using System.Security.Claims;
using Microsoft.AspNetCore.Authorization;
using Microsoft.Extensions.DependencyInjection;
using Tiku.Application.Security;

namespace Tiku.Api.Security;

public sealed record CurrentTenantMemberRequirement : IAuthorizationRequirement;

public sealed record CurrentPlatformAccessRequirement : IAuthorizationRequirement;

public sealed record TenantPermissionRequirement : IAuthorizationRequirement
{
    public TenantPermissionRequirement(string permissionCode)
    {
        BackendPermissions.EnsureTenant(permissionCode);
        PermissionCode = permissionCode;
    }

    public string PermissionCode { get; }
}

public sealed record PlatformPermissionRequirement : IAuthorizationRequirement
{
    public PlatformPermissionRequirement(string permissionCode)
    {
        BackendPermissions.EnsurePlatform(permissionCode);
        PermissionCode = permissionCode;
    }

    public string PermissionCode { get; }
}

public sealed record MfaRequirement : IAuthorizationRequirement;

public sealed record AllDataScopeRequirement : IAuthorizationRequirement;

public sealed record TenantResourceAccessRequirement : IAuthorizationRequirement;

public sealed record TenantResourceAuthorizationResource(
    Guid TenantId,
    Guid? OwnerUserId = null,
    Guid? RegionId = null,
    Guid? ClassId = null);

internal sealed class CurrentAccessAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<CurrentTenantMemberRequirement>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        CurrentTenantMemberRequirement requirement)
    {
        if (!IsTenantRealm(context.User))
        {
            return;
        }

        var access = await accessContext.GetAsync();
        if (access.IsCurrentTenantMember &&
            access.TenantId is { } tenantId &&
            FindTenantId(context.User) == tenantId)
        {
            context.Succeed(requirement);
        }
    }

    internal static bool IsTenantRealm(ClaimsPrincipal principal) =>
        string.Equals(principal.FindFirst(TikuClaimTypes.Realm)?.Value, "tenant", StringComparison.Ordinal);

    internal static bool IsPlatformRealm(ClaimsPrincipal principal) =>
        string.Equals(principal.FindFirst(TikuClaimTypes.Realm)?.Value, "platform", StringComparison.Ordinal) &&
        principal.FindFirst(TikuClaimTypes.TenantId) is null;

    private static Guid? FindTenantId(ClaimsPrincipal principal) =>
        Guid.TryParse(principal.FindFirst(TikuClaimTypes.TenantId)?.Value, out var tenantId) ? tenantId : null;
}

internal sealed class TenantPermissionAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<TenantPermissionRequirement>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        TenantPermissionRequirement requirement)
    {
        if (!CurrentAccessAuthorizationHandler.IsTenantRealm(context.User))
        {
            return;
        }

        var access = await accessContext.GetAsync();
        if (access.HasTenantPermission(requirement.PermissionCode))
        {
            context.Succeed(requirement);
        }
    }
}

internal sealed class CurrentPlatformAccessAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<CurrentPlatformAccessRequirement>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        CurrentPlatformAccessRequirement requirement)
    {
        if (!CurrentAccessAuthorizationHandler.IsPlatformRealm(context.User))
        {
            return;
        }

        var access = await accessContext.GetAsync();
        if (access.IsUserActive && access.PlatformPermissions.Count > 0)
        {
            context.Succeed(requirement);
        }
    }
}

internal sealed class TenantResourceAccessAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<TenantResourceAccessRequirement, TenantResourceAuthorizationResource>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        TenantResourceAccessRequirement requirement,
        TenantResourceAuthorizationResource resource)
    {
        if (!CurrentAccessAuthorizationHandler.IsTenantRealm(context.User))
        {
            return;
        }

        var access = await accessContext.GetAsync();
        if (access.UserId is { } userId &&
            access.IsCurrentTenantMember &&
            access.TenantId == resource.TenantId &&
            access.DataScope.AllowsResource(userId, resource.OwnerUserId, resource.RegionId, resource.ClassId))
        {
            context.Succeed(requirement);
        }
    }
}

internal sealed class PlatformPermissionAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<PlatformPermissionRequirement>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        PlatformPermissionRequirement requirement)
    {
        if (!CurrentAccessAuthorizationHandler.IsPlatformRealm(context.User))
        {
            return;
        }

        var access = await accessContext.GetAsync();
        if (access.HasPlatformPermission(requirement.PermissionCode))
        {
            context.Succeed(requirement);
        }
    }
}

internal sealed class MfaAuthorizationHandler : AuthorizationHandler<MfaRequirement>
{
    protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, MfaRequirement requirement)
    {
        if (context.User.FindAll(TikuClaimTypes.Mfa).Any(claim =>
                string.Equals(claim.Value, "mfa", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(claim.Value, "totp", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(claim.Value, bool.TrueString, StringComparison.OrdinalIgnoreCase)))
        {
            context.Succeed(requirement);
        }

        return Task.CompletedTask;
    }
}

internal sealed class AllDataScopeAuthorizationHandler(ICurrentAccessContext accessContext) :
    AuthorizationHandler<AllDataScopeRequirement>
{
    protected override async Task HandleRequirementAsync(
        AuthorizationHandlerContext context,
        AllDataScopeRequirement requirement)
    {
        var access = await accessContext.GetAsync();
        if (access.IsCurrentTenantMember && access.DataScope.Mode == DataScopeMode.All)
        {
            context.Succeed(requirement);
        }
    }
}

public static class AccessAuthorizationServiceCollectionExtensions
{
    public static IServiceCollection AddTikuRbacAuthorization(this IServiceCollection services)
    {
        services.AddScoped<IAuthorizationHandler, CurrentAccessAuthorizationHandler>();
        services.AddScoped<IAuthorizationHandler, CurrentPlatformAccessAuthorizationHandler>();
        services.AddScoped<IAuthorizationHandler, TenantPermissionAuthorizationHandler>();
        services.AddScoped<IAuthorizationHandler, PlatformPermissionAuthorizationHandler>();
        services.AddSingleton<IAuthorizationHandler, MfaAuthorizationHandler>();
        services.AddScoped<IAuthorizationHandler, AllDataScopeAuthorizationHandler>();
        services.AddScoped<IAuthorizationHandler, TenantResourceAccessAuthorizationHandler>();

        services.AddAuthorization(options =>
        {
            options.AddPolicy(
                TikuPolicies.CurrentTenantMember,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(new CurrentTenantMemberRequirement()));
            options.AddPolicy(
                TikuPolicies.Mfa,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(new MfaRequirement()));
            options.AddPolicy(
                TikuPolicies.TenantBackofficeBootstrap,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(
                        new CurrentTenantMemberRequirement(),
                        new MfaRequirement()));
            options.AddPolicy(
                TikuPolicies.PlatformBackofficeBootstrap,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(
                        new CurrentPlatformAccessRequirement(),
                        new MfaRequirement()));
            // Temporary compatibility for controllers that have not yet been
            // split into their module-specific permission policy. This must
            // remain database-backed; an authenticated-only alias would reopen
            // every legacy tenant administration endpoint to ordinary users.
            options.AddPolicy(
                TikuPolicies.TenantAdmin,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(
                        new CurrentTenantMemberRequirement(),
                        new TenantPermissionRequirement(BackendPermissions.TenantRoleManage),
                        new MfaRequirement()));
            options.AddPolicy(
                TikuPolicies.TenantContentManageAllScope,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(
                        new CurrentTenantMemberRequirement(),
                        new TenantPermissionRequirement(BackendPermissions.TenantContentManage),
                        new AllDataScopeRequirement(),
                        new MfaRequirement()));
            options.AddPolicy(
                TikuPolicies.TenantCommerceOperateAllScope,
                policy => policy
                    .RequireAuthenticatedUser()
                    .AddRequirements(
                        new CurrentTenantMemberRequirement(),
                        new TenantPermissionRequirement(BackendPermissions.TenantCommerceOperate),
                        new AllDataScopeRequirement(),
                        new MfaRequirement()));

            foreach (var permissionCode in BackendPermissions.Tenant)
            {
                options.AddPolicy(
                    permissionCode,
                    policy => policy
                        .RequireAuthenticatedUser()
                        .AddRequirements(
                            new CurrentTenantMemberRequirement(),
                            new TenantPermissionRequirement(permissionCode),
                            new MfaRequirement()));
            }

            foreach (var permissionCode in BackendPermissions.Platform)
            {
                options.AddPolicy(
                    permissionCode,
                    policy => policy
                        .RequireAuthenticatedUser()
                        .AddRequirements(
                            new PlatformPermissionRequirement(permissionCode),
                            new MfaRequirement()));
            }
        });

        return services;
    }
}