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

namespace Foodsoft.Alpm
{
    public class CachePackageList : IPackageList<CachePackage>, ICollection<CachePackage>
    {
        private readonly Database _db;
        private readonly IntPtr _listPtr;
        private readonly SafeDatabaseHandle _parentHandle;

        internal CachePackageList(IntPtr listPtr, SafeDatabaseHandle parentHandle, Database db)
        {
            _parentHandle = parentHandle;
            _listPtr = listPtr;
            _db = db;
        }

        public bool Contains(CachePackage item)
        {
            var name = item.Name;

            return _parentHandle.UseHandle(_listPtr, list =>
            {
                for (; list != IntPtr.Zero; list = Detail.ListNext(list))
                    if (name == alpm.alpm_pkg_get_name(list))
                        return true;

                return false;
            });
        }

        public void CopyTo(CachePackage[] array, int arrayIndex)
        {
            _parentHandle.UseHandle(_listPtr, list =>
            {
                for (; list != IntPtr.Zero; list = Detail.ListNext(list))
                    array[arrayIndex++] = new CachePackage(
                        new SafeCachePackageHandle(Detail.ListData(list), _parentHandle), _db);

                return 0;
            });
        }

        public void Add(CachePackage item)
        {
            throw new NotSupportedException();
        }

        public bool Remove(CachePackage item)
        {
            throw new NotSupportedException();
        }

        public void Clear()
        {
            throw new NotSupportedException();
        }

        public int Count => _listPtr == IntPtr.Zero
            ? 0
            : _parentHandle.UseHandle(_listPtr, list => (int) alpm.alpm_list_count(list));

        public bool IsReadOnly => true;

        [PrePrepareMethod]
        public IEnumerator<CachePackage> GetEnumerator()
        {
            if (_listPtr == IntPtr.Zero)
                yield break;
            var release = false;

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

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

        public CachePackage? FindSatisfier(string depString)
        {
            return _parentHandle.UseHandle(_listPtr, list =>
            {
                var pkgPtr = alpm.alpm_find_satisfier(list, depString);
                return pkgPtr != IntPtr.Zero
                    ? new CachePackage(new SafeCachePackageHandle(pkgPtr, _parentHandle), _db)
                    : null;
            });
        }
    }
}