package middleware

import (
	"base-go-v2/internal/logx"
	"base-go-v2/internal/reponse"
	"base-go-v2/internal/router"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
)

// 仅初始化一次的项目信息
var (
	initOnce              sync.Once
	projectBase           string // 例：base-farmework
	projectAbsPrefix      string // 例：/abs/path/to/base-farmework/
	projectAbsPrefixLower string // 小写版，用于不区分大小写前缀比较（Windows 安全）
)

func ErrorMiddleware() router.HandlerFunc {
	initOnce.Do(initProjectInfo)

	return func(c *router.Context) error {
		err := c.Next()
		if err == nil {
			return nil
		}

		errs := c.Errors()
		if len(errs) == 0 {
			return nil
		}

		lastErr := errs[len(errs)-1]
		stack := lastErr.StackTrace()
		location := extractBusinessLocation(stack)

		logx.Logger.Error("请求错误",
			logx.String("path", string(c.RequestCtx.Path())),
			logx.String("method", string(c.RequestCtx.Method())),
			logx.String("location", location),
			logx.String("error", err.Error()),
			logx.String("stack", stack),
		)

		return response.Fail(c).Message("服务器内部错误").Send()
	}
}

// 仅在注册时执行：确定 go.mod 根目录并缓存前缀
func initProjectInfo() {
	// 以当前源文件为起点向上找 go.mod
	_, file, _, _ := runtime.Caller(0)
	if root, ok := findGoModRoot(file); ok {
		projectBase = filepath.Base(root)

		p := filepath.ToSlash(root)
		if !strings.HasSuffix(p, "/") {
			p += "/"
		}
		projectAbsPrefix = p
		projectAbsPrefixLower = strings.ToLower(p)
	}
}

// extractBusinessLocation：获取 AddError 后的业务 Handler 文件行（仅返回 <project>/<subpath>.go:<line>）
func extractBusinessLocation(stack string) string {
	lines := strings.Split(stack, "\n")
	foundAddError := false
	countGo := 0

	for _, raw := range lines {
		line := strings.TrimSpace(raw)

		if strings.Contains(line, "AddError") {
			foundAddError = true
			continue
		}
		if !foundAddError {
			continue
		}

		if strings.Contains(line, ".go:") {
			countGo++
			if countGo == 2 {
				// 去掉 " +0x..." 偏移
				if i := strings.Index(line, " +"); i != -1 {
					line = line[:i]
				}
				return trimToProject(line)
			}
		}
	}
	return ""
}

// 将绝对路径裁剪为 "<project>/<subpath>.go:<line>"
func trimToProject(goLine string) string {
	// 统一斜杠
	line := strings.ReplaceAll(goLine, "\\", "/")

	// 用最后一个冒号分离（避免 Windows 盘符）
	idx := strings.LastIndex(line, ":")
	if idx == -1 || idx+1 >= len(line) {
		return line
	}
	filePath, lineNo := line[:idx], line[idx+1:]

	// 优先：前缀裁剪（O(1)），比 filepath.Rel 更快
	if projectAbsPrefix != "" {
		fp := filepath.ToSlash(filePath)
		fpl := strings.ToLower(fp)
		if strings.HasPrefix(fpl, projectAbsPrefixLower) {
			rel := fp[len(projectAbsPrefix):]
			return projectBase + "/" + rel + ":" + lineNo
		}
	}

	// 其次：internal/cmd/pkg 作为锚点
	segs := strings.Split(filePath, "/")
	for i, s := range segs {
		if s == "internal" || s == "cmd" || s == "pkg" {
			if i > 0 {
				return strings.Join(segs[i-1:], "/") + ":" + lineNo
			}
		}
	}

	// 启发式：目录名包含 '-' 或 '_'，当作仓库名
	for i, s := range segs {
		if strings.ContainsAny(s, "-_") {
			return strings.Join(segs[i:], "/") + ":" + lineNo
		}
	}

	// 兜底：末尾 4 级
	start := len(segs) - 4
	if start < 0 {
		start = 0
	}
	return strings.Join(segs[start:], "/") + ":" + lineNo
}

// 从给定文件路径向上查找包含 go.mod 的目录（仅注册时调用一次）
func findGoModRoot(filePath string) (string, bool) {
	dir := filepath.Clean(filepath.Dir(filepath.FromSlash(filePath)))
	for {
		if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
			return dir, true
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			return "", false
		}
		dir = parent
	}
}