<?php
# A PHP script to return book data.  Author: Marty Stepp
$BOOKS_FILE = "books.txt";

# Removes all characters except letters/numbers from query parameters
function filter_chars($str) {
	return preg_replace("/[^A-Za-z0-9_]*/", "", $str);
}


# main program
if (!isset($_SERVER["REQUEST_METHOD"]) || $_SERVER["REQUEST_METHOD"] != "GET") {
	header("HTTP/1.1 400 Invalid Request");
	die("ERROR 400: Invalid request - This service accepts only GET requests.");
}

$category = "";
$delay = 0;

if (isset($_GET["category"])) {
	$category = filter_chars($_GET["category"]);
}
if (isset($_GET["delay"])) {
	# for debugging; makes the service delay for a given number of seconds to test 'loading' animations
	$delay = max(0, min(60, (int) filter_chars($_GET["delay"])));
}

if ($delay > 0) {
	sleep($delay);
}

# read file
if (!file_exists($BOOKS_FILE)) {
	header("HTTP/1.1 500 Server Error");
	die("ERROR 500: Server error - Unable to read input file: $BOOKS_FILE");
}

header("Content-type: application/json");

# this code was written in the pre- json_encode days; alas
if ($category) {
	print "{\n  \"books\": [\n";
	$lines = file($BOOKS_FILE);
	
	# count matches (to avoid trailing comma later)
	$matches = 0;
	for ($i = 0; $i < count($lines); $i++) {
		list($title, $author, $book_category, $year, $price) = explode("|", trim($lines[$i]));
		if ($book_category == $category) {
			$matches++;
		}
	}
	
	$matches_found = 0;
	for ($i = 0; $i < count($lines); $i++) {
		# Bachelor Chow in 20 Minutes|Gloria Demartelaere|cooking|2005|30.00
		list($title, $author, $book_category, $year, $price) = explode("|", trim($lines[$i]));
		if ($book_category == $category) {
			# print it as XML
			print "    {\"category\": \"$category\", \"year\": $year, \"price\": $price, \n     \"title\": \"$title\", \"author\": \"$author\"}";
			if ($matches_found < $matches - 1) {
				print ",";
			}
			$matches_found++;
			print "\n";
		}
	}
	print "  ]\n}\n";
} else {
	print "{\n";
	print "\t\"categories\": [\n";
	$categories = array();
	$count = 0;
	foreach (file($BOOKS_FILE) as $line) {
		list($title, $author, $book_category, $year, $price) = explode("|", trim($line));
		if (!isset($categories[$book_category])) {
			$categories[$book_category] = 1;
			$count++;
		}
	}
	ksort($categories);
	foreach ($categories as $book_category => $useless) {
		$count--;
		print "\t\t\"$book_category\"";
		if ($count > 0) {
			print ",";
		}
		print "\n";
	}
	print "\t]\n";
	print "}\n";
}
?>