/**
 * Config-driven in-stream error pattern matching.
 * See docs/2026-08-04-stream-error-patterns-design.md.
 *
 * Settings shape: streamErrorPatterns: { [provider]: string[] }
 * Pattern syntax per entry:
 *   - "plain text"   → case-insensitive substring match
 *   - "/regex/flags" → RegExp match (flags after the last "/")
 */

export function parsePatterns(patterns) {
	if (!Array.isArray(patterns)) return [];
	const out = [];
	for (const entry of patterns) {
		if (typeof entry !== "string" || !entry.trim()) continue;
		const raw = entry.trim();
		const m = raw.match(/^\/(.*)\/([a-z]*)$/s);
		if (m) {
			try {
				out.push({ regex: new RegExp(m[1], m[2]), raw });
			} catch {
				// invalid regex → skip; config errors must never break requests
			}
			continue;
		}
		out.push({ text: raw.toLowerCase(), raw });
	}
	return out;
}

export function matchStreamErrorPatterns(patterns, text) {
	if (!Array.isArray(patterns) || patterns.length === 0) return null;
	if (typeof text !== "string" || !text) return null;
	const lower = text.toLowerCase();
	for (const p of parsePatterns(patterns)) {
		if (p.text && lower.includes(p.text)) return p.raw;
		if (p.regex) {
			p.regex.lastIndex = 0; // stateless even with /g
			if (p.regex.test(text)) return p.raw;
		}
	}
	return null;
}

export function streamStatusForContent(patterns, content) {
	return matchStreamErrorPatterns(patterns, content) ? "error" : "success";
}