ctx context.Context) error {
			return errors.New("boom")
		},
	}
	if err := pl.SubmitWait(context.Background(), job); err == nil {
		t.Fatal("expected error from Run")
	}
	if got := store.state("j1"); got != "failed" {
		t.Fatalf("expected state=failed, got %s", got)
	}
}

// TestPersistedLane_EnqueueErrorAborts verifies that if EnqueueJob
// errors, the inner lane never sees the job.
func TestPersistedLane_EnqueueErrorAborts(t *testing.T) {
	store := newFakeStore()
	store.enqErr = errors.New("disk full")
	inner := New("test", 1).(*pool)
	pl := NewPersistedLane(inner, store)

	job := &funcJob{
		id: "j1", caller: "alice",
		run: func(ctx context.Context) error {
			t.Fatal("Run should not be called when persist enqueue fails")
			return nil
		},
	}
	_, _, err := pl.Submit(context.Background(), job)
	if err == nil {
		t.Fatal("expected Submit to fail")
	}
	// Inner lane should be empty.
	if got := inner.Stats().Running + inner.Stats().Queued; got != 0 {
		t.Fatalf("expected inner lane empty, got running+queued=%d", got)
	}
}

// TestPersistedLane_Cancel_QueuedWritesCancelled verifies cancelling a
// queued job writes state=cancelled.
func TestPersistedLane_Cancel_QueuedWritesCancelled(t *testing.T) {
	store := newFakeStore()
	inner := New("test", 1).(*pool)
	pl := NewPersistedLane(inner, store)

	blocker := newTestJob("blocker")
	if _, _, err := pl.Submit(context.Background(), blocker); err != nil {
		t.Fatal(err)
	}
	<-blocker.started

	target := newTestJob("target")
	if _, _, err := pl.Submit(context.Background(), target); err != nil {
		t.Fatal(err)
	}
	if got := inner.Stats().Queued; got != 1 {
		t.Fatalf("expected queued=1, got %d", got)
	}

	if err := pl.Cancel("target"); err != nil {
		t.Fatal(err)
	}
	waitFor(t, func() bool { return store.state("target") == "cancelled" })

	close(blocker.release)
}

// TestRecover_RunningMarkedFailed verifies that running rows at
// recovery time are marked failed (lost-on-restart).
func TestRecover_RunningMarkedFailed(t *testing.T) {
	store := newFakeStore()
	now := time.Now()
	store.rows["r1"] = &storeRow{
		jobID: "r1", lane: "ollama", callerID: "alice",
		state: "running", enqueuedAt: now.Add(-1 * time.Hour),
		startedAt: &now,
	}

	inner := New("ollama", 1)
	pl := NewPersistedLane(inner, store)

	// reconstructFn never called for running rows.
	if err := pl.Recover(context.Background(), nil); err != nil {
		t.Fatal(err)
	}
	if got := store.state("r1"); got != "failed" {
		t.Fatalf("expected r1 → failed, got %s", got)
	}
}

// TestRecover_QueuedReSubmitted verifies queued rows are re-submitted
// to the inner lane via reconstructFn.
func TestRecover_QueuedReSubmitted(t *testing.T) {
	store := newFakeStore()
	store.rows["q1"] = &storeRow{
		jobID: "q1", lane: "ollama", callerID: "alice",
		state: "queued", enqueuedAt: time.Now(),
		metadata: []byte("opaque"),
	}
	store.rows["q2"] = &storeRow{
		jobID: "q2", lane: "ollama", callerID: "bob",
		state: "queued", enqueuedAt: time.Now(),
	}

	inner := New("ollama", 2)
	pl := NewPersistedLane(inner, store)

	calls := make(chan string, 2)
	reconstruct := func(ref QueuedJobRef) Job {
		return &funcJob{
			id: ref.JobID, caller: ref.CallerID,
			run: func(ctx context.Context) error {
				calls <- ref.JobID
				return nil
			},
		}
	}
	if err := pl.Recover(context.Background(), reconstruct); err != nil {
		t.Fatal(err)
	}

	got := map[string]bool{}
	for i := 0; i < 2; i++ {
		select {
		case id := <-calls:
			got[id] = true
		case <-time.After(time.Second):
			t.Fatalf("expected 2 reconstructed runs; only got %v", got)
		}
	}
	if !got["q1"] || !got["q2"] {
		t.Fatalf("expected both q1 and q2 reconstructed; got %v", got)
	}

	// After Run completes, both rows should be state=finished.
	waitFor(t, func() bool {
		return store.state("q1") == "finished" && store.state("q2") == "finished"
	})
}

// TestRecover_NilReconstructMarksFailed verifies that when
// reconstructFn returns nil for a queued row, the row is marked
// failed.
func TestRecover_NilReconstructMarksFailed(t *testing.T) {
	store := newFakeStore()
	store.rows["q1"] = &storeRow{
		jobID: "q1", lane: "ollama", callerID: "alice",
		state: "queued", enqueuedAt: time.Now(),
	}
	inner := New("ollama", 1)
	pl := NewPersistedLane(inner, store)

	if err := pl.Recover(context.Background(), func(QueuedJobRef) Job { return nil }); err != nil {
		t.Fatal(err)
	}
	if got := store.state("q1"); got != "failed" {
		t.Fatalf("expected q1 → failed, got %s", got)
	}
}

// TestSweeper_PurgesFinishedRows verifies Sweep calls
// PurgeFinishedJobs with the right cutoff.
func TestSweeper_PurgesFinishedRows(t *testing.T) {
	store := newFakeStore()
	old := time.Now().Add(-25 * time.Hour)
	finished := time.Now()
	store.rows["old"] = &storeRow{
		jobID: "old", lane: "x", state: "finished",
		enqueuedAt: old, finishedAt: &old,
	}
	store.rows["recent"] = &storeRow{
		jobID: "recent", lane: "x", state: "finished",
		enqueuedAt: finished, finishedAt: &finished,
	}
	sw := NewSweeper(store, func() time.Duration { return 24 * time.Hour }, nil)
	sw.Sweep(context.Background())
	if _, ok := store.rows["old"]; ok {
		t.Fatal("old row should have been purged")
	}
	if _, ok := store.rows["recent"]; !ok {
		t.Fatal("recent row should remain")
	}
}

// TestSweeper_RetentionIsDynamic verifies the retention function is
// called per Sweep, so a runtime convar change takes effect.
func TestSweeper_RetentionIsDynamic(t *testing.T) {
	store := newFakeStore()
	called := 0
	retention := func() time.Duration {
		called++
		return time.Hour
	}
	sw := NewSweeper(store, retention, nil)
	sw.Sweep(context.Background())
	sw.Sweep(context.Background())
	if called != 2 {
		t.Fatalf("expected retention called twice, got %d", called)
	}
}