import { useMutation, useQueryClient } from '@tanstack/react-query';
import { supabase } from '@/integrations/supabase/client';
import { queryKeys } from '@/lib/queryKeys';
import { toast } from 'sonner';

type ValidRole = 'admin' | 'moderator' | 'user';

interface GrantRoleParams {
  userId: string;
  role: ValidRole;
}

interface RevokeRoleParams {
  roleId: string;
}

interface UserWithRoles {
  id: string;
  user_id: string;
  username: string;
  email: string;
  display_name: string | null;
  avatar_url: string | null;
  banned: boolean;
  created_at: string;
}

/**
 * useRoleMutations Hook
 * 
 * Provides TanStack Query mutations for granting and revoking user roles
 * with optimistic updates for instant UI feedback.
 * 
 * Features:
 * - Optimistic updates for immediate UI response
 * - Automatic cache invalidation on success
 * - Error handling with rollback
 * - Toast notifications
 * 
 * @example
 * ```tsx
 * const { grantRole, revokeRole } = useRoleMutations();
 * 
 * grantRole.mutate({ userId: 'user-id', role: 'moderator' });
 * revokeRole.mutate({ roleId: 'role-id' });
 * ```
 */
export function useRoleMutations() {
  const queryClient = useQueryClient();

  const grantRole = useMutation({
    mutationFn: async ({ userId, role }: GrantRoleParams) => {
      const { data, error } = await supabase
        .from('user_roles')
        .insert([{ user_id: userId, role }])
        .select()
        .single();

      if (error) throw error;
      return data;
    },
    onMutate: async ({ userId, role }) => {
      // Cancel outgoing refetches
      await queryClient.cancelQueries({ queryKey: queryKeys.users.roles() });

      // Snapshot previous value
      const previousUsers = queryClient.getQueryData<UserWithRoles[]>(queryKeys.users.roles());

      // Optimistically update cache - add role to user
      queryClient.setQueryData<UserWithRoles[]>(queryKeys.users.roles(), (old) => {
        if (!old) return old;
        return old.map((user) =>
          user.user_id === userId
            ? { ...user, role } // Optimistically assign role
            : user
        );
      });

      return { previousUsers };
    },
    onError: (error, variables, context) => {
      // Rollback on error
      if (context?.previousUsers) {
        queryClient.setQueryData(queryKeys.users.roles(), context.previousUsers);
      }
      toast.error(`Failed to grant role: ${error.message}`);
    },
    onSuccess: (data, { role }) => {
      toast.success(`Role ${role} granted successfully`);
    },
    onSettled: () => {
      // Refetch to ensure consistency
      queryClient.invalidateQueries({ queryKey: queryKeys.users.roles() });
      queryClient.invalidateQueries({ queryKey: ['user-roles'] });
    },
  });

  const revokeRole = useMutation({
    mutationFn: async ({ roleId }: RevokeRoleParams) => {
      const { error } = await supabase
        .from('user_roles')
        .delete()
        .eq('id', roleId);

      if (error) throw error;
    },
    onMutate: async ({ roleId }) => {
      // Cancel outgoing refetches
      await queryClient.cancelQueries({ queryKey: queryKeys.users.roles() });

      // Snapshot previous value
      const previousUsers = queryClient.getQueryData<UserWithRoles[]>(queryKeys.users.roles());

      // Optimistically remove role from cache
      queryClient.setQueryData<UserWithRoles[]>(queryKeys.users.roles(), (old) => {
        if (!old) return old;
        // Remove the user from the list since they no longer have a role
        return old.filter((user) => user.id !== roleId);
      });

      return { previousUsers };
    },
    onError: (error, variables, context) => {
      // Rollback on error
      if (context?.previousUsers) {
        queryClient.setQueryData(queryKeys.users.roles(), context.previousUsers);
      }
      toast.error(`Failed to revoke role: ${error.message}`);
    },
    onSuccess: () => {
      toast.success('Role revoked successfully');
    },
    onSettled: () => {
      // Refetch to ensure consistency
      queryClient.invalidateQueries({ queryKey: queryKeys.users.roles() });
      queryClient.invalidateQueries({ queryKey: ['user-roles'] });
    },
  });

  return {
    grantRole,
    revokeRole,
  };
}