export const selectorKinds = ["css", "xpath", "accessibility"] as const;
export type SelectorKind = typeof selectorKinds[number];

export type SelectorPolicy = {
	readonly css: boolean;
	readonly xpath: boolean;
	readonly accessibility: boolean;
};

export type SelectorPolicyInput = {
	readonly enable?: readonly SelectorKind[];
	readonly disable?: readonly SelectorKind[];
};

export type SelectorPolicyResult = {
	readonly ok: true;
	readonly policy: SelectorPolicy;
} | {
	readonly ok: false;
	readonly problem: "unknown_selector_kind" | "conflicting_selector_kind" | "empty_selector_policy";
	readonly selector_kind: string | null;
};

export function resolveSelectorPolicy(input: SelectorPolicyInput): SelectorPolicyResult {
	const explicitEnable = input.enable !== undefined;
	const enabled = new Set<SelectorKind>(input.enable ?? selectorKinds);
	const disabled = new Set<SelectorKind>(input.disable ?? []);
	for (const kind of [...enabled, ...disabled]) {
		if (!isSelectorKind(kind)) {
			return { ok: false, problem: "unknown_selector_kind", selector_kind: String(kind) };
		}
	}
	for (const kind of disabled) {
		if (explicitEnable && enabled.has(kind)) {
			return { ok: false, problem: "conflicting_selector_kind", selector_kind: kind };
		}
	}
	for (const kind of disabled) enabled.delete(kind);
	const policy: SelectorPolicy = {
		css: enabled.has("css"),
		xpath: enabled.has("xpath"),
		accessibility: enabled.has("accessibility"),
	};
	if (!policy.css && !policy.xpath && !policy.accessibility) {
		return { ok: false, problem: "empty_selector_policy", selector_kind: null };
	}
	return { ok: true, policy };
}

function isSelectorKind(value: string): value is SelectorKind {
	return (selectorKinds as readonly string[]).includes(value);
}