Beam/Beam.Downloaders/UnitDownloaderOptions.cs

using Beam.Models;

namespace Beam.Downloaders;

public record class UnitDownloaderOptions<RawType, OutType> {
    public HttpClient Client { get; init; } = new();
    
    public FailurePredicateOptions<RawType>? FailurePredicateOptions { get; init; }
    public FragmentOptions? FragmentOptions { get; init; }
    public required AsyncTransformer<RawType, OutType> AsyncTransformer { get; init; }
    public string? DownloadFolder { get; init; } = null;
    public int BufferSize { get; init; } = 80 * 1024; // 80kb
}

public record class FailurePredicateOptions<RawType> {
    public required AsyncDownloadFailurePredicate<RawType>?[]? AsyncDownloadFailurePredicates { get; init; }
    public bool ProcessInParallel { get; init; } = false;
    public int? ParallelThreads { get; init; }
}

public record class FragmentOptions {
    public required int FragmentSize { get; init; }
    public bool DownloadInParallel { get; init; } = false;
    public int? ParallelThreads { get; init; }
}


    // ---------- UnitDownloaderOptions Builder ----------
    public sealed class UnitDownloaderOptionsBuilder<TRaw, TOut>
    {
        private HttpClient _client = new HttpClient();
        private FailurePredicateOptions<TRaw>? _failureOptions;
        private FragmentOptions? _fragmentOptions;
        private AsyncTransformer<TRaw, TOut>? _asyncTransformer;
        private string? _downloadFolder = null;
        private int _bufferSize = 80 * 1024;

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithClient(HttpClient client)
        {
            _client = client ?? throw new System.ArgumentNullException(nameof(client));
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithFailurePredicateOptions(FailurePredicateOptions<TRaw>? options)
        {
            _failureOptions = options;
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithFailurePredicates(System.Action<FailurePredicateOptionsBuilder<TRaw>> configure)
        {
            if (configure == null) throw new System.ArgumentNullException(nameof(configure));
            var b = new FailurePredicateOptionsBuilder<TRaw>();
            configure(b);
            _failureOptions = b.Build();
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithFragmentOptions(FragmentOptions? options)
        {
            _fragmentOptions = options;
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithFragments(System.Action<FragmentOptionsBuilder> configure)
        {
            if (configure == null) throw new System.ArgumentNullException(nameof(configure));
            var b = new FragmentOptionsBuilder();
            configure(b);
            _fragmentOptions = b.Build();
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithAsyncTransformer(AsyncTransformer<TRaw, TOut> transformer)
        {
            _asyncTransformer = transformer ?? throw new System.ArgumentNullException(nameof(transformer));
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithDownloadFolder(string? downloadFolder)
        {
            _downloadFolder = downloadFolder;
            return this;
        }

        public UnitDownloaderOptionsBuilder<TRaw, TOut> WithBufferSize(int bytes)
        {
            if (bytes <= 0) throw new System.ArgumentOutOfRangeException(nameof(bytes));
            _bufferSize = bytes;
            return this;
        }

        public UnitDownloaderOptions<TRaw, TOut> Build()
        {
            if (_asyncTransformer == null)
                throw new System.InvalidOperationException("AsyncTransformer must be provided.");

            return new UnitDownloaderOptions<TRaw, TOut>
            {
                Client = _client,
                FailurePredicateOptions = _failureOptions,
                FragmentOptions = _fragmentOptions,
                AsyncTransformer = _asyncTransformer,
                DownloadFolder = _downloadFolder,
                BufferSize = _bufferSize
            };
        }
    }

    // ---------- FailurePredicateOptions Builder ----------
    public sealed class FailurePredicateOptionsBuilder<TRaw>
    {
        private readonly System.Collections.Generic.List<AsyncDownloadFailurePredicate<TRaw>?> _predicates =
            new System.Collections.Generic.List<AsyncDownloadFailurePredicate<TRaw>?>();
        private bool _processInParallel = false;
        private int? _parallelThreads = null;

        public FailurePredicateOptionsBuilder<TRaw> WithPredicate(AsyncDownloadFailurePredicate<TRaw>? predicate)
        {
            _predicates.Add(predicate);
            return this;
        }

        public FailurePredicateOptionsBuilder<TRaw> WithPredicates(System.Collections.Generic.IEnumerable<AsyncDownloadFailurePredicate<TRaw>?> predicates)
        {
            if (predicates == null) throw new System.ArgumentNullException(nameof(predicates));
            _predicates.AddRange(predicates);
            return this;
        }

        public FailurePredicateOptionsBuilder<TRaw> WithPredicates(params AsyncDownloadFailurePredicate<TRaw>?[] predicates)
        {
            _predicates.Clear();
            if (predicates != null) _predicates.AddRange(predicates);
            return this;
        }

        public FailurePredicateOptionsBuilder<TRaw> WithProcessInParallel(bool value = true)
        {
            _processInParallel = value;
            return this;
        }

        public FailurePredicateOptionsBuilder<TRaw> WithParallelThreads(int? threads)
        {
            if (threads.HasValue && threads.Value <= 0)
                throw new System.ArgumentOutOfRangeException(nameof(threads));
            _parallelThreads = threads;
            return this;
        }

        public FailurePredicateOptions<TRaw> Build()
        {
            var arr = _predicates.Count == 0 ? [] : _predicates.ToArray();
            return new FailurePredicateOptions<TRaw>
            {
                AsyncDownloadFailurePredicates = arr,
                ProcessInParallel = _processInParallel,
                ParallelThreads = _parallelThreads
            };
        }
    }

    // ---------- FragmentOptions Builder ----------
    public sealed class FragmentOptionsBuilder {
        private int? _fragmentSize;
        private bool _downloadInParallel = false;
        private int? _parallelThreads = null;

        public FragmentOptionsBuilder WithFragmentSize(int bytes) {
            if (bytes <= 0) throw new System.ArgumentOutOfRangeException(nameof(bytes));
            _fragmentSize = bytes;
            return this;
        }

        public FragmentOptionsBuilder WithDownloadInParallel(bool value = true) {
            _downloadInParallel = value;
            return this;
        }

        public FragmentOptionsBuilder WithParallelThreads(int? threads) {
            if (threads.HasValue && threads.Value <= 0)
                throw new System.ArgumentOutOfRangeException(nameof(threads));
            _parallelThreads = threads;
            return this;
        }

        public FragmentOptions Build() {
            if (!_fragmentSize.HasValue)
                throw new System.InvalidOperationException("FragmentSize must be provided.");

            return new FragmentOptions {
                FragmentSize = _fragmentSize.Value,
                DownloadInParallel = _downloadInParallel,
                ParallelThreads = _parallelThreads
            };
        }
    }