using System.IO;
using System.Text.Json;
using Futonizer.Models;

namespace Futonizer.Services;

/// <summary>
/// Persists a rolling history of previously processed files (newest first,
/// capped at <see cref="MaxEntries"/>) as a JSON file stored next to the
/// application executable.
/// </summary>
public static class HistoryService
{
    private const int MaxEntries = 1000;
    private static readonly string HistoryFilePath =
        Path.Combine(AppContext.BaseDirectory, "history.json");
    private static readonly object FileLock = new();

    public static List<HistoryEntry> Load()
    {
        lock (FileLock)
        {
            try
            {
                if (!File.Exists(HistoryFilePath)) return new List<HistoryEntry>();
                string json = File.ReadAllText(HistoryFilePath);
                var list = JsonSerializer.Deserialize<List<HistoryEntry>>(json);
                return list ?? new List<HistoryEntry>();
            }
            catch
            {
                return new List<HistoryEntry>();
            }
        }
    }

    /// <summary>
    /// Adds a new entry at the front of the history and trims it down to
    /// <see cref="MaxEntries"/> items. Safe to call concurrently from
    /// multiple in-flight strip jobs.
    /// </summary>
    public static void Add(HistoryEntry entry)
    {
        lock (FileLock)
        {
            try
            {
                var list = File.Exists(HistoryFilePath)
                    ? JsonSerializer.Deserialize<List<HistoryEntry>>(File.ReadAllText(HistoryFilePath)) ?? new List<HistoryEntry>()
                    : new List<HistoryEntry>();

                list.Insert(0, entry);
                if (list.Count > MaxEntries)
                    list.RemoveRange(MaxEntries, list.Count - MaxEntries);

                string json = JsonSerializer.Serialize(list, new JsonSerializerOptions { WriteIndented = true });
                File.WriteAllText(HistoryFilePath, json);
            }
            catch
            {
                // Best effort — history is a convenience feature, never worth failing a strip job over.
            }
        }
    }
}