// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.ViewFeatures.Infrastructure;
 
namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
 
/// <summary>
/// Provides session-state data to the current <see cref="ITempDataDictionary"/> object.
/// </summary>
public class SessionStateTempDataProvider : ITempDataProvider
{
    // Internal for testing
    internal const string TempDataSessionStateKey = "__ControllerTempData";
    private readonly TempDataSerializer _tempDataSerializer;
 
    /// <summary>
    /// Initializes a new instance of <see cref="SessionStateTempDataProvider"/>.
    /// </summary>
    /// <param name="tempDataSerializer">The <see cref="TempDataSerializer"/>.</param>
    public SessionStateTempDataProvider(TempDataSerializer tempDataSerializer)
    {
        _tempDataSerializer = tempDataSerializer;
    }
 
    /// <inheritdoc />
    public virtual IDictionary<string, object> LoadTempData(HttpContext context)
    {
        ArgumentNullException.ThrowIfNull(context);
 
        // Accessing Session property will throw if the session middleware is not enabled.
        var session = context.Session;
 
        if (session.TryGetValue(TempDataSessionStateKey, out var value))
        {
            // If we got it from Session, remove it so that no other request gets it
            session.Remove(TempDataSessionStateKey);
 
            return _tempDataSerializer.Deserialize(value);
        }
 
        return new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
    }
 
    /// <inheritdoc />
    public virtual void SaveTempData(HttpContext context, IDictionary<string, object> values)
    {
        ArgumentNullException.ThrowIfNull(context);
 
        // Accessing Session property will throw if the session middleware is not enabled.
        var session = context.Session;
 
        var hasValues = (values != null && values.Count > 0);
        if (hasValues)
        {
            var bytes = _tempDataSerializer.Serialize(values);
            session.Set(TempDataSessionStateKey, bytes);
        }
        else
        {
            session.Remove(TempDataSessionStateKey);
        }
    }
}