import { Request, Response, NextFunction } from 'express';
import pool from '../config/database';
import logger from '../utils/logger';
import { auditPermissionDenied } from './audit.middleware';
import { AuditResourceType } from '../services/audit.service';

// ---------------------------------------------------------------------------
// AppRole — mirrors the roles defined in the project spec.
// Tier 1 (RBAC) is assumed complete and adds a `role` column to users.
// This middleware reads that column to enforce permissions.
// ---------------------------------------------------------------------------
export type AppRole =
  | 'admin'
  | 'kommandant'
  | 'gruppenfuehrer'
  | 'mitglied'
  | 'bewerber';

/**
 * Role hierarchy: higher index = more permissions.
 * Used to implement "at least X role" checks.
 */
const ROLE_HIERARCHY: AppRole[] = [
  'bewerber',
  'mitglied',
  'gruppenfuehrer',
  'kommandant',
  'admin',
];

/**
 * Permission map: defines which roles hold a given permission string.
 * All roles at or above the listed minimum also hold the permission.
 */
const PERMISSION_ROLE_MIN: Record<string, AppRole> = {
  'incidents:read': 'mitglied',
  'incidents:write': 'gruppenfuehrer',
  'incidents:delete': 'kommandant',
  'incidents:read_bericht_text': 'kommandant',
  'incidents:manage_personnel': 'gruppenfuehrer',
  // Training / Calendar
  'training:read':  'mitglied',
  'training:write': 'gruppenfuehrer',
  'training:cancel': 'kommandant',
  'training:mark_attendance': 'gruppenfuehrer',
  'reports:read':   'kommandant',
  // Audit log and admin panel — restricted to admin role only
  'admin:access': 'admin',
  'audit:read':   'admin',
  'audit:export': 'admin',
  'members:read': 'mitglied',
  'members:write': 'kommandant',
  'vehicles:write': 'kommandant',
  'vehicles:status': 'gruppenfuehrer',
  'vehicles:delete': 'admin',
  'equipment:write': 'gruppenfuehrer',
  'equipment:delete': 'admin',
  'events:write': 'gruppenfuehrer',
  'events:categories': 'gruppenfuehrer',
  'atemschutz:write': 'gruppenfuehrer',
  'atemschutz:delete': 'kommandant',
  'bookings:write': 'gruppenfuehrer',
  'bookings:delete': 'admin',
};

function hasPermission(role: AppRole, permission: string): boolean {
  const minRole = PERMISSION_ROLE_MIN[permission];
  if (!minRole) {
    logger.warn('Unknown permission checked', { permission });
    return false;
  }
  const userLevel = ROLE_HIERARCHY.indexOf(role);
  const minLevel = ROLE_HIERARCHY.indexOf(minRole);
  return userLevel >= minLevel;
}

/**
 * Retrieves the role for a given user ID from the database.
 * Falls back to 'mitglied' if the users table does not yet have a role column
 * (graceful degradation while Tier 1 migration is pending).
 */
async function getUserRole(userId: string): Promise<AppRole> {
  try {
    const result = await pool.query(
      `SELECT role FROM users WHERE id = $1`,
      [userId]
    );
    if (result.rows.length === 0) return 'mitglied';
    return (result.rows[0].role as AppRole) ?? 'mitglied';
  } catch (error) {
    // If the column doesn't exist yet (Tier 1 not deployed), degrade gracefully
    const errMsg = error instanceof Error ? error.message : String(error);
    if (errMsg.includes('column "role" does not exist')) {
      logger.warn('users.role column not found — Tier 1 RBAC migration pending. Defaulting to mitglied.');
      return 'mitglied';
    }
    logger.error('Error fetching user role', { error, userId });
    return 'mitglied';
  }
}

/**
 * Middleware factory: requires the authenticated user to hold the given
 * permission (or a role with sufficient hierarchy level).
 *
 * Usage:
 *   router.post('/api/incidents', authenticate, requirePermission('incidents:write'), handler)
 */
export function requirePermission(permission: string) {
  return async (req: Request, res: Response, next: NextFunction): Promise<void> => {
    if (!req.user) {
      res.status(401).json({
        success: false,
        message: 'Authentication required',
      });
      return;
    }

    const role = (req.user as any).role
      ? (req.user as any).role as AppRole
      : await getUserRole(req.user.id);

    // Attach role to request for downstream use (e.g., bericht_text redaction)
    (req as Request & { userRole?: AppRole }).userRole = role;

    if (!hasPermission(role, permission)) {
      // Fallback: dashboard_admin group grants admin:access
      if (permission === 'admin:access') {
        const userGroups: string[] = req.user?.groups ?? [];
        if (userGroups.includes('dashboard_admin')) {
          (req as Request & { userRole?: AppRole }).userRole = 'admin';
          next();
          return;
        }
      }

      logger.warn('Permission denied', {
        userId: req.user.id,
        role,
        permission,
        path: req.path,
      });

      // GDPR audit trail — fire-and-forget, never throws
      auditPermissionDenied(req, AuditResourceType.SYSTEM, undefined, {
        required_permission: permission,
        user_role:           role,
      });

      res.status(403).json({
        success: false,
        message: 'Keine Berechtigung',
      });
      return;
    }

    next();
  };
}

export { getUserRole, hasPermission };

/**
 * Middleware factory: requires the authenticated user to belong to at least
 * one of the given Authentik groups (sourced from the JWT `groups` claim).
 *
 * Usage:
 *   router.post('/api/vehicles', authenticate, requireGroups(['dashboard_admin']), handler)
 */
export function requireGroups(requiredGroups: string[]) {
  return async (req: Request, res: Response, next: NextFunction): Promise<void> => {
    if (!req.user) {
      res.status(401).json({ success: false, message: 'Authentication required' });
      return;
    }

    logger.warn('DEPRECATED: requireGroups() — migrate to requirePermission()', { requiredGroups });

    const userGroups: string[] = req.user?.groups ?? [];
    const hasAccess = requiredGroups.some(g => userGroups.includes(g));

    if (!hasAccess) {
      logger.warn('Group-based access denied', {
        userId:         req.user.id,
        userGroups,
        requiredGroups,
        path:           req.path,
      });

      auditPermissionDenied(req, AuditResourceType.SYSTEM, undefined, {
        required_groups: requiredGroups,
        user_groups:     userGroups,
      });

      res.status(403).json({
        success: false,
        message: 'Keine Berechtigung für diese Aktion',
      });
      return;
    }

    next();
  };
}