package handler

import (
	"context"
	"encoding/json"
	"errors"
	"strings"

	"git.ikuban.com/server/kratos-utils/v2/transport/middleware"
	"github.com/go-kratos/kratos/v2/transport/http"
	"google.golang.org/grpc"
	"google.golang.org/grpc/metadata"
)

func serverStreamHandler(srv any, stream grpc.StreamDesc, option *middleware.Option) http.HandlerFunc {
	return func(ctx http.Context) error {
		http.SetOperation(ctx, option.Path)

		dec := func(in any) error {
			if err := ctx.Bind(&in); err != nil {
				return err
			}
			if err := ctx.BindQuery(&in); err != nil {
				return err
			}
			return nil
		}

		httpCtx := ctx
		h := ctx.Middleware(func(ctx context.Context, _ interface{}) (interface{}, error) {
			err := stream.Handler(srv, newServerStream(ctx, dec, httpCtx.Response()))
			return nil, err
		})

		newCtx := middleware.NewOptionContext(ctx, option)
		_, err := h(newCtx, nil)
		if err != nil {
			return err
		}

		return nil
	}
}

var _ grpc.ServerStream = (*serverStream)(nil)

type serverStream struct {
	ctx          context.Context
	dec          func(interface{}) error
	w            http.ResponseWriter
	metadata     metadata.MD
	isSendHeader bool
}

func newServerStream(ctx context.Context, dec func(interface{}) error, w http.ResponseWriter) grpc.ServerStream {
	s := &serverStream{
		ctx: ctx,
		dec: dec,
		w:   w,
	}

	return s
}

// 设置header，SendHeader主动发送或者第一次SendMsg时发送
func (s *serverStream) SetHeader(md metadata.MD) error {
	if md == nil {
		return nil
	}

	s.metadata = metadata.Join(s.metadata, md)
	return nil
}

// 主动发送header (只调一次)
func (s *serverStream) SendHeader(md metadata.MD) error {
	if s.isSendHeader {
		return errors.New("header has been sent")
	}
	s.isSendHeader = true

	if err := s.SetHeader(md); err != nil {
		return err
	}

	for k, v := range s.metadata {
		if len(v) == 0 {
			continue
		}
		s.w.Header().Set(k, strings.Join(v, "; "))
	}
	return nil
}

func (s *serverStream) SetTrailer(md metadata.MD) {
	return
}

func (s *serverStream) Context() context.Context {
	return s.ctx
}

func (s *serverStream) SendMsg(m interface{}) error {
	if !s.isSendHeader {
		err := s.SendHeader(nil)
		if err != nil {
			return err
		}
	}

	switch data := m.(type) {
	case []byte:
		_, err := s.w.Write(data)
		if err != nil {
			return err
		}

	default:
		j, err := json.Marshal(data)
		if err != nil {
			return err
		}
		_, err = s.w.Write(append(j, byte('\n')))
		if err != nil {
			return err
		}
	}

	s.w.(http.Flusher).Flush()
	return nil
}

func (s *serverStream) RecvMsg(m any) error {
	return s.dec(m)
}