/**
 * Renders a given map
 *
 *  Copyright (C) 2012  Mike Gerwitz
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


/**
 * Renders a map to a canvas
 */
ltjs.MapRender = Class( 'MapRender',
{
    /**
     * Tunnel bitmask
     * @type {number}
     */
    'private const _TMASK': 0x40,


    /**
     * 2d context to which map should be drawn
     * @type {CanvasRenderingContext2d}
     */
    'private _ctx': null,

    /**
     * 2d context to which masked game objects should be drawn
     * @type {CanvasRenderingContext2d}
     */
    'private _ctxObj': null,

    /**
     * Tile set to be rendered
     * @type {Object}
     */
    'private _tiles': {},

    /**
     * Maps each "game object" in the map to a tile id
     * TODO: abstract
     * @type {Array.<string>}
     */
    'private _objMap': [
        'dirt', 'tup', 'base', 'water', 'block', 'mblock', 'brick',
        'atup', 'atright', 'atdown', 'atleft', 'mirrorul', 'mirrorur',
        'mirrordr', 'mirrordl', 'owup', 'owright', 'owdown', 'owleft',
        'cblock', 'rmirrorul', 'rmirrorur', 'rmirrordr', 'rmirrordl',
        'ice', 'thinice'
    ],

    /**
     * Colors used to identify tunnels
     *
     * These colors will be rendered in the background and will bleed through
     * the transparent portions of the tile. We use explicit HEX codes rather
     * than CSS color names because environments may vary the colors used.
     *
     * Taken from ColorList in LTANK2.C in the original sources. Note that there
     * is an endianness difference.
     *
     * TODO: abstract
     *
     * @type {Array.<string>}
     */
    'private _tunnelColors': [
        '#ff0000', '#00ff00', '#0000ff', '#00ffff', // r g b c
        '#ffff00', '#ff00ff', '#ffffff', '#808080'  // y m w b
    ],


    /**
     * Initialize renderer with a canvas context and a tile set
     *
     * An additional canvas of equal dimensions will be created and laid atop of
     * the provided canvas to render masked game objects.
     *
     * @param  {CanvasRenderingContext2d}  ctx    canvas 2d context
     * @param  {Object}                    tiles  tile set to render
     */
    __construct: function( ctx, tiles )
    {
        this._ctx   = ctx;
        this._tiles = tiles;

        this._ctxObj = this._getObjCanvas();
    },


    /**
     * Create the overlaying canvas for masked elements and return a 2d context
     *
     * @return  {CanvasRenderingContext2d}  2d context for new canvas element
     */
    'private _getObjCanvas': function()
    {
        var canvas     = this._ctx.canvas,
            canvas_obj = document.createElement( 'canvas' );

        // mimic the dimensions and positions of the original canvas
        canvas_obj.style.position = 'absolute';
        canvas_obj.width          = canvas.width;
        canvas_obj.height         = canvas.height;
        canvas_obj.style.left     = ( canvas.offsetLeft + 'px' );
        canvas_obj.style.top      = ( canvas.offsetTop + 'px' );

        // append the new canvas to the DOM under the same parent
        canvas.parentNode.appendChild( canvas_obj );

        return canvas_obj.getContext( '2d' );
    },


    /**
     * Render the provided map
     *
     * @param  {Map}  map  map to render
     *
     * @return  {MapRender}  self
     */
    'public render': function( map )
    {
        if ( !( Class.isA( ltjs.Map, map ) ) )
        {
            throw TypeError( 'Invalid Map provided' );
        }

        var objs  = map.getObjects(),
            size  = map.getDimensions(),
            i     = objs.length,
            tiles = this._tiles,

            // get the width and height from one of the tiles
            t = this._tiles.dirt.data,
            w = t.width,
            h = t.height;

        // render each object (remember, we're dealing with columns, not rows;
        // see Map.getObjects())
        while ( i-- )
        {
            var oid = objs[ i ],
                tid = this._objMap[ oid ],
                x   = ( Math.floor( i / size[ 0 ] ) * w ),
                y   = ( ( i % size[ 1 ] ) * h );

            // tunnels are handled a bit differently than other objects
            if ( this._isTunnel( oid ) )
            {
                this._renderTunnel( oid, x, y );
                continue;
            }

            this._drawTile( tid, x, y );
        }

        return this;
    },


    /**
     * Draw the tile identified by the given id
     *
     * The tile will be drawn to the appropriate canvas depending on whether or
     * not it has been masked. If it does have a mask, it will be drawn to the
     * overlaying canvas and the dirt tile will be drawn underneath it.
     *
     * @param  {string}  tid  tile id
     * @param  {number}  x    left position
     * @param  {number}  y    top position
     *
     * @return  {undefined}
     */
    'private _drawTile': function( tid, x, y )
    {
        var tile = this._tiles[ tid ],
            ctx  = ( tile.masked ) ? this._ctxObj : this._ctx;

        ctx.putImageData( this._tiles[ tid ].first.data, x, y );

        if ( tile.masked )
        {
            this._ctx.putImageData( this._tiles.dirt.data, x, y );
        }
    },


    /**
     * Returns whether the given object id is a tunnel
     *
     * @param  {number}  oid  object id
     *
     * @return  {boolean}  TRUE if object is a tunnel, otherwise false
     */
    'private _isTunnel': function( oid )
    {
        return ( oid & this.__self.$( '_TMASK' ) );
    },


    /**
     * Render the given tunnel
     *
     * The tunnel background color (which will peek through the mask) is
     * rendered to the base canvas, whereas the tunnel tile itself is rendered
     * on the overlaying canvas.
     *
     * @param  {number}  oid  tunnel object id
     * @param  {number}  x    left position
     * @param  {number}  y    top position
     *
     * @return  {undefined}
     */
    'private _renderTunnel': function( oid, x, y )
    {
        // get the tunnel id by stripping off the tunnel bitmask and grab the
        // associated color
        var tunnel_id = ( ( +oid ^ this.__self.$( '_TMASK' ) ) / 2 ),
            color     = this._tunnelColors[ tunnel_id ] || 'black';

        // fill tile with the appropriate background color for this tile
        this._ctx.fillStyle = color;
        this._ctx.fillRect( x, y, 32, 32 );

        // render the tile to the overlay canvas
        this._ctxObj.putImageData( this._tiles.tunnel.data, x, y );
    }
} );