package com.jenkov.nioserver.http;

import java.io.UnsupportedEncodingException;

/**
 * Project: <strong>java-nio-server</strong><br>
 * File: <strong>HttpUtil.java</strong><br>
 * Created: <strong>19 Oct 2015</strong><br>
 *
 * @author jjenkov
 */
public class HttpUtil {

	private static final byte[]	GET		= new byte[] { 'G', 'E', 'T' };
	private static final byte[]	POST	= new byte[] { 'P', 'O', 'S', 'T' };
	private static final byte[]	PUT		= new byte[] { 'P', 'U', 'T' };
	private static final byte[]	HEAD	= new byte[] { 'H', 'E', 'A', 'D' };
	private static final byte[]	DELETE	= new byte[] { 'D', 'E', 'L', 'E', 'T', 'E' };

	@SuppressWarnings("unused")
	private static final byte[]	HOST			= new byte[] { 'H', 'o', 's', 't' };
	private static final byte[]	CONTENT_LENGTH	= new byte[] { 'C', 'o', 'n', 't', 'e', 'n', 't', '-', 'L', 'e', 'n', 'g', 't', 'h' };

	public static int parseHttpRequest(byte[] src, int startIndex, int endIndex, HttpHeaders httpHeaders) {

		/*
		 * int endOfHttpMethod = findNext(src, startIndex, endIndex, (byte) ' ');
		 * if(endOfHttpMethod == -1) return false;
		 * resolveHttpMethod(src, startIndex, httpHeaders);
		 */

		// parse HTTP request line
		int endOfFirstLine = findNextLineBreak(src, startIndex, endIndex);
		if (endOfFirstLine == -1) return -1;

		// parse HTTP headers
		int	prevEndOfHeader	= endOfFirstLine + 1;
		int	endOfHeader		= findNextLineBreak(src, prevEndOfHeader, endIndex);

		while (endOfHeader != -1 && endOfHeader != prevEndOfHeader + 1) { // prevEndOfHeader + 1 = end of previous header + 2 (+2 = CR + LF)

			if (matches(src, prevEndOfHeader, CONTENT_LENGTH)) {
				try {
					findContentLength(src, prevEndOfHeader, endIndex, httpHeaders);
				} catch (UnsupportedEncodingException e) {
					e.printStackTrace();
				}
			}

			prevEndOfHeader	= endOfHeader + 1;
			endOfHeader		= findNextLineBreak(src, prevEndOfHeader, endIndex);
		}

		if (endOfHeader == -1) { return -1; }

		// check that byte array contains full HTTP message.
		int	bodyStartIndex	= endOfHeader + 1;
		int	bodyEndIndex	= bodyStartIndex + httpHeaders.contentLength;

		if (bodyEndIndex <= endIndex) {
			// byte array contains a full HTTP request
			httpHeaders.bodyStartIndex	= bodyStartIndex;
			httpHeaders.bodyEndIndex	= bodyEndIndex;
			return bodyEndIndex;
		}

		return -1;
	}

	private static void findContentLength(byte[] src, int startIndex, int endIndex, HttpHeaders httpHeaders) throws UnsupportedEncodingException {
		int indexOfColon = findNext(src, startIndex, endIndex, (byte) ':');

		// skip spaces after colon
		int index = indexOfColon + 1;
		while (src[index] == ' ') {
			index++;
		}

		int		valueStartIndex	= index;
		int		valueEndIndex	= index;
		boolean	endOfValueFound	= false;

		while (index < endIndex && !endOfValueFound) {
			switch (src[index]) {
				case '0':
				case '1':
				case '2':
				case '3':
				case '4':
				case '5':
				case '6':
				case '7':
				case '8':
				case '9':
					index++;
					break;
				default:
					endOfValueFound = true;
					valueEndIndex = index;
			}
		}
		httpHeaders.contentLength = Integer.parseInt(new String(src, valueStartIndex, valueEndIndex - valueStartIndex, "UTF-8"));
	}

	public static int findNext(byte[] src, int startIndex, int endIndex, byte value) {
		for (int index = startIndex; index < endIndex; index++)
			if (src[index] == value) return index;
		return -1;
	}

	public static int findNextLineBreak(byte[] src, int startIndex, int endIndex) {
		for (int index = startIndex; index < endIndex; index++)
			if (src[index] == '\n') if (src[index - 1] == '\r') return index;
		return -1;
	}

	public static void resolveHttpMethod(byte[] src, int startIndex, HttpHeaders httpHeaders) {
		if (matches(src, startIndex, GET)) {
			httpHeaders.httpMethod = HttpHeaders.HTTP_METHOD_GET;
			return;
		}
		if (matches(src, startIndex, POST)) {
			httpHeaders.httpMethod = HttpHeaders.HTTP_METHOD_POST;
			return;
		}
		if (matches(src, startIndex, PUT)) {
			httpHeaders.httpMethod = HttpHeaders.HTTP_METHOD_PUT;
			return;
		}
		if (matches(src, startIndex, HEAD)) {
			httpHeaders.httpMethod = HttpHeaders.HTTP_METHOD_HEAD;
			return;
		}
		if (matches(src, startIndex, DELETE)) {
			httpHeaders.httpMethod = HttpHeaders.HTTP_METHOD_DELETE;
			return;
		}
	}

	public static boolean matches(byte[] src, int offset, byte[] value) {
		for (int i = offset, n = 0; n < value.length; i++, n++)
			if (src[i] != value[n]) return false;
		return true;
	}
}