/**
 * OpenRouter OAuth PKCE flow.
 *
 * OpenRouter exchanges an authorization code for a permanent, user-controlled
 * API key rather than an expiring access/refresh token pair. The callback is
 * handled by a one-shot loopback server on an ephemeral port, raced against a
 * manual prompt so remote/headless sessions can paste the redirect URL when
 * the browser cannot reach the loopback server.
 *
 * NOTE: This module uses node:http (via callback-server.ts) for the OAuth callback server.
 * It is only intended for CLI use, not browser environments.
 */

import { getProviderEnvValue } from "../../utils/provider-env.ts";
import type { OAuthAuth, OAuthCredential, ProviderAuthInteraction } from "../types.ts";
import { startOAuthCallbackServer, waitForCallbackOrManualInput } from "./callback-server.ts";
import { generatePKCE } from "./pkce.ts";

const AUTHORIZE_URL = "https://openrouter.ai/auth";
const TOKEN_URL = "https://openrouter.ai/api/v1/auth/keys";
const LOGIN_TIMEOUT_MS = 5 * 60 * 1000;
const TOKEN_EXCHANGE_TIMEOUT_MS = 30_000;

function getCallbackHost(): string {
	return getProviderEnvValue("PI_OAUTH_CALLBACK_HOST") || "127.0.0.1";
}

type JsonObject = Record<string, unknown>;

function parseAuthorizationInput(input: string): string | undefined {
	const value = input.trim();
	if (!value) return undefined;

	try {
		return new URL(value).searchParams.get("code") ?? undefined;
	} catch {
		// not a URL
	}

	if (value.includes("code=")) {
		return new URLSearchParams(value).get("code") ?? undefined;
	}

	return value;
}

function errorDetail(body: JsonObject): string | undefined {
	if (typeof body.error_description === "string") return body.error_description;
	if (typeof body.message === "string") return body.message;
	if (typeof body.error === "string") return body.error;
	if (body.error && typeof body.error === "object" && !Array.isArray(body.error)) {
		const message = (body.error as JsonObject).message;
		if (typeof message === "string") return message;
	}
	return undefined;
}

async function exchangeAuthorizationCode(
	code: string,
	verifier: string,
	signal: AbortSignal,
): Promise<OAuthCredential> {
	if (signal.aborted) throw new Error("Login cancelled");
	const controller = new AbortController();
	const onAbort = () => controller.abort(signal.reason);
	signal.addEventListener("abort", onAbort, { once: true });
	const timeout = setTimeout(
		() => controller.abort(new Error("OpenRouter OAuth token exchange timed out")),
		TOKEN_EXCHANGE_TIMEOUT_MS,
	);

	let response: Response;
	let body: JsonObject = {};
	try {
		response = await fetch(TOKEN_URL, {
			method: "POST",
			headers: { accept: "application/json", "content-type": "application/json" },
			body: JSON.stringify({ code, code_verifier: verifier, code_challenge_method: "S256" }),
			signal: controller.signal,
		});
		try {
			const parsed = (await response.json()) as unknown;
			if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) body = parsed as JsonObject;
		} catch {
			if (response.ok) throw new Error("OpenRouter OAuth returned invalid JSON");
		}
	} catch (error) {
		if (signal.aborted) throw new Error("Login cancelled");
		if (controller.signal.aborted) throw new Error("OpenRouter OAuth token exchange timed out");
		throw error;
	} finally {
		clearTimeout(timeout);
		signal.removeEventListener("abort", onAbort);
	}

	if (!response.ok) {
		const detail = errorDetail(body);
		throw new Error(`OpenRouter OAuth key exchange failed (HTTP ${response.status})${detail ? `: ${detail}` : ""}`);
	}

	if (typeof body.key !== "string" || body.key.length === 0) {
		throw new Error('OpenRouter OAuth response carries no "key"');
	}

	return {
		type: "oauth",
		access: body.key,
		refresh: "",
		expires: Number.MAX_SAFE_INTEGER,
	};
}

async function loginOpenRouter(interaction: ProviderAuthInteraction): Promise<OAuthCredential> {
	const { verifier, challenge } = await generatePKCE();
	// OpenRouter sends no `state`; the random path keeps stray requests from completing the sign-in.
	const callback = await startOAuthCallbackServer({
		providerName: "OpenRouter",
		host: getCallbackHost(),
		port: 0,
		path: `/oauth/callback/${crypto.randomUUID()}`,
		complete: (code) => exchangeAuthorizationCode(code, verifier, interaction.signal),
		signal: interaction.signal,
		timeoutMs: LOGIN_TIMEOUT_MS,
	});

	try {
		const authorizeUrl = new URL(AUTHORIZE_URL);
		authorizeUrl.search = new URLSearchParams({
			callback_url: callback.redirectUri,
			code_challenge: challenge,
			code_challenge_method: "S256",
		}).toString();

		interaction.notify({
			type: "progress",
			message: `Listening for OpenRouter OAuth callback on ${callback.redirectUri}`,
		});
		interaction.notify({
			type: "auth_url",
			url: authorizeUrl.toString(),
			instructions:
				"Complete sign-in in your browser. If the browser is on another machine, paste the final redirect URL here.",
		});

		const result = await waitForCallbackOrManualInput(interaction, callback, {
			message: "Complete sign-in in your browser, or paste the authorization code / redirect URL here:",
			placeholder: callback.redirectUri,
		});
		if (result.type === "callback") return result.value;
		const code = parseAuthorizationInput(result.input);
		if (!code) throw new Error("Missing authorization code");
		interaction.notify({ type: "progress", message: "Exchanging authorization code for an API key..." });
		return await exchangeAuthorizationCode(code, verifier, interaction.signal);
	} finally {
		callback.close();
	}
}

export const openRouterOAuth: OAuthAuth = {
	name: "OpenRouter OAuth",
	loginLabel: "Sign in with OpenRouter",
	login: loginOpenRouter,
	async refresh(credential, _signal) {
		return credential;
	},
	async toAuth(credential) {
		return { apiKey: credential.access };
	},
};