/**
 * Copyright (c) 2018-2020 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author Alexander Rose <alexander.rose@weirdbyte.de>
 */

import { ShaderCode, DefineValues, addShaderDefines } from '../shader-code';
import { WebGLState } from './state';
import { WebGLExtensions } from './extensions';
import { getUniformSetters, UniformsList, getUniformType, UniformSetters } from './uniform';
import { AttributeBuffers, getAttribType } from './buffer';
import { TextureId, Textures } from './texture';
import { idFactory } from '../../mol-util/id-factory';
import { RenderableSchema } from '../renderable/schema';
import { isDebugMode } from '../../mol-util/debug';
import { GLRenderingContext } from './compat';
import { ShaderType, Shader } from './shader';

const getNextProgramId = idFactory();

export interface Program {
    readonly id: number

    use: () => void
    setUniforms: (uniformValues: UniformsList) => void
    bindAttributes: (attribueBuffers: AttributeBuffers) => void
    bindTextures: (textures: Textures, startingTargetUnit?: number) => void

    reset: () => void
    destroy: () => void
}

type Locations = { [k: string]: number }

function getLocations(gl: GLRenderingContext, program: WebGLProgram, schema: RenderableSchema) {
    const locations: Locations = {};
    Object.keys(schema).forEach(k => {
        const spec = schema[k];
        if (spec.type === 'attribute') {
            const loc = gl.getAttribLocation(program, k);
            // unused attributes will result in a `-1` location which is usually fine
            // if (loc === -1) console.info(`Could not get attribute location for '${k}'`)
            locations[k] = loc;
        } else if (spec.type === 'uniform' || spec.type === 'texture') {
            const loc = gl.getUniformLocation(program, k);
            // unused uniforms will result in a `null` location which is usually fine
            // if (loc === null) console.info(`Could not get uniform location for '${k}'`)
            locations[k] = loc as number;
        }
    });
    return locations;
}

function checkActiveAttributes(gl: GLRenderingContext, program: WebGLProgram, schema: RenderableSchema) {
    const attribCount = gl.getProgramParameter(program, gl.ACTIVE_ATTRIBUTES);
    for (let i = 0; i < attribCount; ++i) {
        const info = gl.getActiveAttrib(program, i);
        if (info) {
            const { name, type } = info;
            if (name.startsWith('__activeAttribute')) {
                // name assigned by `gl.shim.ts`, ignore for checks
                continue;
            }
            if (name === 'gl_InstanceID') continue; // WebGL2 built-in
            if (name === 'gl_VertexID') continue; // WebGL2 built-in
            const spec = schema[name];
            if (spec === undefined) {
                throw new Error(`missing 'uniform' or 'texture' with name '${name}' in schema`);
            }
            if (spec.type !== 'attribute') {
                throw new Error(`'${name}' must be of type 'attribute' but is '${spec.type}'`);
            }
            const attribType = getAttribType(gl, spec.kind, spec.itemSize);
            if (attribType !== type) {
                throw new Error(`unexpected attribute type for ${name}`);
            }
        }
    }
}

function checkActiveUniforms(gl: GLRenderingContext, program: WebGLProgram, schema: RenderableSchema) {
    const attribCount = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
    for (let i = 0; i < attribCount; ++i) {
        const info = gl.getActiveUniform(program, i);
        if (info) {
            const { name, type } = info;
            if (name.startsWith('__activeUniform')) {
                // name assigned by `gl.shim.ts`, ignore for checks
                continue;
            }
            const baseName = name.replace(/[[0-9]+\]$/, ''); // 'array' uniforms
            const spec = schema[baseName];
            if (spec === undefined) {
                throw new Error(`missing 'uniform' or 'texture' with name '${name}' in schema`);
            }
            if (spec.type === 'uniform') {
                const uniformType = getUniformType(gl, spec.kind);
                if (uniformType !== type) {
                    throw new Error(`unexpected uniform type for ${name}`);
                }
            } else if (spec.type === 'texture') {
                if (spec.kind === 'image-float32' || spec.kind === 'image-uint8') {
                    if (type !== gl.SAMPLER_2D) {
                        throw new Error(`unexpected sampler type for '${name}'`);
                    }
                } else if (spec.kind === 'volume-float32' || spec.kind === 'volume-uint8') {
                    if (type !== (gl as WebGL2RenderingContext).SAMPLER_3D) {
                        throw new Error(`unexpected sampler type for '${name}'`);
                    }
                } else {
                    // TODO
                }
            } else {
                throw new Error(`'${name}' must be of type 'uniform' or 'texture' but is '${spec.type}'`);
            }
        }
    }
}

function checkProgram(gl: GLRenderingContext, program: WebGLProgram) {
    // no-op in FF on Mac, see https://bugzilla.mozilla.org/show_bug.cgi?id=1284425
    // gl.validateProgram(program)
    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
        throw new Error(`Could not compile WebGL program. \n\n${gl.getProgramInfoLog(program)}`);
    }
}

export interface ProgramProps {
    defineValues: DefineValues,
    shaderCode: ShaderCode,
    schema: RenderableSchema
}

export function getProgram(gl: GLRenderingContext) {
    const program = gl.createProgram();
    if (program === null) {
        throw new Error('Could not create WebGL program');
    }
    return program;
}

type ShaderGetter = (type: ShaderType, source: string) => Shader

export function createProgram(gl: GLRenderingContext, state: WebGLState, extensions: WebGLExtensions, getShader: ShaderGetter, props: ProgramProps): Program {
    const { defineValues, shaderCode: _shaderCode, schema } = props;

    let program = getProgram(gl);
    const programId = getNextProgramId();

    const shaderCode = addShaderDefines(gl, extensions, defineValues, _shaderCode);
    const vertShader = getShader('vert', shaderCode.vert);
    const fragShader = getShader('frag', shaderCode.frag);

    let locations: Locations;
    let uniformSetters: UniformSetters;

    function init() {
        vertShader.attach(program);
        fragShader.attach(program);
        gl.linkProgram(program);
        if (isDebugMode) {
            checkProgram(gl, program);
        }

        locations = getLocations(gl, program, schema);
        uniformSetters = getUniformSetters(schema);

        if (isDebugMode) {
            checkActiveAttributes(gl, program, schema);
            checkActiveUniforms(gl, program, schema);
        }
    }
    init();

    let destroyed = false;

    return {
        id: programId,

        use: () => {
            // console.log('use', programId)
            state.currentProgramId = programId;
            gl.useProgram(program);
        },
        setUniforms: (uniformValues: UniformsList) => {
            for (let i = 0, il = uniformValues.length; i < il; ++i) {
                const [k, v] = uniformValues[i];
                if (v) {
                    const l = locations[k];
                    if (l !== null) uniformSetters[k](gl, l, v.ref.value);
                }
            }
        },
        bindAttributes: (attributeBuffers: AttributeBuffers) => {
            for (let i = 0, il = attributeBuffers.length; i < il; ++i) {
                const [k, buffer] = attributeBuffers[i];
                const l = locations[k];
                if (l !== -1) buffer.bind(l);
            }
        },
        bindTextures: (textures: Textures, startingTargetUnit?: number) => {
            startingTargetUnit = startingTargetUnit ?? 0;

            for (let i = 0, il = textures.length; i < il; ++i) {
                const [k, texture] = textures[i];
                const l = locations[k];
                if (l !== null && l !== undefined) {
                    texture.bind((i + startingTargetUnit) as TextureId);
                    uniformSetters[k](gl, l, (i + startingTargetUnit) as TextureId);
                }
            }
        },

        reset: () => {
            program = getProgram(gl);
            init();
        },
        destroy: () => {
            if (destroyed) return;
            vertShader.destroy();
            fragShader.destroy();
            gl.deleteProgram(program);
            destroyed = true;
        }
    };
}