/**
 * @fileoverview TSM - A TypeScript vector and matrix math library
 * @author Matthias Ferch
 * @version 0.6
 */

/*
 * Copyright (c) 2012 Matthias Ferch
 *
 * Project homepage: https://github.com/matthiasferch/tsm
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 *    1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 *
 *    2. Altered source versions must be plainly marked as such, and must not
 *    be misrepresented as being the original software.
 *
 *    3. This notice may not be removed or altered from any source
 *    distribution.
 */


import {vec2} from './vec2';

export class mat2
{
    static identity = new mat2().setIdentity();

    private values = new Float32Array(4);

    static product(m1: mat2, m2: mat2, result: mat2 | null = null): mat2
    {
        const a11 = m1.at(0),
            a12 = m1.at(1),
            a21 = m1.at(2),
            a22 = m1.at(3);

        if (result)
        {
            result.init([
                a11 * m2.at(0) + a12 * m2.at(2),
                a11 * m2.at(1) + a12 * m2.at(3),
                a21 * m2.at(0) + a22 * m2.at(2),
                a21 * m2.at(1) + a22 * m2.at(3)
            ]);

            return result;
        }
        else
        {
            return new mat2([
                a11 * m2.at(0) + a12 * m2.at(2),
                a11 * m2.at(1) + a12 * m2.at(3),
                a21 * m2.at(0) + a22 * m2.at(2),
                a21 * m2.at(1) + a22 * m2.at(3)
            ]);
        }
    }

    constructor(values: number[] | null = null)
    {
        if (values)
        {
            this.init(values);
        }
    }

    at(index: number): number
    {
        return this.values[index];
    }

    init(values: number[]): mat2
    {
        for (let i = 0; i < 4; i++)
        {
            this.values[i] = values[i];
        }

        return this;
    }

    reset(): void
    {
        for (let i = 0; i < 4; i++)
        {
            this.values[i] = 0;
        }
    }

    copy(dest: mat2 | null = null): mat2
    {
        if (!dest)
        {
            dest = new mat2();
        }

        for (let i = 0; i < 4; i++)
        {
            dest.values[i] = this.values[i];
        }

        return dest;
    }

    all(): number[]
    {
        const data: number[] = [];
        for (let i = 0; i < 4; i++)
        {
            data[i] = this.values[i];
        }

        return data;
    }

    row(index: number): number[]
    {
        return [
            this.values[index * 2 + 0],
            this.values[index * 2 + 1]
        ];
    }

    col(index: number): number[]
    {
        return [
            this.values[index],
            this.values[index + 2]
        ];
    }

    equals(matrix: mat2, threshold = EPSILON): boolean
    {
        for (let i = 0; i < 4; i++)
        {
            if (Math.abs(this.values[i] - matrix.at(i)) > threshold)
            {
                return false;
            }
        }

        return true;
    }

    determinant(): number
    {
        return this.values[0] * this.values[3] - this.values[2] * this.values[1];
    }

    setIdentity(): mat2
    {
        this.values[0] = 1;
        this.values[1] = 0;
        this.values[2] = 0;
        this.values[3] = 1;

        return this;
    }

    transpose(): mat2
    {
        const temp = this.values[1];

        this.values[1] = this.values[2];
        this.values[2] = temp;

        return this;
    }

    inverse(): mat2 | null
    {
        let det = this.determinant();

        if (!det)
        {
            return null;
        }

        det = 1.0 / det;

        this.values[0] = det * (this.values[3]);
        this.values[1] = det * (-this.values[1]);
        this.values[2] = det * (-this.values[2]);
        this.values[3] = det * (this.values[0]);

        return this;
    }

    multiply(matrix: mat2): mat2
    {
        const a11 = this.values[0],
            a12 = this.values[1],
            a21 = this.values[2],
            a22 = this.values[3];

        this.values[0] = a11 * matrix.at(0) + a12 * matrix.at(2);
        this.values[1] = a11 * matrix.at(1) + a12 * matrix.at(3);
        this.values[2] = a21 * matrix.at(0) + a22 * matrix.at(2);
        this.values[3] = a21 * matrix.at(1) + a22 * matrix.at(3);

        return this;
    }

    rotate(angle: number): mat2
    {
        const a11 = this.values[0],
            a12 = this.values[1],
            a21 = this.values[2],
            a22 = this.values[3];

        const sin = Math.sin(angle),
            cos = Math.cos(angle);

        this.values[0] = a11 * cos + a12 * sin;
        this.values[1] = a11 * -sin + a12 * cos;
        this.values[2] = a21 * cos + a22 * sin;
        this.values[3] = a21 * -sin + a22 * cos;

        return this;
    }

    multiplyVec2(vector: vec2, result: vec2 | null = null): vec2
    {
        const x = vector.x,
            y = vector.y;

        if (result)
        {
            result.xy = [
                x * this.values[0] + y * this.values[1],
                x * this.values[2] + y * this.values[3]
            ];

            return result;
        }
        else
        {
            return new vec2([
                x * this.values[0] + y * this.values[1],
                x * this.values[2] + y * this.values[3]
            ]);
        }
    }

    scale(vector: vec2): mat2
    {
        const a11 = this.values[0],
            a12 = this.values[1],
            a21 = this.values[2],
            a22 = this.values[3];

        const x = vector.x,
            y = vector.y;

        this.values[0] = a11 * x;
        this.values[1] = a12 * y;
        this.values[2] = a21 * x;
        this.values[3] = a22 * y;

        return this;
    }
}