using System.IO;
using ImageMagick;

namespace GifResizer.Models;

public class Gif : IDisposable
{
    private readonly string _path;
    private MagickImageCollection? _images;
    
    public Gif(string path)
    {
        ArgumentNullException.ThrowIfNull(path);
        if (string.IsNullOrWhiteSpace(path) || !File.Exists(path)) 
            throw new ArgumentException($"File '{path}' does not exist");
        _path = path;
    }

    public void Load()
    {
        _images?.Dispose();
        _images = new MagickImageCollection(_path);
        _images.Coalesce();
    }
    
    public void Resize(int width, int height)
    {
        if (_images == null) 
            throw new InvalidOperationException("Image hasn't been loaded yet");
        if (width <= 0 || height <= 0) 
            throw new InvalidOperationException("Please specify a valid width or height.");
    
        foreach (var image in _images)
        {
            if (image.Width == width && image.Height == height) continue;
            image.Resize((uint)width, (uint)height);
        }
    }

    public void Save(string outputPath)
    {
        if (_images == null) 
            throw new InvalidOperationException("Image hasn't been loaded yet");
        
        var directory = Path.GetDirectoryName(outputPath);
        if (!string.IsNullOrEmpty(directory))
        {
            Directory.CreateDirectory(directory);
        }
        
        _images.Write(outputPath);
    }

    public void Dispose()
    {
        _images?.Dispose();
    }
}