import { MAX_ROUTES_RULE_LENGTH, MAX_ROUTES_RULES } from "./constants";
import type { StaticRouting } from "../types";

// copy of what EWC does. Wrangler uploads the rules in one array (so the API is consistent with Wrangler config),
// but router Worker expects the rules to be split into two arrays, which we do here.
// This logic is translated from assets/staticrouting.go.

export function parseStaticRouting(input: string[]): StaticRouting {
	if (input.length === 0) {
		throw new Error(
			"No `run_worker_first` rules were provided; must provide at least 1 rule."
		);
	}
	if (input.length > MAX_ROUTES_RULES) {
		throw new Error(
			`Too many \`run_worker_first\` rules were provided; ${input.length} rules provided exceeds max of ${MAX_ROUTES_RULES}.`
		);
	}

	const rawAssetWorkerRules = [];
	const assetWorkerRules = [];
	const userWorkerRules = [];
	const invalidRules = [];

	for (const rule of input) {
		if (rule.startsWith("!/")) {
			assetWorkerRules.push(rule.slice(1)); // Remove leading !
			rawAssetWorkerRules.push(rule);
		} else if (rule.startsWith("/")) {
			userWorkerRules.push(rule);
		} else if (rule.startsWith("!")) {
			invalidRules.push(`'${rule}': negative rules must start with '!/'`);
		} else {
			invalidRules.push(`'${rule}': rules must start with '/' or '!/'`);
		}
	}

	if (assetWorkerRules.length > 0 && userWorkerRules.length === 0) {
		throw new Error(
			"Only negative `run_worker_first` rules were provided; must provide at least 1 non-negative rule"
		);
	}

	const invalidAssetWorkerRules =
		validateStaticRoutingRules(rawAssetWorkerRules);
	const invalidUserWorkerRules = validateStaticRoutingRules(userWorkerRules);
	const errorMessage = formatInvalidRoutes([
		...invalidRules,
		...invalidUserWorkerRules,
		...invalidAssetWorkerRules,
	]);

	if (errorMessage) {
		throw new Error(errorMessage);
	}

	return { asset_worker: assetWorkerRules, user_worker: userWorkerRules };
}

function validateStaticRoutingRules(rules: string[]): string[] {
	const invalid: string[] = [];
	const seen = new Set<string>();
	for (const rule of rules) {
		if (rule.length > MAX_ROUTES_RULE_LENGTH) {
			invalid.push(
				`'${rule}': all rules must be less than ${MAX_ROUTES_RULE_LENGTH} characters in length`
			);
		}
		if (seen.has(rule)) {
			invalid.push(`'${rule}': rule is a duplicate; rules must be unique`);
		}
		if (rule.endsWith("*")) {
			// Check for redundant rules due to a glob
			for (const otherRule of rules) {
				if (otherRule !== rule && otherRule.startsWith(rule.slice(0, -1))) {
					invalid.push(`'${otherRule}': rule '${rule}' makes it redundant`);
				}
			}
		}
		seen.add(rule);
	}
	return invalid;
}

const formatInvalidRoutes = (invalidRules: string[]) => {
	if (invalidRules.length === 0) {
		return undefined;
	}
	return `Invalid routes in \`run_worker_first\`:\n` + invalidRules.join("\n");
};