import { continueRender, delayRender, RemotionVideoProps } from 'remotion';

import { GlslVarType, setUniform } from './glUtils';

export interface VideoShaderOptions {
    variables?: {
        type: GlslVarType;
        name: string;
    }[];
}

export const ATTR_UV = 'a_uv';
export const ATTR_POS = 'a_pos';

export const VAR_UV = 'uv';
export const VAR_XY = 'xy';

const defaultVertexShader = `
precision highp float;

attribute vec4 ${ATTR_POS};
attribute vec2 ${ATTR_UV};

varying vec2 ${VAR_UV};
varying vec2 ${VAR_XY};

uniform vec2 size;

void main(void) {
    gl_Position = ${ATTR_POS};
    ${VAR_UV} = ${ATTR_UV};
    ${VAR_XY} = vec2(
        (${ATTR_POS}.x * 0.5 + 0.5) * float(size.x),
        (0.5 - ${ATTR_POS}.y * 0.5) * float(size.y)
    );
}`;

export function createFragmentShader(content: string, options: VideoShaderOptions = {}) {
    const { variables } = options;
    return `
precision highp float;

varying vec2 ${VAR_UV};
varying vec2 ${VAR_XY};

uniform vec2 size;
uniform int frame;
uniform float t;
uniform sampler2D u_tex;

${!variables ? '' : variables.map(v => `uniform ${v.type} ${v.name};`).join('\n')}

vec2 xyToUv(in vec2 _xy) {
    return vec2(_xy.x, _xy.y) / size;
}

void main(void) {
${content}
}`;
}

export const defaultShader = createFragmentShader(`gl_FragColor = vec4(texture2D(u_tex, ${VAR_UV}).rgb, 1);`);

// Example for animation using frame uniform variable inside shader
// float r = radius * (sin(float(frame) * 0.02) * 0.5 + 0.5);

export const swirlShader = createFragmentShader(`
    vec2 cUV = ${VAR_XY} - size / 2. - offset;
    float dist = length(cUV);
    if (dist < radius)
    {
        float percent = (radius - dist) / radius;
        float theta = percent * percent * angle * 8.0;
        float s = sin(theta);
        float c = cos(theta);
        cUV = vec2(dot(cUV, vec2(c, -s)), dot(cUV, vec2(s, c)));
    }
    cUV = xyToUv(cUV + offset + size / 2.); // / vec2(width, height) + vec2(0.5, 0.5);
    gl_FragColor = vec4(texture2D(u_tex, cUV).rgb, 0.5);`,
    {
        variables: [
            { type: 'float', name: 'radius' },
            { type: 'float', name: 'angle' },
            { type: 'vec2', name: 'offset' },
        ],
    }
);

export interface ShaderVariable {
    name: string;
    type: GlslVarType;
    value: any;
}

export default class WebGlVideoProcessor {

    public readonly gl: WebGLRenderingContext;

    private _stop?: () => void;

    private _texture: WebGLTexture;

    private _program: WebGLProgram;
    private _vertexShader: WebGLShader;
    private _fragmentShader: WebGLShader;
    private _verticesBuffer: WebGLBuffer;
    private _uvBuffer: WebGLBuffer;

    private _delayRenderHandle?: number;

    private _videoLoaded = false;

    private _variables: ShaderVariable[] = [];

    private _frame: number = 0;

    constructor(
        public readonly canvas: HTMLCanvasElement,
        public readonly video: HTMLVideoElement,
        fragmentShader = defaultShader,
        vertexShader = defaultVertexShader
    ) {
        const gl = canvas.getContext('webgl', { preserveDrawingBuffer: true });
        if (!gl) {
            throw new Error('Error initializing WebGl context');
        }
        this.gl = gl;

        // Initialize resources
        this._texture = this._createTexture();

        this._verticesBuffer = this._createBuffer([
            1.0, 1.0,
            0.0, -1.0,
            1.0, 0.0,
            //
            1.0, -1.0,
            0.0, -1.0,
            -1.0, 0.0
        ]);

        this._uvBuffer = this._createBuffer([
            1.0, 0.0,
            0.0, 0.0,
            1.0, 1.0,
            0.0, 1.0
        ]);

        this._vertexShader = this._createShader(vertexShader, gl.VERTEX_SHADER);
        this._fragmentShader = this._createShader(fragmentShader, gl.FRAGMENT_SHADER);
        this._program = this._createProgram();

        this.videoChanged();
    }

    private delayRender() {
        if (!this._delayRenderHandle && this.isRunning) {
            this._delayRenderHandle = delayRender();
        }
    }

    private continueRender() {
        if (this._delayRenderHandle) {
            continueRender(this._delayRenderHandle);
            this._delayRenderHandle = undefined;
        }
    }

    private _createBuffer(data: number[]) {
        const gl = this.gl;
        const buffer = gl.createBuffer();
        if (!buffer) {
            throw new Error('Error creating vertex buffer');
        }
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(data), gl.STATIC_DRAW);
        return buffer;
    }

    private _createTexture() {
        const gl = this.gl;
        const texture = gl.createTexture();
        if (!texture) {
            throw new Error('Error creating texture');
        }
        gl.bindTexture(gl.TEXTURE_2D, texture);
        // Fill with yellow pixel
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, 1, 1, 0, gl.RGB, gl.UNSIGNED_BYTE, new Uint8Array([255, 255, 0]));
        // Set texture parameters
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
        return texture;
    }

    private _createShader(source: string, type: number) {
        const gl = this.gl;
        const shader = gl.createShader(type);
        if (!shader) {
            throw new Error('Error creating shader');
        }
        gl.shaderSource(shader, source);
        gl.compileShader(shader);
        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            console.debug('Shader source:', source.split('\n').map((l, idx) => `${idx + 1}: ${l}`).join('\n'));
            throw new Error('Error compiling shader: ' + gl.getShaderInfoLog(shader));
        }
        return shader;
    }

    private _createProgram() {
        if (!this._vertexShader || !this._fragmentShader) {
            throw new Error();
        }
        const gl = this.gl;
        const program = gl.createProgram();
        if (!program) {
            throw new Error('Error creating program');
        }

        gl.attachShader(program, this._vertexShader);
        gl.attachShader(program, this._fragmentShader);

        // Link program
        gl.linkProgram(program);
        if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
            throw new Error('Error linking shader program: ' + gl.getProgramInfoLog(program));
        }

        // Set program parameters

        const posAttribute = gl.getAttribLocation(program, ATTR_POS);
        gl.bindBuffer(gl.ARRAY_BUFFER, this._verticesBuffer);
        gl.enableVertexAttribArray(posAttribute);
        gl.vertexAttribPointer(posAttribute, 3, gl.FLOAT, false, 0, 0);

        const uvAttribute = gl.getAttribLocation(program, ATTR_UV);
        gl.bindBuffer(gl.ARRAY_BUFFER, this._uvBuffer);
        gl.enableVertexAttribArray(uvAttribute);
        gl.vertexAttribPointer(uvAttribute, 2, gl.FLOAT, false, 0, 0);

        // Use new program
        gl.useProgram(program);
        return program;
    }

    public get isRunning() {
        return Boolean(this._stop);
    }

    public start() {
        let stopped = false;
        this._stop = () => { stopped = true; };

        let lastTime = -1;
        const update = () => {
            if (stopped) {
                return;
            }
            if (this._videoLoaded) {
                // Check, if we actually have to update the frame
                if (lastTime !== this.video.currentTime) {
                    lastTime = this.video.currentTime;
                    this.render();
                }
                // Continue render
                this.continueRender();
            }
            window.requestAnimationFrame(update);
        };
        window.requestAnimationFrame(update);
    }

    private render() {
        const gl = this.gl;
        const video = this.video;

        // Update video texture
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, video);

        // Update variables
        for (const v of this._variables) {
            setUniform(gl, gl.getUniformLocation(this._program, v.name), v.type, v.value);
        }
        setUniform(gl, gl.getUniformLocation(this._program, 'frame'), 'int', this._frame);
        setUniform(gl, gl.getUniformLocation(this._program, 'size'), 'vec2', [video.videoWidth, video.videoHeight]);
        setUniform(gl, gl.getUniformLocation(this._program, 't'), 'float', video.currentTime);

        gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
    }

    public stop() {
        this._stop?.();
        this.continueRender();
    }

    public videoChanged() {
        const gl = this.gl;
        const canvas = this.canvas;
        const video = this.video;
        this._videoLoaded = false;
        const delayRenderHandle = delayRender();
        video.addEventListener('loadeddata', () => {
            // Set canvas size
            canvas.width = video.videoWidth;
            canvas.height = video.videoHeight;
            gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

            continueRender(delayRenderHandle);
            this._videoLoaded = true;
        }, { once: true });
    }

    public setFrame(frame: number) {
        this.delayRender();
        this._frame = frame;
    }

    public setShader(fragmentShader = defaultShader, vertexShader = defaultVertexShader) {
        this._vertexShader = this._createShader(vertexShader, this.gl.VERTEX_SHADER);
        this._fragmentShader = this._createShader(fragmentShader, this.gl.FRAGMENT_SHADER);
        this._program = this._createProgram();
    }

    public setVariables(variables: ShaderVariable[] | undefined) {
        this._variables = variables || [];
    }
}