import {GuildEmoji} from "discord.js";
import {MessageEmbed} from "discord.js";
import Command from "../../core/command";
import {split} from "../../core/lib";
import {paginate} from "../../core/libd";
import vm from "vm";
import {TextChannel} from "discord.js";
import {DMChannel} from "discord.js";
import {NewsChannel} from "discord.js";
import {User} from "discord.js";

const REGEX_TIMEOUT_MS = 1000;

export default new Command({
    description: "Lists all emotes the bot has in it's registry,",
    usage: "<regex pattern> (-flags)",
    async run($) {
        displayEmoteList($.client.emojis.cache.array(), $.channel, $.author);
    },
    any: new Command({
        description:
            "Filters emotes by via a regular expression. Flags can be added by adding a dash at the end. For example, to do a case-insensitive search, do %prefix%lsemotes somepattern -i",
        async run($) {
            // If a guild ID is provided, filter all emotes by that guild (but only if there aren't any arguments afterward)
            if ($.args.length === 1 && /^\d{17,19}$/.test($.args[0])) {
                const guildID: string = $.args[0];

                displayEmoteList(
                    $.client.emojis.cache.filter((emote) => emote.guild.id === guildID).array(),
                    $.channel,
                    $.author
                );
            } else {
                // Otherwise, search via a regex pattern
                let flags: string | undefined = undefined;

                if (/^-[dgimsuy]{1,7}$/.test($.args[$.args.length - 1])) {
                    flags = $.args.pop().substring(1);
                }

                let emoteCollection = $.client.emojis.cache.array();
                // Creates a sandbox to stop a regular expression if it takes too much time to search.
                // To avoid passing in a giant data structure, I'll just pass in the structure {[id: string]: [name: string]}.
                //let emotes: {[id: string]: string} = {};
                let emotes = new Map<string, string>();

                for (const emote of emoteCollection) {
                    emotes.set(emote.id, emote.name);
                }

                // The result will be sandbox.emotes because it'll be modified in-place.
                const sandbox = {
                    regex: new RegExp($.args.join(" "), flags),
                    emotes
                };
                const context = vm.createContext(sandbox);

                if (vm.isContext(sandbox)) {
                    // Restrict an entire query to the timeout specified.
                    try {
                        const script = new vm.Script(
                            "for(const [id, name] of emotes.entries()) if(!regex.test(name)) emotes.delete(id);"
                        );
                        script.runInContext(context, {timeout: REGEX_TIMEOUT_MS});
                        emotes = sandbox.emotes;
                        emoteCollection = emoteCollection.filter((emote) => emotes.has(emote.id)); // Only allow emotes that haven't been deleted.
                        displayEmoteList(emoteCollection, $.channel, $.author);
                    } catch (error) {
                        if (error.code === "ERR_SCRIPT_EXECUTION_TIMEOUT") {
                            $.channel.send(
                                `The regular expression you entered exceeded the time limit of ${REGEX_TIMEOUT_MS} milliseconds.`
                            );
                        } else {
                            throw new Error(error);
                        }
                    }
                } else {
                    $.channel.send("Failed to initialize sandbox.");
                }
            }
        }
    })
});

async function displayEmoteList(emotes: GuildEmoji[], channel: TextChannel | DMChannel | NewsChannel, author: User) {
    emotes.sort((a, b) => {
        const first = a.name.toLowerCase();
        const second = b.name.toLowerCase();

        if (first > second) return 1;
        else if (first < second) return -1;
        else return 0;
    });
    const sections = split(emotes, 20);
    const pages = sections.length;
    const embed = new MessageEmbed().setTitle("**Emotes**").setColor("AQUA");
    let desc = "";

    // Gather the first page (if it even exists, which it might not if there no valid emotes appear)
    if (pages > 0) {
        for (const emote of sections[0]) {
            desc += `${emote} ${emote.name} (**${emote.guild.name}**)\n`;
        }

        embed.setDescription(desc);

        if (pages > 1) {
            embed.setTitle(`**Emotes** (Page 1 of ${pages})`);
            const msg = await channel.send({embed});

            paginate(msg, author.id, pages, (page) => {
                let desc = "";
                for (const emote of sections[page]) {
                    desc += `${emote} ${emote.name} (**${emote.guild.name}**)\n`;
                }
                embed.setTitle(`**Emotes** (Page ${page + 1} of ${pages})`);
                embed.setDescription(desc);
                msg.edit(embed);
            });
        } else {
            channel.send({embed});
        }
    } else {
        channel.send("No valid emotes found by that query.");
    }
}