import { createHash, randomBytes } from "node:crypto";
import type { FastifyInstance, FastifyReply, FastifyRequest } from "fastify";
import { createRemoteJWKSet, jwtVerify, SignJWT } from "jose";
import type { Identity } from "../../../packages/core/src/index";
import type { AppConfig } from "./config";

const stateCookie = "altdock_oidc_state";
const verifierCookie = "altdock_oidc_verifier";
const nonceCookie = "altdock_oidc_nonce";
const sessionCookie = "altdock_session";

function base64Url(value: Buffer) {
  return value.toString("base64url");
}

function pkceChallenge(verifier: string) {
  return createHash("sha256").update(verifier).digest("base64url");
}

export async function createSession(identity: Identity, appConfig: AppConfig) {
  return new SignJWT({ ...identity })
    .setProtectedHeader({ alg: "HS256" })
    .setIssuedAt()
    .setExpirationTime("7d")
    .sign(new TextEncoder().encode(appConfig.SESSION_SECRET));
}

export async function readSession(token: string | undefined, appConfig: AppConfig): Promise<Identity | null> {
  if (!token) return null;
  try {
    const result = await jwtVerify(token, new TextEncoder().encode(appConfig.SESSION_SECRET), { algorithms: ["HS256"] });
    const payload = result.payload;
    if (typeof payload.subject !== "string" || typeof payload.email !== "string" || typeof payload.displayName !== "string") return null;
    return { subject: payload.subject, email: payload.email, displayName: payload.displayName };
  } catch {
    return null;
  }
}

export async function getIdentity(request: FastifyRequest, appConfig: AppConfig): Promise<Identity | null> {
  if (appConfig.AUTH_MODE === "demo") {
    const email = String(request.headers["x-demo-user"] || "demo@altdock.local");
    return { subject: `demo:${email}`, email, displayName: email.split("@")[0] || "Demo Developer" };
  }
  return readSession(request.cookies[sessionCookie], appConfig);
}

function setSession(reply: FastifyReply, token: string) {
  reply.setCookie(sessionCookie, token, {
    httpOnly: true,
    sameSite: "lax",
    secure: process.env.NODE_ENV === "production",
    path: "/",
    maxAge: 60 * 60 * 24 * 7,
  });
}

async function oidcDiscovery(appConfig: AppConfig) {
  if (!appConfig.OIDC_ISSUER_URL) throw new Error("OIDC_ISSUER_URL_REQUIRED");
  const response = await fetch(`${appConfig.OIDC_ISSUER_URL.replace(/\/$/, "")}/.well-known/openid-configuration`);
  if (!response.ok) throw new Error(`OIDC_DISCOVERY_FAILED:${response.status}`);
  return response.json() as Promise<{ authorization_endpoint: string; token_endpoint: string; jwks_uri: string; issuer: string }>;
}

export async function registerAuthRoutes(app: FastifyInstance, appConfig: AppConfig) {
  app.get("/auth/login", async (_request, reply) => {
    if (appConfig.AUTH_MODE === "demo") return reply.redirect(appConfig.WEB_ORIGIN);
    if (!appConfig.OIDC_CLIENT_ID || !appConfig.OIDC_REDIRECT_URI) throw new Error("OIDC_CONFIGURATION_REQUIRED");
    const provider = await oidcDiscovery(appConfig);
    const state = base64Url(randomBytes(24));
    const verifier = base64Url(randomBytes(32));
    const nonce = base64Url(randomBytes(24));
    const params = new URLSearchParams({
      client_id: appConfig.OIDC_CLIENT_ID,
      redirect_uri: appConfig.OIDC_REDIRECT_URI,
      response_type: "code",
      scope: "openid profile email",
      state,
      nonce,
      code_challenge: pkceChallenge(verifier),
      code_challenge_method: "S256",
    });
    reply.setCookie(stateCookie, state, { httpOnly: true, sameSite: "lax", secure: process.env.NODE_ENV === "production", path: "/auth" });
    reply.setCookie(verifierCookie, verifier, { httpOnly: true, sameSite: "lax", secure: process.env.NODE_ENV === "production", path: "/auth" });
    reply.setCookie(nonceCookie, nonce, { httpOnly: true, sameSite: "lax", secure: process.env.NODE_ENV === "production", path: "/auth" });
    return reply.redirect(`${provider.authorization_endpoint}?${params.toString()}`);
  });

  app.get("/auth/callback", async (request, reply) => {
    if (appConfig.AUTH_MODE === "demo") return reply.redirect(appConfig.WEB_ORIGIN);
    if (!appConfig.OIDC_CLIENT_ID || !appConfig.OIDC_REDIRECT_URI || !appConfig.OIDC_CLIENT_SECRET) throw new Error("OIDC_CONFIGURATION_REQUIRED");
    const query = request.query as { code?: string; state?: string; error?: string };
    if (query.error) return reply.code(400).send({ error: "OIDC_LOGIN_FAILED", detail: query.error });
    if (!query.code || query.state !== request.cookies[stateCookie]) return reply.code(400).send({ error: "OIDC_STATE_INVALID" });
    const verifier = request.cookies[verifierCookie];
    const nonce = request.cookies[nonceCookie];
    if (!verifier || !nonce) return reply.code(400).send({ error: "OIDC_VERIFIER_MISSING" });
    const provider = await oidcDiscovery(appConfig);
    const tokenResponse = await fetch(provider.token_endpoint, {
      method: "POST",
      headers: { "content-type": "application/x-www-form-urlencoded" },
      body: new URLSearchParams({ grant_type: "authorization_code", code: query.code, redirect_uri: appConfig.OIDC_REDIRECT_URI, client_id: appConfig.OIDC_CLIENT_ID, client_secret: appConfig.OIDC_CLIENT_SECRET, code_verifier: verifier }),
    });
    if (!tokenResponse.ok) return reply.code(400).send({ error: "OIDC_TOKEN_EXCHANGE_FAILED" });
    const tokens = await tokenResponse.json() as { id_token?: string; access_token?: string };
    if (!tokens.id_token) return reply.code(400).send({ error: "OIDC_ID_TOKEN_MISSING" });
    const jwks = createRemoteJWKSet(new URL(provider.jwks_uri));
    const verified = await jwtVerify(tokens.id_token, jwks, { issuer: provider.issuer, audience: appConfig.OIDC_CLIENT_ID });
    const claims = verified.payload;
    if (claims.nonce !== nonce) return reply.code(400).send({ error: "OIDC_NONCE_INVALID" });
    const subject = String(claims.sub || "");
    if (!subject) return reply.code(400).send({ error: "OIDC_SUBJECT_MISSING" });
    const email = String(claims.email || `${subject}@oidc.local`);
    const displayName = String(claims.name || claims.preferred_username || email.split("@")[0] || "Developer");
    setSession(reply, await createSession({ subject, email, displayName }, appConfig));
    reply.clearCookie(stateCookie, { path: "/auth" });
    reply.clearCookie(verifierCookie, { path: "/auth" });
    reply.clearCookie(nonceCookie, { path: "/auth" });
    // SSO成功後はランディングではなく管理ダッシュボードへ直接向かう。
    return reply.redirect(`${appConfig.WEB_ORIGIN.replace(/\/$/, "")}/dashboard`);
  });

  app.get("/auth/logout", async (_request, reply) => {
    reply.clearCookie(sessionCookie, { path: "/" });
    return reply.redirect(appConfig.WEB_ORIGIN);
  });
}