package test

import (
	"context"
	"crypto/rand"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"reflect"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	"github.com/GopeedLab/gopeed/pkg/base"
	"github.com/armon/go-socks5"
	"golang.org/x/text/encoding/simplifiedchinese"
)

const (
	BuildName = "build.data"
	BuildSize = 200 * 1024 * 1024
	Dir       = "./"
	BuildFile = Dir + BuildName

	ExternalDownloadUrl  = "https://raw.githubusercontent.com/GopeedLab/gopeed/v1.5.6/_docs/img/banner.png"
	ExternalDownloadName = "banner.png"
	ExternalDownloadSize = 26416
	//ExternalDownloadMd5 = "c67c6e3cae79a95342485676571e8a5c"

	DownloadName       = "download.data"
	DownloadRename     = "download (1).data"
	DownloadFile       = Dir + DownloadName
	DownloadRenameFile = Dir + DownloadRename

	// TestChineseFileName is a common test filename with Chinese characters
	// Used to test Content-Disposition parsing with various encodings
	TestChineseFileName = "测试.zip"
)

func StartTestFileServer() net.Listener {
	return startTestServer(func(sl *shutdownListener) http.Handler {
		return http.FileServer(http.Dir(Dir))
	})
}

type SlowFileServer struct {
	delay   time.Duration
	handler http.Handler
}

func (s *SlowFileServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	time.Sleep(s.delay)
	s.handler.ServeHTTP(w, r)
}

func StartTestSlowFileServer(delay time.Duration) net.Listener {
	return startTestServer(func(sl *shutdownListener) http.Handler {
		return &SlowFileServer{
			delay:   delay,
			handler: http.FileServer(http.Dir(Dir)),
		}
	})
}

func StartTestCustomServer() net.Listener {
	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		mux.HandleFunc("/disposition", func(writer http.ResponseWriter, request *http.Request) {
			writer.Header().Set("Content-Disposition", "attachment; filename=\""+BuildName+"\"")
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		mux.HandleFunc("/encoded-word", func(writer http.ResponseWriter, request *http.Request) {
			writer.Header().Set("Content-Disposition", "attachment; filename=\"=?UTF8?B?5rWL6K+VLnppcA==?=\"")
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		mux.HandleFunc("/%E6%B5%8B%E8%AF%95.zip", func(writer http.ResponseWriter, request *http.Request) {
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		mux.HandleFunc("/no-encode", func(writer http.ResponseWriter, request *http.Request) {
			writer.Header().Set("Content-Disposition", "attachment; filename="+TestChineseFileName)
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		// Test endpoint for mixed encoding: filename= with garbled characters (including special chars)
		// and filename*= with proper UTF-8. This tests the case where mime.ParseMediaType fails
		// due to invalid characters like <a> tags in the filename.
		mux.HandleFunc("/mixed-encoding", func(writer http.ResponseWriter, request *http.Request) {
			// This simulates a server that sends a garbled filename= with special chars that cause
			// mime.ParseMediaType to fail, plus a proper filename*=UTF-8''...
			// The filename*= should be preferred and correctly parsed.
			writer.Header().Set("Content-Disposition", `attachment;filename="garbled<invalid>chars.zip";filename*=UTF-8''%E6%B5%8B%E8%AF%95.zip`)
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		// Test endpoint for filename*= only (RFC 5987 format)
		mux.HandleFunc("/filename-star", func(writer http.ResponseWriter, request *http.Request) {
			// URL-encoded TestChineseFileName: 测试.zip -> %E6%B5%8B%E8%AF%95.zip
			writer.Header().Set("Content-Disposition", `attachment; filename*=UTF-8''%E6%B5%8B%E8%AF%95.zip`)
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		// Test endpoint for GBK-encoded filename (common on Chinese Windows servers)
		// This simulates the case where Chinese characters are sent as GBK bytes
		// which appear as garbled characters when interpreted as UTF-8.
		// For example, "测试" in GBK is [B2 E2 CA D4] which is invalid UTF-8.
		// Our fix detects invalid UTF-8 and attempts GBK decoding.
		mux.HandleFunc("/gbk-encoded", func(writer http.ResponseWriter, request *http.Request) {
			// Encode TestChineseFileName as GBK
			gbkEncoder := simplifiedchinese.GBK.NewEncoder()
			gbkBytes, _ := gbkEncoder.Bytes([]byte(TestChineseFileName))
			// Send GBK bytes directly in filename (simulating broken server behavior)
			writer.Header().Set("Content-Disposition", `attachment; filename="`+string(gbkBytes)+`"`)
			writer.Header().Set("Content-Type", "application/octet-stream")
			writer.Header().Set("Content-Length", fmt.Sprintf("%d", BuildSize))
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		return mux
	})
}

func StartTestRetryServer() net.Listener {
	counter := 0
	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			counter++
			if counter != 1 && counter < 2 {
				writer.WriteHeader(500)
				return
			}
			file, err := os.Open(BuildFile)
			if err != nil {
				panic(err)
			}
			defer file.Close()
			io.Copy(writer, file)
		})
		return mux
	})
}

func StartTestPostServer() net.Listener {
	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			if request.Method == "POST" && request.Header.Get("Authorization") != "" {
				var data map[string]interface{}
				if err := json.NewDecoder(request.Body).Decode(&data); err != nil {
					panic(err)
				}
				if data["name"] == BuildName {
					file, err := os.Open(BuildFile)
					if err != nil {
						panic(err)
					}
					defer file.Close()
					io.Copy(writer, file)
				}
			}
		})
		return mux
	})
}

func StartTestErrorServer() net.Listener {
	counter := 0
	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			counter++
			if counter != 1 {
				writer.WriteHeader(500)
				return
			}
		})
		return mux
	})
}

// StartTestLimitServer connections limit server
func StartTestLimitServer(maxConnections int32, delay int64) net.Listener {
	var connections atomic.Int32

	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			defer func() {
				connections.Add(-1)
			}()
			connections.Add(1)
			if maxConnections != 0 && connections.Load() > maxConnections {
				writer.WriteHeader(403)
				return
			}
			rangeFileHandle(
				writer,
				request,
				nil,
				func(file *os.File, n int64) {
					slowCopyN(sl, writer, file, n, delay)
				},
			)
		})
		return mux
	})
}

// StartTestRangeBugServer simulate bug server:
// Don't follow Range request rules, always return more data than range, e.g. Range: bytes=0-100, return 150 bytes
func StartTestRangeBugServer() net.Listener {
	return startTestServer(func(sl *shutdownListener) http.Handler {
		mux := http.NewServeMux()
		mux.HandleFunc("/"+BuildName, func(writer http.ResponseWriter, request *http.Request) {
			rangeFileHandle(
				writer,
				request,
				func(end int64) int64 {
					var bugEnd = end
					if end != 0 {
						bugEnd = end + 50
						if bugEnd >= BuildSize {
							bugEnd = end
						}
					}
					return bugEnd
				},
				func(file *os.File, n int64) {
					io.CopyN(writer, file, n)
				},
			)
		})
		return mux
	})
}

func rangeFileHandle(writer http.ResponseWriter, request *http.Request, modifyEnd func(end int64) int64, iocpN func(file *os.File, n int64)) {
	r := request.Header.Get("Range")
	// split range
	s := strings.Split(r, "=")
	if len(s) != 2 {
		writer.WriteHeader(400)
		return
	}
	s = strings.Split(s[1], "-")
	if len(s) != 2 {
		writer.WriteHeader(400)
		return
	}
	start, err := strconv.ParseInt(s[0], 10, 64)
	if err != nil {
		writer.WriteHeader(400)
		return
	}
	end, err := strconv.ParseInt(s[1], 10, 64)
	if err != nil {
		writer.WriteHeader(400)
		return
	}
	if start < 0 || end < 0 || start > end {
		writer.WriteHeader(400)
		return
	}
	if end >= BuildSize {
		end = BuildSize - 1
	}

	if modifyEnd != nil {
		end = modifyEnd(end)
	}

	writer.Header().Set("Content-Length", fmt.Sprintf("%d", end-start+1))
	writer.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, BuildSize))
	writer.Header().Set("Accept-Ranges", "bytes")
	writer.WriteHeader(206)
	(writer.(http.Flusher)).Flush()

	file, err := os.Open(BuildFile)
	if err != nil {
		writer.WriteHeader(500)
		return
	}
	defer file.Close()
	file.Seek(start, 0)
	iocpN(file, end-start+1)
}

// slowCopyN copies n bytes from src to dst, speed limit is bytes per second
func slowCopy(sl *shutdownListener, dst io.Writer, src io.Reader, delay int64) (written int64, err error) {
	buf := make([]byte, 32*1024)
	for {
		if sl.isShutdown {
			return 0, errors.New("server shutdown")
		}
		nr, er := src.Read(buf)
		if nr > 0 {
			nw, ew := dst.Write(buf[0:nr])
			if nw > 0 {
				written += int64(nw)
			}
			if ew != nil {
				err = ew
				break
			}
			if nr != nw {
				err = io.ErrShortWrite
				break
			}
		}
		if er != nil {
			if er != io.EOF {
				err = er
			}
			break
		}
		if delay > 0 {
			time.Sleep(time.Millisecond * time.Duration(delay))
		}
	}
	return written, err
}

func slowCopyN(sl *shutdownListener, dst io.Writer, src io.Reader, n int64, delay int64) (written int64, err error) {
	written, err = slowCopy(sl, dst, io.LimitReader(src, n), delay)
	if written == n {
		return n, nil
	}
	if written < n && err == nil {
		// src stopped early; must have been EOF.
		err = io.EOF
	}
	return
}

func startTestServer(serverHandle func(sl *shutdownListener) http.Handler) net.Listener {
	listener, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		panic(err)
	}
	file, err := os.Create(BuildFile)
	if err != nil {
		panic(err)
	}
	defer file.Close()
	// Write random data
	l := int64(8192)
	buf := make([]byte, l)
	size := int64(0)
	for {
		_, err := rand.Read(buf)
		if err != nil {
			panic(err)
		}
		if size+l >= BuildSize {
			file.WriteAt(buf[0:BuildSize-size], size)
			break
		}
		file.WriteAt(buf, size)
		size += l
	}
	server := &http.Server{}
	sl := &shutdownListener{
		server:   server,
		Listener: listener,
	}
	server.Handler = serverHandle(sl)
	go server.Serve(listener)

	return sl
}

type shutdownListener struct {
	server     *http.Server
	isShutdown bool
	net.Listener
}

func (c *shutdownListener) Close() error {
	c.isShutdown = true
	closeErr := c.server.Shutdown(context.Background())
	if err := ifExistAndRemove(BuildFile); err != nil {
		fmt.Println(err)
	}
	if err := ifExistAndRemove(DownloadFile); err != nil {
		fmt.Println(err)
	}
	if err := ifExistAndRemove(DownloadRenameFile); err != nil {
		fmt.Println(err)
	}
	return closeErr
}

func ifExistAndRemove(name string) error {
	if _, err := os.Stat(name); !os.IsNotExist(err) {
		return os.Remove(name)
	}
	return nil
}

func StartSocks5Server(usr, pwd string) net.Listener {
	conf := &socks5.Config{}
	if usr != "" && pwd != "" {
		conf.Credentials = socks5.StaticCredentials{
			usr: pwd,
		}
	}

	server, err := socks5.New(conf)
	if err != nil {
		panic(err)
	}

	listener, err := net.Listen("tcp", "127.0.0.1:0") // 你可以根据需要更改监听地址
	if err != nil {
		panic(err)
	}
	go server.Serve(listener)
	return listener
}

func AssertResourceEqual(want, got *base.Resource) bool {
	// Ignore ctime
	if got != nil && len(got.Files) > 0 {
		got.Files[0].Ctime = nil
	}
	return reflect.DeepEqual(want, got)
}