package httpapi

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"strings"

	"scout/internal/registry"
)

type Server struct {
	Registry       *registry.Registry
	DeveloperToken string
	MaxUploadBytes int64
}

func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", s.health)
	mux.HandleFunc("POST /api/v1/packages/upload", s.upload)
	mux.HandleFunc("GET /api/v1/updates/stream", s.stream)
	mux.HandleFunc("GET /api/v1/packages", s.packageList)
	mux.HandleFunc("GET /api/v1/packages/", s.packageRoute)
	return cors(logging(mux))
}

func (s *Server) health(writer http.ResponseWriter, _ *http.Request) {
	writeJSON(writer, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) packageList(writer http.ResponseWriter, _ *http.Request) {
	writeJSON(writer, http.StatusOK, map[string]any{"packages": s.Registry.List()})
}

func (s *Server) upload(writer http.ResponseWriter, request *http.Request) {
	if !s.authorized(request) {
		writeError(writer, http.StatusUnauthorized, "开发者令牌无效")
		return
	}
	maxBytes := s.MaxUploadBytes
	if maxBytes <= 0 {
		maxBytes = 512 << 20
	}
	request.Body = http.MaxBytesReader(writer, request.Body, maxBytes)
	if err := request.ParseMultipartForm(32 << 20); err != nil {
		writeError(writer, http.StatusBadRequest, "上传表单无效: "+err.Error())
		return
	}
	file, _, err := request.FormFile("file")
	if err != nil {
		writeError(writer, http.StatusBadRequest, "缺少包文件字段 file")
		return
	}
	defer file.Close()

	item, err := s.Registry.AddPackage(registry.Package{
		Name:         request.FormValue("name"),
		Version:      request.FormValue("version"),
		Description:  request.FormValue("description"),
		Platform:     request.FormValue("platform"),
		Architecture: request.FormValue("architecture"),
	}, file)
	if err != nil {
		status := http.StatusBadRequest
		if strings.Contains(err.Error(), "已经存在") {
			status = http.StatusConflict
		}
		writeError(writer, status, err.Error())
		return
	}
	writeJSON(writer, http.StatusCreated, item)
}

func (s *Server) packageRoute(writer http.ResponseWriter, request *http.Request) {
	path := strings.TrimPrefix(request.URL.Path, "/api/v1/packages/")
	parts := strings.Split(strings.Trim(path, "/"), "/")
	if len(parts) == 1 && parts[0] != "" {
		item, ok := s.Registry.Latest(parts[0])
		if !ok {
			writeError(writer, http.StatusNotFound, "包不存在")
			return
		}
		writeJSON(writer, http.StatusOK, item)
		return
	}
	if len(parts) == 2 && parts[0] != "" {
		if parts[1] == "versions" {
			writeJSON(writer, http.StatusOK, map[string]any{"name": parts[0], "versions": s.Registry.Versions(parts[0])})
			return
		}
		writeError(writer, http.StatusNotFound, "接口不存在")
		return
	}
	if len(parts) == 3 && parts[2] == "download" {
		s.download(writer, request, parts[0], parts[1])
		return
	}
	writeError(writer, http.StatusNotFound, "接口不存在")
}

func (s *Server) download(writer http.ResponseWriter, request *http.Request, name, version string) {
	file, item, err := s.Registry.OpenPackage(name, version)
	if err != nil {
		writeError(writer, http.StatusNotFound, "包版本不存在")
		return
	}
	defer file.Close()
	writer.Header().Set("Content-Type", "application/octet-stream")
	writer.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s-%s.pkg"`, name, version))
	writer.Header().Set("X-Scout-SHA256", item.SHA256)
	writer.Header().Set("Content-Length", strconv.FormatInt(item.Size, 10))
	if request.Method == http.MethodHead {
		return
	}
	_, _ = io.Copy(writer, file)
}

func (s *Server) stream(writer http.ResponseWriter, request *http.Request) {
	flusher, ok := writer.(http.Flusher)
	if !ok {
		writeError(writer, http.StatusInternalServerError, "当前服务器不支持实时通知")
		return
	}
	wanted := make(map[string]bool)
	for _, name := range strings.Split(request.URL.Query().Get("packages"), ",") {
		if name = strings.TrimSpace(name); name != "" {
			wanted[name] = true
		}
	}
	updates, unsubscribe := s.Registry.Subscribe()
	defer unsubscribe()
	writer.Header().Set("Content-Type", "text/event-stream; charset=utf-8")
	writer.Header().Set("Cache-Control", "no-cache")
	writer.Header().Set("Connection", "keep-alive")
	fmt.Fprint(writer, ": 已连接\n\n")
	flusher.Flush()
	for {
		select {
		case <-request.Context().Done():
			return
		case update, ok := <-updates:
			if !ok {
				return
			}
			if len(wanted) > 0 && !wanted[update.Package.Name] {
				continue
			}
			payload, _ := json.Marshal(update)
			fmt.Fprintf(writer, "event: package_updated\ndata: %s\n\n", payload)
			flusher.Flush()
		}
	}
}

func (s *Server) authorized(request *http.Request) bool {
	if s.DeveloperToken == "" {
		return false
	}
	value := request.Header.Get("Authorization")
	if strings.HasPrefix(value, "Bearer ") {
		return strings.TrimPrefix(value, "Bearer ") == s.DeveloperToken
	}
	return request.Header.Get("X-Developer-Token") == s.DeveloperToken
}

func writeJSON(writer http.ResponseWriter, status int, value any) {
	writer.Header().Set("Content-Type", "application/json; charset=utf-8")
	writer.WriteHeader(status)
	_ = json.NewEncoder(writer).Encode(value)
}

func writeError(writer http.ResponseWriter, status int, message string) {
	writeJSON(writer, status, map[string]string{"error": message})
}

func cors(next http.Handler) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
		writer.Header().Set("Access-Control-Allow-Origin", "*")
		writer.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization, X-Developer-Token")
		writer.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
		if request.Method == http.MethodOptions {
			writer.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(writer, request)
	})
}

func logging(next http.Handler) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
		next.ServeHTTP(writer, request)
	})
}