using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Services;

namespace ZB.MOM.WW.OtOpcUa.Security.Ldap;

/// <summary>
///     Driver-only-node stand-in for the EF-backed <see cref="ILdapGroupRoleMappingService"/>.
///     A driver-only node (Akka role <c>driver</c>, not <c>admin</c>) has no ConfigDb connection
///     (Phase 4 gated <c>AddOtOpcUaConfigDb</c> on <c>hasAdmin</c>), so it can never read the
///     control-plane <c>LdapGroupRoleMapping</c> DB grants that <see cref="OtOpcUaGroupRoleMapper"/>
///     normally unions into its result. This implementation always reports "no DB grants" so the
///     data-path mapper falls back to exactly the appsettings <c>Security:Ldap:GroupToRole</c>
///     baseline — the same safe fallback the mapper already takes when the real service simply
///     has no matching rows. <see cref="LdapGroupRoleMapping"/> rows are not composed into the
///     deployment artifact either, so a driver node never had DB grants via config; reporting
///     empty here is honest, not lossy.
/// </summary>
/// <remarks>
///     The write surface (<see cref="CreateAsync"/>/<see cref="DeleteAsync"/>) is control-plane-only
///     Admin UI functionality that a driver-only node — which has no Admin UI — never calls. It
///     throws rather than silently no-opping so an accidental call surfaces immediately instead of
///     pretending to persist a grant that a driver-only node cannot store.
/// </remarks>
public sealed class NullLdapGroupRoleMappingService : ILdapGroupRoleMappingService
{
    /// <inheritdoc />
    public Task<IReadOnlyList<LdapGroupRoleMapping>> GetByGroupsAsync(
        IEnumerable<string> ldapGroups, CancellationToken cancellationToken)
        => Task.FromResult<IReadOnlyList<LdapGroupRoleMapping>>(Array.Empty<LdapGroupRoleMapping>());

    /// <inheritdoc />
    public Task<IReadOnlyList<LdapGroupRoleMapping>> ListAllAsync(CancellationToken cancellationToken)
        => Task.FromResult<IReadOnlyList<LdapGroupRoleMapping>>(Array.Empty<LdapGroupRoleMapping>());

    /// <inheritdoc />
    public Task<LdapGroupRoleMapping> CreateAsync(LdapGroupRoleMapping row, CancellationToken cancellationToken)
        => throw new NotSupportedException(
            "LDAP group-role grants are control-plane only; a driver-only node has no ConfigDb.");

    /// <inheritdoc />
    public Task DeleteAsync(Guid id, CancellationToken cancellationToken)
        => throw new NotSupportedException(
            "LDAP group-role grants are control-plane only; a driver-only node has no ConfigDb.");
}