// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 Google Inc.  All rights reserved.
// http://code.google.com/p/goprotobuf/
//
// 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 proto

/*
 * Routines for encoding data into the wire format for protocol buffers.
 */

import (
	"os"
	"reflect"
	"runtime"
	"unsafe"
)

// ErrRequiredNotSet is the error returned if Marshal is called with
// a protocol buffer struct whose required fields have not
// all been initialized. It is also the error returned if Unmarshal is
// called with an encoded protocol buffer that does not include all the
// required fields.
type ErrRequiredNotSet struct {
	t reflect.Type
}

func (e *ErrRequiredNotSet) String() string {
	return "proto: required fields not set in " + e.t.String()
}

var (
	// ErrRepeatedHasNil is the error returned if Marshal is called with
	// a struct with a repeated field containing a nil element.
	ErrRepeatedHasNil = os.NewError("proto: repeated field has nil")

	// ErrNil is the error returned if Marshal is called with nil.
	ErrNil = os.NewError("proto: Marshal called with nil")

	// ErrNotPtr is the error returned if Marshal is called with a non-pointer.
	ErrNotPtr = os.NewError("proto: Marshal called with a non-pointer")
)

// The fundamental encoders that put bytes on the wire.
// Those that take integer types all accept uint64 and are
// therefore of type valueEncoder.

const maxVarintBytes = 10 // maximum length of a varint

// EncodeVarint returns the varint encoding of x.
// This is the format for the
// int32, int64, uint32, uint64, bool, and enum
// protocol buffer types.
// Not used by the package itself, but helpful to clients
// wishing to use the same encoding.
func EncodeVarint(x uint64) []byte {
	var buf [maxVarintBytes]byte
	var n int
	for n = 0; x > 127; n++ {
		buf[n] = 0x80 | uint8(x&0x7F)
		x >>= 7
	}
	buf[n] = uint8(x)
	n++
	return buf[0:n]
}

// EncodeVarint writes a varint-encoded integer to the Buffer.
// This is the format for the
// int32, int64, uint32, uint64, bool, and enum
// protocol buffer types.
func (p *Buffer) EncodeVarint(x uint64) os.Error {
	for x >= 1<<7 {
		p.buf = append(p.buf, uint8(x&0x7f|0x80))
		x >>= 7
	}
	p.buf = append(p.buf, uint8(x))
	return nil
}

// EncodeFixed64 writes a 64-bit integer to the Buffer.
// This is the format for the
// fixed64, sfixed64, and double protocol buffer types.
func (p *Buffer) EncodeFixed64(x uint64) os.Error {
	p.buf = append(p.buf,
		uint8(x),
		uint8(x>>8),
		uint8(x>>16),
		uint8(x>>24),
		uint8(x>>32),
		uint8(x>>40),
		uint8(x>>48),
		uint8(x>>56))
	return nil
}

// EncodeFixed32 writes a 32-bit integer to the Buffer.
// This is the format for the
// fixed32, sfixed32, and float protocol buffer types.
func (p *Buffer) EncodeFixed32(x uint64) os.Error {
	p.buf = append(p.buf,
		uint8(x),
		uint8(x>>8),
		uint8(x>>16),
		uint8(x>>24))
	return nil
}

// EncodeZigzag64 writes a zigzag-encoded 64-bit integer
// to the Buffer.
// This is the format used for the sint64 protocol buffer type.
func (p *Buffer) EncodeZigzag64(x uint64) os.Error {
	// use signed number to get arithmetic right shift.
	return p.EncodeVarint(uint64((x << 1) ^ uint64((int64(x) >> 63))))
}

// EncodeZigzag32 writes a zigzag-encoded 32-bit integer
// to the Buffer.
// This is the format used for the sint32 protocol buffer type.
func (p *Buffer) EncodeZigzag32(x uint64) os.Error {
	// use signed number to get arithmetic right shift.
	return p.EncodeVarint(uint64((uint32(x) << 1) ^ uint32((int32(x) >> 31))))
}

// EncodeRawBytes writes a count-delimited byte buffer to the Buffer.
// This is the format used for the bytes protocol buffer
// type and for embedded messages.
func (p *Buffer) EncodeRawBytes(b []byte) os.Error {
	lb := len(b)
	p.EncodeVarint(uint64(lb))
	p.buf = append(p.buf, b...)
	return nil
}

// EncodeStringBytes writes an encoded string to the Buffer.
// This is the format used for the proto2 string type.
func (p *Buffer) EncodeStringBytes(s string) os.Error {

	// this works because strings and slices are the same.
	y := *(*[]byte)(unsafe.Pointer(&s))
	p.EncodeRawBytes(y)
	return nil
}

// Marshaler is the interface representing objects that can marshal themselves.
type Marshaler interface {
	Marshal() ([]byte, os.Error)
}

// Marshal takes the protocol buffer struct represented by pb
// and encodes it into the wire format, returning the data.
func Marshal(pb interface{}) ([]byte, os.Error) {
	// Can the object marshal itself?
	if m, ok := pb.(Marshaler); ok {
		return m.Marshal()
	}
	p := NewBuffer(nil)
	err := p.Marshal(pb)
	if err != nil {
		return nil, err
	}
	return p.buf, err
}

// Marshal takes the protocol buffer struct represented by pb
// and encodes it into the wire format, writing the result to the
// Buffer.
func (p *Buffer) Marshal(pb interface{}) os.Error {
	// Can the object marshal itself?
	if m, ok := pb.(Marshaler); ok {
		data, err := m.Marshal()
		if err != nil {
			return err
		}
		p.buf = append(p.buf, data...)
		return nil
	}

	mstat := runtime.MemStats.Mallocs

	t, b, err := getbase(pb)
	if t.Kind() != reflect.Ptr {
		return ErrNotPtr
	}
	if err == nil {
		err = p.enc_struct(t.Elem(), b)
	}

	mstat = runtime.MemStats.Mallocs - mstat
	stats.Emalloc += mstat
	stats.Encode++

	return err
}

// Individual type encoders.

// Encode a bool.
func (o *Buffer) enc_bool(p *Properties, base uintptr) os.Error {
	v := *(**uint8)(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}
	x := *v
	if x != 0 {
		x = 1
	}
	o.buf = append(o.buf, p.tagcode...)
	p.valEnc(o, uint64(x))
	return nil
}

// Encode an int32.
func (o *Buffer) enc_int32(p *Properties, base uintptr) os.Error {
	v := *(**uint32)(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}
	x := *v
	o.buf = append(o.buf, p.tagcode...)
	p.valEnc(o, uint64(x))
	return nil
}

// Encode an int64.
func (o *Buffer) enc_int64(p *Properties, base uintptr) os.Error {
	v := *(**uint64)(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}
	x := *v
	o.buf = append(o.buf, p.tagcode...)
	p.valEnc(o, uint64(x))
	return nil
}

// Encode a string.
func (o *Buffer) enc_string(p *Properties, base uintptr) os.Error {
	v := *(**string)(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}
	x := *v
	o.buf = append(o.buf, p.tagcode...)
	o.EncodeStringBytes(x)
	return nil
}

// All protocol buffer fields are nillable, but be careful.
func isNil(v reflect.Value) bool {
	switch v.Kind() {
	case reflect.Map, reflect.Ptr, reflect.Slice:
		return v.IsNil()
	}
	return false
}

// Encode a message struct.
func (o *Buffer) enc_struct_message(p *Properties, base uintptr) os.Error {
	// Can the object marshal itself?
	iv := unsafe.Unreflect(p.stype, unsafe.Pointer(base+p.offset))
	if m, ok := iv.(Marshaler); ok {
		if isNil(reflect.ValueOf(iv)) {
			return ErrNil
		}
		data, err := m.Marshal()
		if err != nil {
			return err
		}
		o.buf = append(o.buf, p.tagcode...)
		o.EncodeRawBytes(data)
		return nil
	}
	v := *(**struct{})(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}

	// need the length before we can write out the message itself,
	// so marshal into a separate byte buffer first.
	obuf := o.buf
	o.buf = o.bufalloc()

	b := uintptr(unsafe.Pointer(v))
	typ := p.stype.Elem()
	err := o.enc_struct(typ, b)

	nbuf := o.buf
	o.buf = obuf
	if err != nil {
		o.buffree(nbuf)
		return err
	}
	o.buf = append(o.buf, p.tagcode...)
	o.EncodeRawBytes(nbuf)
	o.buffree(nbuf)
	return nil
}

// Encode a group struct.
func (o *Buffer) enc_struct_group(p *Properties, base uintptr) os.Error {
	v := *(**struct{})(unsafe.Pointer(base + p.offset))
	if v == nil {
		return ErrNil
	}

	o.EncodeVarint(uint64((p.Tag << 3) | WireStartGroup))
	b := uintptr(unsafe.Pointer(v))
	typ := p.stype.Elem()
	err := o.enc_struct(typ, b)
	if err != nil {
		return err
	}
	o.EncodeVarint(uint64((p.Tag << 3) | WireEndGroup))
	return nil
}

// Encode a slice of bools ([]bool).
func (o *Buffer) enc_slice_bool(p *Properties, base uintptr) os.Error {
	s := *(*[]uint8)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	for _, x := range s {
		o.buf = append(o.buf, p.tagcode...)
		if x != 0 {
			x = 1
		}
		p.valEnc(o, uint64(x))
	}
	return nil
}

// Encode a slice of bools ([]bool) in packed format.
func (o *Buffer) enc_slice_packed_bool(p *Properties, base uintptr) os.Error {
	s := *(*[]uint8)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	o.buf = append(o.buf, p.tagcode...)
	o.EncodeVarint(uint64(l)) // each bool takes exactly one byte
	for _, x := range s {
		if x != 0 {
			x = 1
		}
		p.valEnc(o, uint64(x))
	}
	return nil
}

// Encode a slice of bytes ([]byte).
func (o *Buffer) enc_slice_byte(p *Properties, base uintptr) os.Error {
	s := *(*[]uint8)(unsafe.Pointer(base + p.offset))
	if s == nil {
		return ErrNil
	}
	o.buf = append(o.buf, p.tagcode...)
	o.EncodeRawBytes(s)
	return nil
}

// Encode a slice of int32s ([]int32).
func (o *Buffer) enc_slice_int32(p *Properties, base uintptr) os.Error {
	s := *(*[]uint32)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	for i := 0; i < l; i++ {
		o.buf = append(o.buf, p.tagcode...)
		x := s[i]
		p.valEnc(o, uint64(x))
	}
	return nil
}

// Encode a slice of int32s ([]int32) in packed format.
func (o *Buffer) enc_slice_packed_int32(p *Properties, base uintptr) os.Error {
	s := *(*[]uint32)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	// TODO: Reuse a Buffer.
	buf := NewBuffer(nil)
	for i := 0; i < l; i++ {
		p.valEnc(buf, uint64(s[i]))
	}

	o.buf = append(o.buf, p.tagcode...)
	o.EncodeVarint(uint64(len(buf.buf)))
	o.buf = append(o.buf, buf.buf...)
	return nil
}

// Encode a slice of int64s ([]int64).
func (o *Buffer) enc_slice_int64(p *Properties, base uintptr) os.Error {
	s := *(*[]uint64)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	for i := 0; i < l; i++ {
		o.buf = append(o.buf, p.tagcode...)
		x := s[i]
		p.valEnc(o, uint64(x))
	}
	return nil
}

// Encode a slice of int64s ([]int64) in packed format.
func (o *Buffer) enc_slice_packed_int64(p *Properties, base uintptr) os.Error {
	s := *(*[]uint64)(unsafe.Pointer(base + p.offset))
	l := len(s)
	if l == 0 {
		return ErrNil
	}
	// TODO: Reuse a Buffer.
	buf := NewBuffer(nil)
	for i := 0; i < l; i++ {
		p.valEnc(buf, s[i])
	}

	o.buf = append(o.buf, p.tagcode...)
	o.EncodeVarint(uint64(len(buf.buf)))
	o.buf = append(o.buf, buf.buf...)
	return nil
}

// Encode a slice of slice of bytes ([][]byte).
func (o *Buffer) enc_slice_slice_byte(p *Properties, base uintptr) os.Error {
	ss := *(*[][]uint8)(unsafe.Pointer(base + p.offset))
	l := len(ss)
	if l == 0 {
		return ErrNil
	}
	for i := 0; i < l; i++ {
		o.buf = append(o.buf, p.tagcode...)
		s := ss[i]
		o.EncodeRawBytes(s)
	}
	return nil
}

// Encode a slice of strings ([]string).
func (o *Buffer) enc_slice_string(p *Properties, base uintptr) os.Error {
	ss := *(*[]string)(unsafe.Pointer(base + p.offset))
	l := len(ss)
	for i := 0; i < l; i++ {
		o.buf = append(o.buf, p.tagcode...)
		s := ss[i]
		o.EncodeStringBytes(s)
	}
	return nil
}

// Encode a slice of message structs ([]*struct).
func (o *Buffer) enc_slice_struct_message(p *Properties, base uintptr) os.Error {
	s := *(*[]*struct{})(unsafe.Pointer(base + p.offset))
	l := len(s)
	typ := p.stype.Elem()

	for i := 0; i < l; i++ {
		v := s[i]
		if v == nil {
			return ErrRepeatedHasNil
		}

		// Can the object marshal itself?
		iv := unsafe.Unreflect(p.stype, unsafe.Pointer(&s[i]))
		if m, ok := iv.(Marshaler); ok {
			if isNil(reflect.ValueOf(iv)) {
				return ErrNil
			}
			data, err := m.Marshal()
			if err != nil {
				return err
			}
			o.buf = append(o.buf, p.tagcode...)
			o.EncodeRawBytes(data)
			continue
		}

		obuf := o.buf
		o.buf = o.bufalloc()

		b := uintptr(unsafe.Pointer(v))
		err := o.enc_struct(typ, b)

		nbuf := o.buf
		o.buf = obuf
		if err != nil {
			o.buffree(nbuf)
			if err == ErrNil {
				return ErrRepeatedHasNil
			}
			return err
		}
		o.buf = append(o.buf, p.tagcode...)
		o.EncodeRawBytes(nbuf)

		o.buffree(nbuf)
	}
	return nil
}

// Encode a slice of group structs ([]*struct).
func (o *Buffer) enc_slice_struct_group(p *Properties, base uintptr) os.Error {
	s := *(*[]*struct{})(unsafe.Pointer(base + p.offset))
	l := len(s)
	typ := p.stype.Elem()

	for i := 0; i < l; i++ {
		v := s[i]
		if v == nil {
			return ErrRepeatedHasNil
		}

		o.EncodeVarint(uint64((p.Tag << 3) | WireStartGroup))

		b := uintptr(unsafe.Pointer(v))
		err := o.enc_struct(typ, b)

		if err != nil {
			if err == ErrNil {
				return ErrRepeatedHasNil
			}
			return err
		}

		o.EncodeVarint(uint64((p.Tag << 3) | WireEndGroup))
	}
	return nil
}

// Encode an extension map.
func (o *Buffer) enc_map(p *Properties, base uintptr) os.Error {
	v := *(*map[int32]Extension)(unsafe.Pointer(base + p.offset))
	if err := encodeExtensionMap(v); err != nil {
		return err
	}
	for _, e := range v {
		o.buf = append(o.buf, e.enc...)
	}
	return nil
}

// Encode a struct.
func (o *Buffer) enc_struct(t reflect.Type, base uintptr) os.Error {
	prop := GetProperties(t)
	required := prop.reqCount
	for _, p := range prop.Prop {
		if p.enc != nil {
			err := p.enc(o, p, base)
			if err != nil {
				if err != ErrNil {
					return err
				}
			} else if p.Required {
				required--
			}
		}
	}
	// See if we encoded all required fields.
	if required > 0 {
		return &ErrRequiredNotSet{t}
	}

	return nil
}