// the json formats from MODS.md, and converting them to and from the engine's registry entries.
// the mod loader uses the from_json direction, tools/export_bworld_mod.ts the other one
import type { BlockRegistry, BlockStateDefinition, ItemRegistry } from "./everything_registry.ts";

export const FORMAT_VERSION = 1;
export const ID_PATTERN = /^[a-z0-9_]+:[a-z0-9_]+$/;
export const NAMESPACE_PATTERN = /^[a-z0-9_]{1,32}$/;
export const RESERVED_NAMESPACES = ["bworld", "engine"];

type BlockTextures = BlockRegistry["textures"];

export interface ManifestJson {
	format_version: number;
	id: string;
	name: string;
	description?: string;
	version: string;
	authors?: string[];
	game_version?: string;
	dependencies?: { id: string; version: string }[];
	scripts?: { server?: string; client?: string; worldgen?: string };
	credits?: string;
}

export interface BlockJson {
	id: string;
	textures: BlockTextures;
	transparent?: boolean;
	alpha?: number;
	collision?: boolean;
	mining?: { toughness: number; tool?: string; requires_tool?: boolean };
	drops?: string;
	item?: boolean;
	interactive?: boolean;
	replaceable?: boolean;
	states?: BlockStateDefinition[];
	components?: Record<string, unknown>;
}

export interface ItemJson {
	id: string;
	texture: string;
	tool?: string;
	places?: string;
	max_stack?: number;
	lore?: string;
	components?: Record<string, unknown>;
}

export type RecipeJson =
	| {
		type: "shaped";
		pattern: string[];
		key: Record<string, string>;
		result: { id: string; count: number };
	}
	| { type: "furnace"; input: string; output: { id: string; count: number }; cook_time: number }
	| { type: "fuel"; item: string; burn_time: number };

// the crafting grid's format, see server/game/crafting.ts
export interface GridRecipe {
	width: number;
	height: number;
	pattern: (string | undefined)[];
	result: { id: string; count: number };
}

// blocks

export function block_to_json(block: BlockRegistry, has_item: boolean): BlockJson {
	const json: BlockJson = { id: block.id, textures: block.textures };
	if (block.transparent) json.transparent = true;
	if (block.alpha !== undefined) json.alpha = block.alpha;
	if (!block.has_collision) json.collision = false;
	if (block.toughness !== undefined) {
		json.mining = { toughness: block.toughness };
		if (block.tool_to_break !== undefined) json.mining.tool = block.tool_to_break;
		if (block.requires_tool) json.mining.requires_tool = true;
	}
	if (block.drop_table !== undefined) json.drops = block.drop_table;
	if (!has_item) json.item = false;
	if (block.interactive) json.interactive = true;
	if (block.replaceable) json.replaceable = true;
	if (block.states) json.states = block.states;
	return json;
}

export function block_from_json(json: BlockJson): { block: BlockRegistry; has_item: boolean } {
	const block: BlockRegistry = {
		id: json.id,
		textures: json.textures,
		has_collision: json.collision ?? true,
	};
	if (json.transparent) block.transparent = true;
	if (json.alpha !== undefined) block.alpha = json.alpha;
	if (json.mining) {
		block.toughness = json.mining.toughness;
		block.requires_tool = json.mining.requires_tool ?? false;
		if (json.mining.tool !== undefined) block.tool_to_break = json.mining.tool;
	}
	if (json.drops !== undefined) block.drop_table = json.drops;
	if (json.interactive) block.interactive = true;
	if (json.replaceable) block.replaceable = true;
	if (json.states) block.states = json.states;
	return { block, has_item: json.item ?? true };
}

// items that aren't the item form of a block

export function item_to_json(id: string, item: ItemRegistry): ItemJson {
	if (typeof item.texture_id !== "string") {
		throw new Error(`${id} picks its texture with a function, which json can't hold`);
	}
	const json: ItemJson = { id, texture: item.texture_id };
	if (item.tool_type !== undefined) json.tool = item.tool_type;
	if (item.block_id !== undefined) json.places = item.block_id;
	return json;
}

export function item_from_json(json: ItemJson): ItemRegistry {
	const item: ItemRegistry = { texture_id: json.texture };
	if (json.tool !== undefined) item.tool_type = json.tool;
	if (json.places !== undefined) item.block_id = json.places;
	return item;
}

// shaped recipes <-> the grid format

export function grid_recipe_to_json(recipe: GridRecipe): RecipeJson {
	const key: Record<string, string> = {};
	const letters = new Map<string, string>();
	for (const id of recipe.pattern) {
		if (id === undefined || letters.has(id)) continue;
		const letter = pick_letter(id, new Set(letters.values()));
		letters.set(id, letter);
		key[letter] = id;
	}

	const pattern: string[] = [];
	for (let y = 0; y < recipe.height; y++) {
		let row = "";
		for (let x = 0; x < recipe.width; x++) {
			const id = recipe.pattern[y * recipe.width + x];
			row += id === undefined ? " " : letters.get(id);
		}
		pattern.push(row);
	}

	return { type: "shaped", pattern, key, result: recipe.result };
}

export function grid_recipe_from_json(json: Extract<RecipeJson, { type: "shaped" }>): GridRecipe {
	const height = json.pattern.length;
	const width = Math.max(...json.pattern.map((row) => row.length));
	const pattern: (string | undefined)[] = [];
	for (const row of json.pattern) {
		for (let x = 0; x < width; x++) {
			const letter = row[x] ?? " ";
			pattern.push(letter === " " ? undefined : json.key[letter]);
		}
	}
	return { width, height, pattern, result: json.result };
}

// a readable letter for an item in a pattern: its first letter if free, like P for planks
function pick_letter(id: string, taken: Set<string>) {
	const name = id.split(":")[1].toUpperCase();
	for (const letter of [...name, ..."ABCDEFGHIJKLMNOPQRSTUVWXYZ"]) {
		if (/[A-Z]/.test(letter) && !taken.has(letter)) {
			return letter;
		}
	}
	throw new Error(`Ran out of letters for ${id}`);
}

// validation. every function returns a list of problems, empty when it's fine

type Problems = string[];

export function validate_manifest(json: unknown, folder_name: string): Problems {
	const problems: Problems = [];
	if (!is_object(json)) return ["manifest.json must be an object"];

	if (json.format_version !== FORMAT_VERSION) {
		problems.push(`format_version must be ${FORMAT_VERSION}`);
	}
	if (typeof json.id !== "string" || !NAMESPACE_PATTERN.test(json.id)) {
		problems.push("id must be 1-32 characters of a-z, 0-9 and _");
	} else if (json.id !== folder_name) {
		problems.push(`id "${json.id}" must match the folder name "${folder_name}"`);
	}
	if (typeof json.name !== "string" || json.name.length === 0) problems.push("name is required");
	if (typeof json.version !== "string" || !/^\d+\.\d+\.\d+/.test(json.version)) {
		problems.push("version must be semver, like 1.0.0");
	}
	if (json.dependencies !== undefined) {
		if (!Array.isArray(json.dependencies)) {
			problems.push("dependencies must be a list");
		} else {
			for (const dep of json.dependencies) {
				if (!is_object(dep) || typeof dep.id !== "string" || typeof dep.version !== "string") {
					problems.push("each dependency needs an id and a version range");
				}
			}
		}
	}
	if (json.scripts !== undefined) {
		if (!is_object(json.scripts)) {
			problems.push("scripts must be an object");
		} else {
			for (const [side, path] of Object.entries(json.scripts)) {
				if (!["server", "client", "worldgen"].includes(side)) problems.push(`unknown script "${side}"`);
				if (typeof path !== "string") problems.push(`scripts.${side} must be a path`);
			}
		}
	}
	return problems;
}

export function validate_block(json: unknown): Problems {
	if (!is_object(json)) return ["block must be an object"];
	const problems = validate_id(json.id, "id");
	const textures = json.textures;
	const texture_ok = typeof textures === "string" ||
		(is_object(textures) &&
			(["top", "bottom", "side"].every((k) => typeof textures[k] === "string") ||
				["front", "side"].every((k) => typeof textures[k] === "string")));
	if (!texture_ok) problems.push("textures must be a texture id, { top, bottom, side } or { front, side }");
	for (const key of ["transparent", "collision", "item", "interactive", "replaceable"]) {
		if (json[key] !== undefined && typeof json[key] !== "boolean") problems.push(`${key} must be true or false`);
	}
	if (json.alpha !== undefined && (typeof json.alpha !== "number" || json.alpha < 0 || json.alpha > 1)) {
		problems.push("alpha must be between 0 and 1");
	}
	if (json.mining !== undefined) {
		if (!is_object(json.mining) || typeof json.mining.toughness !== "number" || json.mining.toughness < 0) {
			problems.push("mining.toughness must be a number of seconds");
		}
	}
	if (json.drops !== undefined) problems.push(...validate_id(json.drops, "drops"));
	if (json.states !== undefined) {
		const states = json.states;
		if (!Array.isArray(states)) {
			problems.push("states must be a list");
		} else {
			const bits = states.reduce((sum, s) => sum + (is_object(s) && typeof s.bits === "number" ? s.bits : 0), 0);
			if (bits > 16) problems.push(`states use ${bits} bits, the most is 16`);
		}
	}
	return problems;
}

export function validate_item(json: unknown): Problems {
	if (!is_object(json)) return ["item must be an object"];
	const problems = validate_id(json.id, "id");
	problems.push(...validate_id(json.texture, "texture"));
	if (json.places !== undefined) problems.push(...validate_id(json.places, "places"));
	if (json.max_stack !== undefined && (!Number.isInteger(json.max_stack) || (json.max_stack as number) < 1)) {
		problems.push("max_stack must be a positive whole number");
	}
	return problems;
}

export function validate_recipe(json: unknown): Problems {
	if (!is_object(json)) return ["recipe must be an object"];
	const problems: Problems = [];
	switch (json.type) {
		case "shaped": {
			const pattern = json.pattern;
			if (
				!Array.isArray(pattern) || pattern.length < 1 || pattern.length > 3 ||
				!pattern.every((row) => typeof row === "string" && row.length >= 1 && row.length <= 3)
			) {
				problems.push("pattern must be 1-3 rows of 1-3 characters");
			} else if (is_object(json.key)) {
				for (const letter of pattern.join("").replaceAll(" ", "")) {
					if (!(letter in json.key)) problems.push(`pattern uses "${letter}" but key doesn't define it`);
				}
			}
			if (!is_object(json.key)) {
				problems.push("key must map letters to item ids");
			} else {
				for (const id of Object.values(json.key)) problems.push(...validate_id(id, "key"));
			}
			problems.push(...validate_stack(json.result, "result"));
			break;
		}
		case "furnace":
			problems.push(...validate_id(json.input, "input"), ...validate_stack(json.output, "output"));
			if (!Number.isInteger(json.cook_time) || (json.cook_time as number) < 1) {
				problems.push("cook_time must be a positive number of ticks");
			}
			break;
		case "fuel":
			problems.push(...validate_id(json.item, "item"));
			if (!Number.isInteger(json.burn_time) || (json.burn_time as number) < 1) {
				problems.push("burn_time must be a positive number of ticks");
			}
			break;
		default:
			problems.push('type must be "shaped", "furnace" or "fuel"');
	}
	return problems;
}

function validate_id(value: unknown, field: string): Problems {
	return typeof value === "string" && ID_PATTERN.test(value) ? [] : [`${field} must be an id like "my_mod:thing"`];
}

function validate_stack(value: unknown, field: string): Problems {
	if (!is_object(value)) return [`${field} must be { id, count }`];
	const problems = validate_id(value.id, `${field}.id`);
	if (!Number.isInteger(value.count) || (value.count as number) < 1) {
		problems.push(`${field}.count must be a positive whole number`);
	}
	return problems;
}

function is_object(value: unknown): value is Record<string, unknown> {
	return typeof value === "object" && value !== null && !Array.isArray(value);
}