import { Router, type IRouter, type Request } from "express";
import {
  discovery,
  randomPKCECodeVerifier,
  calculatePKCECodeChallenge,
  randomState,
  buildAuthorizationUrl,
  authorizationCodeGrant,
  fetchUserInfo,
  buildEndSessionUrl,
  skipSubjectCheck,
  type Configuration,
} from "openid-client";
import bcrypt from "bcryptjs";
import { eq, and, inArray, isNull } from "drizzle-orm";
import { z } from "zod";
import { db, usersTable, toolsTable, ratingsTable } from "@workspace/db";
import { logger } from "../lib/logger";
import { writeAuditLog } from "../lib/audit";
import { loginRateLimit, passwordRateLimit } from "../lib/rate-limit";
import { getEntitlements, requireFeature } from "../middleware/feature";
import { getCsrfToken } from "../middleware/csrf";

const router: IRouter = Router();

let cachedConfig: Configuration | null = null;

function isOidcConfigured(): boolean {
  return !!(
    process.env.KEYCLOAK_URL &&
    process.env.KEYCLOAK_REALM &&
    process.env.KEYCLOAK_CLIENT_ID &&
    process.env.KEYCLOAK_CLIENT_SECRET
  );
}

function getBaseUrl(req: Request): string {
  if (process.env.APP_URL) return process.env.APP_URL;
  const host = req.get("x-forwarded-host") || req.get("host") || "localhost";
  const proto = req.get("x-forwarded-proto") || "https";
  return `${proto}://${host}`;
}

function isSafeReturnTo(value: string): boolean {
  if (!value.startsWith("/") || value.startsWith("//")) return false;
  try {
    return new URL(value, "http://localhost").origin === "http://localhost";
  } catch {
    return false;
  }
}

async function getClient(): Promise<Configuration | null> {
  if (cachedConfig) return cachedConfig;

  const keycloakUrl = process.env.KEYCLOAK_URL;
  const realm = process.env.KEYCLOAK_REALM;
  const clientId = process.env.KEYCLOAK_CLIENT_ID;
  const clientSecret = process.env.KEYCLOAK_CLIENT_SECRET;

  if (!keycloakUrl || !realm || !clientId || !clientSecret) {
    return null;
  }

  try {
    const issuerUrl = new URL(`${keycloakUrl}/realms/${realm}`);
    cachedConfig = await discovery(issuerUrl, clientId, clientSecret);
    return cachedConfig;
  } catch (err) {
    logger.error({ err }, "Failed to discover Keycloak issuer");
    return null;
  }
}

async function upsertUserFromOidc(userinfo: Record<string, unknown>): Promise<{ id: number; tier: string; role: string }> {
  const sub = String(userinfo.sub ?? "");
  if (!sub) throw new Error("Missing sub claim");

  const email = typeof userinfo.email === "string" ? userinfo.email : undefined;
  const preferredUsername = typeof userinfo.preferred_username === "string" ? userinfo.preferred_username : undefined;
  const name = typeof userinfo.name === "string" ? userinfo.name : preferredUsername;
  const username = preferredUsername ?? email ?? `oidc-${sub.slice(0, 8)}`;

  const [existing] = await db
    .select({ id: usersTable.id, tier: usersTable.tier, role: usersTable.role })
    .from(usersTable)
    .where(eq(usersTable.authProviderId, sub))
    .limit(1);

  if (existing) {
    await db
      .update(usersTable)
      .set({ email, displayName: name })
      .where(eq(usersTable.id, existing.id));
    return existing;
  }

  const [created] = await db
    .insert(usersTable)
    .values({
      username,
      email,
      displayName: name,
      role: "user",
      tier: "free",
      authProvider: "oidc",
      authProviderId: sub,
    })
    .returning({ id: usersTable.id, tier: usersTable.tier, role: usersTable.role });

  logger.info({ username, sub }, "OIDC user created");
  return created;
}

router.get("/auth/mode", (_req, res): void => {
  res.json({ mode: isOidcConfigured() ? "oidc" : "local" });
});

router.get("/auth/csrf", (req, res): void => {
  res.json({ token: getCsrfToken(req) });
});

router.post("/auth/login", loginRateLimit, async (req, res): Promise<void> => {
  if (isOidcConfigured()) {
    res.status(400).json({ error: "Use OIDC login when Keycloak is configured." });
    return;
  }

  const { username, password } = req.body;
  if (!username || !password) {
    res.status(400).json({ error: "username and password are required" });
    return;
  }

  const [user] = await db
    .select()
    .from(usersTable)
    .where(eq(usersTable.username, String(username)))
    .limit(1);

  if (!user || !user.passwordHash) {
    res.status(401).json({ error: "Invalid username or password" });
    return;
  }

  const valid = await bcrypt.compare(String(password), user.passwordHash);
  if (!valid) {
    res.status(401).json({ error: "Invalid username or password" });
    return;
  }

  await new Promise<void>((resolve, reject) => {
    req.session.regenerate((err) => (err ? reject(err) : resolve()));
  });

  req.session.user = {
    sub: String(user.id),
    name: user.username,
    preferred_username: user.username,
    email: user.email ?? undefined,
    role: (user.role as "admin" | "user") ?? "user",
    tier: (user.tier as "free" | "premium" | "enterprise") ?? "free",
    isLocal: true,
  };

  res.json({
    sub: String(user.id),
    email: user.email ?? null,
    name: user.username,
    preferredUsername: user.username,
    role: user.role,
    tier: user.tier,
    entitlements: getEntitlements(user.tier, user.role),
    isLocal: true,
  });
});

router.get("/auth/login", async (req, res): Promise<void> => {
  const client = await getClient();
  if (!client) {
    res.status(503).json({ error: "Keycloak is not configured." });
    return;
  }

  const codeVerifier = randomPKCECodeVerifier();
  const codeChallenge = await calculatePKCECodeChallenge(codeVerifier);
  const state = randomState();

  req.session.codeVerifier = codeVerifier;
  req.session.oidcState = state;
  if (req.query.returnTo && typeof req.query.returnTo === "string" && isSafeReturnTo(req.query.returnTo)) {
    req.session.returnTo = req.query.returnTo;
  }

  const redirectUri = `${getBaseUrl(req)}/api/auth/callback`;
  const url = buildAuthorizationUrl(client, {
    scope: "openid email profile",
    code_challenge: codeChallenge,
    code_challenge_method: "S256",
    redirect_uri: redirectUri,
    state,
  });

  res.redirect(url.href);
});

router.get("/auth/callback", async (req, res): Promise<void> => {
  const client = await getClient();
  if (!client) {
    res.status(503).json({ error: "Keycloak is not configured." });
    return;
  }

  const codeVerifier = req.session.codeVerifier;
  if (!codeVerifier) {
    res.status(400).json({ error: "Invalid session state." });
    return;
  }

  const state = typeof req.query.state === "string" ? req.query.state : "";
  if (!state || state !== req.session.oidcState) {
    res.status(400).json({ error: "Invalid OAuth state." });
    return;
  }
  delete req.session.oidcState;

  const redirectUri = `${getBaseUrl(req)}/api/auth/callback`;

  try {
    const tokens = await authorizationCodeGrant(
      client,
      new URL(req.originalUrl ?? "/", getBaseUrl(req)),
      { pkceCodeVerifier: codeVerifier, expectedState: state },
    );

    const userinfo = await fetchUserInfo(client, tokens.access_token, skipSubjectCheck);
    const dbUser = await upsertUserFromOidc(userinfo);

    await new Promise<void>((resolve, reject) => {
      req.session.regenerate((err) => (err ? reject(err) : resolve()));
    });

    req.session.user = {
      sub: dbUser.id.toString(),
      email: typeof userinfo.email === "string" ? userinfo.email : undefined,
      name: typeof userinfo.name === "string" ? userinfo.name : undefined,
      preferred_username: typeof userinfo.preferred_username === "string" ? userinfo.preferred_username : undefined,
      role: (dbUser.role as "admin" | "user") ?? "user",
      tier: (dbUser.tier as "free" | "premium" | "enterprise") ?? "free",
      isLocal: false,
    };
    delete req.session.codeVerifier;

    const returnTo = req.session.returnTo ?? "/";
    delete req.session.returnTo;

    res.redirect(isSafeReturnTo(returnTo) ? returnTo : "/");
  } catch (err) {
    logger.error({ err }, "Keycloak callback failed");
    res.status(500).json({ error: "Authentication failed." });
  }
});

router.get("/auth/logout", async (req, res): Promise<void> => {
  req.session.destroy(() => {});

  const client = await getClient();
  if (client && client.serverMetadata().end_session_endpoint) {
    const logoutUrl = buildEndSessionUrl(client, { post_logout_redirect_uri: getBaseUrl(req) });
    res.redirect(logoutUrl.href);
    return;
  }

  res.redirect("/");
});

router.get("/auth/me", async (req, res): Promise<void> => {
  if (!req.session.user) {
    res.status(401).json({ error: "Not authenticated" });
    return;
  }
  const u = req.session.user;
  res.json({
    sub: u.sub,
    email: u.email ?? null,
    name: u.name ?? null,
    preferredUsername: u.preferred_username ?? null,
    role: u.role ?? "user",
    tier: u.tier ?? "free",
    entitlements: getEntitlements(u.tier, u.role),
    isLocal: u.isLocal ?? false,
  });
});

router.get("/auth/password-redirect", async (req, res): Promise<void> => {
  const client = await getClient();
  if (!client) {
    res.json({ url: null });
    return;
  }
  const realm = client.serverMetadata().issuer ?? "";
  res.json({ url: `${realm}/account/password` });
});

const ChangePasswordSchema = z.object({
  currentPassword: z.string().min(1),
  newPassword: z.string().min(6),
});

router.post("/auth/me/password", passwordRateLimit, async (req, res): Promise<void> => {
  if (!req.session.user) {
    res.status(401).json({ error: "Not authenticated" });
    return;
  }
  const dbUser = await resolveDbUser(req.session.user);
  if (!dbUser) {
    res.status(401).json({ error: "User not found" });
    return;
  }
  if (dbUser.authProvider !== "local") {
    res.status(422).json({ error: "oidc" });
    return;
  }
  const parsed = ChangePasswordSchema.safeParse(req.body);
  if (!parsed.success) {
    res.status(400).json({ error: parsed.error.message });
    return;
  }
  const { currentPassword, newPassword } = parsed.data;
  if (currentPassword === newPassword) {
    res.status(400).json({ error: "New password must differ from current password" });
    return;
  }
  if (!dbUser.passwordHash || !(await bcrypt.compare(currentPassword, dbUser.passwordHash))) {
    res.status(400).json({ error: "Current password is incorrect" });
    return;
  }
  const passwordHash = await bcrypt.hash(newPassword, 12);
  await db.update(usersTable).set({ passwordHash }).where(eq(usersTable.id, dbUser.id));
  await writeAuditLog(req, "user", dbUser.id, "change_password", {});
  await new Promise<void>((resolve, reject) => {
    req.session.regenerate((err) => (err ? reject(err) : resolve()));
  });
  res.sendStatus(204);
});

type SessionUser = NonNullable<import("express-session").SessionData["user"]>;

async function resolveDbUser(u: SessionUser) {
  if (u.isLocal) {
    const id = Number(u.sub);
    if (Number.isFinite(id)) {
      const [byId] = await db.select().from(usersTable).where(eq(usersTable.id, id)).limit(1);
      if (byId) return byId;
    }
    if (u.preferred_username) {
      const [byName] = await db.select().from(usersTable).where(eq(usersTable.username, u.preferred_username)).limit(1);
      if (byName) return byName;
    }
    return null;
  }
  const [byProvider] = await db.select().from(usersTable).where(eq(usersTable.authProviderId, u.sub)).limit(1);
  return byProvider ?? null;
}

const PreferenceSchema = z.object({
  view: z.enum(["grid", "table", "rows"]).optional(),
  density: z.enum(["cozy", "compact"]).optional(),
  watchlist: z.array(z.number().int().positive()).max(50).optional(),
});

router.get("/auth/me/preferences", async (req, res): Promise<void> => {
  if (!req.session.user) {
    res.status(401).json({ error: "Not authenticated" });
    return;
  }
  const dbUser = await resolveDbUser(req.session.user);
  if (!dbUser) {
    res.status(401).json({ error: "User not found" });
    return;
  }
  res.json(dbUser.preferences ?? {});
});

router.get("/auth/me/watchlist", requireFeature("watchlist"), async (req, res): Promise<void> => {
  const dbUser = await resolveDbUser(req.session.user!);
  if (!dbUser) {
    res.status(401).json({ error: "User not found" });
    return;
  }
  const ids = (dbUser.preferences?.watchlist ?? []).filter((id) => Number.isInteger(id));
  if (ids.length === 0) {
    res.json([]);
    return;
  }
  const tools = await db
    .select()
    .from(toolsTable)
    .where(and(isNull(toolsTable.deletedAt), inArray(toolsTable.id, ids)));
  const ratings = await db
    .select({ toolId: ratingsTable.toolId, usefulness: ratingsTable.usefulness, usability: ratingsTable.usability })
    .from(ratingsTable)
    .where(inArray(ratingsTable.toolId, tools.map((t) => t.id)));
  const byTool = new Map<number, { usefulness: number; usability: number }[]>();
  for (const r of ratings) {
    const list = byTool.get(r.toolId) ?? [];
    list.push({ usefulness: r.usefulness, usability: r.usability });
    byTool.set(r.toolId, list);
  }
  const byId = new Map(tools.map((t) => [t.id, t]));
  const ordered = ids
    .filter((id) => byId.has(id))
    .map((id) => {
      const tool = byId.get(id)!;
      const toolRatings = byTool.get(id) ?? [];
      const ratingCount = toolRatings.length;
      const avgUsefulness = ratingCount > 0 ? toolRatings.reduce((s, r) => s + r.usefulness, 0) / ratingCount : null;
      const avgUsability = ratingCount > 0 ? toolRatings.reduce((s, r) => s + r.usability, 0) / ratingCount : null;
      const avgCombined = avgUsefulness != null && avgUsability != null ? (avgUsefulness + avgUsability) / 2 : null;
      return { ...tool, ratingCount, avgUsefulness, avgUsability, avgCombined };
    });
  res.json(ordered);
});

router.put("/auth/me/preferences", async (req, res): Promise<void> => {
  if (!req.session.user) {
    res.status(401).json({ error: "Not authenticated" });
    return;
  }
  const parsed = PreferenceSchema.safeParse(req.body);
  if (!parsed.success) {
    res.status(400).json({ error: parsed.error.message });
    return;
  }
  const dbUser = await resolveDbUser(req.session.user);
  if (!dbUser) {
    res.status(401).json({ error: "User not found" });
    return;
  }
  const merged = { ...(dbUser.preferences ?? {}), ...parsed.data };
  await db.update(usersTable).set({ preferences: merged }).where(eq(usersTable.id, dbUser.id));
  res.json(merged);
});

export default router;