package libv2ray

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	coreapplog "github.com/xtls/xray-core/app/log"
	corecommlog "github.com/xtls/xray-core/common/log"
	corenet "github.com/xtls/xray-core/common/net"
	corefilesystem "github.com/xtls/xray-core/common/platform/filesystem"
	"github.com/xtls/xray-core/common/serial"
	core "github.com/xtls/xray-core/core"
	corestats "github.com/xtls/xray-core/features/stats"
	coreserial "github.com/xtls/xray-core/infra/conf/serial"
	_ "github.com/xtls/xray-core/main/distro/all"
	mobasset "golang.org/x/mobile/asset"
)

// Constants for environment variables
const (
	coreAsset   = "xray.location.asset"
	coreCert    = "xray.location.cert"
	xudpBaseKey = "xray.xudp.basekey"
)

// CoreController represents a controller for managing Xray core instance lifecycle
type CoreController struct {
	CallbackHandler CoreCallbackHandler
	statsManager    corestats.Manager
	coreMutex       sync.Mutex
	coreInstance    *core.Instance
	IsRunning       bool
}

// CoreCallbackHandler defines interface for receiving callbacks and notifications from the core service
type CoreCallbackHandler interface {
	Startup() int
	Shutdown() int
	OnEmitStatus(int, string) int
}

// consoleLogWriter implements a log writer without datetime stamps
// as Android system already adds timestamps to each log line
type consoleLogWriter struct {
	logger *log.Logger // Standard logger
}

// setEnvVariable safely sets an environment variable and logs any errors encountered.
func setEnvVariable(key, value string) {
	if err := os.Setenv(key, value); err != nil {
		log.Printf("Failed to set environment variable %s: %v. Please check your configuration.", key, err)
	}
}

// InitCoreEnv initializes environment variables and file system handlers for the core
// It sets up asset path, certificate path, XUDP base key and customizes the file reader
// to support Android asset system
func InitCoreEnv(envPath string, key string) {
	// Set asset/cert paths
	if len(envPath) > 0 {
		setEnvVariable(coreAsset, envPath)
		setEnvVariable(coreCert, envPath)
	}

	// Set XUDP encryption key
	if len(key) > 0 {
		setEnvVariable(xudpBaseKey, key)
	}

	// Custom file reader with path validation
	corefilesystem.NewFileReader = func(path string) (io.ReadCloser, error) {
		if _, err := os.Stat(path); os.IsNotExist(err) {
			_, file := filepath.Split(path)
			return mobasset.Open(file)
		}
		return os.Open(path)
	}
}

// NewCoreController initializes and returns a new CoreController instance
// Sets up the console log handler and associates it with the provided callback handler
func NewCoreController(s CoreCallbackHandler) *CoreController {
	// Register custom logger
	if err := coreapplog.RegisterHandlerCreator(
		coreapplog.LogType_Console,
		func(lt coreapplog.LogType, options coreapplog.HandlerCreatorOptions) (corecommlog.Handler, error) {
			return corecommlog.NewLogger(createStdoutLogWriter()), nil
		},
	); err != nil {
		log.Printf("Failed to register log handler: %v", err)
	}

	return &CoreController{
		CallbackHandler: s,
	}
}

// StartLoop initializes and starts the core processing loop
// Thread-safe method that configures and runs the Xray core with the provided configuration
// Returns immediately if the core is already running
func (x *CoreController) StartLoop(configContent string) (err error) {
	x.coreMutex.Lock()
	defer x.coreMutex.Unlock()

	if x.IsRunning {
		log.Println("Core is already running")
		return nil
	}

	return x.doStartLoop(configContent)
}

// StopLoop safely stops the core processing loop and releases resources
// Thread-safe method that shuts down the core instance and triggers necessary callbacks
func (x *CoreController) StopLoop() error {
	x.coreMutex.Lock()
	defer x.coreMutex.Unlock()

	if x.IsRunning {
		x.doShutdown()
		x.CallbackHandler.OnEmitStatus(0, "Core stopped")
	}
	return nil
}

// QueryStats retrieves and resets traffic statistics for a specific outbound tag and direction
// Returns the accumulated traffic value and resets the counter to zero
// Returns 0 if the stats manager is not initialized or the counter doesn't exist
func (x *CoreController) QueryStats(tag string, direct string) int64 {
	if x.statsManager == nil {
		return 0
	}
	counter := x.statsManager.GetCounter(fmt.Sprintf("outbound>>>%s>>>traffic>>>%s", tag, direct))
	if counter == nil {
		return 0
	}
	return counter.Set(0)
}

// MeasureDelay measures network latency to a specified URL through the current core instance
// Uses a 12-second timeout context and returns the round-trip time in milliseconds
// An error is returned if the connection fails or returns an unexpected status
func (x *CoreController) MeasureDelay(url string) (int64, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 12*time.Second)
	defer cancel()

	return measureInstDelay(ctx, x.coreInstance, url)
}

// MeasureOutboundDelay measures the outbound delay for a given configuration and URL
func MeasureOutboundDelay(ConfigureFileContent string, url string) (int64, error) {
	config, err := coreserial.LoadJSONConfig(strings.NewReader(ConfigureFileContent))
	if err != nil {
		return -1, fmt.Errorf("config load error: %w", err)
	}

	// Simplify config for testing
	config.Inbound = nil
	var essentialApp []*serial.TypedMessage
	for _, app := range config.App {
		if app.Type == "xray.app.proxyman.OutboundConfig" ||
			app.Type == "xray.app.dispatcher.Config" ||
			app.Type == "xray.app.log.Config" {
			essentialApp = append(essentialApp, app)
		}
	}
	config.App = essentialApp

	inst, err := core.New(config)
	if err != nil {
		return -1, fmt.Errorf("instance creation failed: %w", err)
	}

	if err := inst.Start(); err != nil {
		return -1, fmt.Errorf("startup failed: %w", err)
	}
	defer inst.Close()
	return measureInstDelay(context.Background(), inst, url)
}

// CheckVersionX returns the library and Xray versions
func CheckVersionX() string {
	var version = 33
	return fmt.Sprintf("Lib v%d, Xray-core v%s", version, core.Version())
}

// doShutdown shuts down the Xray instance and cleans up resources
func (x *CoreController) doShutdown() {
	if x.coreInstance != nil {
		if err := x.coreInstance.Close(); err != nil {
			log.Printf("core shutdown error: %v", err)
		}
		x.coreInstance = nil
	}
	x.IsRunning = false
	x.statsManager = nil
}

// doStartLoop sets up and starts the Xray core
func (x *CoreController) doStartLoop(configContent string) error {
	log.Println("initializing core...")
	config, err := coreserial.LoadJSONConfig(strings.NewReader(configContent))
	if err != nil {
		return fmt.Errorf("config error: %w", err)
	}

	x.coreInstance, err = core.New(config)
	if err != nil {
		return fmt.Errorf("core init failed: %w", err)
	}
	x.statsManager = x.coreInstance.GetFeature(corestats.ManagerType()).(corestats.Manager)

	log.Println("starting core...")
	x.IsRunning = true
	if err := x.coreInstance.Start(); err != nil {
		x.IsRunning = false
		return fmt.Errorf("startup failed: %w", err)
	}

	x.CallbackHandler.Startup()
	x.CallbackHandler.OnEmitStatus(0, "Started successfully, running")

	log.Println("Starting core successfully")
	return nil
}

// measureInstDelay measures the delay for an instance to a given URL
func measureInstDelay(ctx context.Context, inst *core.Instance, url string) (int64, error) {
	if inst == nil {
		return -1, errors.New("core instance is nil")
	}

	tr := &http.Transport{
		TLSHandshakeTimeout: 6 * time.Second,
		DisableKeepAlives:   false,
		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
			dest, err := corenet.ParseDestination(fmt.Sprintf("%s:%s", network, addr))
			if err != nil {
				return nil, err
			}
			return core.Dial(ctx, inst, dest)
		},
	}

	client := &http.Client{
		Transport: tr,
		Timeout:   12 * time.Second,
	}

	if url == "" {
		url = "https://www.google.com/generate_204"
	}

	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return -1, fmt.Errorf("failed to create HTTP request: %w", err)
	}

	var minDuration int64 = -1
	success := false
	var lastErr error

	// Add exception handling and increase retry attempts
	const attempts = 2
	for i := 0; i < attempts; i++ {
		select {
		case <-ctx.Done():
			// Return immediately when context is canceled
			if !success {
				return -1, ctx.Err()
			}
			return minDuration, nil
		default:
			// Continue execution
		}

		start := time.Now()
		resp, err := client.Do(req)
		if err != nil {
			lastErr = err
			continue
		}

		// Ensure response body is closed
		defer func(resp *http.Response) {
			if resp != nil && resp.Body != nil {
				resp.Body.Close()
			}
		}(resp)

		if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNoContent {
			lastErr = fmt.Errorf("invalid status: %s", resp.Status)
			continue
		}

		// Handle possible errors when reading response body
		if _, err := io.Copy(io.Discard, resp.Body); err != nil {
			lastErr = fmt.Errorf("failed to read response body: %w", err)
			continue
		}

		duration := time.Since(start).Milliseconds()
		if !success || duration < minDuration {
			minDuration = duration
		}

		success = true
	}
	if !success {
		return -1, lastErr
	}
	return minDuration, nil
}

// Log writer implementation
func (w *consoleLogWriter) Write(s string) error {
	w.logger.Print(s)
	return nil
}

func (w *consoleLogWriter) Close() error {
	return nil
}

// createStdoutLogWriter creates a logger that won't print date/time stamps
func createStdoutLogWriter() corecommlog.WriterCreator {
	return func() corecommlog.Writer {
		return &consoleLogWriter{
			logger: log.New(os.Stdout, "", 0),
		}
	}
}