/**
 * @author tschw
 */

import { Matrix3 } from '../../math/Matrix3';
import { Plane } from '../../math/Plane';

function WebGLClipping() {

	var scope = this,

		globalState = null,
		numGlobalPlanes = 0,
		localClippingEnabled = false,
		renderingShadows = false,

		plane = new Plane(),
		viewNormalMatrix = new Matrix3(),

		uniform = { value: null, needsUpdate: false };

	this.uniform = uniform;
	this.numPlanes = 0;

	this.init = function( planes, enableLocalClipping, camera ) {

		var enabled =
			planes.length !== 0 ||
			enableLocalClipping ||
			// enable state of previous frame - the clipping code has to
			// run another frame in order to reset the state:
			numGlobalPlanes !== 0 ||
			localClippingEnabled;

		localClippingEnabled = enableLocalClipping;

		globalState = projectPlanes( planes, camera, 0 );
		numGlobalPlanes = planes.length;

		return enabled;

	};

	this.beginShadows = function() {

		renderingShadows = true;
		projectPlanes( null );

	};

	this.endShadows = function() {

		renderingShadows = false;
		resetGlobalState();

	};

	this.setState = function( planes, clipShadows, camera, cache, fromCache ) {

		if ( ! localClippingEnabled ||
				planes === null || planes.length === 0 ||
				renderingShadows && ! clipShadows ) {
			// there's no local clipping

			if ( renderingShadows ) {
				// there's no global clipping

				projectPlanes( null );

			} else {

				resetGlobalState();
			}

		} else {

			var nGlobal = renderingShadows ? 0 : numGlobalPlanes,
				lGlobal = nGlobal * 4,

				dstArray = cache.clippingState || null;

			uniform.value = dstArray; // ensure unique state

			dstArray = projectPlanes( planes, camera, lGlobal, fromCache );

			for ( var i = 0; i !== lGlobal; ++ i ) {

				dstArray[ i ] = globalState[ i ];

			}

			cache.clippingState = dstArray;
			this.numPlanes += nGlobal;

		}


	};

	function resetGlobalState() {

		if ( uniform.value !== globalState ) {

			uniform.value = globalState;
			uniform.needsUpdate = numGlobalPlanes > 0;

		}

		scope.numPlanes = numGlobalPlanes;

	}

	function projectPlanes( planes, camera, dstOffset, skipTransform ) {

		var nPlanes = planes !== null ? planes.length : 0,
			dstArray = null;

		if ( nPlanes !== 0 ) {

			dstArray = uniform.value;

			if ( skipTransform !== true || dstArray === null ) {

				var flatSize = dstOffset + nPlanes * 4,
					viewMatrix = camera.matrixWorldInverse;

				viewNormalMatrix.getNormalMatrix( viewMatrix );

				if ( dstArray === null || dstArray.length < flatSize ) {

					dstArray = new Float32Array( flatSize );

				}

				for ( var i = 0, i4 = dstOffset;
									i !== nPlanes; ++ i, i4 += 4 ) {

					plane.copy( planes[ i ] ).
							applyMatrix4( viewMatrix, viewNormalMatrix );

					plane.normal.toArray( dstArray, i4 );
					dstArray[ i4 + 3 ] = plane.constant;

				}

			}

			uniform.value = dstArray;
			uniform.needsUpdate = true;

		}

		scope.numPlanes = nPlanes;
		return dstArray;

	}

}

export { WebGLClipping };
