import { randomUUID } from "node:crypto";
import type { FastifyInstance } from "fastify";
import { eq, rolePermissions, roles, users, type Db } from "@parking/db";
import { ADMIN_ROLE_ID, PERMISSIONS, type Permission } from "@parking/shared";
import { bumpPermsCache, permissionsFor, requirePermission } from "../auth.js";

// Role management (admin). Roles are DATA: an admin composes a role from the
// code-defined PERMISSIONS grid (resource:action), and users are assigned one
// role. The built-in `admin` role (id ADMIN_ROLE_ID) is PROTECTED — it can't be
// edited or deleted and always resolves to every permission in code. Every write
// here bumps the in-memory permission cache so changes take effect on the next
// request. See @parking/shared PERMISSIONS and ../auth.ts.
//
// PRIVILEGE-ESCALATION GUARD: `role:update`/`role:create` must NOT let a caller
// grant a permission they don't themselves hold — otherwise a non-admin with
// `role:*` could edit their own role to add (say) `tariff:update`, or mint a role
// that grants admin-equivalent powers, and escalate. So a non-admin caller may
// only put permissions they ALREADY hold onto a role. An admin (full set) is
// unrestricted, which is the intended behaviour.

interface RoleBody {
  name: string;
  permissions: string[];
}
interface UpdateBody {
  name?: string;
  permissions?: string[];
}

const VALID = new Set<string>(PERMISSIONS);

/** Validate + dedupe a requested permission list against the code-defined grid. */
function cleanPermissions(input: unknown): { ok: true; perms: Permission[] } | { ok: false; bad: string } {
  if (!Array.isArray(input)) return { ok: false, bad: "permissions must be an array" };
  const out = new Set<Permission>();
  for (const p of input) {
    if (typeof p !== "string" || !VALID.has(p)) return { ok: false, bad: `unknown permission: ${String(p)}` };
    out.add(p as Permission);
  }
  return { ok: true, perms: [...out] };
}

export async function roleRoutes(app: FastifyInstance, db: Db): Promise<void> {
  const readGuard = requirePermission("role:read");
  const createGuard = requirePermission("role:create");
  const updateGuard = requirePermission("role:update");
  const deleteGuard = requirePermission("role:delete");

  /** A role + its permission list + how many users hold it. */
  function roleView(roleId: string) {
    const role = db.select().from(roles).where(eq(roles.id, roleId)).get();
    if (!role) return null;
    const perms = db
      .select({ permission: rolePermissions.permission })
      .from(rolePermissions)
      .where(eq(rolePermissions.roleId, roleId))
      .all()
      .map((r) => r.permission);
    const userCount = db.select().from(users).where(eq(users.roleId, roleId)).all().length;
    // The admin role always reports the full grid (it's enforced in code).
    return {
      id: role.id,
      name: role.name,
      builtin: role.builtin === 1,
      permissions: role.id === ADMIN_ROLE_ID ? [...PERMISSIONS] : perms,
      userCount,
    };
  }

  /** Replace a role's permission rows with `perms` (in a single pass). */
  function setPermissions(roleId: string, perms: Permission[]): void {
    db.delete(rolePermissions).where(eq(rolePermissions.roleId, roleId)).run();
    for (const p of perms) {
      db.insert(rolePermissions).values({ roleId, permission: p }).run();
    }
  }

  // The full permission grid (for the role-composer checkbox UI) + every role.
  app.get("/api/roles", { preHandler: readGuard }, async () => {
    const all = db.select().from(roles).all();
    return {
      catalog: PERMISSIONS,
      roles: all.map((r) => roleView(r.id)).filter((r) => r != null),
    };
  });

  /** Reject any permission in `perms` the caller does not themselves hold — so a
   *  non-admin can't grant privileges beyond their own. Returns the offending
   *  permission, or null if all are within the caller's set. (Admin holds the full
   *  set, so it never trips.) */
  function escalates(callerRoleId: string, perms: Permission[]): Permission | null {
    const held = permissionsFor(callerRoleId);
    return perms.find((p) => !held.has(p)) ?? null;
  }

  // Create a composable role from a name + a permission set.
  app.post<{ Body: RoleBody }>("/api/roles", { preHandler: createGuard }, async (req, reply) => {
    const name = (req.body?.name ?? "").trim();
    if (!name) return reply.code(400).send({ error: "name required" });
    if (db.select().from(roles).where(eq(roles.name, name)).get()) {
      return reply.code(409).send({ error: "a role with that name already exists" });
    }
    const cleaned = cleanPermissions(req.body?.permissions ?? []);
    if (!cleaned.ok) return reply.code(400).send({ error: cleaned.bad });
    const over = escalates(req.user.roleId, cleaned.perms);
    if (over) return reply.code(403).send({ error: `cannot grant a permission you do not hold: ${over}` });

    const id = randomUUID();
    db.insert(roles).values({ id, name, builtin: 0 }).run();
    setPermissions(id, cleaned.perms);
    bumpPermsCache();
    return reply.code(201).send(roleView(id));
  });

  // Edit a role's name and/or permission set. The built-in admin role is locked.
  app.put<{ Params: { id: string }; Body: UpdateBody }>(
    "/api/roles/:id",
    { preHandler: updateGuard },
    async (req, reply) => {
      const id = req.params.id;
      const role = db.select().from(roles).where(eq(roles.id, id)).get();
      if (!role) return reply.code(404).send({ error: "role not found" });
      if (role.builtin === 1) {
        return reply.code(409).send({ error: "the built-in admin role cannot be edited" });
      }

      if (req.body?.name != null) {
        const name = req.body.name.trim();
        if (!name) return reply.code(400).send({ error: "name cannot be empty" });
        const clash = db.select().from(roles).where(eq(roles.name, name)).get();
        if (clash && clash.id !== id) return reply.code(409).send({ error: "a role with that name already exists" });
        db.update(roles).set({ name }).where(eq(roles.id, id)).run();
      }
      if (req.body?.permissions != null) {
        const cleaned = cleanPermissions(req.body.permissions);
        if (!cleaned.ok) return reply.code(400).send({ error: cleaned.bad });
        const over = escalates(req.user.roleId, cleaned.perms);
        if (over) return reply.code(403).send({ error: `cannot grant a permission you do not hold: ${over}` });
        setPermissions(id, cleaned.perms);
      }
      bumpPermsCache();
      return roleView(id);
    },
  );

  // Delete a role. Refused if it's built-in or any user still holds it.
  app.delete<{ Params: { id: string } }>(
    "/api/roles/:id",
    { preHandler: deleteGuard },
    async (req, reply) => {
      const id = req.params.id;
      const role = db.select().from(roles).where(eq(roles.id, id)).get();
      if (!role) return reply.code(404).send({ error: "role not found" });
      if (role.builtin === 1) {
        return reply.code(409).send({ error: "the built-in admin role cannot be deleted" });
      }
      const holders = db.select().from(users).where(eq(users.roleId, id)).all().length;
      if (holders > 0) {
        return reply.code(409).send({ error: `cannot delete a role still assigned to ${holders} user(s)` });
      }
      db.delete(rolePermissions).where(eq(rolePermissions.roleId, id)).run();
      db.delete(roles).where(eq(roles.id, id)).run();
      bumpPermsCache();
      return { ok: true };
    },
  );
}