using Microsoft.SharePoint.Client;
using SharepointToolbox.Web.Core.Models;
using SharepointToolbox.Web.Services;
using SharepointToolbox.Web.Services.Auth;
using SharepointToolbox.Web.Services.Session;

namespace SharepointToolbox.Web.Infrastructure.Auth;

/// <summary>
/// Delegated session manager using OAuth2 refresh tokens.
/// Tokens come from ISessionCredentialStore (ProtectedSessionStorage — browser-side only).
/// Caches access tokens in-memory per scope for the duration of the Blazor circuit.
/// Scoped per Blazor circuit.
/// </summary>
public class SessionManager : ISessionManager
{
    private readonly ISessionCredentialStore _credentialStore;
    private readonly ITokenRefreshService _tokenRefresh;
    private readonly Dictionary<string, ClientContext> _contexts = new();
    private readonly Dictionary<string, (string Token, DateTimeOffset ExpiresAt)> _accessTokenCache = new();
    private readonly SemaphoreSlim _lock = new(1, 1);

    public SessionManager(ISessionCredentialStore credentialStore, ITokenRefreshService tokenRefresh)
    {
        _credentialStore = credentialStore;
        _tokenRefresh    = tokenRefresh;
    }

    public bool IsAuthenticated(string tenantUrl) => _contexts.ContainsKey(NormalizeUrl(tenantUrl));

    public async Task<(string Token, DateTimeOffset ExpiresAt)> GetAccessTokenWithExpiryAsync(
        string scope, CancellationToken ct = default)
    {
        await _lock.WaitAsync(ct);
        try
        {
            if (_accessTokenCache.TryGetValue(scope, out var cached) && cached.ExpiresAt > DateTimeOffset.UtcNow)
                return cached;

            var tokens = await _credentialStore.GetAsync()
                         ?? throw new InvalidOperationException(
                             "No session tokens found. Please authenticate via Microsoft first.");

            var result = await _tokenRefresh.RefreshAsync(tokens.RefreshToken, tokens.TenantId, tokens.ClientId, scope);

            // Persist rotated refresh token back to browser storage
            if (result.RefreshToken != tokens.RefreshToken)
                await _credentialStore.UpdateRefreshTokenAsync(result.RefreshToken);

            var entry = (result.AccessToken, result.ExpiresAt);
            _accessTokenCache[scope] = entry;
            return entry;
        }
        finally { _lock.Release(); }
    }

    public async Task<ClientContext> GetOrCreateContextAsync(TenantProfile profile, CancellationToken ct = default)
    {
        ArgumentException.ThrowIfNullOrEmpty(profile.TenantUrl);
        ArgumentException.ThrowIfNullOrEmpty(profile.TenantId);

        var key     = NormalizeUrl(profile.TenantUrl);
        var spScope = NormalizeScopeUrl(profile.TenantUrl) + "/.default";

        await _lock.WaitAsync(ct);
        try
        {
            if (_contexts.TryGetValue(key, out var existing))
                return existing;

            // Validate tokens are present before creating context
            var tokens = await _credentialStore.GetAsync()
                         ?? throw new InvalidOperationException(
                             "No session tokens found. Please authenticate via Microsoft first.");

            _ = tokens; // validated; actual token acquired per-request below

            var ctx = new ClientContext(profile.TenantUrl);
            ctx.ExecutingWebRequest += async (_, e) =>
            {
                var (token, _) = await GetAccessTokenWithExpiryAsyncInternal(spScope, tokens.TenantId);
                e.WebRequestExecutor.RequestHeaders["Authorization"] = "Bearer " + token;
            };

            _contexts[key] = ctx;
            return ctx;
        }
        finally { _lock.Release(); }
    }

    public async Task<ClientContext> GetOrCreateContextAsync(string siteUrl, TenantProfile profile, CancellationToken ct = default)
    {
        var profileForSite = new TenantProfile
        {
            Id         = profile.Id,
            Name       = profile.Name,
            TenantUrl  = siteUrl,
            TenantId   = profile.TenantId,
            ClientId   = profile.ClientId,
            ClientLogo = profile.ClientLogo,
        };
        return await GetOrCreateContextAsync(profileForSite, ct);
    }

    public async Task ClearSessionAsync(string tenantUrl)
    {
        var key = NormalizeUrl(tenantUrl);
        await _lock.WaitAsync();
        try
        {
            if (_contexts.TryGetValue(key, out var ctx))
            {
                ctx.Dispose();
                _contexts.Remove(key);
            }
        }
        finally { _lock.Release(); }
    }

    public async Task ClearAllAsync()
    {
        await _lock.WaitAsync();
        try
        {
            foreach (var ctx in _contexts.Values) ctx.Dispose();
            _contexts.Clear();
            _accessTokenCache.Clear();
        }
        finally { _lock.Release(); }
    }

    // Internal version that bypasses the outer lock (called from ExecutingWebRequest which may run concurrently)
    private async Task<(string Token, DateTimeOffset ExpiresAt)> GetAccessTokenWithExpiryAsyncInternal(
        string scope, string tenantId)
    {
        if (_accessTokenCache.TryGetValue(scope, out var cached) && cached.ExpiresAt > DateTimeOffset.UtcNow)
            return cached;

        var tokens = await _credentialStore.GetAsync()
                     ?? throw new InvalidOperationException("No session tokens in store.");

        var result = await _tokenRefresh.RefreshAsync(tokens.RefreshToken, tenantId, tokens.ClientId, scope);

        if (result.RefreshToken != tokens.RefreshToken)
            await _credentialStore.UpdateRefreshTokenAsync(result.RefreshToken);

        var entry = (result.AccessToken, result.ExpiresAt);
        _accessTokenCache[scope] = entry;
        return entry;
    }

    private static string NormalizeUrl(string url) => url.TrimEnd('/').ToLowerInvariant();

    private static string NormalizeScopeUrl(string siteUrl)
    {
        if (Uri.TryCreate(siteUrl, UriKind.Absolute, out var uri))
            return $"{uri.Scheme}://{uri.Host}";
        return siteUrl.TrimEnd('/');
    }
}