package rtmp

import (
	"net"
	"time"
	"encoding/binary"
)

type chnk_stream struct {
	timestamp uint32
	last_msg_strm_id uint32
	timedelta uint32
}

type message struct {
//	msg_strm_id uint32
	data []byte
	curr_bytes_read uint32
	timestamp uint32
	msg_type uint8
	msg_len uint32
}


func read_basic_header(conn net.Conn) (uint8, uint32, error) {
	fmt_csid_byte := make([]byte, 1)
	if _, err := conn.Read(fmt_csid_byte); err != nil {
		return 0, 0, err
	}
	format := uint8(fmt_csid_byte[0] >> 6)
	var csid uint32
	switch fmt_csid_byte[0] & 0x3f {
	case 0:
		csid_true := make([]byte, 1)
		if _, err := conn.Read(csid_true); err != nil {
			return 0, 0, err
		}
		csid = uint32(csid_true[0]) + 64
	case 1:
		csid_true := make([]byte, 2)
		if _, err := conn.Read(csid_true); err != nil {
			return 0, 0, err
		}
		csid = uint32(binary.LittleEndian.Uint16(csid_true)) + 64
	default:
		csid = uint32(fmt_csid_byte[0] & 0x3f)
	}
	return format, csid, nil
}

func read_message_header_0(conn net.Conn, chnk_stream_ptr *chnk_stream, msg_ptr *message) (error) {
	var extended_time bool
	timestamp := make([]byte, 4)
	if _, err := conn.Read(timestamp[1:]); err != nil {
		return err
	}
	chnk_stream_ptr.timestamp = binary.BigEndian.Uint32(timestamp)
	
	if chnk_stream_ptr.timestamp ^ 0xffffff == 0 {
		extended_time = true
	}

	msg_len := make([]byte, 4)
	if _, err := conn.Read(msg_len[1:]); err != nil {
		return err
	}
	msg_ptr.msg_len = binary.BigEndian.Uint32(msg_len)
	msg_ptr.data = make([]byte, msg_ptr.msg_len)

	msg_typeid := make([]byte, 1)
	if _, err := conn.Read(msg_typeid); err != nil {
		return err
	}
	msg_ptr.msg_type = msg_typeid[0]

	msg_streamid := make([]byte, 4)
	if _, err := conn.Read(msg_typeid); err != nil {
		return err
	}
	chnk_stream_ptr.last_msg_strm_id = binary.BigEndian.Uint32(msg_streamid)

	if extended_time {
		if _, err := conn.Read(timestamp); err != nil {
			return err
		}
		chnk_stream_ptr.timestamp = binary.BigEndian.Uint32(timestamp)
	}
	msg_ptr.timestamp = chnk_stream_ptr.timestamp

	return nil
}

func read_chunk_data(conn net.Conn, msg_ptr *message, chnk_size uint32) (error) {
	bytes_left := msg_ptr.msg_len - msg_ptr.curr_bytes_read
	var buffer_end uint32
	if bytes_left < chnk_size {
		buffer_end = bytes_left + msg_ptr.curr_bytes_read + 1
	} else {
		buffer_end = chnk_size + msg_ptr.curr_bytes_read + 1
	}
	n, err := conn.Read(msg_ptr.data[msg_ptr.curr_bytes_read:buffer_end])
	if err != nil {
		return err
	}
	msg_ptr.curr_bytes_read += uint32(n)
	return nil

}

func ReadChunk(conn net.Conn, open_chnkstrms map[uint32]*chnk_stream, open_msgs map[uint32]*message, chnk_size uint32) (*message, error){
	conn.SetDeadline(time.Now().Add(10 * time.Second))

	format, csid, err := read_basic_header(conn)
	if err != nil {
		return nil, err
	}

	switch format {
	case 0:
		chnkstream_ptr := new(chnk_stream)
		open_chnkstrms[csid] = chnkstream_ptr
		msg_ptr := new(message)

		if err := read_message_header_0(conn, chnkstream_ptr, msg_ptr); err != nil {
			return nil, err
		}
		if err := read_chunk_data(conn, msg_ptr, chnk_size); err != nil {
			return nil, err
		}
		if msg_ptr.msg_len > chnk_size {
			open_msgs[chnkstream_ptr.last_msg_strm_id] = msg_ptr
			return nil, nil
		} else {
			return msg_ptr, nil
		}
	}

	conn.SetDeadline(time.Time{})
	return nil, nil
}