// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System.Security.Claims;
using Squidex.Domain.Apps.Entities.Apps;
using Squidex.Infrastructure;
using Squidex.Infrastructure.Security;
using Squidex.Shared;
using Squidex.Shared.Identity;
using ClaimsPermissions = Squidex.Infrastructure.Security.PermissionSet;

#pragma warning disable MA0048 // File name must match type name

namespace Squidex.Domain.Apps.Entities
{
    public sealed class Context
    {
        private static readonly IReadOnlyDictionary<string, string> EmptyHeaders = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

        public IReadOnlyDictionary<string, string> Headers { get; private set; }

        public ClaimsPermissions UserPermissions { get; }

        public ClaimsPrincipal UserPrincipal { get; }

        public IAppEntity App { get; set; }

        public bool IsFrontendClient => UserPrincipal.IsInClient(DefaultClients.Frontend);

        public Context(ClaimsPrincipal user, IAppEntity app)
            : this(app, user, user.Claims.Permissions(), EmptyHeaders)
        {
            Guard.NotNull(user);
        }

        private Context(
            IAppEntity app,
            ClaimsPrincipal userPrincipal,
            ClaimsPermissions userPermissions,
            IReadOnlyDictionary<string, string> headers)
        {
            App = app;

            UserPrincipal = userPrincipal;
            UserPermissions = userPermissions;

            Headers = headers;
        }

        public static Context Anonymous(IAppEntity app)
        {
            var claimsIdentity = new ClaimsIdentity();
            var claimsPrincipal = new ClaimsPrincipal(claimsIdentity);

            return new Context(claimsPrincipal, app);
        }

        public static Context Admin(IAppEntity app)
        {
            var claimsIdentity = new ClaimsIdentity();
            var claimsPrincipal = new ClaimsPrincipal(claimsIdentity);

            claimsIdentity.AddClaim(new Claim(SquidexClaimTypes.Permissions, PermissionIds.All));

            return new Context(claimsPrincipal, app);
        }

        public bool Allows(string permissionId, string schema = Permission.Any)
        {
            return UserPermissions.Allows(permissionId, App.Name, schema);
        }

        private sealed class HeaderBuilder : ICloneBuilder
        {
            private readonly Context context;
            private Dictionary<string, string>? headers;

            public HeaderBuilder(Context context)
            {
                this.context = context;
            }

            public Context Build()
            {
                if (headers != null)
                {
                    return new Context(context.App!, context.UserPrincipal, context.UserPermissions, headers);
                }

                return context;
            }

            public Context Update()
            {
                context.Headers = headers ?? context.Headers;

                return context;
            }

            public void Remove(string key)
            {
                headers ??= new Dictionary<string, string>(context.Headers, StringComparer.OrdinalIgnoreCase);
                headers.Remove(key);
            }

            public void SetHeader(string key, string value)
            {
                headers ??= new Dictionary<string, string>(context.Headers, StringComparer.OrdinalIgnoreCase);
                headers[key] = value;
            }
        }

        public Context Change(Action<ICloneBuilder> action)
        {
            var builder = new HeaderBuilder(this);

            action(builder);

            return builder.Update();
        }

        public Context Clone(Action<ICloneBuilder> action)
        {
            var builder = new HeaderBuilder(this);

            action(builder);

            return builder.Build();
        }
    }

    public interface ICloneBuilder
    {
        void SetHeader(string key, string value);

        void Remove(string key);
    }
}