// Package logger 提供结构化日志配置。
package logger

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"os"
	"strings"
	"sync"
)

// Config 日志配置。
type Config struct {
	Level     slog.Level
	AddSource bool
	JSON      bool // true = JSONHandler，false = 彩色 TextHandler
}

// New 创建配置好的 Logger。
// 开发环境（JSON=false）输出彩色终端文本，生产环境输出 JSON 供采集。
func New(cfg Config) *slog.Logger {
	var h slog.Handler
	opts := &slog.HandlerOptions{
		Level:     cfg.Level,
		AddSource: cfg.AddSource,
	}
	if cfg.JSON {
		h = slog.NewJSONHandler(os.Stdout, opts)
	} else {
		h = newColorHandler(os.Stdout, opts)
	}
	return slog.New(h)
}

// ANSI 颜色代码
const (
	colorReset  = "\033[0m"
	colorRed    = "\033[31m"
	colorGreen  = "\033[32m"
	colorYellow = "\033[33m"
	colorBlue   = "\033[34m"
	colorPurple = "\033[35m"
	colorCyan   = "\033[36m"
	colorGray   = "\033[37m"
)

// levelColor 日志级别 → ANSI 颜色映射
var levelColor = map[slog.Level]string{
	slog.LevelDebug: colorGray,
	slog.LevelInfo:  colorGreen,
	slog.LevelWarn:  colorYellow,
	slog.LevelError: colorRed,
}

// levelLabel 日志级别 → 短标签映射
var levelLabel = map[slog.Level]string{
	slog.LevelDebug: "DEBUG",
	slog.LevelInfo:  "INFO",
	slog.LevelWarn:  "WARN",
	slog.LevelError: "ERROR",
}

// colorHandler 带颜色的 slog.Handler 包装。
type colorHandler struct {
	inner  slog.Handler
	mu     sync.Mutex
	writer io.Writer
}

func newColorHandler(w io.Writer, opts *slog.HandlerOptions) *colorHandler {
	return &colorHandler{
		inner:  slog.NewTextHandler(w, opts),
		writer: w,
	}
}

func (h *colorHandler) Enabled(ctx context.Context, level slog.Level) bool {
	return h.inner.Enabled(ctx, level)
}

func (h *colorHandler) Handle(ctx context.Context, r slog.Record) error {
	h.mu.Lock()
	defer h.mu.Unlock()

	// 时间（使用 -07:00 让 Go 自动填充时区偏移）
	timeStr := r.Time.Format("2006-01-02T15:04:05.000-07:00")

	// Level 带颜色
	lvl := r.Level
	color := levelColor[lvl]
	label := levelLabel[lvl]

	// 消息
	msg := r.Message

	// 组装属性
	var attrs []string
	r.Attrs(func(a slog.Attr) bool {
		attrs = append(attrs, fmt.Sprintf("%s=%v", a.Key, a.Value.Any()))
		return true
	})

	// 输出格式：[时间] Level颜色(LEVEL) 消息  attr1=val1 attr2=val2
	var buf strings.Builder
	buf.WriteString(timeStr)
	buf.WriteString(" ")
	buf.WriteString(color)
	buf.WriteString(fmt.Sprintf("%-5s", label))
	buf.WriteString(colorReset)
	buf.WriteString(" ")
	buf.WriteString(msg)
	for _, a := range attrs {
		buf.WriteString(" ")
		buf.WriteString(a)
	}
	buf.WriteString("\n")

	_, err := fmt.Fprint(h.writer, buf.String())
	return err
}

func (h *colorHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	return &colorHandler{
		inner:  h.inner.WithAttrs(attrs),
		writer: h.writer,
	}
}

func (h *colorHandler) WithGroup(name string) slog.Handler {
	return &colorHandler{
		inner:  h.inner.WithGroup(name),
		writer: h.writer,
	}
}