export class Renderer {
    constructor() {
        this.canvas = document.createElement('canvas');
        this.canvas.style.display = 'none';
        document.body.appendChild(this.canvas);
        this.gl = this.canvas.getContext('webgl2', {antialias: false, alpha: true})
    }
}

function renderVariantCondition(key) {
    if (key) {
        return key.split(',').map(
            it => it.split("=")
        ).map(
            ([n, v]) => `state[${JSON.stringify(n)}] === ${JSON.stringify(v)}`
        ).join(" && ")
    } else {
        return 'true';
    }
}

function renderApply(data) {
    if (Array.isArray(data)) {
        const parts = [];

        let total = 0.0;
        for (const {weight = 1.0} of data) total += weight;

        let accum = 0.0;
        for (const elem of data) {
            const {weight = 1.0} = elem;
            accum += weight;

            if (accum === total) {
                parts.push(JSON.stringify(elem));
            } else {
                parts.push(`(hash % ${total}) < ${accum} ? ${JSON.stringify(elem)} : `)
            }
        }
        return parts.join('');
    } else {
        return JSON.stringify(data)
    }
}

/**
 * @param {Object} data
 * @returns {String}
 */
function renderBlockstateResolver(data) {
    const {variants, multipart} = data;

    if (variants) {
        if (Object.keys(variants).length === 1 && variants[""]) {
            return `return ${(renderApply(variants[""]))};`;
        } else {
            let cases = [];
            for (const [key, defn] of Object.entries(variants)) {
                cases.push(`if (${(renderVariantCondition(key))}) return ${(renderApply(defn))};`)
            }
            cases.push(`return {"model": ":missing"};`)
            return cases.join('else ')
        }
    } else if (multipart) {
        return 'console.warn("NOT IMPLEMENTED")'
    } else {
        console.warn('invalid blockstate', data)
    }
}

/**
 * @param {String} src
 * @returns {Promise<void>}
 */
async function parse(src) {
    const lines = src.replace(/#.*?(?:\n|$)/, '\n').trim().split(/(?:\n[ \t]*)+/);

    for (const line of lines) {
        const args = line.split(/[ \t]+/);
        const cmd = args[0].toLowerCase();

        if (cmd === 'p') {
            const block = args[1];

            try {
                const res = await fetch(`assets/minecraft/blockstates/${block}.json`);
                let data = await res.json();
                let resolver_src = renderBlockstateResolver(data);
                // console.log(beautify.js(`${block} = (state, hash) => {${resolver_src}}`))

                let resolver = new Function("state", "hash", resolver_src);
                console.log(resolver)

            } catch (ex) {
                console.warn(`Fetch for ${block} failed:`, ex);
            }
        }
    }
}

export class MCDioramaElement extends HTMLElement {
    connectedCallback() {
        const canvas = document.createElement('canvas');
        this.appendChild(canvas);
        const ctx = canvas.getContext('2d');

        setTimeout(() => {
            const script = this.querySelector('script[type="text/mc-world"]');
            parse(script.textContent);
        }, 0)
    }
}

customElements.define('mc-diorama', MCDioramaElement);