#!/usr/bin/php

<?php

	require_once __DIR__.'/../../include/php/const';

	$f_auth;
	$f_gstate;
	$f_accesslog;
	$f_actions;

	$actions  = [];

	$last_user = null;
	$timeout   = 0;






	/* RETURN CURRENT GLOBAL STATE
	*
	* @return gstate<string>					Current global state as string
	*
	*/
	function get_gstate(){

		/* (1) Export global file descriptor */
		global $f_gstate;

		/* (2) Read first line */
		$f_gstate->seek(0);
		$state = $f_gstate->current();

		$state = preg_replace('@^\s+@', '', $state);
		$state = preg_replace('@\s+$@', '', $state);

		/* (3) Check data */
		if( strlen($state) < 1 )
			return false;

		/* (4) Return global state */
		return $state;
	}



	/* RETURNS THE PERMISSIONS FOR A SPECIFIC CODE AND AN ACTION
	*
	* @code<string>							Some RFID code
	*
	* @return user<array>						User info if found ; else NULL
	*
	*/
	function auth($code){

		global $f_auth;


		/* (1) Goto first line */
		$f_auth->seek(0);

		/* (2) Parse each line */
		while( !$f_auth->eof() ){
			
			/* (3) Try to parse line */
			$parsed = json_decode($f_auth->fgets(), true);

			/* (3) Ignore if parse error */
			if( is_null($parsed) )
				continue;

			/* (4) If wrong code -> go to next */
			if( $parsed[0] != $code )
				continue;
		
			/* (5) return user info */
			return [
				'id'  => $parsed[1],
				'can' => $parsed[2]
			];

		}

		/* (6) Return FALSE if not found */
		return null;

	}



	/* PROCESS ACTIONS IF ACTION CAN BE PERFORMED BY USER (DEPENDING ON TIMEOUT/STATE)
	*
	* @user<array>							Current user information
	*
	* @return success<bool>						If success (action performed) | FALSE
	*
	*/
	function act($user){

		/* [1] Export global caches + variables
		=========================================================*/
		/* (1) Variables */
		global $timeout;

		/* (2) Caches */
		global $actions;

		/* (3) Log history file descriptor */
		global $f_accesslog;

		/* (5) Update global state */
		$state = get_gstate();

		// manage error
		if( $state === false )
			return false;


		/* [2] Manage timeout
		=========================================================*/
		/* (1) If no action for this @timeout -> reset to 0 */
		if( !isset($actions[$timeout]) || !is_array($actions[$timeout]) )
			$timeout = 0;
		
		/* (2) fetch actions for the current @timeout */
		$actionlist = $actions[$timeout];


		/* [3] Manage permissions (action that can be performed)
		=========================================================*/
		/* (1) Will contain available @id_action-s granted for the user */
		$grantedFor = [];

		/* (2) Search an action the user can perform in the list */
		foreach($actionlist as $id_action=>$acttion){

			/* (3) If have permission -> add to list */
			if( in_array($id_action, $user['can']) )
				$grantedFor[] = $id_action;

		}

		/* (4) If no action found -> abort */
		if( count($grantedFor) == 0 ){
			slog('user not granted to any action', 'mfrc522:loop');
			return false;
		}


		/* [4] Manage action depending on the actual STATE
		=========================================================*/
		/* (1) Will contain the first available action depending on STATE */
		$toPerform = null;

		/* (2) For each granted action, check the STATE */
		foreach($grantedFor as $id_action){

			$failed = false;

			/* (3) Fetch action data */
			$action = $actionlist[$id_action];

			/* (4) Check if the state allows the action to be performed */
			for( $c = 0 ; $c < strlen($state) || $c < strlen($action['prev']) ; $c++ ){
				// {1} 'X' = any state -> so ignore //
				if( $action['prev'][$c] == 'X' )
					continue;

				// {2} Other state : if not equal -> set as FAILED //
				else if( $action['prev'][$c] != $state[$c] ){
					$failed = true;
					break;
				}
			}

			/* (5) If not failed -> save action in @toPerform */
			if( !$failed ){
				$toPerform = $id_action;
				break;
			}

		}

		/* (6) If no action cant be performed -> abort */
		if( is_null($toPerform) ){
			slog('global state allows no action to be performed', 'mfrc522:loop');
			return false;
		}

		/* (7) Extract corresponding action */
		$action = $grantedFor[$toPerform];


		/* [5] Process the action on the STATE
		=========================================================*/
		/* (1) Update the state with the found action */
		for( $c = 0 ; $c < strlen($state) || $c < strlen($action['next']) ; $c++ ){

			// {1} If 'x' -> let the current state //
			if( $action['next'][$c] == 'X' )
				continue;

			// {2} If other state -> update it //
			else
				$state[$c] = $action['next'][$c];

		}


		/* (2) Update the state file */
		$written = @file_put_contents(STATE_CONF, $state);

		/* (3) Manage error */
		if( $written === false )
			slog('cannot update STATE file', 'mfrc522:loop');
		


		/* [6] Log action
		=========================================================*/
		/* (1) Log action to default log file */
		$f_accesslog->fwrite( json_encode([
			time(),
			$user['id'],
			$toPerform
		]).PHP_EOL );

		/* (2) Return status */
		return true;

	}













	function mfrc522_setup(){

		/* [0] Initialize global variables
		=========================================================*/
		/* (1) File descriptiors */
		global $f_auth, $f_accesslog, $f_gstate;

		/* (2) Caches */
		global $actions;



		/* [1] Open file descriptors on useful files
		=========================================================*/
		/* (1) Read accesses */
		$f_auth      = new SplFileObject(AUTH_CONF, 'r');
		$f_actions   = new SplFileObject(ACTIONS_CONF, 'r');
		$f_gstate    = new SplFileObject(STATE_CONF, 'r');

		/* (2) Append accesses (logs) */
		$f_accesslog = new SplFileObject(DEFAULT_DATA, 'a');



		/* [2] Parse ACTIONS and cache them
		=========================================================*/
		/* (1) Parse each line */
		while( !$f_actions->eof() ){
			
			/* (2) Try to parse line */
			$parsed = json_decode($f_actions->fgets(), true);

			/* (2) Ignore if parse error */
			if( is_null($parsed) )
				continue;

			/* (3) Add key (timeout) to cache */
			if( !isset($actions[$parsed[0]]) )
				$actions[$parsed[0]] = [];

			/* (4) Add entry to cache */
			$actions[$parsed[0]][$parsed[1]] = [
				'prev' => $parsed[2],
				'next' => $parsed[3]
			];

		}

		/* (5) Free file descriptor */
		$f_actions = null;



		/* [3] Check global state
		=========================================================*/
		/* (1) Check file */
		$gstate = get_gstate();

		/* (2) Manage error */
		if( $gstate === false )
			return 127;



		return 0;
	}





	function mfrc522_loop(){

		/* [1] Load global variables
		=========================================================*/
		/* (1) Persistent variabes */
		global $last_user;
		global $timeout;

		/* (2) Caches */
		global $actions;

		/* (3) Get global state */
		$gstate = get_gstate();

		// Manage error
		if( $gstate === false )
			return false;



		/* [1] Wait for rfid card
		=========================================================*/
		/* (1) Read card */
		$code = syscall(SOURCE_DIR.'/lib/mfrc522/read');
		
		/* (2) If no card read -> reset @last_user / @timeout + abort */
		if( $code === false ){

			$last_user = null;
			$timeout   = 0;
			return false;

		}


		/* (3) If code -> format it */
		$code = strtoupper($code);

		slog("card '$code' read", 'mfrc522:read');


		
		/* [2] Check for user in auth list
		=========================================================*/
		/* (1) Check user for this code */
		$user = auth($code);


		/* (2) If not found -> reset @last_user / @timeout + abort */
		if( is_null($user) ){
			
			slog("Unknown user (not authenticated)", "mfrc522:loop");
			$last_user = null;
			$timeout   = 0;
			return false;

		}


		/* [3] Manage @timeout incrementation + @last_user
		=========================================================*/
		/* (1) If same as last -> increment @timeout */
		if( $last_user == $user['id'] )
			$timeout++;

		/* (2) If different -> reset @timeout to 0 */
		else
			$timeout = 0;


		/* [4] Manage action
		=========================================================*/
		/* (1) Try to process action */
		$performed = act($user);

		/* (2) If performed -> update chip according to new state */
		if( $performed ){

			// {1} Try to update state //
			$updateds = syscall(SOURCE_DIR.'/lib/global-state/update');

			// {2} If not updated -> error //
			if( !$updateds )
				slog("Cannot update chips to '{$gstate}'", 'mfrc522:loop');
			// {3} If updated -> success //
			else
				slog("Chips updated to '{$gstate}'", 'mfrc522:loop');

		/* (3) If not performed -> log error */
		}else
			slog("Cannot perform action by '$code' at timeout $timeout", 'mfrc522:loop');

		/* (4) Store user for next loop */
		$last_user = $user['id'];
		
	}









	/* [1] Set up daemon
	=========================================================*/
	/* (1) Set up */
	$exec = mfrc522_setup();

	/* (2) Manage error */
	if( $exec != 0 ){
		slog('cannot set up the daemon', 'mfrc522:loop');
		echo $exec;
		die($exec);
	}

	/* (3) Success message */
	slog('daemon started (loop)', 'mfrc522:loop');




	/* [2] Daemon loop
	=========================================================*/
	while( true ){

		$start_ts = microtime(true);

		mfrc522_loop();

		while( microtime(true) - $start_ts < 0.5 );
	
	}
?>