import picomatch from "picomatch";
import type { Config, Phase } from "./types.js";

/**
 * Match a file path against a list of glob patterns with !exclusion support.
 *
 * Positive patterns (no ! prefix) include a file in the match.
 * Negative patterns (! prefix) exclude a file from the match.
 * A file matches if it matches any positive pattern AND no negative pattern.
 * Empty pattern list = no match.
 */
function matchPatterns(patterns: string[], filePath: string): boolean {
	const positive: string[] = [];
	const negative: string[] = [];

	for (const p of patterns) {
		if (p.startsWith("!")) {
			negative.push(p.slice(1));
		} else {
			positive.push(p);
		}
	}

	if (positive.length === 0) return false;

	const matchesPositive = positive.some((p) => picomatch(p)(filePath));
	if (!matchesPositive) return false;

	const matchesNegative = negative.some((p) => picomatch(p)(filePath));
	return !matchesNegative;
}

/**
 * Check if a file path is allowed to be modified in the current phase.
 *
 * Rules:
 * - REFACTOR: everything allowed
 * - RED: files in implFiles are blocked, everything else is free
 * - GREEN: files in testFiles are blocked, everything else is free
 * - ! negation patterns exclude subsets from a block list
 */
export function isAllowed(
	filePath: string,
	phase: Phase,
	config: Config,
	hasRedSnapshot: boolean = false,
): boolean {
	if (phase === "refactor") return true;
	if (phase === "green" && hasRedSnapshot) return true;

	const blocked = phase === "red" ? config.implFiles : config.testFiles;
	return !matchPatterns(blocked, filePath);
}

/**
 * Filter a list of file paths to those that are disallowed in the current phase.
 */
export function disallowedFiles(
	files: string[],
	phase: Phase,
	config: Config,
	hasRedSnapshot: boolean = false,
): string[] {
	if (phase === "refactor") return [];
	return files.filter((f) => !isAllowed(f, phase, config, hasRedSnapshot));
}