export type TargetRole = { guild_id: string; role_id: string };
type SerializedRule = { group_id: string; target_role: TargetRole };

/**
 * A set of rules for associating CRI groups with Discord roles.
 */
export class RuleSet {
	private rules;

	public constructor() {
		this.rules = new Map<string, TargetRole[]>();
	}

	/**
	 * Reads a RuleSet from a JSON serialized file.
	 */
	public static async from_file(path: string) {
		const result = new RuleSet();
		const file_content = await Deno.readTextFile(path);
		const parsed = JSON.parse(file_content) as SerializedRule[];
		for (const { group_id, target_role } of parsed) result.append_rule(group_id, target_role);
		return result;
	}

	/**
	 * Gets which Discord roles must be assigned to a user which is part of a given CRI group.
	 */
	public roles_for_group(group_id: string) {
		return this.rules.get(group_id) ?? [];
	}

	/**
	 * Number of managed Discord roles.
	 */
	public size() {
		let result = 0;
		for (const roles of this.rules.values()) result += roles.length;
		return result;
	}

	private append_rule(group_id: string, target_role: TargetRole) {
		let roles = this.rules.get(group_id);
		if (roles === undefined) {
			roles = [];
			this.rules.set(group_id, roles);
		}
		roles.push(target_role);
	}
}