package utils

import (
	"bufio"
	"fmt"
	"os"
	"strings"
	"sync"
	"time"
)

const (
	LOG_LEVEL_DEBUG = iota
	LOG_LEVEL_INFO
	LOG_LEVEL_WARNING
	LOG_LEVEL_ERROR
	LOG_LEVEL_FATAL
)
const rfc3339milli = "2006-01-02T15:04:05.000Z07:00"
const Seperator = " | "

var log_level_msg = [...]string{"DEBUG", "INFO", "WARN", "ERROR", "FATAL"}

var (
	once   sync.Once
	stdout *bufio.Writer
	stderr *bufio.Writer
)

// Logger includes the module name and an output destination.
type Logger struct {
	mu     sync.Mutex
	Module string
	Symbol string
}

// NewLogger creates a new Logger with output set to os.Stdout by default.
func NewLogger(module, symbol string) *Logger {
	once.Do(func() {
		stdout = bufio.NewWriter(os.Stdout)
		stderr = bufio.NewWriter(os.Stderr)
	})
	ret := &Logger{
		Module: module,
		Symbol: symbol,
	}
	if ret.Symbol == "" {
		ret.Symbol = "-"
	}
	return ret
}

// logMessage logs a message with the given severity.
func (l *Logger) logMessage(severity int, format string, a ...any) {
	timestamp := time.Now().Format(rfc3339milli)

	formattedMessage := fmt.Sprintf(format, a...)
	var out *bufio.Writer
	if severity < LOG_LEVEL_ERROR {
		out = stdout
	} else {
		out = stderr
	}

	l.mu.Lock()
	defer l.mu.Unlock()
	out.WriteString(strings.Join([]string{
		timestamp,
		l.Module,
		l.Symbol,
		log_level_msg[severity],
		formattedMessage}, Seperator))
	out.WriteByte('\n')
	out.Flush()
}

// Debug logs an debug message.
func (l *Logger) Debug(format string, a ...any) {
	l.logMessage(LOG_LEVEL_DEBUG, format, a...)
}

// Info logs an info message.
func (l *Logger) Info(format string, a ...any) {
	l.logMessage(LOG_LEVEL_INFO, format, a...)
}

// Warn logs an warn message.
func (l *Logger) Warn(format string, a ...any) {
	l.logMessage(LOG_LEVEL_WARNING, format, a...)
}

// Error logs an error message.
func (l *Logger) Error(format string, a ...any) {
	l.logMessage(LOG_LEVEL_ERROR, format, a...)
}

// Fatal logs an fatal message and exit.
func (l *Logger) Fatal(format string, a ...any) {
	l.logMessage(LOG_LEVEL_FATAL, format, a...)
	os.Exit(125)
}