AMO_Housing/Services/LoginHistoryStore.cs

using System.IO;
using System.Text.Json;

namespace Housing.Services;

public sealed class LoginHistoryStore
{
    private const int MaxHistoryCount = 3;
    private readonly string _filePath;
    private readonly LoginHistoryData _data;

    private LoginHistoryStore(string filePath, LoginHistoryData data)
    {
        _filePath = filePath;
        _data = data;
    }

    public static LoginHistoryStore Load(string filePath)
    {
        try
        {
            if (!File.Exists(filePath))
            {
                return new LoginHistoryStore(filePath, new LoginHistoryData());
            }

            var json = File.ReadAllText(filePath);
            var data = JsonSerializer.Deserialize<LoginHistoryData>(json) ?? new LoginHistoryData();
            data.Fields ??= new Dictionary<string, List<string>>();
            return new LoginHistoryStore(filePath, data);
        }
        catch
        {
            return new LoginHistoryStore(filePath, new LoginHistoryData());
        }
    }

    public IReadOnlyList<string> GetValues(string fieldName)
    {
        return _data.Fields.TryGetValue(fieldName, out var values)
            ? values.Where(value => !string.IsNullOrWhiteSpace(value)).Take(MaxHistoryCount).ToArray()
            : Array.Empty<string>();
    }

    public void Remember(string fieldName, string value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return;
        }

        if (!_data.Fields.TryGetValue(fieldName, out var values))
        {
            values = new List<string>();
            _data.Fields[fieldName] = values;
        }

        values.RemoveAll(item => string.Equals(item, value, StringComparison.OrdinalIgnoreCase));
        values.Insert(0, value);
        if (values.Count > MaxHistoryCount)
        {
            values.RemoveRange(MaxHistoryCount, values.Count - MaxHistoryCount);
        }
    }

    public bool Forget(string fieldName, string value)
    {
        if (string.IsNullOrWhiteSpace(value) ||
            !_data.Fields.TryGetValue(fieldName, out var values))
        {
            return false;
        }

        var removedCount = values.RemoveAll(item => string.Equals(item, value, StringComparison.OrdinalIgnoreCase));
        if (values.Count == 0)
        {
            _data.Fields.Remove(fieldName);
        }

        return removedCount > 0;
    }

    public void Save()
    {
        var directory = Path.GetDirectoryName(_filePath);
        if (!string.IsNullOrWhiteSpace(directory))
        {
            Directory.CreateDirectory(directory);
        }

        var json = JsonSerializer.Serialize(_data, new JsonSerializerOptions { WriteIndented = true });
        File.WriteAllText(_filePath, json);
    }

    private sealed class LoginHistoryData
    {
        public Dictionary<string, List<string>> Fields { get; set; } = new(StringComparer.OrdinalIgnoreCase);
    }
}