import NextAuth from "next-auth";
import type { DefaultSession, NextAuthConfig } from "next-auth";
import Authentik from "next-auth/providers/authentik";
import Credentials from "next-auth/providers/credentials";
import GitHub from "next-auth/providers/github";
import Google from "next-auth/providers/google";

/**
 * Session strategy is JWT (no `@auth/drizzle-adapter`). We still want every
 * authenticated request to carry a real `users.id` so workspace-scoped tRPC
 * procedures can resolve membership, so OAuth sign-ins go through
 * `ensureUserIdByEmail` to upsert a row in `users` (matched case-insensitively
 * on email) and stamp `token.id` with the DB UUID. Credentials sign-in already
 * returns the DB id from `authorize`.
 *
 * `db` is loaded dynamically inside callbacks so this module stays importable
 * from edge contexts (middleware, etc.); the actual SQL only runs on the
 * Node route handler.
 */

type Sql = (t: TemplateStringsArray, ...v: unknown[]) => Promise<unknown[]>;

async function getSql(): Promise<Sql> {
  const { db } = await import("@tasks/database/client");
  return (db as { $client: Sql }).$client;
}

async function ensureUserIdByEmail(args: {
  email: string;
  name?: string | null;
  image?: string | null;
}): Promise<string | null> {
  const email = args.email.trim();
  if (!email) return null;
  const sql = await getSql();

  const existing = (await sql`
    SELECT id FROM users WHERE lower(email) = lower(${email}) LIMIT 1
  `) as { id: string }[];
  if (existing[0]) return existing[0].id;

  await sql`
    INSERT INTO users (email, name, avatar_url)
    VALUES (${email.toLowerCase()}, ${args.name ?? null}, ${args.image ?? null})
    ON CONFLICT (email) DO NOTHING
  `;
  const after = (await sql`
    SELECT id FROM users WHERE lower(email) = lower(${email}) LIMIT 1
  `) as { id: string }[];
  return after[0]?.id ?? null;
}

function slugifyForWorkspace(seed: string): string {
  const cleaned = seed
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "")
    .slice(0, 50);
  return cleaned || "workspace";
}

/**
 * Idempotent: if the user already owns or is a member of any workspace, no-op.
 * Otherwise mint a personal workspace and add them as `owner`. Runs on every
 * first sign-in (credentials and OAuth alike) so freshly-created OAuth users
 * don't land in the app with no tenant scope and an unusable session.
 *
 * Slug collisions are handled by retrying with a random 6-char suffix; we cap
 * attempts so a misbehaving DB can't lock the sign-in flow.
 */
async function ensureUserHasWorkspace(args: {
  userId: string;
  displayName: string | null;
  email: string;
}): Promise<void> {
  const sql = await getSql();

  const existing = (await sql`
    SELECT 1
    FROM workspaces w
    LEFT JOIN workspace_members m
      ON m.workspace_id = w.id AND m.user_id = ${args.userId}
    WHERE w.owner_user_id = ${args.userId} OR m.user_id = ${args.userId}
    LIMIT 1
  `) as unknown[];
  if (existing.length > 0) return;

  const trimmedName = args.displayName?.trim() ?? "";
  const seed = trimmedName || args.email.split("@")[0] || "workspace";
  const baseSlug = slugifyForWorkspace(seed);
  const workspaceName = trimmedName ? `${trimmedName}'s workspace` : "My workspace";

  let workspaceId: string | null = null;
  let candidate = baseSlug;
  for (let attempt = 0; attempt < 5 && !workspaceId; attempt += 1) {
    const inserted = (await sql`
      INSERT INTO workspaces (slug, name, owner_user_id)
      VALUES (${candidate}, ${workspaceName}, ${args.userId})
      ON CONFLICT (slug) DO NOTHING
      RETURNING id
    `) as { id: string }[];
    if (inserted[0]) {
      workspaceId = inserted[0].id;
      break;
    }
    candidate = `${baseSlug}-${Math.random().toString(36).slice(2, 8)}`;
  }
  if (!workspaceId) {
    console.warn("[auth] Failed to provision workspace for user", args.userId);
    return;
  }

  await sql`
    INSERT INTO workspace_members (workspace_id, user_id, role)
    VALUES (${workspaceId}, ${args.userId}, 'owner')
    ON CONFLICT (workspace_id, user_id) DO NOTHING
  `;
}

declare module "next-auth" {
  interface Session {
    user: {
      id: string;
    } & DefaultSession["user"];
  }
}

const providers: NextAuthConfig["providers"] = [
  Credentials({
    name: "Email",
    credentials: {
      email: { label: "Email", type: "email" },
      password: { label: "Password", type: "password" },
    },
    async authorize(credentials) {
      const email = credentials?.email as string | undefined;
      const password = credentials?.password as string | undefined;
      if (!email?.trim() || !password) return null;

      const devPassword = process.env.AUTH_DEV_PASSWORD;
      if (!devPassword) {
        console.warn("[auth] AUTH_DEV_PASSWORD is not set; credentials sign-in disabled.");
        return null;
      }
      if (password !== devPassword) return null;

      const sql = await getSql();
      const rows = (await sql`
        SELECT id, email, name, avatar_url AS "avatarUrl"
        FROM users
        WHERE lower(email) = lower(${email.trim()})
        LIMIT 1
      `) as { id: string; email: string; name: string | null; avatarUrl: string | null }[];
      const user = rows[0];
      if (!user) return null;

      return {
        id: user.id,
        email: user.email,
        name: user.name ?? undefined,
        image: user.avatarUrl ?? undefined,
      };
    },
  }),
];

if (process.env.AUTH_GITHUB_ID && process.env.AUTH_GITHUB_SECRET) {
  providers.push(
    GitHub({
      clientId: process.env.AUTH_GITHUB_ID,
      clientSecret: process.env.AUTH_GITHUB_SECRET,
    }),
  );
}

if (process.env.AUTH_GOOGLE_ID && process.env.AUTH_GOOGLE_SECRET) {
  providers.push(
    Google({
      clientId: process.env.AUTH_GOOGLE_ID,
      clientSecret: process.env.AUTH_GOOGLE_SECRET,
    }),
  );
}

if (
  process.env.AUTH_AUTHENTIK_ID &&
  process.env.AUTH_AUTHENTIK_SECRET &&
  process.env.AUTH_AUTHENTIK_ISSUER
) {
  providers.push(
    Authentik({
      clientId: process.env.AUTH_AUTHENTIK_ID,
      clientSecret: process.env.AUTH_AUTHENTIK_SECRET,
      issuer: process.env.AUTH_AUTHENTIK_ISSUER,
    }),
  );
}

export const { handlers, auth, signIn, signOut } = NextAuth({
  session: { strategy: "jwt" },
  pages: {
    signIn: "/sign-in",
  },
  providers,
  callbacks: {
    async signIn({ user, account }) {
      // OAuth providers must give us an email so we can map to a `users` row.
      if (account && account.provider !== "credentials" && !user?.email) {
        return false;
      }
      return true;
    },
    async jwt({ token, user, account }) {
      // First call (sign-in): `user` and `account` are present.
      if (account && user) {
        let dbId: string | null = null;
        if (account.provider === "credentials") {
          // `authorize` already returns a real DB UUID in `user.id`.
          dbId = user.id ?? null;
        } else if (user.email) {
          dbId = await ensureUserIdByEmail({
            email: user.email,
            name: user.name ?? null,
            image: user.image ?? null,
          });
        }

        if (dbId) {
          token.id = dbId;
          // Make sure every authenticated user has a tenant they can land in.
          // Cheap idempotent check; only mints a workspace on the first sign-in.
          await ensureUserHasWorkspace({
            userId: dbId,
            displayName: user.name ?? null,
            email: user.email ?? "",
          });
        }
      }
      return token;
    },
    async session({ session, token }) {
      if (session.user && token.id) {
        session.user.id = token.id as string;
      }
      return session;
    },
  },
  trustHost: true,
});