import type {
	CodexDiagnosticsFailure,
	CodexDiagnosticsFailureCategory,
	CodexDiagnosticsSink,
} from "./types.ts";

function record(value: unknown): Record<string, unknown> | undefined {
	return value && typeof value === "object"
		? value as Record<string, unknown>
		: undefined;
}

function safeCode(value: unknown): string | undefined {
	return typeof value === "string" && /^[a-z0-9_.-]{1,64}$/i.test(value)
		? value
		: undefined;
}

function statusCode(value: unknown): number | undefined {
	const parsed = typeof value === "string" && /^\d{3}$/.test(value)
		? Number(value)
		: value;
	return typeof parsed === "number" && Number.isInteger(parsed) && parsed >= 100 && parsed <= 599
		? parsed
		: undefined;
}

function category(description: string): CodexDiagnosticsFailureCategory {
	if (/abort/i.test(description)) return "aborted";
	if (/401|403|unauthori[sz]ed|forbidden|authentication|token expired/i.test(description)) return "authentication";
	if (/websocket_connection_limit_reached|connection limit/i.test(description)) return "connection_limit";
	if (/1009|message too big/i.test(description)) return "message_too_big";
	if (/previous_response_not_found|previous response.*not found/i.test(description)) return "previous_response_missing";
	if (/server_is_overloaded|slow_down|overload/i.test(description)) return "overload";
	if (/rate.?limit|429/i.test(description)) return "rate_limit";
	if (/timed? out|timeout/i.test(description)) return "timeout";
	if (/protocol|invalid response|unhandled.*status/i.test(description)) return "protocol";
	if (/websocket|socket|connection|network|fetch/i.test(description)) return "connection";
	if (description) return "transport";
	return "unknown";
}

export function codexDiagnosticsFailure(error: unknown): CodexDiagnosticsFailure {
	const outer = record(error);
	const payload = record(outer?.["payload"]);
	const response = record(payload?.["response"]);
	const responseError = record(response?.["error"]);
	const code = safeCode(outer?.["code"])
		?? safeCode(payload?.["code"])
		?? safeCode(responseError?.["code"])
		?? safeCode(responseError?.["type"]);
	const status = statusCode(outer?.["status"])
		?? statusCode(payload?.["status"])
		?? statusCode(responseError?.["status"]);
	const description = [
		error instanceof Error ? error.name : undefined,
		error instanceof Error ? error.message : typeof error === "string" ? error : undefined,
		code,
		status,
	].filter((value) => value !== undefined).join(" ");
	return {
		category: category(description),
		...(code ? { code } : {}),
		...(status !== undefined ? { status } : {}),
	};
}

export function noThrowCodexDiagnosticsSink(
	sink: CodexDiagnosticsSink | undefined,
): CodexDiagnosticsSink | undefined {
	if (!sink) return undefined;
	return (event) => {
		try {
			sink(event);
		} catch {
			// Optional diagnostics must never change provider execution.
		}
	};
}