package app

import (
	"context"
	"os"
	"syscall"
	"testing"
	"time"

	"github.com/labstack/echo/v4"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// mockHandler is a mock implementation of the Handler interface for testing
type mockHandler struct {
	startSchedulerCalled bool
	stopSchedulerCalled  bool
	startDelay           time.Duration
	stopDelay            time.Duration
	startError           error
	stopError            error
}

func (m *mockHandler) StartScheduler() {
	m.startSchedulerCalled = true
	if m.startDelay > 0 {
		time.Sleep(m.startDelay)
	}
	if m.startError != nil {
		panic(m.startError)
	}
}

func (m *mockHandler) StopScheduler() {
	m.stopSchedulerCalled = true
	if m.stopDelay > 0 {
		time.Sleep(m.stopDelay)
	}
	if m.stopError != nil {
		panic(m.stopError)
	}
}

// reset resets the mock handler state
func (m *mockHandler) reset() {
	m.startSchedulerCalled = false
	m.stopSchedulerCalled = false
}

// TestApp_New tests App constructor
func TestApp_New(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{}

	app := New(e, handler)

	assert.NotNil(t, app, "App should not be nil")
	assert.Equal(t, e, app.echo, "Echo instance should be stored")
	assert.Equal(t, handler, app.handler, "Handler should be stored")
	assert.Equal(t, 30*time.Second, app.shutdownTimeout, "Default shutdown timeout should be 30 seconds")
	assert.NotNil(t, app.shutdownDone, "Shutdown done channel should be initialized")
}

// TestApp_SetShutdownTimeout tests configurable shutdown timeout
func TestApp_SetShutdownTimeout(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{}
	app := New(e, handler)

	customTimeout := 15 * time.Second
	app.SetShutdownTimeout(customTimeout)

	assert.Equal(t, customTimeout, app.shutdownTimeout, "Shutdown timeout should be updated")
}

// TestApp_ShutdownDone tests shutdown done channel
func TestApp_ShutdownDone(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{}
	app := New(e, handler)

	channel := app.ShutdownDone()
	assert.NotNil(t, channel, "ShutdownDone should return a channel")
	// Verify it's the same channel by checking if it's readable
	select {
	case <-channel:
		// Channel should not be closed yet
		t.Error("ShutdownDone channel should not be closed immediately")
	default:
		// Expected - channel is open but not ready
	}
}

// TestApp_Start_BackgroundServices tests background service startup
func TestApp_Start_BackgroundServices(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{
		startDelay: 100 * time.Millisecond, // Short delay to verify async startup
	}
	app := New(e, handler)

	// Start the app in a goroutine (simulating main.go)
	done := make(chan error, 1)
	go func() {
		// This will block until shutdown signal
		err := app.Start()
		done <- err
	}()

	// Wait a bit for background services to start
	time.Sleep(150 * time.Millisecond)

	// Verify scheduler was started
	assert.True(t, handler.startSchedulerCalled, "StartScheduler should be called")

	// Send shutdown signal to clean up
	done2 := make(chan bool)
	go func() {
		// Send shutdown signal
		process, err := os.FindProcess(os.Getpid())
		require.NoError(t, err, "Should find current process")
		err = process.Signal(syscall.SIGTERM)
		done2 <- (err == nil)
	}()

	// Wait for app to finish
	select {
	case err := <-done:
		assert.NoError(t, err, "App should shut down without error")
	case <-time.After(5 * time.Second):
		t.Fatal("App did not shut down within timeout")
	}

	<-done2
}

// TestApp_Shutdown_GracefulShutdown tests graceful shutdown sequence
func TestApp_Shutdown_GracefulShutdown(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{
		stopDelay: 50 * time.Millisecond,
	}
	app := New(e, handler)

	// Test shutdown
	err := app.Shutdown()

	assert.NoError(t, err, "Shutdown should complete without error")
	assert.True(t, handler.stopSchedulerCalled, "StopScheduler should be called")
}

// TestApp_Shutdown_ThreadSafety tests thread-safe shutdown
func TestApp_Shutdown_ThreadSafety(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{}
	app := New(e, handler)

	// Call shutdown multiple times concurrently
	errors := make(chan error, 3)
	for i := 0; i < 3; i++ {
		go func() {
			errors <- app.Shutdown()
		}()
	}

	// Collect results
	for i := 0; i < 3; i++ {
		err := <-errors
		// First call should succeed, subsequent calls should also succeed (no-op)
		assert.NoError(t, err, "Concurrent shutdown calls should not error")
	}

	// Verify handler was stopped only once
	assert.True(t, handler.stopSchedulerCalled, "StopScheduler should be called at least once")
}

// TestApp_Shutdown_Timeout tests shutdown timeout handling
func TestApp_Shutdown_Timeout(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{
		stopDelay: 2 * time.Second, // Longer than shutdown timeout
	}
	app := New(e, handler)
	app.SetShutdownTimeout(100 * time.Millisecond) // Set very short timeout

	// Test shutdown with timeout
	err := app.Shutdown()

	assert.Error(t, err, "Shutdown should timeout and return error")
	assert.True(t, handler.stopSchedulerCalled, "StopScheduler should still be called")
}

// TestApp_Shutdown_ClosesEchoServer tests HTTP server shutdown
func TestApp_Shutdown_ClosesEchoServer(t *testing.T) {
	e := echo.New()
	handler := &mockHandler{}

	// Start a simple server
	go func() {
		e.Start(":0") // Use random port
	}()

	// Give server time to start
	time.Sleep(100 * time.Millisecond)

	app := New(e, handler)

	// Shutdown should close the echo server
	err := app.Shutdown()

	assert.NoError(t, err, "Shutdown should complete")
	assert.True(t, handler.stopSchedulerCalled, "StopScheduler should be called")
}

// TestApp_SignalHandling tests signal handling (SIGINT, SIGTERM, SIGQUIT)
func TestApp_SignalHandling(t *testing.T) {
	tests := []struct {
		name   string
		signal os.Signal
	}{
		{"SIGINT", syscall.SIGINT},
		{"SIGTERM", syscall.SIGTERM},
		{"SIGQUIT", syscall.SIGQUIT},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			e := echo.New()
			handler := &mockHandler{}
			app := New(e, handler)

			// Start app in goroutine
			done := make(chan error, 1)
			go func() {
				done <- app.Start()
			}()

			// Wait for background services to start
			time.Sleep(100 * time.Millisecond)
			assert.True(t, handler.startSchedulerCalled, "StartScheduler should be called")

			// Send signal
			process, err := os.FindProcess(os.Getpid())
			require.NoError(t, err, "Should find current process")

			err = process.Signal(tt.signal)
			require.NoError(t, err, "Should send signal")

			// Wait for shutdown
			select {
			case err := <-done:
				assert.NoError(t, err, "App should shut down without error")
				assert.True(t, handler.stopSchedulerCalled, "StopScheduler should be called")
			case <-time.After(5 * time.Second):
				t.Fatal("App did not shut down within timeout")
			}
		})
	}
}

// TestApp_Integration_StartupSequence tests complete startup sequence
func TestApp_Integration_StartupSequence(t *testing.T) {
	if testing.Short() {
		t.Skip("Skipping integration test in short mode")
	}

	e := echo.New()
	handler := &mockHandler{}
	app := New(e, handler)

	// This test simulates the sequence in cmd/server/main.go:
	// 1. Create app
	// 2. Start HTTP server in background
	// 3. Call app.Start() which blocks until signal

	// Step 1: App already created above
	assert.NotNil(t, app, "App should be created")

	// Step 2: Start HTTP server (simulated)
	serverReady := make(chan bool)
	go func() {
		// In real main.go, this would be: e.Start(":" + cfg.ServerPort)
		// For testing, we don't actually start the server
		serverReady <- true
		<-context.Background().Done() // Block until done
	}()

	<-serverReady

	// Step 3: Start app lifecycle in background
	appDone := make(chan error, 1)
	go func() {
		appDone <- app.Start()
	}()

	// Verify background services started
	time.Sleep(150 * time.Millisecond)
	assert.True(t, handler.startSchedulerCalled, "Scheduler should be started")

	// Send shutdown signal (simulating user pressing Ctrl+C)
	process, err := os.FindProcess(os.Getpid())
	require.NoError(t, err)
	err = process.Signal(syscall.SIGINT)
	require.NoError(t, err)

	// Wait for graceful shutdown
	select {
	case err := <-appDone:
		assert.NoError(t, err, "App should shut down gracefully")
		assert.True(t, handler.stopSchedulerCalled, "Scheduler should be stopped")
	case <-time.After(5 * time.Second):
		t.Fatal("App did not complete shutdown within timeout")
	}
}

// TestApp_HandlerInterface tests that Handler interface is properly implemented
func TestApp_HandlerInterface(t *testing.T) {
	// This test verifies that the mock handler satisfies the Handler interface
	var _ Handler = &mockHandler{}
}

// TestApp_AutoStartVerification tests auto-start functionality
func TestApp_AutoStartVerification(t *testing.T) {
	t.Run("Auto-start runs asynchronously", func(t *testing.T) {
		e := echo.New()
		handler := &mockHandler{
			startDelay: 100 * time.Millisecond,
		}
		app := New(e, handler)

		// Start the app - it should start background services and return immediately
		// Then we send a shutdown signal right away
		done := make(chan error, 1)
		go func() {
			// This will start services in background, then wait for signal
			err := app.Start()
			done <- err
		}()

		// Wait a bit for background services to start
		time.Sleep(150 * time.Millisecond)

		// Verify scheduler was started in background
		assert.True(t, handler.startSchedulerCalled, "StartScheduler should be called in background")

		// Send shutdown signal
		process, err := os.FindProcess(os.Getpid())
		require.NoError(t, err)
		_ = process.Signal(syscall.SIGTERM)

		// Wait for clean shutdown
		select {
		case err := <-done:
			assert.NoError(t, err, "App should shut down gracefully")
		case <-time.After(5 * time.Second):
			t.Fatal("App did not shut down within timeout")
		}
	})
}

// BenchmarkApp_Shutdown benchmarks the shutdown process
func BenchmarkApp_Shutdown(b *testing.B) {
	e := echo.New()
	handler := &mockHandler{}

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		handler.reset()
		app := New(e, handler)
		app.Shutdown()
	}
}