/*
 *
 * Copyright 2014, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

package grpc

import (
	"bytes"
	"context"
	"encoding/binary"
	"fmt"
	"io"
	"math"
	"os"

	"github.com/micro/grpc-go"
	"github.com/micro/grpc-go/codes"
	"github.com/micro/grpc-go/encoding"
	"github.com/micro/grpc-go/stats"
	"github.com/micro/grpc-go/transport"
)

// The format of the payload: compressed or not?
type payloadFormat uint8

const (
	compressionNone payloadFormat = iota // no compression
	compressionMade
)

// parser reads complete gRPC messages from the underlying reader.
type parser struct {
	// r is the underlying reader.
	// See the comment on recvMsg for the permissible
	// error types.
	r io.Reader

	// The header of a gRPC message. Find more detail
	// at http://www.grpc.io/docs/guides/wire.html.
	header [5]byte
}

// recvMsg reads a complete gRPC message from the stream.
//
// It returns the message and its payload (compression/encoding)
// format. The caller owns the returned msg memory.
//
// If there is an error, possible values are:
//   * io.EOF, when no messages remain
//   * io.ErrUnexpectedEOF
//   * of type transport.ConnectionError
//   * of type transport.StreamError
// No other error values or types must be returned, which also means
// that the underlying io.Reader must not return an incompatible
// error.
func (p *parser) recvMsg(maxMsgSize int) (pf payloadFormat, msg []byte, err error) {
	if _, err := io.ReadFull(p.r, p.header[:]); err != nil {
		return 0, nil, err
	}

	pf = payloadFormat(p.header[0])
	length := binary.BigEndian.Uint32(p.header[1:])

	if length == 0 {
		return pf, nil, nil
	}
	if length > uint32(maxMsgSize) {
		return 0, nil, Errorf(codes.Internal, "grpc: received message length %d exceeding the max size %d", length, maxMsgSize)
	}
	// TODO(bradfitz,zhaoq): garbage. reuse buffer after proto decoding instead
	// of making it for each message:
	msg = make([]byte, int(length))
	if _, err := io.ReadFull(p.r, msg); err != nil {
		if err == io.EOF {
			err = io.ErrUnexpectedEOF
		}
		return 0, nil, err
	}
	return pf, msg, nil
}

// encode serializes msg and prepends the message header. If msg is nil, it
// generates the message header of 0 message length.
func encode(c encoding.Codec, msg interface{}, cp grpc.Compressor, cbuf *bytes.Buffer, outPayload *stats.OutPayload) ([]byte, []byte, error) {
	var b []byte
	const (
		payloadLen = 1
		sizeLen    = 4
	)

	if msg != nil {
		var err error
		b, err = c.Marshal(msg)
		if err != nil {
			return nil, nil, Errorf(codes.Internal, "grpc: error while marshaling: %v", err.Error())
		}
		if outPayload != nil {
			outPayload.Payload = msg
			// TODO truncate large payload.
			outPayload.Data = b
			outPayload.Length = len(b)
		}
		if cp != nil {
			if err := cp.Do(cbuf, b); err != nil {
				return nil, nil, Errorf(codes.Internal, "grpc: error while compressing: %v", err.Error())
			}
			b = cbuf.Bytes()
		}
	}

	if len(b) > math.MaxUint32 {
		return nil, nil, Errorf(codes.ResourceExhausted, "grpc: message too large (%d bytes)", len(b))
	}

	bufHeader := make([]byte, payloadLen+sizeLen)
	if cp == nil {
		bufHeader[0] = byte(compressionNone)
	} else {
		bufHeader[0] = byte(compressionMade)
	}
	// Write length of b into buf
	binary.BigEndian.PutUint32(bufHeader[payloadLen:], uint32(len(b)))
	if outPayload != nil {
		outPayload.WireLength = payloadLen + sizeLen + len(b)
	}
	return bufHeader, b, nil
}

func checkRecvPayload(pf payloadFormat, recvCompress string, dc grpc.Decompressor) error {
	switch pf {
	case compressionNone:
	case compressionMade:
		if dc == nil || recvCompress != dc.Type() {
			return Errorf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", recvCompress)
		}
	default:
		return Errorf(codes.Internal, "grpc: received unexpected payload format %d", pf)
	}
	return nil
}

func recv(p *parser, c encoding.Codec, s *transport.Stream, dc grpc.Decompressor, m interface{}, maxMsgSize int) error {
	pf, d, err := p.recvMsg(maxMsgSize)
	if err != nil {
		return err
	}
	if err := checkRecvPayload(pf, s.RecvCompress(), dc); err != nil {
		return err
	}
	if pf == compressionMade {
		d, err = dc.Do(bytes.NewReader(d))
		if err != nil {
			return Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
		}
	}
	if len(d) > maxMsgSize {
		// TODO: Revisit the error code. Currently keep it consistent with java
		// implementation.
		return Errorf(codes.Internal, "grpc: received a message of %d bytes exceeding %d limit", len(d), maxMsgSize)
	}
	if err := c.Unmarshal(d, m); err != nil {
		return Errorf(codes.Internal, "grpc: failed to unmarshal the received message %v", err)
	}
	return nil
}

// rpcError defines the status from an RPC.
type rpcError struct {
	code codes.Code
	desc string
}

func (e *rpcError) Error() string {
	return fmt.Sprintf("rpc error: code = %d desc = %s", e.code, e.desc)
}

// Code returns the error code for err if it was produced by the rpc system.
// Otherwise, it returns codes.Unknown.
func Code(err error) codes.Code {
	if err == nil {
		return codes.OK
	}
	if e, ok := err.(*rpcError); ok {
		return e.code
	}
	return codes.Unknown
}

// ErrorDesc returns the error description of err if it was produced by the rpc system.
// Otherwise, it returns err.Error() or empty string when err is nil.
func ErrorDesc(err error) string {
	if err == nil {
		return ""
	}
	if e, ok := err.(*rpcError); ok {
		return e.desc
	}
	return err.Error()
}

// Errorf returns an error containing an error code and a description;
// Errorf returns nil if c is OK.
func Errorf(c codes.Code, format string, a ...interface{}) error {
	if c == codes.OK {
		return nil
	}
	return &rpcError{
		code: c,
		desc: fmt.Sprintf(format, a...),
	}
}

// toRPCErr converts an error into a rpcError.
func toRPCErr(err error) error {
	switch e := err.(type) {
	case *rpcError:
		return err
	case transport.ConnectionError:
		return &rpcError{
			code: codes.Internal,
			desc: e.Desc,
		}
	default:
		switch err {
		case context.DeadlineExceeded:
			return &rpcError{
				code: codes.DeadlineExceeded,
				desc: err.Error(),
			}
		case context.Canceled:
			return &rpcError{
				code: codes.Canceled,
				desc: err.Error(),
			}
		case grpc.ErrClientConnClosing:
			return &rpcError{
				code: codes.FailedPrecondition,
				desc: err.Error(),
			}
		}

	}
	return Errorf(codes.Unknown, "%v", err)
}

// convertCode converts a standard Go error into its canonical code. Note that
// this is only used to translate the error returned by the server applications.
func convertCode(err error) codes.Code {
	switch err {
	case nil:
		return codes.OK
	case io.EOF:
		return codes.OutOfRange
	case io.ErrClosedPipe, io.ErrNoProgress, io.ErrShortBuffer, io.ErrShortWrite, io.ErrUnexpectedEOF:
		return codes.FailedPrecondition
	case os.ErrInvalid:
		return codes.InvalidArgument
	case context.Canceled:
		return codes.Canceled
	case context.DeadlineExceeded:
		return codes.DeadlineExceeded
	}
	switch {
	case os.IsExist(err):
		return codes.AlreadyExists
	case os.IsNotExist(err):
		return codes.NotFound
	case os.IsPermission(err):
		return codes.PermissionDenied
	}
	return codes.Unknown
}

func wait(ctx context.Context) bool {
	if ctx == nil {
		return false
	}
	wait, ok := ctx.Value("wait").(bool)
	if !ok {
		return false
	}
	return wait
}