// pathfinder/client/src/aa-strategy.ts
//
// Copyright © 2017 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

import * as glmatrix from 'gl-matrix';

import {createFramebuffer, createFramebufferColorTexture, UniformMap} from './gl-utils';
import {createFramebufferDepthTexture} from './gl-utils';
import {Renderer} from './renderer';
import {unwrapNull} from './utils';
import {DemoView} from './view';

const SUBPIXEL_AA_KERNELS: {readonly [kind in SubpixelAAType]: glmatrix.vec4} = {
    // These intentionally do not precisely match what Core Graphics does (a Lanczos function),
    // because we don't want any ringing artefacts.
    'core-graphics': glmatrix.vec4.clone([0.033165660, 0.102074051, 0.221434336, 0.286651906]),
    'freetype': glmatrix.vec4.clone([0.0, 0.031372549, 0.301960784, 0.337254902]),
    'none': glmatrix.vec4.clone([0.0, 0.0, 0.0, 1.0]),
};

export type AntialiasingStrategyName = 'none' | 'ssaa' | 'xcaa';

export type DirectRenderingMode = 'none' | 'conservative' | 'color';

export type SubpixelAAType = 'none' | 'freetype' | 'core-graphics';

export type GammaCorrectionMode = 'off' | 'on';

export type StemDarkeningMode = 'none' | 'dark';

export interface TileInfo {
    size: glmatrix.vec2;
    position: glmatrix.vec2;
}

export abstract class AntialiasingStrategy {
    // The type of direct rendering that should occur, if any.
    abstract readonly directRenderingMode: DirectRenderingMode;

    // How many rendering passes this AA strategy requires.
    abstract readonly passCount: number;

    protected subpixelAA: SubpixelAAType;

    constructor(subpixelAA: SubpixelAAType) {
        this.subpixelAA = subpixelAA;
    }

    // Prepares any OpenGL data. This is only called on startup and canvas resize.
    init(renderer: Renderer): void {
        this.setFramebufferSize(renderer);
    }

    // Uploads any mesh data. This is called whenever a new set of meshes is supplied.
    abstract attachMeshes(renderer: Renderer): void;

    // This is called whenever the framebuffer has changed.
    abstract setFramebufferSize(renderer: Renderer): void;

    // Returns the transformation matrix that should be applied when directly rendering.
    abstract get transform(): glmatrix.mat4;

    // Called before rendering.
    //
    // Typically, this redirects rendering to a framebuffer of some sort.
    abstract prepareForRendering(renderer: Renderer): void;

    // Called before directly rendering.
    //
    // Typically, this redirects rendering to a framebuffer of some sort.
    abstract prepareForDirectRendering(renderer: Renderer): void;

    // Called before directly rendering a single object.
    abstract prepareToRenderObject(renderer: Renderer, objectIndex: number): void;

    abstract finishDirectlyRenderingObject(renderer: Renderer, objectIndex: number): void;

    // Called after direct rendering.
    //
    // This usually performs the actual antialiasing.
    abstract antialiasObject(renderer: Renderer, objectIndex: number): void;

    // Called after antialiasing each object.
    abstract finishAntialiasingObject(renderer: Renderer, objectIndex: number): void;

    // Called before rendering each object directly.
    abstract resolveAAForObject(renderer: Renderer, objectIndex: number): void;

    // Called after antialiasing.
    //
    // This usually blits to the real framebuffer.
    abstract resolve(pass: number, renderer: Renderer): void;

    setSubpixelAAKernelUniform(renderer: Renderer, uniforms: UniformMap): void {
        const renderContext = renderer.renderContext;
        const gl = renderContext.gl;

        const kernel = SUBPIXEL_AA_KERNELS[this.subpixelAA];
        gl.uniform4f(uniforms.uKernel, kernel[0], kernel[1], kernel[2], kernel[3]);
    }

    worldTransformForPass(renderer: Renderer, pass: number): glmatrix.mat4 {
        return glmatrix.mat4.create();
    }
}

export class NoAAStrategy extends AntialiasingStrategy {
    framebufferSize: glmatrix.vec2;

    get passCount(): number {
        return 1;
    }

    constructor(level: number, subpixelAA: SubpixelAAType) {
        super(subpixelAA);
        this.framebufferSize = glmatrix.vec2.create();
    }

    attachMeshes(renderer: Renderer) {}

    setFramebufferSize(renderer: Renderer) {
        this.framebufferSize = renderer.destAllocatedSize;
    }

    get transform(): glmatrix.mat4 {
        return glmatrix.mat4.create();
    }

    prepareForRendering(renderer: Renderer): void {
        const renderContext = renderer.renderContext;
        const gl = renderContext.gl;
        gl.bindFramebuffer(gl.FRAMEBUFFER, renderer.destFramebuffer);
        gl.viewport(0, 0, this.framebufferSize[0], this.framebufferSize[1]);
        gl.disable(gl.SCISSOR_TEST);
    }

    prepareForDirectRendering(renderer: Renderer): void {}

    prepareToRenderObject(renderer: Renderer, objectIndex: number): void {
        const renderContext = renderer.renderContext;
        const gl = renderContext.gl;

        gl.bindFramebuffer(gl.FRAMEBUFFER, renderer.destFramebuffer);
        gl.viewport(0, 0, this.framebufferSize[0], this.framebufferSize[1]);
        gl.disable(gl.SCISSOR_TEST);
    }

    finishDirectlyRenderingObject(renderer: Renderer, objectIndex: number): void {}

    antialiasObject(renderer: Renderer, objectIndex: number): void {}

    finishAntialiasingObject(renderer: Renderer, objectIndex: number): void {}

    resolveAAForObject(renderer: Renderer): void {}

    resolve(pass: number, renderer: Renderer): void {}

    get directRenderingMode(): DirectRenderingMode {
        return 'color';
    }
}