/**
 * Copyright (c) 2019 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author Alexander Rose <alexander.rose@weirdbyte.de>
 */

import { createComputeRenderable, ComputeRenderable } from '../../renderable'
import { WebGLContext } from '../../webgl/context';
import { createComputeRenderItem } from '../../webgl/render-item';
import { Values, TextureSpec, UniformSpec } from '../../renderable/schema';
import { Texture, createTexture } from 'mol-gl/webgl/texture';
import { ShaderCode } from 'mol-gl/shader-code';
import { ValueCell } from 'mol-util';
import { QuadSchema, QuadValues } from '../util';
import { Vec2 } from 'mol-math/linear-algebra';
import { getHistopyramidSum } from './sum';
import { Framebuffer, createFramebuffer } from 'mol-gl/webgl/framebuffer';
import { isPowerOfTwo } from 'mol-math/misc';
import quad_vert from 'mol-gl/shader/quad.vert'
import reduction_frag from 'mol-gl/shader/histogram-pyramid/reduction.frag'

const HistopyramidReductionSchema = {
    ...QuadSchema,
    tPreviousLevel: TextureSpec('texture', 'rgba', 'float', 'nearest'),
    uSize: UniformSpec('f'),
    uTexSize: UniformSpec('f'),
}

let HistopyramidReductionRenderable: ComputeRenderable<Values<typeof HistopyramidReductionSchema>>
function getHistopyramidReductionRenderable(ctx: WebGLContext, initialTexture: Texture) {
    if (HistopyramidReductionRenderable) {
        ValueCell.update(HistopyramidReductionRenderable.values.tPreviousLevel, initialTexture)
        HistopyramidReductionRenderable.update()
        return HistopyramidReductionRenderable
    } else {
        const values: Values<typeof HistopyramidReductionSchema> = {
            ...QuadValues,
            tPreviousLevel: ValueCell.create(initialTexture),
            uSize: ValueCell.create(0),
            uTexSize: ValueCell.create(0),
        }

        const schema = { ...HistopyramidReductionSchema }
        const shaderCode = ShaderCode(quad_vert, reduction_frag)
        const renderItem = createComputeRenderItem(ctx, 'triangles', shaderCode, schema, values)

        HistopyramidReductionRenderable = createComputeRenderable(renderItem, values);
        return HistopyramidReductionRenderable
    }
}

type TextureFramebuffer = { texture: Texture, framebuffer: Framebuffer }
const LevelTexturesFramebuffers: TextureFramebuffer[] = []
function getLevelTextureFramebuffer(ctx: WebGLContext, level: number) {
    let textureFramebuffer  = LevelTexturesFramebuffers[level]
    const size = Math.pow(2, level)
    if (textureFramebuffer === undefined) {
        const texture = createTexture(ctx, 'image-float32', 'rgba', 'float', 'nearest')
        const framebuffer = createFramebuffer(ctx.gl, ctx.stats)
        texture.attachFramebuffer(framebuffer, 0)
        textureFramebuffer = { texture, framebuffer }
        textureFramebuffer.texture.define(size, size)
        LevelTexturesFramebuffers[level] = textureFramebuffer
    }
    return textureFramebuffer
}

function setRenderingDefaults(ctx: WebGLContext) {
    const { gl, state } = ctx
    state.disable(gl.CULL_FACE)
    state.disable(gl.BLEND)
    state.disable(gl.DEPTH_TEST)
    state.disable(gl.SCISSOR_TEST)
    state.depthMask(false)
    state.colorMask(true, true, true, true)
    state.clearColor(0, 0, 0, 0)
}

export interface HistogramPyramid {
    pyramidTex: Texture
    count: number
    height: number
    levels: number
    scale: Vec2
}

export function createHistogramPyramid(ctx: WebGLContext, inputTexture: Texture, scale: Vec2): HistogramPyramid {
    const { gl, framebufferCache } = ctx

    // printTexture(ctx, inputTexture, 2)
    if (inputTexture.width !== inputTexture.height || !isPowerOfTwo(inputTexture.width)) {
        throw new Error('inputTexture must be of square power-of-two size')
    }

    // This part set the levels
    const levels = Math.ceil(Math.log(inputTexture.width) / Math.log(2))
    const maxSize = Math.pow(2, levels)
    // console.log('levels', levels, 'maxSize', maxSize)

    const pyramidTexture = createTexture(ctx, 'image-float32', 'rgba', 'float', 'nearest')
    pyramidTexture.define(maxSize, maxSize)

    const framebuffer = framebufferCache.get('reduction').value
    pyramidTexture.attachFramebuffer(framebuffer, 0)
    gl.clear(gl.COLOR_BUFFER_BIT)

    const levelTexturesFramebuffers: TextureFramebuffer[] = []
    for (let i = 0; i < levels; ++i) levelTexturesFramebuffers.push(getLevelTextureFramebuffer(ctx, i))

    const renderable = getHistopyramidReductionRenderable(ctx, inputTexture)
    ctx.state.currentRenderItemId = -1
    setRenderingDefaults(ctx)

    let offset = 0;
    for (let i = 0; i < levels; i++) {
        const currLevel = levels - 1 - i
        const tf = levelTexturesFramebuffers[currLevel]
        tf.framebuffer.bind()
        // levelTextures[currLevel].attachFramebuffer(framebuffer, 0)

        const size = Math.pow(2, currLevel)
        // console.log('size', size, 'draw-level', currLevel, 'read-level', levels - i)
        gl.clear(gl.COLOR_BUFFER_BIT)
        gl.viewport(0, 0, size, size)

        ValueCell.update(renderable.values.uSize, Math.pow(2, i + 1) / maxSize)
        ValueCell.update(renderable.values.uTexSize, size)
        if (i > 0) {
            ValueCell.update(renderable.values.tPreviousLevel, levelTexturesFramebuffers[levels - i].texture)
            renderable.update()
        }
        ctx.state.currentRenderItemId = -1
        renderable.render()

        pyramidTexture.bind(0)
        gl.copyTexSubImage2D(gl.TEXTURE_2D, 0, offset, 0, 0, 0, size, size);
        pyramidTexture.unbind(0)

        offset += size;
    }

    gl.finish()

    // printTexture(ctx, pyramidTexture, 2)

    //

    const finalCount = getHistopyramidSum(ctx, levelTexturesFramebuffers[0].texture)
    const height = Math.ceil(finalCount / Math.pow(2, levels))
    // const scale = Vec2.create(maxSize / inputTexture.width, maxSize / inputTexture.height)
    // console.log('height', height, 'finalCount', finalCount, 'scale', scale)


    return {
        pyramidTex: pyramidTexture,
        count: finalCount,
        height,
        levels,
        scale
    }
}