/*
 *     Copyright 2020 The Dragonfly Authors
 *
 * 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.
 */

//go:generate mockgen -destination piece_downloader_mock.go -source piece_downloader.go -package peer

package peer

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/propagation"
	"google.golang.org/grpc/status"

	commonv1 "d7y.io/api/pkg/apis/common/v1"

	"d7y.io/dragonfly/v2/client/daemon/storage"
	logger "d7y.io/dragonfly/v2/internal/dflog"
	"d7y.io/dragonfly/v2/pkg/digest"
	"d7y.io/dragonfly/v2/pkg/source"
)

type DownloadPieceRequest struct {
	piece      *commonv1.PieceInfo
	log        *logger.SugaredLoggerOnWith
	storage    storage.TaskStorageDriver
	TaskID     string
	PeerID     string
	DstPid     string
	DstAddr    string
	CalcDigest bool
}

type DownloadPieceResult struct {
	// Size of piece
	Size int64
	// BeginTime nanosecond
	BeginTime int64
	// FinishTime nanosecond
	FinishTime int64
}

type PieceDownloader interface {
	DownloadPiece(context.Context, *DownloadPieceRequest) (io.Reader, io.Closer, error)
}

type PieceDownloaderOption func(*pieceDownloader) error

type pieceDownloader struct {
	scheme     string
	httpClient *http.Client
}

type pieceDownloadError struct {
	connectionError bool
	status          string
	statusCode      int
	target          string
	err             error
}

type backSourceError struct {
	err error
	st  *status.Status
}

func isConnectionError(err error) bool {
	if e, ok := err.(*pieceDownloadError); ok {
		return e.connectionError
	}
	return false
}

func isPieceNotFound(err error) bool {
	if e, ok := err.(*pieceDownloadError); ok {
		return e.statusCode == http.StatusNotFound
	}
	return false
}

func isBackSourceError(err error) bool {
	if _, ok := err.(*backSourceError); ok {
		return true
	}
	if _, ok := err.(*source.UnexpectedStatusCodeError); ok {
		return true
	}
	return false
}

func (e *pieceDownloadError) Error() string {
	if e.connectionError {
		return fmt.Sprintf("connect with %s with error: %s", e.target, e.err)
	}
	return fmt.Sprintf("download %s with error status: %s", e.target, e.status)
}

func (e *backSourceError) Error() string {
	if e.st != nil {
		return e.st.Err().Error()
	}
	return e.err.Error()
}

var _ PieceDownloader = (*pieceDownloader)(nil)

var defaultTransport http.RoundTripper = &http.Transport{
	Proxy: http.ProxyFromEnvironment,
	DialContext: (&net.Dialer{
		Timeout:   2 * time.Second,
		KeepAlive: 30 * time.Second,
		DualStack: true,
	}).DialContext,
	MaxIdleConns:          100,
	IdleConnTimeout:       90 * time.Second,
	ResponseHeaderTimeout: 2 * time.Second,
	TLSHandshakeTimeout:   10 * time.Second,
	ExpectContinueTimeout: 2 * time.Second,
}

func NewPieceDownloader(timeout time.Duration, caCertPool *x509.CertPool) PieceDownloader {
	pd := &pieceDownloader{
		scheme: "http",
		httpClient: &http.Client{
			Transport: defaultTransport,
			Timeout:   timeout,
		},
	}

	if caCertPool != nil {
		pd.scheme = "https"
		defaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{ClientCAs: caCertPool}
	}

	return pd
}

func (p *pieceDownloader) DownloadPiece(ctx context.Context, req *DownloadPieceRequest) (io.Reader, io.Closer, error) {
	httpRequest := p.buildDownloadPieceHTTPRequest(ctx, req)
	resp, err := p.httpClient.Do(httpRequest)
	if err != nil {
		logger.Errorf("task id: %s, piece num: %d, dst: %s, download piece failed: %s",
			req.TaskID, req.piece.PieceNum, req.DstAddr, err)
		return nil, nil, &pieceDownloadError{
			target:          httpRequest.URL.String(),
			err:             err,
			connectionError: true,
		}
	}
	if resp.StatusCode > 299 {
		_, _ = io.Copy(io.Discard, resp.Body)
		_ = resp.Body.Close()
		return nil, nil, &pieceDownloadError{
			target:          httpRequest.URL.String(),
			err:             err,
			connectionError: false,
			status:          resp.Status,
			statusCode:      resp.StatusCode,
		}
	}
	reader, closer := resp.Body.(io.Reader), resp.Body.(io.Closer)
	if req.CalcDigest {
		req.log.Debugf("calculate digest for piece %d, digest: %s", req.piece.PieceNum, req.piece.PieceMd5)
		reader, err = digest.NewReader(io.LimitReader(resp.Body, int64(req.piece.RangeSize)), digest.WithDigest(req.piece.PieceMd5), digest.WithLogger(req.log))
		if err != nil {
			_ = closer.Close()
			req.log.Errorf("init digest reader error: %s", err.Error())
			return nil, nil, err
		}
	}
	return reader, closer, nil
}

func (p *pieceDownloader) buildDownloadPieceHTTPRequest(ctx context.Context, d *DownloadPieceRequest) *http.Request {
	// FIXME switch to https when tls enabled
	targetURL := url.URL{
		Scheme:   p.scheme,
		Host:     d.DstAddr,
		Path:     fmt.Sprintf("download/%s/%s", d.TaskID[:3], d.TaskID),
		RawQuery: fmt.Sprintf("peerId=%s", d.DstPid),
	}

	logger.Debugf("built request url: %s", targetURL.String())
	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, targetURL.String(), nil)

	// TODO use string.Builder
	req.Header.Add("Range", fmt.Sprintf("bytes=%d-%d",
		d.piece.RangeStart, d.piece.RangeStart+uint64(d.piece.RangeSize)-1))

	// inject trace id into request header
	otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(req.Header))
	return req
}