import { parse } from "twemoji-parser";
import { loadImage, Image } from "canvas";

const emojiCache = new Map<string, Image>();
const discordEmojiPattern = "<a?:\\w+:(\\d{17,19})>";
const defaultHeight = 16;

export type ParsedChunks = (string | { url: string })[];

class Util {

    constructor() {
        throw new Error(`The ${this.constructor.name} class may not be instantiated!`);
    }

    static parseDiscordEmojis(textEntities: string[]): ParsedChunks {
        const newTextEntities = [];

        for (const entity of textEntities) {
            if (typeof entity === "string") {
                const words = entity.replace(new RegExp(discordEmojiPattern, "g"), "\u200b$&\u200b").split("\u200b");
                for (const word of words) newTextEntities.push(word.match(new RegExp(discordEmojiPattern)) ? { url: `https://cdn.discordapp.com/emojis/${word.match(new RegExp(discordEmojiPattern))[1]}.png` } : word);
            }

            else newTextEntities.push(entity);
        }

        return newTextEntities;
    }

    static split(text: string): ParsedChunks {
        const twemojiEntities = parse(text, { assetType: "png" });

        let unparsedText = text;
        let lastTwemojiIndice = 0;
        const textEntities = [];

        twemojiEntities.forEach((twemoji) => {
            textEntities.push(unparsedText.slice(0, twemoji.indices[0] - lastTwemojiIndice));

            textEntities.push(twemoji);

            unparsedText = unparsedText.slice(twemoji.indices[1] - lastTwemojiIndice);
            lastTwemojiIndice = twemoji.indices[1];
        });

        textEntities.push(unparsedText);

        return Util.parseDiscordEmojis(textEntities);
    }

    static async loadEmojis(url: string): Promise<Image> {
        if (emojiCache.has(url)) return emojiCache.get(url);

        const image = await loadImage(url);
        if (!url.includes("cdn.discordapp.com")) emojiCache.set(url, image);

        return image;
    }

    static getFontSize(font: string): number {
        if (typeof font !== "string") return defaultHeight;

        const sizeFamily = font.match(/([0-9.]+)(px|pt|pc|in|cm|mm|%|em|ex|ch|rem|q)/);

        if (sizeFamily.length !== 3) {
            return defaultHeight;
        }

        switch (sizeFamily[2]) {
            case "pt":
                return Number(sizeFamily[1]) / 0.75;
            case "pc":
                return Number(sizeFamily[1]) * 16;
            case "in":
                return Number(sizeFamily[1]) * 96;
            case "cm":
                return Number(sizeFamily[1]) * (96.0 / 2.54);
            case "mm":
                return Number(sizeFamily[1]) * (96.0 / 25.4);
            case "%":
                return Number(sizeFamily[1]) * (defaultHeight / 100 / 0.75);
            case "em":
            case "rem":
                return Number(sizeFamily[1]) * (defaultHeight / 0.75);
            case "q":
                return Number(sizeFamily[1]) * (96 / 25.4 / 4);
            case "px":
            default:
                return Number(sizeFamily[1]);
        }
    }
}

export { Util };