using Serilog;
using SharepointToolbox.Web.Core.Helpers;
using SharepointToolbox.Web.Services.Session;

namespace SharepointToolbox.Web.Services;

/// <summary>
/// Scoped per Blazor circuit. Catches <see cref="SharePointAccessDeniedException"/> from any
/// wrapped operation and, when AutoTakeOwnership is enabled, grants the current user
/// site-collection admin on the failing site (via the tenant admin endpoint) before retrying.
///
/// Retry is safe because the wrapped operation closure re-issues its own CSOM loads on each
/// attempt; the granted permission is server-side and takes effect for the existing delegated
/// token without re-authentication. Each site is elevated at most once per circuit to prevent loops.
/// </summary>
public class ElevationCoordinator : IElevationCoordinator
{
    private readonly ISessionManager _sessionManager;
    private readonly IOwnershipElevationService _ownership;
    private readonly IUserSessionService _session;
    private readonly HashSet<string> _elevatedSites = new(StringComparer.OrdinalIgnoreCase);

    public ElevationCoordinator(
        ISessionManager sessionManager,
        IOwnershipElevationService ownership,
        IUserSessionService session)
    {
        _sessionManager = sessionManager;
        _ownership = ownership;
        _session = session;
    }

    public async Task RunAsync(Func<CancellationToken, Task> operation, CancellationToken ct) =>
        await RunAsync<object?>(async c => { await operation(c); return null; }, ct);

    public async Task<T> RunAsync<T>(Func<CancellationToken, Task<T>> operation, CancellationToken ct)
    {
        try
        {
            return await operation(ct);
        }
        catch (SharePointAccessDeniedException ex)
        {
            if (!_session.Settings.AutoTakeOwnership)
                throw;

            var siteUrl = ex.SiteUrl.TrimEnd('/');
            var key = siteUrl.ToLowerInvariant();

            // Already elevated this site and still denied → elevation can't fix it. Surface original.
            if (_elevatedSites.Contains(key))
                throw;

            // Elevation targets the tenant admin endpoint; denials there aren't site-ownership issues.
            if (siteUrl.Contains("-admin.sharepoint.com", StringComparison.OrdinalIgnoreCase))
                throw;

            await ElevateAsync(siteUrl, ct);
            _elevatedSites.Add(key);

            // Re-run once. The closure re-issues its loads; the now-granted admin right applies.
            return await operation(ct);
        }
    }

    private async Task ElevateAsync(string siteUrl, CancellationToken ct)
    {
        var profile = _session.CurrentProfile
            ?? throw new InvalidOperationException("Cannot elevate ownership: no active profile.");

        var adminProfile = new Core.Models.TenantProfile
        {
            Id = profile.Id,
            Name = profile.Name,
            TenantUrl = BuildAdminUrl(siteUrl),
            TenantId = profile.TenantId,
            ClientId = profile.ClientId,
            ClientLogo = profile.ClientLogo,
        };

        try
        {
            var adminCtx = await _sessionManager.GetOrCreateContextAsync(adminProfile, ct);
            Log.Information("Auto-elevating site-collection admin ownership for {Site} via {Admin}",
                siteUrl, adminProfile.TenantUrl);
            // loginName empty → ElevateAsync resolves the current (delegated) user from the admin context.
            await _ownership.ElevateAsync(adminCtx, siteUrl, loginName: string.Empty, ct);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            throw new InvalidOperationException(
                $"Auto-elevate ownership failed for {siteUrl}. Granting site-collection admin requires " +
                $"SharePoint tenant administrator rights on the signed-in account. ({ex.Message})", ex);
        }
    }

    // https://abcube.sharepoint.com/sites/Foo → https://abcube-admin.sharepoint.com
    private static string BuildAdminUrl(string siteUrl)
    {
        if (!Uri.TryCreate(siteUrl, UriKind.Absolute, out var uri))
            return siteUrl;
        var adminHost = uri.Host.Replace(".sharepoint.com", "-admin.sharepoint.com",
            StringComparison.OrdinalIgnoreCase);
        return $"{uri.Scheme}://{adminHost}";
    }
}