using System.Collections.Immutable;
using System.Reflection;
using System.Text.RegularExpressions;

namespace Luna.Configuration.Services;

public sealed class EmbeddedResourceLoader
{
    private readonly Assembly? assembly = Assembly.GetExecutingAssembly();
    
    public ImmutableHashSet<string> ListResources(string? pattern = null)
    {
        if (assembly is null)
            throw new InvalidOperationException("Unable to determine the entry assembly.");

        var resourceNames = assembly.GetManifestResourceNames();
        
        if (string.IsNullOrEmpty(pattern))
            return resourceNames.ToImmutableHashSet();

        var regex = new Regex(Regex.Escape(pattern).Replace("\\*", ".*").Replace("\\?", ".?"), RegexOptions.IgnoreCase);
        return resourceNames
            .Where(r => regex.IsMatch(r))
            .ToImmutableHashSet();
    }
    
    public async Task<string> LoadAsync(string name)
    {
        if (assembly is null)
            throw new InvalidOperationException("Unable to determine the entry assembly.");
        
        var resourceName = assembly.GetManifestResourceNames().FirstOrDefault(r => r.EndsWith(name, StringComparison.OrdinalIgnoreCase));
        
        if (resourceName == null)
            throw new FileNotFoundException($"Embedded resource '{name}' not found.");

        await using var stream = assembly.GetManifestResourceStream(resourceName);
        if (stream == null)
            throw new FileNotFoundException($"Unable to load embedded resource '{name}'.");

        using var reader = new StreamReader(stream);
        return await reader.ReadToEndAsync();
    }
}