// internal/logging/logging.go
package logging

import (
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"sync"
)

var (
	// Global logger instance
	logger *Logger
	mu     sync.Mutex // Mutex to protect logger initialization and replacement
)

// LogLevel represents the severity of a log message
type LogLevel int

const (
	DEBUG LogLevel = iota
	INFO
	WARN
	ERROR
	FATAL
)

// String returns the string representation of the log level
func (l LogLevel) String() string {
	switch l {
	case DEBUG:
		return "DEBUG"
	case INFO:
		return "INFO"
	case WARN:
		return "WARN"
	case ERROR:
		return "ERROR"
	case FATAL:
		return "FATAL"
	default:
		return "UNKNOWN"
	}
}

// Logger provides logging functionality
type Logger struct {
	logLevel LogLevel
	output   io.Writer
	stdLog   *log.Logger
	errLog   *log.Logger
	file     *os.File // Store file reference for closing
	mu       sync.Mutex
}

// InitLogger initializes or reinitializes the global logger instance
func InitLogger(level LogLevel, logFilePath string) {
	mu.Lock()
	defer mu.Unlock()

	// Close the existing logger if there is one
	if logger != nil {
		logger.Close()
	}

	fmt.Printf("Initializing logger with level %s and log file: %s\n", level.String(), logFilePath)

	var output io.Writer = os.Stdout
	var fileHandle *os.File

	// Set up log file if specified
	if logFilePath != "" {
		logDir := filepath.Dir(logFilePath)
		if err := os.MkdirAll(logDir, 0755); err != nil {
			fmt.Fprintf(os.Stderr, "Failed to create log directory %s: %v\n", logDir, err)
			os.Exit(1)
		}

		file, err := os.OpenFile(logFilePath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to open log file %s: %v\n", logFilePath, err)
			os.Exit(1)
		}

		fmt.Printf("Successfully opened log file: %s\n", logFilePath)
		fileHandle = file
		output = io.MultiWriter(os.Stdout, file)
	}

	logger = &Logger{
		logLevel: level,
		output:   output,
		stdLog:   log.New(output, "", log.LstdFlags),
		errLog:   log.New(output, "ERROR: ", log.LstdFlags),
		file:     fileHandle,
	}

	// Log initialization message through the logger itself
	logger.Info("Logger initialized with level %s and log file %s", level.String(), logFilePath)
}

// GetLogger returns the global logger instance, initializing it if necessary
func GetLogger() *Logger {
	mu.Lock()
	defer mu.Unlock()

	if logger == nil {
		// Initialize with default settings if not already initialized
		// We need to unlock before calling InitLogger since it will lock mu
		mu.Unlock()
		InitLogger(INFO, "")
		mu.Lock()
	}
	return logger
}

// SetLogLevel changes the current log level
func (l *Logger) SetLogLevel(level LogLevel) {
	l.mu.Lock()
	defer l.mu.Unlock()
	l.logLevel = level
	l.Info("Log level set to %s", level.String())
}

// log is the internal logging function
func (l *Logger) log(level LogLevel, format string, v ...interface{}) {
	if level < l.logLevel {
		return
	}

	l.mu.Lock()
	defer l.mu.Unlock()

	// Get caller information (skip 2 levels to get the actual calling function)
	_, file, line, ok := runtime.Caller(2)
	if !ok {
		file = "unknown"
		line = 0
	}

	// Format message with source location and level
	prefix := fmt.Sprintf("[%s] %s:%d: ", level.String(), filepath.Base(file), line)
	message := fmt.Sprintf(format, v...)
	fullMessage := prefix + message

	if level >= ERROR {
		l.errLog.Println(fullMessage)
	} else {
		l.stdLog.Println(fullMessage)
	}
}

// Debug logs a debug message
func (l *Logger) Debug(format string, v ...interface{}) {
	l.log(DEBUG, format, v...)
}

// Info logs an info message
func (l *Logger) Info(format string, v ...interface{}) {
	l.log(INFO, format, v...)
}

// Warn logs a warning message
func (l *Logger) Warn(format string, v ...interface{}) {
	l.log(WARN, format, v...)
}

// Error logs an error message
func (l *Logger) Error(format string, v ...interface{}) {
	l.log(ERROR, format, v...)
}

// Fatal logs a fatal message and exits the program
func (l *Logger) Fatal(format string, v ...interface{}) {
	l.log(FATAL, format, v...)
	l.Close() // Ensure logs are flushed before exit
	os.Exit(1)
}

// ErrorWithStack logs an error with its stack trace
func (l *Logger) ErrorWithStack(err error, format string, v ...interface{}) {
	if err == nil {
		return
	}

	message := fmt.Sprintf(format, v...)
	buf := make([]byte, 4096) // Larger buffer for more stack trace info
	n := runtime.Stack(buf, false)
	l.Error("%s: %v\n%s", message, err, buf[:n])
}

// Close flushes and closes the log file if one is being used
func (l *Logger) Close() {
	l.mu.Lock()
	defer l.mu.Unlock()

	if l.file != nil {
		l.file.Sync()  // Flush any buffered data
		l.file.Close() // Close the file
		l.file = nil   // Clear the reference
	}
}

// Shutdown properly closes the logger
func Shutdown() {
	mu.Lock()
	defer mu.Unlock()

	if logger != nil {
		logger.Close()
		logger = nil
	}
}