package logger

import (
	"context"
	"fmt"
	"io"
	"os"
	"runtime"
	"strings"
	"time"

	"github.com/google/uuid"
)

// Level represents a log level
type Level int

const (
	// DEBUG level
	DEBUG Level = iota
	// INFO level
	INFO
	// WARN level
	WARN
	// ERROR level
	ERROR
	// FATAL level
	FATAL
)

// String returns the string representation of the log level
func (l Level) 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 represents a logger
type Logger struct {
	level  Level
	output io.Writer
}

// contextKey is a type for context keys
type contextKey string

// requestIDKey is the key for request ID in context
const requestIDKey = contextKey("request_id")

// New creates a new logger
func New(level Level, output io.Writer) *Logger {
	if output == nil {
		output = os.Stdout
	}
	return &Logger{
		level:  level,
		output: output,
	}
}

// WithLevel creates a new logger with the specified level
func (l *Logger) WithLevel(level Level) *Logger {
	return &Logger{
		level:  level,
		output: l.output,
	}
}

// WithOutput creates a new logger with the specified output
func (l *Logger) WithOutput(output io.Writer) *Logger {
	return &Logger{
		level:  l.level,
		output: output,
	}
}

// log logs a message with the specified level
func (l *Logger) log(ctx context.Context, level Level, format string, args ...interface{}) {
	if level < l.level {
		return
	}

	// Get request ID from context
	requestID := getRequestID(ctx)

	// Get caller information
	_, file, line, ok := runtime.Caller(2)
	if !ok {
		file = "unknown"
		line = 0
	}
	// Extract just the filename
	if idx := strings.LastIndex(file, "/"); idx >= 0 {
		file = file[idx+1:]
	}

	// Format message
	message := fmt.Sprintf(format, args...)

	// Format log entry
	timestamp := time.Now().Format(time.RFC3339)
	logEntry := fmt.Sprintf("%s [%s] %s:%d [%s] %s\n",
		timestamp, level.String(), file, line, requestID, message)

	// Write log entry
	_, _ = l.output.Write([]byte(logEntry))

	// Exit if fatal
	if level == FATAL {
		os.Exit(1)
	}
}

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

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

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

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

// Fatal logs a fatal message and exits
func (l *Logger) Fatal(ctx context.Context, format string, args ...interface{}) {
	l.log(ctx, FATAL, format, args...)
}

// WithRequestID adds a request ID to the context
func WithRequestID(ctx context.Context) context.Context {
	requestID := uuid.New().String()
	return context.WithValue(ctx, requestIDKey, requestID)
}

// GetRequestID gets the request ID from the context
func GetRequestID(ctx context.Context) string {
	return getRequestID(ctx)
}

// getRequestID gets the request ID from the context
func getRequestID(ctx context.Context) string {
	if ctx == nil {
		return "-"
	}
	requestID, ok := ctx.Value(requestIDKey).(string)
	if !ok {
		return "-"
	}
	return requestID
}

// Default logger
var defaultLogger = New(INFO, os.Stdout)

// SetDefaultLogger sets the default logger
func SetDefaultLogger(logger *Logger) {
	defaultLogger = logger
}

// Debug logs a debug message using the default logger
func Debug(ctx context.Context, format string, args ...interface{}) {
	defaultLogger.Debug(ctx, format, args...)
}

// Info logs an info message using the default logger
func Info(ctx context.Context, format string, args ...interface{}) {
	defaultLogger.Info(ctx, format, args...)
}

// Warn logs a warning message using the default logger
func Warn(ctx context.Context, format string, args ...interface{}) {
	defaultLogger.Warn(ctx, format, args...)
}

// Error logs an error message using the default logger
func Error(ctx context.Context, format string, args ...interface{}) {
	defaultLogger.Error(ctx, format, args...)
}

// Fatal logs a fatal message and exits using the default logger
func Fatal(ctx context.Context, format string, args ...interface{}) {
	defaultLogger.Fatal(ctx, format, args...)
}