package b1

import (
	"encoding/binary"
	"fmt"
	"io"
)

type Wire struct {
	Len  uint8
	Text [127]rune
}

func MakeWire(s string) Wire {
	l := len(s)
	ss := Wire{}
	if l > len(ss.Text) {
		l = len(ss.Text)
	}
	ss.Len = uint8(l)
	copy(ss.Text[:], ([]rune(s))[0:l])
	return ss
}

func (ss Wire) String() string {
	return string(ss.Text[:ss.Len])
}

type Attr struct {
	Name  Wire
	Value Wire
}

type MessageHeader struct {
	Kind       int64
	From       int64
	To         int64
	Method     Wire
	AttrCount  int8
	BodyLength int64
}

type Message struct {
	MessageHeader
	attrs []Attr
	body  []byte
}

func (m Message) MarshalTo(w io.Writer) error {
	err := binary.Write(w, binary.LittleEndian, m.MessageHeader)
	if err != nil {
		return err
	}
	for i := 0; i < int(m.AttrCount) && i < len(m.attrs); i++ {
		attr := m.attrs[i]
		err = binary.Write(w, binary.LittleEndian, attr)
		if err != nil {
			return err
		}
	}
	if m.BodyLength > 0 {
		l, err := w.Write(m.body[0:m.BodyLength])
		if l != int(m.BodyLength) {
			return fmt.Errorf("Message partial write: %d %d", l, m.BodyLength)
		}
		return err
	}
	return nil
}

func (m *Message) UnmarshalFrom(w io.Reader) error {
	err := binary.Read(w, binary.LittleEndian, &m.MessageHeader)
	if err != nil {
		return err
	}
	if m.AttrCount < 0 {
		return fmt.Errorf("Negative attr count.")
	}
	if m.BodyLength > (2 << 16) {
		return fmt.Errorf("Body too long.")
	}

	m.attrs = make([]Attr, m.AttrCount)
	m.body = make([]byte, m.BodyLength)
	for i := 0; i < int(m.AttrCount); i++ {
		err = binary.Read(w, binary.LittleEndian, &m.attrs[i])
		if err != nil {
			return err
		}
	}
	if m.BodyLength > 0 {
		l, err := w.Read(m.body)
		if l != int(m.BodyLength) {
			return fmt.Errorf("Message partial read: %d %d", l, m.BodyLength)
		}
		return err
	}
	return nil
}

func MakeMessage(kind, from, to int64, method string, body []byte, attrs ...string) Message {
	mh := MessageHeader{kind, from, to, MakeWire(method), int8(len(attrs) / 2), int64(len(body))}
	mm := Message{}
	mm.MessageHeader = mh
	mm.attrs = make([]Attr, len(attrs)/2)
	for i := 1; i < len(attrs); i += 2 {
		mm.attrs[i/2] = Attr{MakeWire(attrs[i-1]), MakeWire(attrs[i])}
	}
	mm.body = body
	return mm
}