package utils

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"
)

// AppendCacheBuster 给 URL 追加时间戳，避免时间接口被缓存。
func AppendCacheBuster(rawURL string) string {
	sep := "?"
	if strings.Contains(rawURL, "?") {
		sep = "&"
	}
	return rawURL + sep + "_=" + strconv.FormatInt(time.Now().UnixNano(), 10)
}

// CloneStringMap 复制 map，避免异步任务读到调用方后续修改。
func CloneStringMap(in map[string]string) map[string]string {
	out := make(map[string]string, len(in))
	for k, v := range in {
		out[k] = v
	}
	return out
}

// MergeCookie 把指定 Cookie 写入原 Cookie 字符串，已有同名 Cookie 会被覆盖。
func MergeCookie(cookie, name, value string) string {
	parts := strings.Split(cookie, ";")
	pairs := make([]string, 0, len(parts)+1)
	replaced := false
	for _, part := range parts {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		key, _, ok := strings.Cut(part, "=")
		if ok && strings.TrimSpace(key) == name {
			pairs = append(pairs, name+"="+value)
			replaced = true
			continue
		}
		pairs = append(pairs, part)
	}
	if !replaced && value != "" {
		pairs = append(pairs, name+"="+value)
	}
	return strings.Join(pairs, "; ")
}

// TrimForLog 截断接口响应，避免日志刷屏。
func TrimForLog(s string, max int) string {
	s = strings.TrimSpace(s)
	if len(s) <= max {
		return s
	}
	return s[:max] + "..."
}

// EmptyDefault 在字符串为空时返回默认值。
func EmptyDefault(value, fallback string) string {
	if strings.TrimSpace(value) == "" {
		return fallback
	}
	return value
}

// SafeFilename 替换文件名中的危险字符。
func SafeFilename(name string) string {
	replacer := strings.NewReplacer("/", "_", "\\", "_", ":", "_", "*", "_", "?", "_", "\"", "_", "<", "_", ">", "_", "|", "_")
	return replacer.Replace(name)
}

// MaskCookie 返回 Cookie 摘要，避免把完整凭据暴露给前端。
func MaskCookie(cookie string) string {
	pairs := strings.Split(cookie, ";")
	masked := make([]string, 0, 3)
	total := 0
	for _, pair := range pairs {
		key, value, ok := strings.Cut(strings.TrimSpace(pair), "=")
		if !ok || key == "" {
			continue
		}
		total++
		if len(masked) >= 3 {
			continue
		}
		masked = append(masked, key+"="+MaskValue(value))
	}
	if total == 0 {
		return ""
	}
	if total > len(masked) {
		masked = append(masked, fmt.Sprintf("...共%d项", total))
	}
	return strings.Join(masked, "; ")
}

// MaskValue 保留少量首尾字符用于识别，其余替换为星号。
func MaskValue(value string) string {
	value = strings.TrimSpace(value)
	if value == "" {
		return "****"
	}
	runes := []rune(value)
	if len(runes) <= 8 {
		return "****"
	}
	return string(runes[:4]) + "****" + string(runes[len(runes)-4:])
}

// RoundDuration 将时间四舍五入到毫秒。
func RoundDuration(d time.Duration) time.Duration {
	return d.Round(time.Millisecond)
}

// ReadJSON 读取请求 JSON。
func ReadJSON(r *http.Request, out any) error {
	defer r.Body.Close()
	return json.NewDecoder(r.Body).Decode(out)
}

// WriteJSON 写出 JSON 响应。
func WriteJSON(w http.ResponseWriter, value any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	_ = json.NewEncoder(w).Encode(value)
}

// WriteError 写出统一错误 JSON，同时设置 HTTP 状态码。
func WriteError(w http.ResponseWriter, status int, err error) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(map[string]any{
		"success": false,
		"error":   err.Error(),
	})
}