package gateway

import (
	"context"
	"fmt"
	"github.com/gin-gonic/gin"
	"github.com/smallnest/rpcx/log"
	"github.com/smallnest/rpcx/share"
	"io"
	"mime"
	"mime/multipart"
	"net"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"

	"github.com/smallnest/rpcx/client"
)

// ServiceHandler converts http.Request into rpcx.Request and send it to rpcx service,
// and then converts the result and writes it into http.Response.
// You should get the http.Request and servicePath in your web handler.
type ServiceHandler func(*http.Request, string) (map[string]string, []byte, error)

// HTTPServer is a golang web interface。
// You can use echo, gin, iris or other go web frameworks to implement it.
// You must wrap ServiceHandler into your handler of your selected web framework and add it into router.
type HTTPServer interface {
	RegisterHandler(base string, handler ServiceHandler)
	Serve() error
}

// Gateway is a rpcx gateway which can convert http invoke into rpcx invoke.
type Gateway struct {
	base       string
	httpserver HTTPServer

	serviceDiscovery client.ServiceDiscovery
	FailMode         client.FailMode
	SelectMode       client.SelectMode
	Option           client.Option

	mu       sync.RWMutex
	xclients map[string]client.XClient

	seq uint64
}

// NewGateway returns a new gateway.
func NewGateway(base string, hs HTTPServer, sd client.ServiceDiscovery, failMode client.FailMode, selectMode client.SelectMode, option client.Option) *Gateway {
	// base is empty or like /abc/
	if base == "" {
		base = "/"
	}

	if base[0] != '/' {
		base = "/" + base
	}

	g := &Gateway{
		base:             base,
		httpserver:       hs,
		serviceDiscovery: sd,
		FailMode:         failMode,
		SelectMode:       selectMode,
		Option:           option,
		xclients:         make(map[string]client.XClient),
	}

	hs.RegisterHandler(base, g.handler)
	return g
}

// Serve listens on the TCP network address addr and then calls
// Serve with handler to handle requests on incoming connections.
// Accepted connections are configured to enable TCP keep-alives.
func (g *Gateway) Serve() error {
	return g.httpserver.Serve()
}

func (g *Gateway) handler(r *http.Request, servicePath string) (meta map[string]string, payload []byte, err error) {
	contentType := r.Header.Get("Content-Type")
	mediaType, _, err := mime.ParseMediaType(contentType)

	var xc client.XClient
	g.mu.Lock()
	if mediaType == gin.MIMEMultipartPOSTForm {
		xc, err = getXClient(g, share.StreamServiceName)
	} else {
		xc, err = getXClient(g, servicePath)
	}
	g.mu.Unlock()

	if err != nil {
		return nil, nil, err
	}

	// 处理Auth
	token := getRequestToken(r)
	xc.Auth(token)

	if mediaType == gin.MIMEMultipartPOSTForm {
		formValues, formFile, err := MultipartRequest2RpcxRequest(r)
		formValues["__AUTH"] = token

		conn, callErr := xc.Stream(context.Background(), formValues)
		if callErr != nil {
			return nil, nil, err
		}

		//判断是否需要传输文件
		if len(formFile) > 0 {
			//发送文件
			err = sendFile(conn, formFile)
			if err != nil {
				return nil, nil, err
			}
		}

		//获取反馈结果
		resp, err := io.ReadAll(conn)
		if err != nil {
			return nil, nil, err
		}
		conn.Close()

		return formValues, resp, err
	} else {
		req, err := HttpRequest2RpcxRequest(r)
		if err != nil {
			return nil, nil, err
		}
		seq := atomic.AddUint64(&g.seq, 1)
		req.SetSeq(seq)

		return xc.SendRaw(context.Background(), req)
	}
}

func getXClient(g *Gateway, servicePath string) (xc client.XClient, err error) {
	defer func() {
		if e := recover(); e != nil {
			if ee, ok := e.(error); ok {
				err = ee
				return
			}

			err = fmt.Errorf("failed to get xclient: %v", e)
		}
	}()

	if g.xclients[servicePath] == nil {
		d, err := g.serviceDiscovery.Clone(servicePath)
		if err != nil {
			return nil, err
		}
		g.xclients[servicePath] = client.NewXClient(servicePath, g.FailMode, g.SelectMode, d, g.Option)
	}
	xc = g.xclients[servicePath]

	return xc, err
}

// 解析token，若无，返回空
func getRequestToken(r *http.Request) string {
	authHeader := r.Header.Get("Authorization")
	if authHeader != "" {
		parts := strings.SplitN(authHeader, " ", 2)
		if !(len(parts) == 2 && parts[0] == "Bearer") {
			//glog.Warning("authHeader:" + authHeader + " get token key fail")
			return ""
		} else if parts[1] == "" {
			//glog.Warning("authHeader:" + authHeader + " get token fail")
			return ""
		}

		return parts[1]
	}
	return ""
}

// sendFile
func sendFile(conn net.Conn, files map[string][]*multipart.FileHeader) error {
	index := 0
	for key, header := range files {
		index++
		file, _ := header[0].Open()
		fileName := header[0].Filename
		fileSize := header[0].Size
		fileHeader := fmt.Sprintf("%s %s %v", key, fileName, fileSize)

		// 发送文件名长度
		length := strconv.Itoa(len(fileHeader))
		conn.Write([]byte(PadLeft(length, 3, "0")))
		// 发送文件名和文件长度给 接收端
		conn.Write([]byte(fileHeader))

		// 从本文件中，读数据，写给网络接收端。
		buf := make([]byte, 1024)
		for {
			n, err := file.Read(buf)
			if n == 0 {
				log.Debug("发送文件完成")
				break
			}
			// 写到网络socket中
			_, err = conn.Write(buf[:n])
			if err != nil {
				log.Debug("conn.Write err:", err)
				break
			}
		}

		if index == len(files) {
			conn.Write([]byte("2"))
		} else {
			conn.Write([]byte("1"))
		}
	}
	return nil
}

func PadLeft(s string, length int, padding string) string {
	sLen := len(s)
	if sLen >= length {
		return s
	}
	padCount := length - sLen
	return strings.Repeat(padding, padCount) + s
}