using System.Collections.ObjectModel;
using System.Text.Json;
using Snake.Model;

namespace Snake.Persistance;

public class SnakeLevelLoader{
    #region Fields
    private readonly string SaveFileName;
    private List<StoredSnakeLevel>? _stored_levels;
    #endregion

    #region Properties
    public ReadOnlyCollection<StoredSnakeLevel> StoredLevels => _stored_levels?.AsReadOnly()
            ?? throw new InvalidOperationException("Can not query stored levels before loading the data");
    #endregion

    #region Constructors
    public SnakeLevelLoader(string saveFileName){
        SaveFileName = saveFileName;
        if(!File.Exists(SaveFileName)){
            throw new FileNotFoundException("Save file not found", SaveFileName);
        }
    }
    #endregion

    #region Methods
    public async Task ReadAllDataAsync()
    {
        string file_content = await File.ReadAllTextAsync(SaveFileName);
        _stored_levels = JsonSerializer.Deserialize<List<StoredSnakeLevel>>(file_content, new JsonSerializerOptions() { PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower })
            ?? throw new JsonException("Failed to deserialize stored levels");
    }

    public SnakeLevel LoadLevel(StoredSnakeLevel level){
        return new SnakeLevel(level.Size, 
            level.Obstacles.Select(a => new Point(a[0], a[1])),
            level.SnakeStartLength,
            level.NewEggRound,
            level.EggLimit);
    }
    #endregion
}