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

namespace Foodsoft.Alpm
{
    public static class ExtensionMethods
    {
        [PrePrepareMethod]
        public static Package? FindSatisfier(this IEnumerable<Package> pkgList, string depString)
        {
            var refs = new Dictionary<IntPtr, Package?>(10);
            var listPtr = IntPtr.Zero;
            
            RuntimeHelpers.PrepareConstrainedRegions();
            try
            {
                foreach (var pkg in pkgList)
                {
                    var release = false;
                    var handle = pkg.Handle;
                    var pkgPtr = handle.DangerousGetHandle();
                    
                    refs.Add(pkgPtr, null);
                    handle.DangerousAddRef(ref release);
                    if (!release) throw new ObjectDisposedException(handle.GetType().FullName);

                    refs[pkgPtr] = pkg;
                    if (alpm.alpm_list_append(ref listPtr, handle.DangerousGetHandle()) == IntPtr.Zero)
                        throw new AlpmException(ErrorCode.Memory);
                }

                var foundPtr = alpm.alpm_find_satisfier(listPtr, depString);
                return foundPtr != IntPtr.Zero
                    ? refs[foundPtr]
                    : null;
            }
            finally
            {
                alpm.alpm_list_free(listPtr);
                foreach (var pkg in refs.Values)
                {
                    pkg?.Handle.DangerousRelease();
                }
            }
        }
    }
}