// loads the mods the server lists: downloads their .bmod files, registers their data, then runs their client scripts.
// see "Delivery to clients" in MODS.md
import { AIR } from "$/common/constants.ts";
import { BlockRegistry, EverythingRegistry } from "$/common/everything_registry.ts";
import type { ClientContext } from "$/common/mod_api/client.ts";
import { ModListing, ModLoadError, register_mod_data } from "$/common/mod_loader.ts";
import { type Bmod, read_bmod } from "$/common/bmod.ts";
import type { OreJson } from "$/common/mod_data.ts";
import { AIR_ID } from "$/common/protocol.ts";
import type { Client } from "./client.ts";
import { code_url, fetch_verified } from "./handshake.ts";

// each loaded mod's credits file, for the credits screen
export const mod_credits: { name: string; version: string; text: string }[] = [];

// what the chunk workers need to generate the same world as the server
export const worldgen_mods: { scripts: { mod: string; url: string }[]; ores: OreJson[] } = { scripts: [], ores: [] };

// set once the game is running, mods can't look at it during setup
let client: Client | undefined;

export function set_mods_client(game_client: Client) {
	client = game_client;
}

// downloads every mod's .bmod and checks it against the hash the server listed. everything a mod runs comes from
// the checked bytes, never fetched twice
export async function download_mods(listings: ModListing[], base: URL): Promise<Bmod[]> {
	return await Promise.all(listings.map(async (listing) => {
		try {
			const bytes = await fetch_verified(new URL(listing.file, base), listing.sha256, `${listing.name}`);
			const bmod = read_bmod(bytes, `${listing.id}.bmod`);
			if (bmod.manifest.id !== listing.id) throw new Error(`the server listed it as ${listing.id}`);
			return bmod;
		} catch (e) {
			throw new ModLoadError(listing.id, (e as Error).message);
		}
	}));
}

// registers the mods' data and runs their client scripts, in the order the server listed them
export async function load_client_mods(listings: ModListing[], bmods: Bmod[]) {
	for (const [i, bmod] of bmods.entries()) {
		if (bmod.credits) {
			mod_credits.push({ name: listings[i].name, version: listings[i].version, text: bmod.credits });
		}
	}

	const recipes = register_mod_data(bmods.map((bmod) => ({ id: bmod.manifest.id, data: bmod.data })));

	worldgen_mods.ores = recipes.ores;
	worldgen_mods.scripts = bmods.flatMap((bmod) =>
		bmod.scripts.worldgen ? [{ mod: bmod.manifest.id, url: script_url(bmod.scripts.worldgen) }] : []
	);

	for (const [i, bmod] of bmods.entries()) {
		if (!bmod.scripts.client) continue;
		const module = await import(script_url(bmod.scripts.client));
		if (typeof module.setup !== "function") {
			throw new ModLoadError(bmod.manifest.id, "the client script doesn't export a setup function");
		}
		await module.setup(client_context(listings[i]));
	}
}

function script_url(code: string) {
	return code_url(new TextEncoder().encode(code));
}

function client_context(listing: ModListing): ClientContext {
	const mod = listing.id;
	const not_yet = (name: string, where: string) =>
		new Proxy({}, {
			get: (_, prop) => () => {
				throw new Error(`[${mod}] ctx.${name}.${String(prop)} isn't implemented yet (${where} in MODS.md)`);
			},
		});
	const need_client = () => {
		if (!client) throw new Error(`[${mod}] the world isn't there yet during setup`);
		return client;
	};

	return {
		mod: { id: mod, version: listing.version },
		ui: not_yet("ui", "step 7") as ClientContext["ui"],
		hud: not_yet("hud", "step 7") as ClientContext["hud"],
		input: not_yet("input", "step 8") as ClientContext["input"],
		net: not_yet("net", "step 8") as ClientContext["net"],
		player: {
			get name() {
				return need_client().connection.name;
			},
			get position() {
				const { x, y, z } = need_client().player;
				return { x, y, z };
			},
		},
		world: {
			get_block(x, y, z) {
				const nid = need_client().level.get_block(x, y, z);
				if (nid === AIR) return AIR_ID;
				return EverythingRegistry.get_by_id<BlockRegistry>("blocks", nid)?.id;
			},
			get time() {
				return need_client().level.time;
			},
		},
		log: (...args) => console.log(`[${mod}]`, ...args),
	};
}