<?php

	// $_GET valid parameters
	define('GET_USER', 'user');
	define('GET_PASS', 'pass');
	define('GET_ACTION', 'action');
	define('GET_LAT', 'lat');
	define('GET_LON', 'lon');

	// Valid values
	define('ACTION_START', 'start');
	define('ACTION_REFRESH', 'refresh');
	define('ACTION_STOP', 'stop');
	$actions = [ACTION_START, ACTION_REFRESH, ACTION_STOP];

	// Error messages
	define('ERR_USER', '-USER:');
	define('ERR_ACTION', '-ACTION:');
	define('ERR_LOCATION', '-TITLE:');

	/****************************************************
	* This function is called from almost everywhere at *
	* the beggining of the page. It initializes the     *
	* session variables, connect to the db, enabling    *
	* the variable $con for futher use everywhere in    *
	* the php code, and populates the arrays $user      *
	* and $permission, with info about the user.        *
	*                                                   *
	* @return: (db connection): The connection handler. *
	****************************************************/
	function startdb(){
		//Include the db configuration file. It's somehow like this
		/*
		 <?php
		  $host = 'XXXX';
		  $db_name = 'XXXX';
		  $username_ro = 'XXXX';
		  $username_rw = 'XXXX';
		  $pass_ro = 'XXXX';
		  $pass_rw = 'XXXX';
		 ?>
		*/
		include('../../.htpasswd');

		//Connect to to database
		$con = mysqli_connect($host, $username_rw, $pass_rw, $db_name);

		//Set encoding options
		mysqli_set_charset($con, 'utf-8');
		header('Content-Type: text/html; charset=utf8');
		mysqli_query($con, 'SET NAMES utf8;');

		//Return the db connection
		return $con;
	}

	$con = startdb('rw');

	//Get fields
	$user = mysqli_real_escape_string($con, $_GET[GET_USER]);
	$pass = mysqli_real_escape_string($con, $_GET[GET_PASS]);
	$lat = mysqli_real_escape_string($con, $_GET[GET_LAT]);
	$lon = mysqli_real_escape_string($con, $_GET[GET_LON]);
	$action = mysqli_real_escape_string($con, $_GET[GET_ACTION]);

	//Validate user
	$q = mysqli_query($con, "SELECT id FROM user WHERE username = '$user' AND md5(concat(password, md5(salt))) = '$pass';");
	if (mysqli_num_rows($q) == 0){
		error_log(":SECURITY: Reporting location with wrong credentials (IP $_SERVER[REMOTE_ADDR])");
		http_response_code(403); // Forbidden
		$error = $error . ERR_TARGET . mysqli_real_escape_string($con, $_GET[GET_TARGET]);
	}
	// Get id
	$r = mysqli_fetch_array($q);
	$uid = $r['id'];

	//Validate fields
	if (!in_array($action, $actions)){
		http_response_code(400); // Bad request
		$error = $error . ERR_ACTION . $action;
	}
	if (is_numeric($lat) == false || is_numeric($lon) == false){
		http_response_code(400); // Bad request
		$error = $error . ERR_LOCATION . '($lat, $lon)';
	}
	if (strlen($lat) == 0 xor strlen($lon) == 0){
		// Only one coordinate.
		http_response_code(400); // Bad request
		$error = $error . ERR_LOCATION . '($lat, $lon)';
	}
	if (strlen($lat) != 0 && ($lat < -90.0 || $lat > 90.0)){
		// Invalid latitude
		http_response_code(400); // Bad request
		$error = $error . ERR_LOCATION . '(Lat: $lat)';
	}
	if (strlen($lon) != 0 && ($lon < -180.0 || $lon > 180.0)){
		// Invalid longitude
		http_response_code(400); // Bad request
		$error = $error . ERR_LOCATION . '(Lon: $lat)';
	}

	// Discern action
	switch ($action){
		case ACTION_START:
			// Insert
			mysqli_query($con, "INSERT INTO location (lat, lon, action, user) VALUES ($lat, $lon, 'S', $uid);");
			break;
		case ACTION_REFRESH:
			// Look for start node.
			$q = mysqli_query($con, "SELECT id, start FROM location WHERE user = $uid AND dtime > NOW() - INTERVAL 30 MINUTE ORDER BY dtime DESC LIMIT 1;");
			if (mysqli_num_rows($q) == 0){
				// No recent reports. Start anew.
				mysqli_query($con, "INSERT INTO location (lat, lon, action, user) VALUES ($lat, $lon, 'S', $uid);");
			}
			else{
				$r = mysqli_fetch_array($q);
				if ($r['action'] == 'F'){
					// Previous track was stoped. Start anew.
					mysqli_query($con, "INSERT INTO location (lat, lon, action, user) VALUES ($lat, $lon, 'S', $uid);");
				}
				else{
					// Continue track.
					$s = $r['start'];
					mysqli_query($con, "INSERT INTO location (lat, lon, action, user, start) VALUES ($lat, $lon, 'S', $uid, $s);");
				}
			}
			break;
		case ACTION_STOP:
			// Look for start node.
			$q = mysqli_query($con, "SELECT id, start FROM location WHERE user = $uid AND dtime > NOW() - INTERVAL 30 MINUTE ORDER BY dtime DESC LIMIT 1;");
			if (mysqli_num_rows($q) > 0){
				$r = mysqli_fetch_array($q);
				if ($r['action'] != 'F'){
					// Finish track.
					$s = $r['start'];
					if (strlen($lat) > 0 && strlen($lon) > 0){
						mysqli_query($con, "INSERT INTO location (lat, lon, action, user, start) VALUES ($lat, $lon, 'F', $uid, $s);");
					}
					else{
						mysqli_query($con, "INSERT INTO location (action, user, start) VALUES ('F', $uid, $s);");
					}
				}
			}
			break;
	}
	http_response_code(204); // No content.
?>
