// Copyright 2019 Yunion
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package appsrv

import (
	"bufio"
	"context"
	"fmt"
	"net"
	"net/http"

	"yunion.io/x/onecloud/pkg/httperrors"
)

type responseWriterResponse struct {
	count int
	err   error
}

type responseWriterChannel struct {
	backend http.ResponseWriter

	bodyChan   chan []byte
	bodyResp   chan responseWriterResponse
	statusChan chan int
	statusResp chan bool

	isClosed bool
}

func newResponseWriterChannel(backend http.ResponseWriter) responseWriterChannel {
	return responseWriterChannel{
		backend:    backend,
		bodyChan:   make(chan []byte),
		bodyResp:   make(chan responseWriterResponse),
		statusChan: make(chan int),
		statusResp: make(chan bool),
		isClosed:   false,
	}
}

func (w *responseWriterChannel) Header() http.Header {
	if w.isClosed {
		// return a dumb header
		return http.Header{}
	}
	return w.backend.Header()
}

func (w *responseWriterChannel) Write(bytes []byte) (int, error) {
	if w.isClosed {
		return 0, fmt.Errorf("response stream has been closed")
	}
	w.bodyChan <- bytes
	v := <-w.bodyResp
	return v.count, v.err
}

func (w *responseWriterChannel) WriteHeader(status int) {
	if w.isClosed {
		return
	}
	w.statusChan <- status
	<-w.statusResp
}

// implent http.Flusher
func (w *responseWriterChannel) Flush() {
	if w.isClosed {
		return
	}
	if f, ok := w.backend.(http.Flusher); ok {
		f.Flush()
	}
}

// Hijack implements the Hijacker.Hijack method. Our response is both a ResponseWriter
// and a Hijacker.
func (w *responseWriterChannel) Hijack() (rwc net.Conn, buf *bufio.ReadWriter, err error) {
	if w.isClosed {
		return nil, nil, fmt.Errorf("response stream has been closed")
	}
	if f, ok := w.backend.(http.Hijacker); ok {
		return f.Hijack()
	}
	return nil, nil, fmt.Errorf("not a hijacker")
}

func (w *responseWriterChannel) wait(ctx context.Context, workerChan chan *SWorker) interface{} {
	var err error
	var worker *SWorker
	stop := false
	for !stop {
		select {
		case curWorker, more := <-workerChan:
			if more {
				worker = curWorker
			} else {
				// ignore, worker is responsible for close the channel
			}
		case <-ctx.Done():
			// ctx deadline reached, timeout
			if worker != nil {
				worker.Detach("timeout")
			}
			err = httperrors.NewTimeoutError("request process timeout")
			stop = true
		case bytes, more := <-w.bodyChan:
			// log.Infof("Recive body: %s, more: %v", len(bytes), more)
			if more {
				c, e := w.backend.Write(bytes)
				w.bodyResp <- responseWriterResponse{count: c, err: e}
			} else {
				stop = true
			}
		case status, more := <-w.statusChan:
			// log.Infof("Recive status %d, more: %v", status, more)
			if more {
				w.backend.WriteHeader(status)
				w.statusResp <- true
			} else {
				stop = true
			}
		}
	}
	return err
}

func (w *responseWriterChannel) closeChannels() {
	if w.isClosed {
		return
	}
	w.isClosed = true

	close(w.bodyChan)
	close(w.bodyResp)
	close(w.statusChan)
	close(w.statusResp)
}