using System;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;

namespace Foodsoft.Alpm
{
    public struct PackageList : IEnumerable<Package>, IDisposable
    {
        private SafeListHandle<SafeDatabaseHandle> _handle;
        private Database _db;

        internal PackageList(SafeListHandle<SafeDatabaseHandle> handle, Database db)
        {
            _handle = handle;
            _db = db;
        }

        public IEnumerator<Package> GetEnumerator()
        {
            var release = false;

            RuntimeHelpers.PrepareConstrainedRegions();
            try
            {
                _handle.DangerousAddRef(ref release);
                if (!release) throw new ObjectDisposedException(_handle.GetType().FullName);
                for (var list = _handle.DangerousGetHandle(); list != IntPtr.Zero; list = Wrapper.ListNext(list))
                {
                    yield return new CachePackage(
                        new SafeCachePackageHandle(Wrapper.ListData(list), _handle.ParentHandle), _db);
                }
            }
            finally
            {
                if (release)
                    _handle.DangerousRelease();
            }
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        public void Dispose()
        {
            _handle.Dispose();
        }
    }
}