import { and, eq } from 'drizzle-orm';
import { NextRequest, NextResponse } from 'next/server';

import { auth } from '@/lib/auth';
import { db } from '@/lib/db';
import { portRoleOverrides, ports, userPortRoles, userProfiles } from '@/lib/db/schema';
import { type RolePermissions } from '@/lib/db/schema/users';
import { createAuditLog } from '@/lib/audit';
import { errorResponse } from '@/lib/errors';
import { logger } from '@/lib/logger';

// ─── Types ────────────────────────────────────────────────────────────────────

/**
 * Authenticated request context resolved by `withAuth`.
 * Passed as the second argument to every wrapped route handler.
 */
export interface AuthContext {
  userId: string;
  portId: string;
  portSlug: string;
  /** true for super_admin users — bypasses all permission checks. */
  isSuperAdmin: boolean;
  /**
   * Effective permissions after role + port override deep-merge.
   * null when isSuperAdmin is true (super admins bypass permission checks).
   */
  permissions: RolePermissions | null;
  user: {
    email: string;
    name: string;
  };
  /** Client IP extracted from X-Forwarded-For header. */
  ipAddress: string;
  userAgent: string;
}

export type RouteHandler<T = unknown> = (
  req: NextRequest,
  ctx: AuthContext,
  params: Record<string, string>,
) => Promise<NextResponse<T>>;

// ─── deepMerge ───────────────────────────────────────────────────────────────

/**
 * Recursively merges `source` into `target`.
 * Used to apply port-level role permission overrides on top of the base role.
 */
export function deepMerge(
  target: Record<string, unknown>,
  source: Record<string, unknown>,
): Record<string, unknown> {
  const result = { ...target };
  for (const key of Object.keys(source)) {
    const sourceVal = source[key];
    const targetVal = result[key];
    if (
      typeof sourceVal === 'object' &&
      sourceVal !== null &&
      !Array.isArray(sourceVal) &&
      typeof targetVal === 'object' &&
      targetVal !== null &&
      !Array.isArray(targetVal)
    ) {
      result[key] = deepMerge(
        targetVal as Record<string, unknown>,
        sourceVal as Record<string, unknown>,
      );
    } else {
      result[key] = sourceVal;
    }
  }
  return result;
}

// ─── withAuth ────────────────────────────────────────────────────────────────

/**
 * Validates the session, loads the user profile, resolves port context and
 * applies port-level role overrides before calling the inner handler.
 *
 * Usage:
 * ```ts
 * export const GET = withAuth(handler);
 * export const POST = withAuth(withPermission('clients', 'create', handler));
 * ```
 */
export function withAuth(
  handler: RouteHandler,
): (
  req: NextRequest,
  routeContext: { params: Promise<Record<string, string>> },
) => Promise<NextResponse> {
  return async (req, routeContext) => {
    try {
      // 1. Validate session via Better Auth.
      const session = await auth.api.getSession({ headers: req.headers });
      if (!session?.user) {
        return NextResponse.json({ error: 'Authentication required' }, { status: 401 });
      }

      // 2. Load the CRM user profile (keyed on Better Auth user ID).
      const profile = await db.query.userProfiles.findFirst({
        where: eq(userProfiles.userId, session.user.id),
      });
      if (!profile || !profile.isActive) {
        return NextResponse.json({ error: 'Account disabled' }, { status: 403 });
      }

      // 3. Resolve port context.
      //    Port ID comes from the X-Port-Id header (set by the client after port
      //    selection), falling back to the user's default port from preferences.
      //    It NEVER comes from the request body — SECURITY-GUIDELINES.md §2.1.
      const portIdFromHeader = req.headers.get('X-Port-Id');
      const portId =
        portIdFromHeader ??
        (profile.preferences as { defaultPortId?: string } | null)?.defaultPortId ??
        null;

      if (!portId && !profile.isSuperAdmin) {
        return NextResponse.json({ error: 'Port context required' }, { status: 400 });
      }

      // 4. Resolve effective permissions.
      let permissions: RolePermissions | null = null;
      let portSlug = '';

      if (!profile.isSuperAdmin && portId) {
        const portRole = await db.query.userPortRoles.findFirst({
          where: and(eq(userPortRoles.userId, profile.userId), eq(userPortRoles.portId, portId)),
          with: {
            role: true,
            port: true,
          },
        });

        if (!portRole) {
          return NextResponse.json({ error: 'No access to this port' }, { status: 403 });
        }

        permissions = { ...(portRole.role.permissions as RolePermissions) };
        portSlug = (portRole.port as { slug: string } | null)?.slug ?? '';

        // Apply port-specific role overrides (deep-merge on top of base role).
        const override = await db.query.portRoleOverrides.findFirst({
          where: and(
            eq(portRoleOverrides.portId, portId),
            eq(portRoleOverrides.roleId, portRole.roleId),
          ),
        });

        if (override?.permissionOverrides) {
          permissions = deepMerge(
            permissions as unknown as Record<string, unknown>,
            override.permissionOverrides as Record<string, unknown>,
          ) as RolePermissions;
        }
      } else if (profile.isSuperAdmin && portId) {
        // Super admin still needs portSlug for response context.
        const port = await db.query.ports.findFirst({
          where: eq(ports.id, portId),
        });
        portSlug = port?.slug ?? '';
      }

      const ctx: AuthContext = {
        userId: profile.userId,
        portId: portId ?? '',
        portSlug,
        isSuperAdmin: profile.isSuperAdmin,
        permissions,
        user: {
          email: session.user.email,
          name: session.user.name,
        },
        ipAddress: req.headers.get('x-forwarded-for')?.split(',')[0]?.trim() ?? 'unknown',
        userAgent: req.headers.get('user-agent') ?? 'unknown',
      };

      const params = await routeContext.params;
      return await handler(req, ctx, params);
    } catch (error) {
      return errorResponse(error);
    }
  };
}

// ─── withPermission ──────────────────────────────────────────────────────────

/**
 * Wraps a route handler with a permission gate.
 * Denied attempts are logged to the audit trail.
 *
 * Compose inside withAuth:
 * ```ts
 * export const DELETE = withAuth(withPermission('clients', 'delete', handler));
 * ```
 */
export function withPermission(
  resource: keyof RolePermissions,
  action: string,
  handler: RouteHandler,
): RouteHandler {
  return async (req, ctx, params) => {
    if (!ctx.isSuperAdmin) {
      const resourcePerms = ctx.permissions?.[resource] as Record<string, boolean> | undefined;

      if (!resourcePerms || !resourcePerms[action]) {
        logger.warn({ userId: ctx.userId, resource, action }, 'Permission denied');

        // Log the denied attempt — fire-and-forget; audit must never block response.
        void createAuditLog({
          userId: ctx.userId,
          portId: ctx.portId,
          action: 'permission_denied',
          entityType: resource,
          entityId: '',
          metadata: { attemptedAction: action },
          ipAddress: ctx.ipAddress,
          userAgent: ctx.userAgent,
        });

        return NextResponse.json({ error: 'Insufficient permissions' }, { status: 403 });
      }
    }

    return handler(req, ctx, params);
  };
}