Implement main game as a mod

server/game/blocks.ts

@@ -1,5 +1,7 @@
 import { Container, ItemStack } from "$/common/inventory.ts";
 import { ScreenLayout } from "$/common/protocol.ts";
+import { EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
+import type { RecipeBook } from "$/common/mod_loader.ts";
 import type { GameServer } from "./game_server.ts";
 import type { ServerPlayer } from "./player.ts";
 import type { Tile } from "./world.ts";
@@ -80,50 +82,6 @@ BLOCK_BEHAVIORS["bworld:chest"] = {
 
 // furnace
 
-export interface FurnaceRecipe {
-	input: string;
-	output: ItemStack;
-	cook_time: number;
-}
-
-export const FURNACE_RECIPES: FurnaceRecipe[] = [
-	{
-		input: "bworld:log",
-		output: new ItemStack("bworld:coal", 1),
-		cook_time: 100,
-	},
-	{
-		input: "bworld:coal_ore",
-		output: new ItemStack("bworld:coal", 1),
-		cook_time: 100,
-	},
-	{
-		input: "bworld:iron_ore",
-		output: new ItemStack("bworld:iron_ingot", 1),
-		cook_time: 200,
-	},
-	{
-		input: "bworld:tin_ore",
-		output: new ItemStack("bworld:tin_ingot", 1),
-		cook_time: 200,
-	},
-	{
-		input: "bworld:copper_ore",
-		output: new ItemStack("bworld:copper_ingot", 1),
-		cook_time: 200,
-	},
-	{
-		input: "bworld:gold_ore",
-		output: new ItemStack("bworld:gold_ingot", 1),
-		cook_time: 200,
-	},
-];
-
-export const FUEL_VALUES: Record<string, number> = {
-	"bworld:coal": 1000,
-	"bworld:log": 100,
-};
-
 interface FurnaceData {
 	progress: number;
 	progress_max: number;
@@ -131,12 +89,17 @@ interface FurnaceData {
 	fuel_max: number;
 }
 
-function get_recipe(input?: ItemStack | undefined): FurnaceRecipe | undefined {
+interface FurnaceRecipe {
+	output: { id: string; count: number };
+	cook_time: number;
+}
+
+function get_recipe(recipes: RecipeBook, input?: ItemStack | undefined): FurnaceRecipe | undefined {
 	if (!input) {
 		return;
 	}
 
-	return FURNACE_RECIPES.find((r) => r.input === input.type_id);
+	return recipes.furnace.get(input.type_id);
 }
 
 function can_craft(container: Container, recipe?: FurnaceRecipe) {
@@ -150,27 +113,27 @@ function can_craft(container: Container, recipe?: FurnaceRecipe) {
 		return true;
 	}
 
-	if (output.type_id !== recipe.output.type_id) {
+	if (output.type_id !== recipe.output.id) {
 		return false;
 	}
 
 	return output.amount < output.max_amount;
 }
 
-function get_fuel_value(item?: ItemStack | undefined): number {
+function get_fuel_value(recipes: RecipeBook, item?: ItemStack | undefined): number {
 	if (!item) {
 		return 0;
 	}
-	return FUEL_VALUES[item.type_id] ?? 0;
+	return recipes.fuel.get(item.type_id) ?? 0;
 }
 
-function has_fuel(container: Container) {
-	return get_fuel_value(container.get_item(1)) > 0;
+function has_fuel(recipes: RecipeBook, container: Container) {
+	return get_fuel_value(recipes, container.get_item(1)) > 0;
 }
 
-function consume_fuel(container: Container): number {
+function consume_fuel(recipes: RecipeBook, container: Container): number {
 	const fuel = container.get_slot(1)!;
-	const value = get_fuel_value(fuel.get_item());
+	const value = get_fuel_value(recipes, fuel.get_item());
 
 	if (fuel.has_item()) {
 		fuel.amount! -= 1;
@@ -184,9 +147,9 @@ function craft(container: Container, recipe: FurnaceRecipe) {
 	const output = container.get_item(2);
 
 	if (!output) {
-		container.set_item(2, recipe.output.clone());
+		container.set_item(2, new ItemStack(recipe.output.id, recipe.output.count));
 	} else {
-		output.amount += recipe.output.amount;
+		output.amount += recipe.output.count;
 	}
 
 	input.amount -= 1;
@@ -241,12 +204,12 @@ BLOCK_BEHAVIORS["bworld:furnace"] = {
 	on_break(_game, tile, player) {
 		give_container_contents(tile, player);
 	},
-	on_tick(_game, tile) {
+	on_tick(game, tile) {
 		const data = tile.data as unknown as FurnaceData;
 		const container = tile.containers.main;
 
 		const input = container.get_item(0);
-		const recipe = get_recipe(input);
+		const recipe = get_recipe(game.recipes, input);
 
 		// burn fuel
 		if (data.fuel > 0) {
@@ -259,8 +222,8 @@ BLOCK_BEHAVIORS["bworld:furnace"] = {
 		}
 
 		// refuel
-		if (data.fuel === 0 && has_fuel(container)) {
-			data.fuel = consume_fuel(container);
+		if (data.fuel === 0 && has_fuel(game.recipes, container)) {
+			data.fuel = consume_fuel(game.recipes, container);
 			data.fuel_max = data.fuel;
 		}
 
@@ -276,3 +239,20 @@ BLOCK_BEHAVIORS["bworld:furnace"] = {
 		}
 	},
 };
+
+// items that still need code, until they're components in mods/bworld (phase 2 in MODS.md)
+
+export interface WateringCanData {
+	water: number;
+	max_water: number;
+}
+
+export function add_base_item_hooks() {
+	const watering_can = EverythingRegistry.get<ItemRegistry<WateringCanData>>("items", "bworld:watering_can");
+	if (watering_can) {
+		watering_can.on_create = (item) => {
+			item.data = { water: 0, max_water: 32 };
+		};
+		watering_can.get_lore = (item) => `Water: ${item.data?.water}/${item.data?.max_water}`;
+	}
+}

server/game/crafting.ts

@@ -1,80 +1,8 @@
 import { Container, ItemStack } from "$/common/inventory.ts";
 import { CRAFTING_RESULT_SLOT } from "$/common/protocol.ts";
+import type { GridRecipe } from "$/common/mod_data.ts";
 
-export interface CraftingRecipe {
-	width: number;
-	height: number;
-	pattern: (string | undefined)[];
-	result: { id: string; count: number };
-}
-
-export const CRAFTING_RECIPES: CraftingRecipe[] = [
-	{
-		width: 3,
-		height: 3,
-		pattern: [
-			"bworld:planks",
-			"bworld:planks",
-			"bworld:planks",
-			"bworld:planks",
-			undefined,
-			"bworld:planks",
-			"bworld:planks",
-			"bworld:planks",
-			"bworld:planks",
-		],
-		result: { id: "bworld:chest", count: 1 },
-	},
-	{
-		width: 3,
-		height: 3,
-		pattern: [
-			"bworld:stone",
-			"bworld:stone",
-			"bworld:stone",
-			"bworld:stone",
-			undefined,
-			"bworld:stone",
-			"bworld:stone",
-			"bworld:stone",
-			"bworld:stone",
-		],
-		result: { id: "bworld:furnace", count: 1 },
-	},
-	{
-		width: 1,
-		height: 1,
-		pattern: [
-			"bworld:log",
-		],
-		result: { id: "bworld:planks", count: 2 },
-	},
-	{
-		width: 1,
-		height: 2,
-		pattern: [
-			"bworld:planks",
-			"bworld:planks",
-		],
-		result: { id: "bworld:stick", count: 2 },
-	},
-	{
-		width: 3,
-		height: 3,
-		pattern: [
-			"bworld:planks",
-			"bworld:planks",
-			"bworld:planks",
-			undefined,
-			"bworld:stick",
-			undefined,
-			undefined,
-			"bworld:stick",
-			undefined,
-		],
-		result: { id: "bworld:wood_pickaxe", count: 1 },
-	},
-];
+// recipes come from mods, see RecipeBook in common/mod_loader.ts
 
 function get_crafting_grid(crafting: Container): (string | undefined)[] {
 	const grid: (string | undefined)[] = [];
@@ -84,7 +12,7 @@ function get_crafting_grid(crafting: Container): (string | undefined)[] {
 	return grid;
 }
 
-function matches_recipe(grid: (string | undefined)[], recipe: CraftingRecipe): boolean {
+function matches_recipe(grid: (string | undefined)[], recipe: GridRecipe): boolean {
 	for (let y = 0; y <= 3 - recipe.height; y++) {
 		for (let x = 0; x <= 3 - recipe.width; x++) {
 			let match = true;
@@ -115,9 +43,9 @@ function matches_recipe(grid: (string | undefined)[], recipe: CraftingRecipe): b
 }
 
 // puts what the grid makes in the result slot
-export function update_crafting_result(crafting: Container) {
+export function update_crafting_result(crafting: Container, recipes: GridRecipe[]) {
 	const grid = get_crafting_grid(crafting);
-	const recipe = CRAFTING_RECIPES.find((recipe) => matches_recipe(grid, recipe));
+	const recipe = recipes.find((recipe) => matches_recipe(grid, recipe));
 	crafting.set_item(CRAFTING_RESULT_SLOT, recipe ? new ItemStack(recipe.result.id, recipe.result.count) : undefined);
 }
 

server/game/game_server.ts

@@ -1,6 +1,3 @@
-import "$/common/blocks/mod.ts";
-import "$/common/items/mod.ts";
-
 import {
 	AIR,
 	CHUNK_HEIGHT,
@@ -23,7 +20,10 @@ import {
 	MAX_NAME_LENGTH,
 	ServerMessage,
 } from "$/common/protocol.ts";
+import type { ModListing, RecipeBook } from "$/common/mod_loader.ts";
+import type { WorldgenSetup } from "$/common/generation.ts";
 import { BLOCK_BEHAVIORS } from "./blocks.ts";
+import { ModRuntime, run_guarded } from "./mod_runtime.ts";
 import { consume_recipe_items, update_crafting_result } from "./crafting.ts";
 import { OpenScreen, SavedPlayer, ServerPlayer } from "./player.ts";
 import { ServerWorld, Tile } from "./world.ts";
@@ -52,8 +52,20 @@ export interface SavedWorld {
 		z: number;
 		data: Record<string, unknown>;
 		containers: Record<string, (ItemData | null)[]>;
+		// a mod block's data, what BlockRef.data holds
+		mod_data?: unknown;
 	}[];
 	players: Record<string, SavedPlayer>;
+	// ctx.storage of every mod, by mod id
+	mod_storage?: Record<string, Record<string, unknown>>;
+}
+
+// the loaded mods, see load_mods.ts
+export interface GameMods {
+	listings: ModListing[];
+	recipes: RecipeBook;
+	worldgen?: WorldgenSetup;
+	runtime: ModRuntime;
 }
 
 export class GameServer {
@@ -62,13 +74,20 @@ export class GameServer {
 	#players = new Map<number, ServerPlayer>();
 	#saved_players: Record<string, SavedPlayer> = {};
 	#tick = 0;
+	#mods: GameMods;
+	mods: ModRuntime;
+	recipes: RecipeBook;
 
-	constructor(host: GameHost, save: string | undefined, default_seed: string) {
+	constructor(host: GameHost, save: string | undefined, default_seed: string, mods: GameMods) {
 		this.#host = host;
+		this.#mods = mods;
+		this.mods = mods.runtime;
+		this.recipes = mods.recipes;
 
 		// version 1 saves only had the seed and block changes
 		const saved: Partial<SavedWorld> | undefined = save ? JSON.parse(save) : undefined;
-		this.world = new ServerWorld(saved?.seed ?? default_seed);
+		this.world = new ServerWorld(saved?.seed ?? default_seed, mods.worldgen);
+		this.mods.storage = saved?.mod_storage ?? {};
 		this.world.load_changes(saved?.changes ?? []);
 		for (const tile of saved?.tiles ?? []) {
 			const containers: Record<string, Container> = {};
@@ -97,6 +116,7 @@ export class GameServer {
 		this.#saved_players[player.name] = player.save();
 		this.world.dirty = true;
 		this.#players.delete(conn);
+		this.mods.after.player_leave.emit({ player: this.mods.player(player) });
 		this.#broadcast({ type: "player_leave", id: player.id });
 		this.#broadcast({ type: "chat", text: `${player.name} left` });
 		console.log(`${player.name} left (${this.#players.size} online)`);
@@ -133,20 +153,35 @@ export class GameServer {
 
 		for (const tile of [...this.world.tiles.values()]) {
 			const behavior = BLOCK_BEHAVIORS[tile.id];
-			if (!behavior?.on_tick && !behavior?.on_second) {
+			const components = this.mods.components_of(tile.id)
+				.filter(({ component }) => component.on_tick || component.on_second);
+			if (!behavior?.on_tick && !behavior?.on_second && components.length === 0) {
 				continue;
 			}
 			if (!this.#near_any_player(tile.x, tile.z)) {
 				continue;
 			}
-			behavior.on_tick?.(this, tile);
+			behavior?.on_tick?.(this, tile);
 			if (second) {
-				behavior.on_second?.(this, tile);
+				behavior?.on_second?.(this, tile);
+			}
+			if (components.length > 0 && tile.mod_data !== undefined) {
+				const block = this.mods.block_ref(tile.x, tile.y, tile.z, tile.id);
+				for (const { mod, id, component, params } of components) {
+					if (component.on_tick) {
+						run_guarded(mod, `${id} on_tick`, () => component.on_tick!(block, params, TICK_DELTA));
+					}
+					if (second && component.on_second) {
+						run_guarded(mod, `${id} on_second`, () => component.on_second!(block, params, 1));
+					}
+				}
 			}
 			// tile data can change on any tick, saving is cheap enough to not track it exactly
 			this.world.dirty = true;
 		}
 
+		this.mods.tick();
+
 		for (const player of this.#players.values()) {
 			this.#sync(player);
 		}
@@ -169,16 +204,60 @@ export class GameServer {
 				containers: Object.fromEntries(
 					Object.entries(tile.containers).map(([name, container]) => [name, container.to_data()]),
 				),
+				mod_data: tile.mod_data,
 			})),
 			players: this.#saved_players,
+			mod_storage: this.mods.storage,
 		};
 		this.world.dirty = false;
 		return JSON.stringify(saved);
 	}
 
-	// used by block behaviors
+	// used by block behaviors and mods
+
+	get current_tick() {
+		return this.#tick;
+	}
+
+	players(): ServerPlayer[] {
+		return [...this.#players.values()];
+	}
+
+	give(player: ServerPlayer, id: string, count: number, data?: unknown) {
+		// split into stacks so max stack sizes are respected
+		let left = count;
+		while (left > 0) {
+			const stack = new ItemStack(id);
+			stack.amount = Math.min(left, stack.max_amount);
+			if (data !== undefined) stack.data = structuredClone(data);
+			left -= stack.amount;
+			player.give(stack);
+		}
+	}
+
+	send_chat(player: ServerPlayer, text: string) {
+		this.#send(player, { type: "chat", text });
+	}
+
+	teleport(player: ServerPlayer, x: number, y: number, z: number) {
+		Object.assign(player, { x, y, z });
+		this.#send(player, { type: "teleport", x, y, z });
+		this.#broadcast({ type: "player_move", id: player.id, x, y, z, yaw: player.yaw, pitch: player.pitch }, player);
+	}
 
 	set_block(x: number, y: number, z: number, id: string, player?: ServerPlayer) {
+		const old_id = this.world.get_block_id(x, y, z);
+		if (old_id !== AIR_ID) {
+			const components = this.mods.components_of(old_id).filter(({ component }) => component.on_break);
+			if (components.length > 0) {
+				const block = this.mods.block_ref(x, y, z, old_id);
+				const player_api = player && this.mods.player(player);
+				for (const { mod, id: component_id, component, params } of components) {
+					run_guarded(mod, `${component_id} on_break`, () => component.on_break!(block, params, player_api));
+				}
+			}
+		}
+
 		const old_tile = this.world.get_tile(x, y, z);
 		if (old_tile) {
 			BLOCK_BEHAVIORS[old_tile.id]?.on_break?.(this, old_tile, player);
@@ -196,6 +275,15 @@ export class GameServer {
 		if (BLOCK_BEHAVIORS[id]?.create_tile) {
 			this.get_or_create_tile(x, y, z);
 		}
+
+		if (id !== AIR_ID) {
+			const block = this.mods.block_ref(x, y, z, id);
+			for (const { mod, id: component_id, component, params } of this.mods.components_of(id)) {
+				if (component.on_create) {
+					run_guarded(mod, `${component_id} on_create`, () => component.on_create!(block, params));
+				}
+			}
+		}
 	}
 
 	get_or_create_tile(x: number, y: number, z: number): Tile {
@@ -230,7 +318,9 @@ export class GameServer {
 		this.#send(player, {
 			type: "welcome",
 			id: player.id,
+			name: player.name,
 			seed: this.world.seed,
+			mods: this.#mods.listings,
 			players: [...this.#players.values()].map((p) => p.info()),
 			changes: this.world.all_changes(),
 			spawn: { x: player.x, y: player.y, z: player.z, yaw: player.yaw, pitch: player.pitch },
@@ -241,6 +331,7 @@ export class GameServer {
 
 		this.#broadcast({ type: "player_join", player: player.info() }, player);
 		this.#broadcast({ type: "chat", text: `${player.name} joined` });
+		this.mods.after.player_join.emit({ player: this.mods.player(player) });
 		console.log(`${player.name} joined (${this.#players.size} online)`);
 	}
 
@@ -290,6 +381,18 @@ export class GameServer {
 			return;
 		}
 
+		const event = {
+			player: this.mods.player(player),
+			block: this.mods.block_ref(x, y, z, info.id),
+			item: this.mods.player(player).held_item,
+		};
+		const before = { ...event, cancel: false };
+		this.mods.before.block_break.emit(before);
+		if (before.cancel) {
+			this.#correct(player, x, y, z);
+			return;
+		}
+
 		const held = EverythingRegistry.get<ItemRegistry>("items", player.held_item?.type_id ?? "");
 		const drops = info.drop_table && (!info.requires_tool || held?.tool_type === info.tool_to_break);
 
@@ -297,6 +400,7 @@ export class GameServer {
 		if (drops) {
 			player.give(new ItemStack(info.drop_table!));
 		}
+		this.mods.after.block_break.emit(event);
 	}
 
 	#use_block(player: ServerPlayer, x: number, y: number, z: number, face: Faces) {
@@ -310,7 +414,28 @@ export class GameServer {
 			return;
 		}
 
-		if (BLOCK_BEHAVIORS[info.id]?.on_interact?.(this, { x, y, z, id: info.id }, player)) {
+		const player_api = this.mods.player(player);
+		const block = this.mods.block_ref(x, y, z, info.id);
+		const interact = { player: player_api, block, item: player_api.held_item };
+		const before_interact = { ...interact, cancel: false };
+		this.mods.before.block_interact.emit(before_interact);
+		if (before_interact.cancel) {
+			this.#correct(player, tx, ty, tz);
+			return;
+		}
+
+		let handled = BLOCK_BEHAVIORS[info.id]?.on_interact?.(this, { x, y, z, id: info.id }, player) ?? false;
+		for (const { mod, id: component_id, component, params } of this.mods.components_of(info.id)) {
+			if (component.on_interact) {
+				handled = run_guarded(mod, `${component_id} on_interact`, () =>
+							component.on_interact!(block, params, player_api)) ===
+						true || handled;
+			}
+		}
+		if (handled) {
+			this.mods.after.block_interact.emit(interact);
+			// the client didn't guess a placement for interactive blocks, but it might have for others
+			this.#correct(player, tx, ty, tz);
 			return;
 		}
 
@@ -322,8 +447,22 @@ export class GameServer {
 			return;
 		}
 
+		const place = {
+			player: player_api,
+			block: { id: held.block_id, x: tx, y: ty, z: tz },
+			face,
+			item: player_api.held_item,
+		};
+		const before_place = { ...place, cancel: false };
+		this.mods.before.block_place.emit(before_place);
+		if (before_place.cancel) {
+			this.#correct(player, tx, ty, tz);
+			return;
+		}
+
 		this.set_block(tx, ty, tz, held.block_id, player);
 		held_slot.amount = held_slot.amount! - 1;
+		this.mods.after.block_place.emit(place);
 	}
 
 	#click(player: ServerPlayer, key: unknown, index: unknown, button: unknown) {
@@ -350,7 +489,7 @@ export class GameServer {
 		}
 
 		if (key === "crafting") {
-			update_crafting_result(container);
+			update_crafting_result(container, this.recipes.shaped);
 		}
 	}
 
@@ -366,8 +505,15 @@ export class GameServer {
 			this.#command(player, text);
 			return;
 		}
-		console.log(`<${player.name}> ${text}`);
-		this.#broadcast({ type: "chat", from: player.name, text });
+		const before = { player: this.mods.player(player), message: text, cancel: false };
+		this.mods.before.chat_send.emit(before);
+		const message = String(before.message).slice(0, MAX_CHAT_LENGTH);
+		if (before.cancel || message.length === 0) {
+			return;
+		}
+		console.log(`<${player.name}> ${message}`);
+		this.#broadcast({ type: "chat", from: player.name, text: message });
+		this.mods.after.chat_send.emit({ player: before.player, message });
 	}
 
 	#command(player: ServerPlayer, text: string) {
@@ -391,14 +537,12 @@ export class GameServer {
 				this.#send(player, { type: "chat", text: `Count must be between 1 and ${MAX_GIVE}` });
 				return;
 			}
-			// split into stacks so max stack sizes are respected
-			let left = amount;
-			while (left > 0) {
-				const stack = new ItemStack(item_id);
-				stack.amount = Math.min(left, stack.max_amount);
-				left -= stack.amount;
-				player.give(stack);
-			}
+			this.give(player, item_id, amount);
+			return;
+		}
+		const mod_command = this.mods.commands.get(command);
+		if (mod_command) {
+			run_guarded(mod_command.mod, `/${command}`, () => mod_command.command.run(args, this.mods.player(player)));
 			return;
 		}
 		this.#send(player, { type: "chat", text: `Unknown command /${command}` });
@@ -417,7 +561,7 @@ export class GameServer {
 				player.crafting.set_item(i, undefined);
 			}
 		}
-		update_crafting_result(player.crafting);
+		update_crafting_result(player.crafting, this.recipes.shaped);
 		if (player.cursor.item) {
 			player.give(player.cursor.item);
 			player.cursor.item = undefined;

server/game/host_protocol.ts

@@ -1,7 +1,15 @@
+import type { ModData, ModListing } from "$/common/mod_loader.ts";
+
 // messages between server/main.ts (the host) and the game server worker
 
 export type HostToGame =
-	| { type: "init"; save: string | undefined; default_seed: string }
+	| {
+		type: "init";
+		save: string | undefined;
+		default_seed: string;
+		// in load order, with the scripts' code since the worker can't read files
+		mods: { listing: ModListing; data: ModData; server_code?: string; worldgen_code?: string }[];
+	}
 	| { type: "connect"; conn: number }
 	| { type: "message"; conn: number; data: string }
 	| { type: "disconnect"; conn: number }
@@ -10,6 +18,7 @@ export type HostToGame =
 
 export type GameToHost =
 	| { type: "ready"; seed: string }
+	| { type: "failed"; error: string }
 	| { type: "send"; conn: number; data: string }
 	| { type: "close"; conn: number }
 	| { type: "save"; data: string; final: boolean };

server/game/load_mods.ts

@@ -0,0 +1,59 @@
+// starts a game server with its mods: registers their data, then imports worldgen and server scripts.
+// the worker loads built mods, tests can load mods straight from their source folders
+import { register_mod_data } from "$/common/mod_loader.ts";
+import type { ModData, ModListing } from "$/common/mod_loader.ts";
+import { load_worldgen } from "$/common/worldgen_loader.ts";
+import { add_base_item_hooks } from "./blocks.ts";
+import { GameHost, GameServer } from "./game_server.ts";
+import { ModRuntime } from "./mod_runtime.ts";
+
+export interface ServerModSource {
+	listing: ModListing;
+	data: ModData;
+	// importable urls of the scripts: data: urls in the worker, file urls in tests
+	server_url?: string;
+	worldgen_url?: string;
+}
+
+export async function start_game(
+	host: GameHost,
+	save: string | undefined,
+	default_seed: string,
+	mods: ServerModSource[],
+): Promise<GameServer> {
+	const recipes = register_mod_data(mods.map((mod) => ({ id: mod.listing.id, data: mod.data })));
+	add_base_item_hooks();
+
+	const worldgen_scripts = mods.flatMap((mod) =>
+		mod.worldgen_url ? [{ mod: mod.listing.id, url: mod.worldgen_url }] : []
+	);
+	const worldgen = await load_worldgen(worldgen_scripts, recipes.ores);
+
+	const runtime = new ModRuntime();
+	const game = new GameServer(host, save, default_seed, {
+		listings: mods.map((mod) => mod.listing),
+		recipes,
+		worldgen,
+		runtime,
+	});
+
+	await runtime.load_scripts(
+		game,
+		mods.flatMap((mod) =>
+			mod.server_url ? [{ mod: mod.listing.id, version: mod.listing.version, url: mod.server_url }] : []
+		),
+	);
+	runtime.finish_setup();
+	runtime.after.server_start.emit({});
+
+	return game;
+}
+
+export function data_url(code: string) {
+	const bytes = new TextEncoder().encode(code);
+	let binary = "";
+	for (let i = 0; i < bytes.length; i += 0x8000) {
+		binary += String.fromCharCode(...bytes.subarray(i, i + 0x8000));
+	}
+	return `data:application/javascript;base64,${btoa(binary)}`;
+}

server/game/mod_runtime.ts

@@ -0,0 +1,429 @@
+// runs mods' server scripts: builds each one's ServerContext and keeps what they register.
+// see "Server scripts" in MODS.md. parts not built yet throw when used, saying so
+import { EverythingRegistry, ItemRegistry } from "$/common/everything_registry.ts";
+import { ItemStack as EngineItemStack } from "$/common/inventory.ts";
+import type {
+	BlockComponent,
+	BlockRef,
+	Command,
+	Container,
+	EventSignal,
+	ItemComponent,
+	ItemStack,
+	Player,
+	ServerAfterEvents,
+	ServerBeforeEvents,
+	ServerContext,
+} from "$/common/mod_api/server.ts";
+import { ModLoadError } from "$/common/mod_loader.ts";
+import { AIR_ID } from "$/common/protocol.ts";
+import type { GameServer } from "./game_server.ts";
+import type { ServerPlayer } from "./player.ts";
+
+// a list of handlers that can't break each other: one throwing is logged under its mod and the rest still run
+export class Signal<T> {
+	#handlers: { mod: string; handler: (event: T) => void }[] = [];
+
+	for_mod(mod: string): EventSignal<T> {
+		return {
+			subscribe: (handler) => {
+				const entry = { mod, handler };
+				this.#handlers.push(entry);
+				return () => {
+					this.#handlers = this.#handlers.filter((h) => h !== entry);
+				};
+			},
+		};
+	}
+
+	emit(event: T) {
+		for (const { mod, handler } of [...this.#handlers]) {
+			run_guarded(mod, "an event handler", () => handler(event));
+		}
+	}
+
+	get empty() {
+		return this.#handlers.length === 0;
+	}
+}
+
+export function run_guarded<T>(mod: string, what: string, fn: () => T): T | undefined {
+	try {
+		return fn();
+	} catch (e) {
+		console.error(`[${mod}] ${what} threw:`, e);
+		return undefined;
+	}
+}
+
+type Before = {
+	[K in keyof ServerBeforeEvents]: ServerBeforeEvents[K] extends EventSignal<infer T> ? Signal<T> : never;
+};
+type After = { [K in keyof ServerAfterEvents]: ServerAfterEvents[K] extends EventSignal<infer T> ? Signal<T> : never };
+
+interface Timer {
+	mod: string;
+	fn: () => void;
+	at: number;
+	every?: number;
+}
+
+export class ModRuntime {
+	block_components = new Map<string, { mod: string; component: BlockComponent }>();
+	item_components = new Map<string, { mod: string; component: ItemComponent }>();
+	commands = new Map<string, { mod: string; name: string; command: Command }>();
+
+	before: Before = {
+		block_break: new Signal(),
+		block_place: new Signal(),
+		block_interact: new Signal(),
+		chat_send: new Signal(),
+	};
+	after: After = {
+		block_break: new Signal(),
+		block_place: new Signal(),
+		block_interact: new Signal(),
+		chat_send: new Signal(),
+		player_join: new Signal(),
+		player_leave: new Signal(),
+		server_start: new Signal(),
+		tick: new Signal(),
+	};
+
+	// per mod key value storage, saved with the world
+	storage: Record<string, Record<string, unknown>> = {};
+
+	#timers = new Map<number, Timer>();
+	#next_timer = 1;
+	#setting_up = true;
+	#players = new WeakMap<ServerPlayer, Player>();
+	game!: GameServer;
+
+	// imports each server script and calls its setup, in load order
+	async load_scripts(game: GameServer, scripts: { mod: string; version: string; url: string }[]) {
+		this.game = game;
+		for (const { mod, version, url } of scripts) {
+			const module = await import(url);
+			if (typeof module.setup !== "function") {
+				throw new ModLoadError(mod, "the server script doesn't export a setup function");
+			}
+			await module.setup(this.#context(mod, version));
+		}
+	}
+
+	// after every setup ran: registration closes and every component blocks and items use must exist
+	finish_setup() {
+		this.#setting_up = false;
+
+		for (const [id, block] of EverythingRegistry.entries<{ components?: Record<string, unknown> }>("blocks")) {
+			for (const component of Object.keys(block.components ?? {})) {
+				if (!this.block_components.has(component)) {
+					throw new ModLoadError(
+						id.split(":")[0],
+						`block ${id} uses component ${component}, which nothing registered`,
+					);
+				}
+			}
+		}
+
+		for (const [id, item] of EverythingRegistry.entries<ItemRegistry>("items")) {
+			const components = Object.entries(item.components ?? {});
+			if (components.length === 0) continue;
+			for (const [component_id] of components) {
+				if (!this.item_components.has(component_id)) {
+					throw new ModLoadError(
+						id.split(":")[0],
+						`item ${id} uses component ${component_id}, which nothing registered`,
+					);
+				}
+			}
+			// items are created all over the engine, hook their creation once here
+			const previous = item.on_create;
+			item.on_create = (stack) => {
+				previous?.(stack);
+				for (const [component_id, params] of components) {
+					const { mod, component } = this.item_components.get(component_id)!;
+					if (component.on_create) {
+						run_guarded(
+							mod,
+							`${component_id} on_create`,
+							() => component.on_create!(item_api(stack), params),
+						);
+					}
+				}
+			};
+		}
+	}
+
+	// components on a block, with their params from its json
+	components_of(block_id: string): { mod: string; id: string; component: BlockComponent; params: unknown }[] {
+		const block = EverythingRegistry.get<{ components?: Record<string, unknown> }>("blocks", block_id);
+		return Object.entries(block?.components ?? {}).map(([id, params]) => ({
+			...this.block_components.get(id)!,
+			id,
+			params,
+		}));
+	}
+
+	tick() {
+		const now = this.game.current_tick;
+		for (const [handle, timer] of [...this.#timers]) {
+			if (timer.at > now) continue;
+			if (timer.every) {
+				timer.at = now + timer.every;
+			} else {
+				this.#timers.delete(handle);
+			}
+			run_guarded(timer.mod, "a timer", timer.fn);
+		}
+		if (!this.after.tick.empty) {
+			this.after.tick.emit({ dt: 1 / 20 });
+		}
+	}
+
+	player(player: ServerPlayer): Player {
+		let api = this.#players.get(player);
+		if (!api) {
+			api = player_api(this.game, player);
+			this.#players.set(player, api);
+		}
+		return api;
+	}
+
+	block_ref(x: number, y: number, z: number, id: string): BlockRef {
+		const game = this.game;
+		return {
+			id,
+			x,
+			y,
+			z,
+			get data() {
+				return game.world.get_tile(x, y, z)?.mod_data;
+			},
+			set data(value) {
+				game.get_or_create_tile(x, y, z).mod_data = value;
+				game.world.dirty = true;
+			},
+		};
+	}
+
+	#context(mod: string, version: string): ServerContext {
+		const setup_only = (what: string) => {
+			if (!this.#setting_up) {
+				throw new Error(`[${mod}] ${what} can only be registered during setup`);
+			}
+		};
+		const own = (id: string, what: string) => {
+			if (!id.startsWith(`${mod}:`)) {
+				throw new ModLoadError(mod, `${what} ${id} must be in the namespace "${mod}"`);
+			}
+		};
+		const game = () => this.game;
+
+		const ctx: ServerContext = {
+			mod: { id: mod, version },
+			components: {
+				register_block: (id, component) => {
+					setup_only("components");
+					own(id, "component");
+					if (this.block_components.has(id)) {
+						throw new ModLoadError(mod, `component ${id} is registered twice`);
+					}
+					this.block_components.set(id, { mod, component: component as BlockComponent });
+				},
+				register_item: (id, component) => {
+					setup_only("components");
+					own(id, "component");
+					if (this.item_components.has(id)) {
+						throw new ModLoadError(mod, `component ${id} is registered twice`);
+					}
+					this.item_components.set(id, { mod, component: component as ItemComponent });
+				},
+			},
+			commands: {
+				register: (name, command) => {
+					setup_only("commands");
+					if (!/^[a-z0-9_]+$/.test(name)) {
+						throw new ModLoadError(mod, `command name "${name}" must be a-z, 0-9 and _`);
+					}
+					if (name === "give") throw new ModLoadError(mod, `/give belongs to the base game`);
+					const existing = this.commands.get(name);
+					if (existing) {
+						throw new ModLoadError(mod, `/${name} is also registered by ${existing.mod}`);
+					}
+					const entry = { mod, name, command };
+					this.commands.set(name, entry);
+					this.commands.set(`${mod}:${name}`, entry);
+				},
+			},
+			events: {
+				before: map_signals(this.before, mod),
+				after: map_signals(this.after, mod),
+			},
+			system: {
+				run_timeout: (fn, ticks) => this.#add_timer(mod, fn, ticks),
+				run_interval: (fn, ticks) => this.#add_timer(mod, fn, ticks, Math.max(1, ticks)),
+				clear_run: (handle) => void this.#timers.delete(handle),
+				get current_tick() {
+					return game().current_tick;
+				},
+			},
+			world: {
+				get_block: (x, y, z) => game().world.get_block_id(x, y, z),
+				set_block: (x, y, z, id) => {
+					if (id !== AIR_ID && !EverythingRegistry.get("blocks", id)) throw new Error(`unknown block ${id}`);
+					game().set_block(x, y, z, id);
+					return true;
+				},
+				get_state: not_yet(mod, "world.get_state", "block states aren't synced or saved yet"),
+				set_state: not_yet(mod, "world.set_state", "block states aren't synced or saved yet"),
+				get_block_data: (x, y, z) => game().world.get_tile(x, y, z)?.mod_data as never,
+				is_loaded: () => true,
+				get seed() {
+					return game().world.seed;
+				},
+			},
+			players: {
+				all: () => game().players().map((p) => this.player(p)),
+				get: (id) => {
+					const p = game().players().find((p) => p.id === id);
+					return p && this.player(p);
+				},
+				by_name: (name) => {
+					const p = game().players().find((p) => p.name === name);
+					return p && this.player(p);
+				},
+			},
+			recipes: {
+				furnace_result: (input) => {
+					const recipe = game().recipes.furnace.get(input);
+					return recipe && { output: { ...recipe.output }, cook_time: recipe.cook_time };
+				},
+				fuel_value: (item) => game().recipes.fuel.get(item) ?? 0,
+				is_fuel: (item) => game().recipes.fuel.has(item),
+				is_smeltable: (item) => game().recipes.furnace.has(item),
+			},
+			containers: not_yet_object(mod, "containers", "step 7 in MODS.md"),
+			ui: not_yet_object(mod, "ui", "step 7 in MODS.md"),
+			net: not_yet_object(mod, "net", "step 8 in MODS.md"),
+			storage: {
+				get: (key) => structuredClone(this.storage[mod]?.[key]) as never,
+				set: (key, value) => {
+					(this.storage[mod] ??= {})[key] = structuredClone(value);
+					game().world.dirty = true;
+				},
+				delete: (key) => {
+					delete this.storage[mod]?.[key];
+					game().world.dirty = true;
+				},
+			},
+			log: (...args) => console.log(`[${mod}]`, ...args),
+		};
+		return ctx;
+	}
+
+	#add_timer(mod: string, fn: () => void, ticks: number, every?: number) {
+		const handle = this.#next_timer++;
+		this.#timers.set(handle, { mod, fn, at: this.game.current_tick + Math.max(0, ticks), every });
+		return handle;
+	}
+}
+
+// each event's signal, as seen by one mod so errors say which mod threw
+function map_signals<T extends { [name: string]: { for_mod(mod: string): unknown } }>(
+	signals: T,
+	mod: string,
+): { [K in keyof T]: ReturnType<T[K]["for_mod"]> } {
+	return Object.fromEntries(Object.entries(signals).map(([name, signal]) => [name, signal.for_mod(mod)])) as {
+		[K in keyof T]: ReturnType<T[K]["for_mod"]>;
+	};
+}
+
+function not_yet(mod: string, name: string, why: string) {
+	return () => {
+		throw new Error(`[${mod}] ctx.${name} isn't implemented yet: ${why}`);
+	};
+}
+
+// every method on it throws, saying what isn't built yet
+function not_yet_object<T>(mod: string, name: string, where: string): T {
+	return new Proxy({}, {
+		get: (_, prop) => not_yet(mod, `${name}.${String(prop)}`, where),
+	}) as T;
+}
+
+// the engine's item stacks as mods see them: { id, count, data }
+export function item_api(stack: EngineItemStack): ItemStack {
+	return {
+		get id() {
+			return stack.type_id;
+		},
+		get count() {
+			return stack.amount;
+		},
+		set count(value) {
+			stack.amount = value;
+		},
+		get data() {
+			return stack.data;
+		},
+		set data(value) {
+			stack.data = value;
+		},
+	};
+}
+
+function new_stack(item: ItemStack): EngineItemStack {
+	if (!EverythingRegistry.get("items", item.id)) throw new Error(`unknown item ${item.id}`);
+	const stack = new EngineItemStack(item.id, item.count);
+	if (item.data !== undefined) stack.data = structuredClone(item.data);
+	return stack;
+}
+
+function player_api(game: GameServer, player: ServerPlayer): Player {
+	const inventory: Container = {
+		id: `player:${player.id}`,
+		size: player.inventory.size,
+		get: (slot) => {
+			const stack = player.inventory.get_item(slot);
+			return stack && item_api(stack);
+		},
+		set: (slot, item) => player.inventory.set_item(slot, item ? new_stack(item) : undefined),
+		add: (item) => {
+			const stack = new_stack(item);
+			const left = player.inventory.add_item(stack);
+			return left > 0 ? { id: item.id, count: left, data: stack.data } : undefined;
+		},
+		on_change: not_yet("player", "inventory.on_change", "containers are step 7 in MODS.md"),
+	};
+
+	return {
+		get id() {
+			return player.id;
+		},
+		get name() {
+			return player.name;
+		},
+		get position() {
+			return { x: player.x, y: player.y, z: player.z };
+		},
+		inventory,
+		get selected_slot() {
+			return player.selected_slot;
+		},
+		get held_item() {
+			const stack = player.held_item;
+			return stack && item_api(stack);
+		},
+		give_item(id, count = 1, data) {
+			if (!EverythingRegistry.get("items", id)) throw new Error(`unknown item ${id}`);
+			game.give(player, id, count, data);
+		},
+		send_message(text) {
+			game.send_chat(player, String(text));
+		},
+		teleport(x, y, z) {
+			game.teleport(player, x, y, z);
+		},
+	};
+}

server/game/worker.ts

@@ -1,41 +1,30 @@
 /// <reference lib="deno.worker" />
 
 // runs the game in a worker without any permissions, the host does files and networking
-import { GameServer, TICK_MS } from "./game_server.ts";
+import type { GameServer } from "./game_server.ts";
+import { TICK_MS } from "./game_server.ts";
 import { GameToHost, HostToGame } from "./host_protocol.ts";
+import { data_url, start_game } from "./load_mods.ts";
 
 const SAVE_INTERVAL_MS = 30_000;
 
 let game: GameServer | undefined;
+let starting: Promise<void> | undefined;
 
 function post(message: GameToHost) {
 	self.postMessage(message);
 }
 
-self.onmessage = (event: MessageEvent<HostToGame>) => {
+self.onmessage = async (event: MessageEvent<HostToGame>) => {
 	const message = event.data;
 
 	if (message.type === "init") {
-		game = new GameServer(
-			{
-				send: (conn, data) => post({ type: "send", conn, data }),
-				close: (conn) => post({ type: "close", conn }),
-			},
-			message.save,
-			message.default_seed,
-		);
-
-		setInterval(() => game!.tick(), TICK_MS);
-		setInterval(() => {
-			if (game!.world.dirty) {
-				post({ type: "save", data: game!.save(), final: false });
-			}
-		}, SAVE_INTERVAL_MS);
-
-		post({ type: "ready", seed: game.world.seed });
+		starting = init(message);
 		return;
 	}
 
+	// players can connect while mods are still loading
+	await starting;
 	if (!game) {
 		return;
 	}
@@ -55,3 +44,35 @@ self.onmessage = (event: MessageEvent<HostToGame>) => {
 			break;
 	}
 };
+
+async function init(message: Extract<HostToGame, { type: "init" }>) {
+	try {
+		game = await start_game(
+			{
+				send: (conn, data) => post({ type: "send", conn, data }),
+				close: (conn) => post({ type: "close", conn }),
+			},
+			message.save,
+			message.default_seed,
+			message.mods.map((mod) => ({
+				listing: mod.listing,
+				data: mod.data,
+				// the worker has no file access, so the host sends the code and it's imported from memory
+				server_url: mod.server_code ? data_url(mod.server_code) : undefined,
+				worldgen_url: mod.worldgen_code ? data_url(mod.worldgen_code) : undefined,
+			})),
+		);
+	} catch (e) {
+		post({ type: "failed", error: e instanceof Error ? e.message : String(e) });
+		return;
+	}
+
+	setInterval(() => game!.tick(), TICK_MS);
+	setInterval(() => {
+		if (game!.world.dirty) {
+			post({ type: "save", data: game!.save(), final: false });
+		}
+	}, SAVE_INTERVAL_MS);
+
+	post({ type: "ready", seed: game.world.seed });
+}

server/game/world.ts

@@ -1,6 +1,6 @@
 import { AIR, CHUNK_AREA, CHUNK_HEIGHT, CHUNK_SIZE, ID_MASK } from "$/common/constants.ts";
 import { BlockRegistry, EverythingRegistry } from "$/common/everything_registry.ts";
-import { generate_raw_chunk, RawChunk } from "$/common/generation.ts";
+import { generate_raw_chunk, RawChunk, WorldgenSetup } from "$/common/generation.ts";
 import { Container } from "$/common/inventory.ts";
 import { AIR_ID, BlockChange } from "$/common/protocol.ts";
 import { chunk_key } from "$/common/utils.ts";
@@ -18,6 +18,8 @@ export interface Tile {
 	z: number;
 	data: Record<string, unknown>;
 	containers: Record<string, Container>;
+	// a mod block's data, what BlockRef.data holds
+	mod_data?: unknown;
 }
 
 export function position_key(x: number, y: number, z: number) {
@@ -28,6 +30,7 @@ export function position_key(x: number, y: number, z: number) {
 export class ServerWorld {
 	readonly seed: string;
 	readonly block_ids: Record<string, number> = {};
+	readonly worldgen: WorldgenSetup | undefined;
 
 	// what generation made, and the final blocks with neighbors' leaves and player changes applied
 	#raw = new LruMap<number, RawChunk>(RAW_CACHE_SIZE);
@@ -42,8 +45,9 @@ export class ServerWorld {
 
 	on_block_change?: (x: number, y: number, z: number, id: string) => void;
 
-	constructor(seed: string) {
+	constructor(seed: string, worldgen?: WorldgenSetup) {
 		this.seed = seed;
+		this.worldgen = worldgen;
 		EverythingRegistry.get_registry<BlockRegistry>("blocks").forEach((block, nid) => {
 			this.block_ids[block.id] = nid;
 		});
@@ -131,7 +135,7 @@ export class ServerWorld {
 		const key = chunk_key(chunk_x, chunk_z);
 		let raw = this.#raw.get(key);
 		if (!raw) {
-			raw = generate_raw_chunk(chunk_x, chunk_z, this.seed, this.block_ids);
+			raw = generate_raw_chunk(chunk_x, chunk_z, this.seed, this.block_ids, this.worldgen);
 			this.#raw.set(key, raw);
 		}
 		return raw;

server/main.ts

@@ -1,9 +1,11 @@
 import { serveDir } from "@std/http/file-server";
 import { GameToHost, HostToGame } from "./game/host_protocol.ts";
+import type { ServerModIndex } from "../build.ts";
 
 const PORT = Number(Deno.env.get("PORT") ?? 8000);
 const WORLD_FILE = Deno.env.get("WORLD_FILE") ?? "world.json";
-const STATIC_ROOT = "build";
+const STATIC_ROOT = Deno.env.get("BUILD_DIR") ?? "build";
+const SERVER_MODS_DIR = Deno.env.get("SERVER_MODS_DIR") ?? "server_mods";
 const MAX_MESSAGE_SIZE = 4096;
 const SHUTDOWN_TIMEOUT_MS = 5000;
 
@@ -43,6 +45,10 @@ game.onmessage = (event: MessageEvent<GameToHost>) => {
 		case "ready":
 			console.log(`World ${WORLD_FILE} ready, seed ${message.seed}`);
 			break;
+		case "failed":
+			console.error(`Couldn't start the game: ${message.error}`);
+			Deno.exit(1);
+			break;
 		case "send": {
 			const socket = sockets.get(message.conn);
 			if (socket?.readyState === WebSocket.OPEN) {
@@ -63,13 +69,32 @@ game.onmessage = (event: MessageEvent<GameToHost>) => {
 	}
 };
 
+// what deno task build made. no index means the build failed or never ran, and the game never runs without its mods
+function read_mods(): Extract<HostToGame, { type: "init" }>["mods"] {
+	let index: ServerModIndex;
+	try {
+		index = JSON.parse(Deno.readTextFileSync(`${SERVER_MODS_DIR}/index.json`));
+	} catch {
+		console.error(`No ${SERVER_MODS_DIR}/index.json, run deno task build first (it also reports mod errors)`);
+		Deno.exit(1);
+	}
+	return index.mods.map(({ listing, server }) => ({
+		listing,
+		data: JSON.parse(Deno.readTextFileSync(`${STATIC_ROOT}/${listing.data}`)),
+		server_code: server ? Deno.readTextFileSync(server) : undefined,
+		worldgen_code: listing.worldgen ? Deno.readTextFileSync(`${STATIC_ROOT}/${listing.worldgen}`) : undefined,
+	}));
+}
+
 game.onerror = (event) => {
 	console.error("Game server crashed:", event.message);
 	Deno.exit(1);
 };
 
+const mods = read_mods();
+console.log(`Mods: ${mods.map((mod) => `${mod.listing.id} ${mod.listing.version}`).join(", ") || "none"}`);
 const save = read_world();
-post({ type: "init", save, default_seed: Deno.env.get("SEED") ?? crypto.randomUUID() });
+post({ type: "init", save, default_seed: Deno.env.get("SEED") ?? crypto.randomUUID(), mods });
 
 function handle_socket(socket: WebSocket) {
 	const conn = next_conn++;