package executor

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sync"
	"testing"
	"time"

	"github.com/thepeterstone/claudomator/internal/storage"
	"github.com/thepeterstone/claudomator/internal/task"
)

// mockRunner implements Runner for testing.
type mockRunner struct {
	mu       sync.Mutex
	calls    int
	delay    time.Duration
	err      error
	exitCode int
}

func (m *mockRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
	m.mu.Lock()
	m.calls++
	m.mu.Unlock()

	if m.delay > 0 {
		select {
		case <-time.After(m.delay):
		case <-ctx.Done():
			return ctx.Err()
		}
	}
	if m.err != nil {
		e.ExitCode = m.exitCode
		return m.err
	}
	return nil
}

func (m *mockRunner) callCount() int {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.calls
}

func testStore(t *testing.T) *storage.DB {
	t.Helper()
	dbPath := filepath.Join(t.TempDir(), "test.db")
	db, err := storage.Open(dbPath)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { db.Close() })
	return db
}

func makeTask(id string) *task.Task {
	now := time.Now().UTC()
	return &task.Task{
		ID: id, Name: "Test " + id,
		Claude:    task.ClaudeConfig{Instructions: "test"},
		Priority:  task.PriorityNormal,
		Retry:     task.RetryConfig{MaxAttempts: 1, Backoff: "linear"},
		Tags:      []string{},
		DependsOn: []string{},
		State:     task.StateQueued,
		CreatedAt: now, UpdatedAt: now,
	}
}

func TestPool_Submit_TopLevel_GoesToReady(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(2, runner, store, logger)

	tk := makeTask("ps-1") // no ParentTaskID → top-level
	store.CreateTask(tk)

	if err := pool.Submit(context.Background(), tk); err != nil {
		t.Fatalf("submit: %v", err)
	}

	result := <-pool.Results()
	if result.Err != nil {
		t.Errorf("expected no error, got: %v", result.Err)
	}
	if result.Execution.Status != "READY" {
		t.Errorf("status: want READY, got %q", result.Execution.Status)
	}

	got, _ := store.GetTask("ps-1")
	if got.State != task.StateReady {
		t.Errorf("task state: want READY, got %v", got.State)
	}
}

func TestPool_Submit_Subtask_GoesToCompleted(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(2, runner, store, logger)

	tk := makeTask("sub-1")
	tk.ParentTaskID = "parent-99" // subtask
	store.CreateTask(tk)

	if err := pool.Submit(context.Background(), tk); err != nil {
		t.Fatalf("submit: %v", err)
	}

	result := <-pool.Results()
	if result.Err != nil {
		t.Errorf("expected no error, got: %v", result.Err)
	}
	if result.Execution.Status != "COMPLETED" {
		t.Errorf("status: want COMPLETED, got %q", result.Execution.Status)
	}

	got, _ := store.GetTask("sub-1")
	if got.State != task.StateCompleted {
		t.Errorf("task state: want COMPLETED, got %v", got.State)
	}
}

func TestPool_Submit_Failure(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{err: fmt.Errorf("boom"), exitCode: 1}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(2, runner, store, logger)

	tk := makeTask("pf-1")
	store.CreateTask(tk)
	pool.Submit(context.Background(), tk)

	result := <-pool.Results()
	if result.Err == nil {
		t.Fatal("expected error")
	}
	if result.Execution.Status != "FAILED" {
		t.Errorf("status: want FAILED, got %q", result.Execution.Status)
	}
}

func TestPool_Submit_Timeout(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{delay: 5 * time.Second}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(2, runner, store, logger)

	tk := makeTask("pt-1")
	tk.Timeout.Duration = 50 * time.Millisecond
	store.CreateTask(tk)
	pool.Submit(context.Background(), tk)

	result := <-pool.Results()
	if result.Execution.Status != "TIMED_OUT" {
		t.Errorf("status: want TIMED_OUT, got %q", result.Execution.Status)
	}
}

func TestPool_Submit_Cancellation(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{delay: 5 * time.Second}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(2, runner, store, logger)

	ctx, cancel := context.WithCancel(context.Background())
	tk := makeTask("pc-1")
	store.CreateTask(tk)
	pool.Submit(ctx, tk)

	time.Sleep(20 * time.Millisecond)
	cancel()

	result := <-pool.Results()
	if result.Execution.Status != "CANCELLED" {
		t.Errorf("status: want CANCELLED, got %q", result.Execution.Status)
	}
}

func TestPool_AtCapacity(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{delay: time.Second}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(1, runner, store, logger)

	tk1 := makeTask("cap-1")
	store.CreateTask(tk1)
	pool.Submit(context.Background(), tk1)

	// Pool is at capacity, second submit should fail.
	time.Sleep(10 * time.Millisecond) // let goroutine start
	tk2 := makeTask("cap-2")
	store.CreateTask(tk2)
	err := pool.Submit(context.Background(), tk2)
	if err == nil {
		t.Fatal("expected capacity error")
	}

	<-pool.Results() // drain
}

func TestPool_ConcurrentExecution(t *testing.T) {
	store := testStore(t)
	runner := &mockRunner{delay: 50 * time.Millisecond}
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
	pool := NewPool(3, runner, store, logger)

	for i := 0; i < 3; i++ {
		tk := makeTask(fmt.Sprintf("cc-%d", i))
		store.CreateTask(tk)
		if err := pool.Submit(context.Background(), tk); err != nil {
			t.Fatalf("submit %d: %v", i, err)
		}
	}

	for i := 0; i < 3; i++ {
		result := <-pool.Results()
		if result.Execution.Status != "READY" {
			t.Errorf("task %s: want READY, got %q", result.TaskID, result.Execution.Status)
		}
	}

	if runner.callCount() != 3 {
		t.Errorf("calls: want 3, got %d", runner.callCount())
	}
}