/*
NAME
  client.go

DESCRIPTION
  client.go provides a Client type providing functionality to send RTSP requests
  of methods DESCRIBE, OPTIONS, SETUP and PLAY to an RTSP server.

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>

LICENSE
  This is Copyright (C) 2019 the Australian Ocean Lab (AusOcean).

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package rtsp

import (
	"net"
	"net/url"
	"strconv"
)

// Client describes an RTSP Client.
type Client struct {
	cSeq      int
	addr      string
	url       *url.URL
	conn      net.Conn
	sessionID string
}

// NewClient returns a pointer to a new Client and the local address of the
// RTSP connection. The address addr will be parsed and a connection to the
// RTSP server will be made.
func NewClient(addr string) (c *Client, local, remote *net.TCPAddr, err error) {
	c = &Client{addr: addr}
	c.url, err = url.Parse(addr)
	if err != nil {
		return nil, nil, nil, err
	}
	c.conn, err = net.Dial("tcp", c.url.Host)
	if err != nil {
		return nil, nil, nil, err
	}
	local = c.conn.LocalAddr().(*net.TCPAddr)
	remote = c.conn.RemoteAddr().(*net.TCPAddr)
	return
}

// Close closes the RTSP connection.
func (c *Client) Close() error {
	return c.conn.Close()
}

// Describe forms and sends an RTSP request of method DESCRIBE to the RTSP server.
func (c *Client) Describe() (*Response, error) {
	req, err := NewRequest("DESCRIBE", c.nextCSeq(), c.url, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Add("Accept", "application/sdp")
	return c.Do(req)
}

// Options forms and sends an RTSP request of method OPTIONS to the RTSP server.
func (c *Client) Options() (*Response, error) {
	req, err := NewRequest("OPTIONS", c.nextCSeq(), c.url, nil)
	if err != nil {
		return nil, err
	}
	return c.Do(req)
}

// Setup forms and sends an RTSP request of method SETUP to the RTSP server.
func (c *Client) Setup(track, transport string) (*Response, error) {
	u, err := url.Parse(c.addr + "/" + track)
	if err != nil {
		return nil, err
	}

	req, err := NewRequest("SETUP", c.nextCSeq(), u, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Add("Transport", transport)

	resp, err := c.Do(req)
	if err != nil {
		return nil, err
	}
	c.sessionID = resp.Header.Get("Session")

	return resp, err
}

// Play forms and sends an RTSP request of method PLAY to the RTSP server
func (c *Client) Play() (*Response, error) {
	req, err := NewRequest("PLAY", c.nextCSeq(), c.url, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Add("Session", c.sessionID)

	return c.Do(req)
}

// Do sends the given RTSP request req, reads any responses and returns the response
// and any errors.
func (c *Client) Do(req *Request) (*Response, error) {
	err := req.Write(c.conn)
	if err != nil {
		return nil, err
	}

	resp, err := ReadResponse(c.conn)
	if err != nil {
		return nil, err
	}

	return resp, nil
}

// nextCSeq provides the next CSeq number for the next RTSP request.
func (c *Client) nextCSeq() string {
	c.cSeq++
	return strconv.Itoa(c.cSeq)
}