/*
 * 	6502 Based Virtual Computer
 *	Copyright (C) 2011  Scott C. Duensing <scott@jaegertech.com>
 *	
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *	
 *	This program 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 along
 *	with this program; if not, write to the Free Software Foundation, Inc.,
 *	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

// Our keyboard object.
function keyboard() {
	
	// OMFGWTFBBQ - http://unixpapa.com/js/key.html
	
	// --- Private variables.

	// Memory location for keyboard status.
	var MEMORY            = null;
	var MEMORY_START      = 0;
	var CHARACTER_ADDRESS = 0;
	var META_ADDRESS      = 0;
	
	// Keymaps.  Swiped from http://jonathan.tang.name/code/js_keycode
	var KEY_MAP         = {};
	var SHIFTED_SYMBOLS = {
		58: 59,     // : -> ;
		43: 61,     // = -> +
		60: 44,     // < -> ,
		95: 45,     // _ -> -
		62: 46,     // > -> .
		63: 47,     // ? -> /
		96: 192,    // ` -> ~
		124: 92,    // | -> \
		39: 222,    // ' -> 222
		34: 222,    // " -> 222
		33: 49,     // ! -> 1
		64: 50,     // @ -> 2
		35: 51,     // # -> 3
		36: 52,     // $ -> 4
		37: 53,     // % -> 5
		94: 54,     // ^ -> 6
		38: 55,     // & -> 7
		42: 56,     // * -> 8
		40: 57,     // ( -> 9
		41: 58,     // ) -> 0
		123: 91,    // { -> [
		125: 93     // } -> ]
	};
	var GECKO_IE_KEYMAP = {
		186: 59, // ;: in IE
		187: 61, // =+ in IE
		188: 44, // ,<
		109: 95, // -_ in Mozilla
		107: 61, // =+ in Mozilla
		189: 95, // -_ in IE
		190: 62, // .>
		191: 47, // /?
		192: 126, // `~
		219: 91, // {[
		220: 92, // \|
		221: 93 // }]
	};
	var OPERA_KEYMAP = {};
	
	// Browser detection taken from quirksmode.org
	var IS_WINDOWS   = navigator.platform.indexOf('Win') != -1;
	var IS_OPERA     = window.opera && window.opera.version() < '9.5';
	var IS_KONQUEROR = navigator.vendor && navigator.vendor.indexOf('KDE') != -1;
	var IS_ICAB      = navigator.vendor && navigator.vendor.indexOf('iCab') != -1;


	// --- Public methods.

	// Attach keyboard to DOM.
	this.attach = function(newMemory, newStartPosition) {
		MEMORY       = newMemory;
		MEMORY_START = newStartPosition;
		CHARACTER_ADDRESS = MEMORY_START;
		META_ADDRESS      = MEMORY_START + 1;
		// Determine key map.  
		if (IS_OPERA && IS_WINDOWS) {
			KEY_MAP = OPERA_KEYMAP;
		} else if (IS_OPERA || IS_KONQUEROR || IS_ICAB) {
			var unshift = [33, 64, 35, 36, 37, 94, 38, 42, 40, 41, 
			               58, 43, 60, 95, 62, 63, 124, 34];
			KEY_MAP = OPERA_KEYMAP;
			for (var i = 0; i < unshift.length; ++i) {
				KEY_MAP[unshift[i]] = SHIFTED_SYMBOLS[unshift[i]];
			}
		} else {
			// IE and Gecko are close enough that we can use the same map for both,
			// and the rest of the world (eg. Opera 9.50) seems to be standardizing
			// on them
			KEY_MAP = GECKO_IE_KEYMAP;
		}
		if (IS_KONQUEROR) {
			KEY_MAP[0] = 45;
			KEY_MAP[127] = 46;
			KEY_MAP[45] = 95;
		}
		// Hook browser for keydown events.
		document.onkeydown = function(e){
	        e = e || window.event;
			// Process the key press.
			var code = e.which || e.keyCode;
			var k = {
				code:  KEY_MAP[code] || code,
				shift: e.shiftKey,
				alt:   e.altKey,
				ctrl:  e.ctrlKey
			};
			// Un-funk the input.
			if (k.shift) {
				// Fix shifted characters.
				var oldC = "1234567890,/=[]\\';";
				var newC = "!@#$%^&*()<?+{}|\":";
				var x = oldC.indexOf(String.fromCharCode(k.code));
				if (x >= 0) k.code = newC.charCodeAt(x);
				if (k.code == 222) k.code = 34;  // "
			} else {
				// Fix unshifted characters.
				var oldC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ~_>";
				var newC = "abcdefghijklmnopqrstuvwxyz`-.";
				var x = oldC.indexOf(String.fromCharCode(k.code));
				if (x >= 0) k.code = newC.charCodeAt(x);
				if (k.code == 222) k.code = 39;  // '
			}
			// Write meta first.  Then we can process on the character being written.
			MEMORY.writeByte(META_ADDRESS, (k.alt * 4) + (k.ctrl * 2) + k.shift);
			// Ignore "naked" meta keys in the character address.
			if ((k.code != 16) && (k.code != 17) && (k.code != 18) && (k.code != 145) && (k.code != 146)) {
				MEMORY.writeByte(CHARACTER_ADDRESS, k.code);
			}
		};
	};

	// Fetch how much RAM the current settings will require.
	this.getMemoryNeeded = function() {
		return 2; // Complicated, huh?
	};
}