// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package gin

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"net/http/httputil"
	"os"
	"runtime"
	"strings"
	"time"
)

var (
	dunno     = []byte("???")
	centerDot = []byte("·")
	dot       = []byte(".")
	slash     = []byte("/")
	fileCache = make(map[string][][]byte) // 优化：缓存文件内容，避免重复读取
)

// RecoveryFunc defines the function passable to CustomRecovery.
type RecoveryFunc func(c *Context, err any)

// Recovery returns a middleware that recovers from any panics and writes a 500 if there was one.
func Recovery() HandlerFunc {
	return RecoveryWithWriter(DefaultErrorWriter)
}

// CustomRecovery returns a middleware that recovers from any panics and calls the provided handle func to handle it.
func CustomRecovery(handle RecoveryFunc) HandlerFunc {
	return RecoveryWithWriter(DefaultErrorWriter, handle)
}

// RecoveryWithWriter returns a middleware for a given writer that recovers from any panics and writes a 500 if there was one.
func RecoveryWithWriter(out io.Writer, recovery ...RecoveryFunc) HandlerFunc {
	if len(recovery) > 0 {
		return CustomRecoveryWithWriter(out, recovery[0])
	}
	return CustomRecoveryWithWriter(out, defaultHandleRecovery)
}

// CustomRecoveryWithWriter returns a middleware for a given writer that recovers from any panics and calls the provided handle func to handle it.
func CustomRecoveryWithWriter(out io.Writer, handle RecoveryFunc) HandlerFunc {
	var logger *log.Logger
	if out != nil {
		logger = log.New(out, "\n\n\x1b[31m", log.LstdFlags)
	}
	return func(c *Context) {
		defer func() {
			if err := recover(); err != nil {
				// Check for a broken connection, as it is not really a condition that warrants a panic stack trace.
				var brokenPipe bool
				if ne, ok := err.(*net.OpError); ok {
					var se *os.SyscallError
					if errors.As(ne, &se) {
						seStr := strings.ToLower(se.Error())
						if strings.Contains(seStr, "broken pipe") || strings.Contains(seStr, "connection reset by peer") {
							brokenPipe = true
						}
					}
				}
				if logger != nil {
					stack := stack(3)
					httpRequest, _ := httputil.DumpRequest(c.Request, false)
					headers := strings.Split(string(httpRequest), "\r\n")
					headersToStr := sanitizeHeaders(headers) // 优化：抽离出对 headers 的处理
					if brokenPipe {
						go logger.Printf("%s\n%s%s", err, headersToStr, reset) // 优化：并行化日志输出
					} else if IsDebugging() {
						go logger.Printf("[Recovery] %s panic recovered:\n%s\n%s\n%s%s",
							timeFormat(time.Now()), headersToStr, err, stack, reset)
					} else {
						go logger.Printf("[Recovery] %s panic recovered:\n%s\n%s%s",
							timeFormat(time.Now()), err, stack, reset)
					}
				}
				if brokenPipe {
					c.Error(err.(error)) //nolint: errcheck
					c.Abort()
				} else {
					handle(c, err)
				}
			}
		}()
		c.Next()
	}
}

func defaultHandleRecovery(c *Context, _ any) {
	c.AbortWithStatus(http.StatusInternalServerError)
}

// stack returns a nicely formatted stack frame, skipping skip frames.
func stack(skip int) []byte {
	buf := new(bytes.Buffer)
	var lines [][]byte
	var lastFile string

	for i := skip; ; i++ {
		pc, file, line, ok := runtime.Caller(i)
		if !ok {
			break
		}

		fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
		if file != lastFile {
			if cachedLines, found := fileCache[file]; found { // 优化：使用缓存避免重复读取文件
				lines = cachedLines
			} else {
				data, err := os.ReadFile(file)
				if err != nil {
					continue
				}
				lines = bytes.Split(data, []byte{'\n'})
				fileCache[file] = lines
			}
			lastFile = file
		}
		fmt.Fprintf(buf, "\t%s: %s\n", function(pc), source(lines, line))
	}
	return buf.Bytes()
}

// sanitizeHeaders masks sensitive header information (e.g., Authorization).
// 优化：抽离出 header 处理函数，简化主逻辑
func sanitizeHeaders(headers []string) string {
	for idx, header := range headers {
		current := strings.Split(header, ":")
		if current[0] == "Authorization" {
			headers[idx] = current[0] + ": *"
		}
	}
	return strings.Join(headers, "\r\n")
}

// source returns a space-trimmed slice of the n'th line.
func source(lines [][]byte, n int) []byte {
	n-- // in stack trace, lines are 1-indexed but our array is 0-indexed
	if n < 0 || n >= len(lines) {
		return dunno
	}
	return bytes.TrimSpace(lines[n])
}

// function returns, if possible, the name of the function containing the PC.
func function(pc uintptr) []byte {
	fn := runtime.FuncForPC(pc)
	if fn == nil {
		return dunno
	}
	name := []byte(fn.Name())
	if lastSlash := bytes.LastIndex(name, slash); lastSlash >= 0 {
		name = name[lastSlash+1:]
	}
	if period := bytes.Index(name, dot); period >= 0 {
		name = name[period+1:]
	}
	name = bytes.ReplaceAll(name, centerDot, dot)
	return name
}

// timeFormat returns a customized time string for logger.
func timeFormat(t time.Time) string {
	return t.Format("2006/01/02 - 15:04:05")
}