using System;
using System.Runtime.CompilerServices;
using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;

namespace Foodsoft.Alpm
{
    internal sealed class SafeDatabaseHandle : SafeHandle
    {
        internal SafeAlpmHandle SafeAlpmHandle
        {
            [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
            [PrePrepareMethod]
            get;
        } = null!;

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
        [PrePrepareMethod]
        internal SafeDatabaseHandle(IntPtr dbPtr, SafeAlpmHandle safeAlpmHandle) : base(IntPtr.Zero, true)
        {
            var success = false;

            RuntimeHelpers.PrepareConstrainedRegions();
            try { }
            finally
            {
                safeAlpmHandle.DangerousAddRef(ref success);
                if (success)
                {
                    SafeAlpmHandle = safeAlpmHandle;
                    handle = dbPtr;
                }
            }

            if (!success) throw new ObjectDisposedException(GetType().FullName);
        }

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail), PrePrepareMethod]
        protected override bool ReleaseHandle()
        {
            var err = alpm.alpm_db_unregister(handle);
            SafeAlpmHandle.DangerousRelease();
            return err == 0;
        }

        public override bool IsInvalid
        {
            [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), PrePrepareMethod]
            get => handle == IntPtr.Zero;
        }
    }
}