import { Camera } from './Camera';
import { Object3D } from '../core/Object3D';
import { _Math } from '../math/Math';

/**
 * @author mrdoob / http://mrdoob.com/
 * @author greggman / http://games.greggman.com/
 * @author zz85 / http://www.lab4games.net/zz85/blog
 * @author tschw
 */

function PerspectiveCamera( fov, aspect, near, far ) {

	Camera.call( this );

	this.type = 'PerspectiveCamera';

	this.fov = fov !== undefined ? fov : 50;
	this.zoom = 1;

	this.near = near !== undefined ? near : 0.1;
	this.far = far !== undefined ? far : 2000;
	this.focus = 10;

	this.aspect = aspect !== undefined ? aspect : 1;
	this.view = null;

	this.filmGauge = 35;	// width of the film (default in millimeters)
	this.filmOffset = 0;	// horizontal film offset (same unit as gauge)

	this.updateProjectionMatrix();

}

PerspectiveCamera.prototype = Object.assign( Object.create( Camera.prototype ), {

	constructor: PerspectiveCamera,

	isPerspectiveCamera: true,

	copy: function ( source ) {

		Camera.prototype.copy.call( this, source );

		this.fov = source.fov;
		this.zoom = source.zoom;

		this.near = source.near;
		this.far = source.far;
		this.focus = source.focus;

		this.aspect = source.aspect;
		this.view = source.view === null ? null : Object.assign( {}, source.view );

		this.filmGauge = source.filmGauge;
		this.filmOffset = source.filmOffset;

		return this;

	},

	/**
	 * Sets the FOV by focal length in respect to the current .filmGauge.
	 *
	 * The default film gauge is 35, so that the focal length can be specified for
	 * a 35mm (full frame) camera.
	 *
	 * Values for focal length and film gauge must have the same unit.
	 */
	setFocalLength: function ( focalLength ) {

		// see http://www.bobatkins.com/photography/technical/field_of_view.html
		var vExtentSlope = 0.5 * this.getFilmHeight() / focalLength;

		this.fov = _Math.RAD2DEG * 2 * Math.atan( vExtentSlope );
		this.updateProjectionMatrix();

	},

	/**
	 * Calculates the focal length from the current .fov and .filmGauge.
	 */
	getFocalLength: function () {

		var vExtentSlope = Math.tan( _Math.DEG2RAD * 0.5 * this.fov );

		return 0.5 * this.getFilmHeight() / vExtentSlope;

	},

	getEffectiveFOV: function () {

		return _Math.RAD2DEG * 2 * Math.atan(
				Math.tan( _Math.DEG2RAD * 0.5 * this.fov ) / this.zoom );

	},

	getFilmWidth: function () {

		// film not completely covered in portrait format (aspect < 1)
		return this.filmGauge * Math.min( this.aspect, 1 );

	},

	getFilmHeight: function () {

		// film not completely covered in landscape format (aspect > 1)
		return this.filmGauge / Math.max( this.aspect, 1 );

	},

	/**
	 * Sets an offset in a larger frustum. This is useful for multi-window or
	 * multi-monitor/multi-machine setups.
	 *
	 * For example, if you have 3x2 monitors and each monitor is 1920x1080 and
	 * the monitors are in grid like this
	 *
	 *   +---+---+---+
	 *   | A | B | C |
	 *   +---+---+---+
	 *   | D | E | F |
	 *   +---+---+---+
	 *
	 * then for each monitor you would call it like this
	 *
	 *   var w = 1920;
	 *   var h = 1080;
	 *   var fullWidth = w * 3;
	 *   var fullHeight = h * 2;
	 *
	 *   --A--
	 *   camera.setOffset( fullWidth, fullHeight, w * 0, h * 0, w, h );
	 *   --B--
	 *   camera.setOffset( fullWidth, fullHeight, w * 1, h * 0, w, h );
	 *   --C--
	 *   camera.setOffset( fullWidth, fullHeight, w * 2, h * 0, w, h );
	 *   --D--
	 *   camera.setOffset( fullWidth, fullHeight, w * 0, h * 1, w, h );
	 *   --E--
	 *   camera.setOffset( fullWidth, fullHeight, w * 1, h * 1, w, h );
	 *   --F--
	 *   camera.setOffset( fullWidth, fullHeight, w * 2, h * 1, w, h );
	 *
	 *   Note there is no reason monitors have to be the same size or in a grid.
	 */
	setViewOffset: function ( fullWidth, fullHeight, x, y, width, height ) {

		this.aspect = fullWidth / fullHeight;

		this.view = {
			fullWidth: fullWidth,
			fullHeight: fullHeight,
			offsetX: x,
			offsetY: y,
			width: width,
			height: height
		};

		this.updateProjectionMatrix();

	},

	clearViewOffset: function() {

		this.view = null;
		this.updateProjectionMatrix();

	},

	updateProjectionMatrix: function () {

		var near = this.near,
			top = near * Math.tan(
					_Math.DEG2RAD * 0.5 * this.fov ) / this.zoom,
			height = 2 * top,
			width = this.aspect * height,
			left = - 0.5 * width,
			view = this.view;

		if ( view !== null ) {

			var fullWidth = view.fullWidth,
				fullHeight = view.fullHeight;

			left += view.offsetX * width / fullWidth;
			top -= view.offsetY * height / fullHeight;
			width *= view.width / fullWidth;
			height *= view.height / fullHeight;

		}

		var skew = this.filmOffset;
		if ( skew !== 0 ) left += near * skew / this.getFilmWidth();

		this.projectionMatrix.makePerspective( left, left + width, top, top - height, near, this.far );

	},

	toJSON: function ( meta ) {

		var data = Object3D.prototype.toJSON.call( this, meta );

		data.object.fov = this.fov;
		data.object.zoom = this.zoom;

		data.object.near = this.near;
		data.object.far = this.far;
		data.object.focus = this.focus;

		data.object.aspect = this.aspect;

		if ( this.view !== null ) data.object.view = Object.assign( {}, this.view );

		data.object.filmGauge = this.filmGauge;
		data.object.filmOffset = this.filmOffset;

		return data;

	}

} );


export { PerspectiveCamera };
