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

namespace Foodsoft.Alpm
{
    public sealed class Database : IDisposable
    {
        [Flags]
        public enum UsageFlags
        {
            Sync = 1,
            Search = 1 << 1,
            Install = 1 << 2,
            Upgrade = 1 << 3,
            All = (1 << 4) - 1
        }

        private readonly SafeDatabaseHandle _handle;

        internal Database(SafeDatabaseHandle handle)
        {
            _handle = handle;
        }

        // FIXME: This is "bug correct", but probably dumb to do it this way, instead just call add_server
        // like all the stuff in handle.
        // Also this stupid thing leaks the duped strings on failure.
        public IEnumerable<string> Servers
        {
            get => EnumerableWrapper.Create(_handle, alpm.alpm_db_get_servers);
            set
            {
                var listPtr = IntPtr.Zero;
                var success = false;
                var err = 0;
                RuntimeHelpers.PrepareConstrainedRegions();
                try
                {
                    // ReSharper disable once LoopCanBeConvertedToQuery
                    foreach (var s in value)
                        if (alpm.alpm_list_append_strdup(ref listPtr, s) == IntPtr.Zero)
                            throw new AlpmException(Error.Memory);

                    success = true;
                }
                finally
                {
                    if (success)
                        err = alpm.alpm_db_set_servers(_handle, listPtr);
                    else
                        alpm.alpm_list_free(listPtr);
                }

                if (err != 0)
                    throw new AlpmException(_handle.SafeAlpmHandle);
            }
        }

        public string Name => alpm.alpm_db_get_name(_handle);

        public SigLevel SigLevel => alpm.alpm_db_get_siglevel(_handle);

        public Error Valid =>
            alpm.alpm_db_get_valid(_handle) != 0 ? alpm.alpm_errno(_handle.SafeAlpmHandle) : Error.OK;

        public CachePackageList PackageCache
        {
            get
            {
                var listPtr = alpm.alpm_db_get_pkgcache(_handle);
                if (listPtr == IntPtr.Zero)
                    throw new AlpmException(_handle.SafeAlpmHandle);
                return new CachePackageList(listPtr, _handle, this);
            }
        }

        public UsageFlags Usage
        {
            get => Detail.WrapErrorOut<SafeDatabaseHandle, UsageFlags>(_handle.SafeAlpmHandle, _handle,
                alpm.alpm_db_get_usage);
            set => Detail.WrapErrorIn(_handle.SafeAlpmHandle, _handle, value, alpm.alpm_db_set_usage);
        }

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

        public void Unregister()
        {
            _handle.Close();
        }

        public void AddServer(string url)
        {
            Detail.WrapError(_handle.SafeAlpmHandle, () => alpm.alpm_db_add_server(_handle, url));
        }

        public bool RemoveServer(string url)
        {
            return Detail.WrapErrorBool(_handle.SafeAlpmHandle, () => alpm.alpm_db_remove_server(_handle, url));
        }

        public bool Update(bool force = false)
        {
            var err = alpm.alpm_db_update(force ? 1 : 0, _handle);
            if (err < 0) throw new AlpmException(_handle.SafeAlpmHandle);

            return err == 0;
        }

        public Package? GetPackage(string name)
        {
            var pkgPtr = alpm.alpm_pkg_get_pkg(_handle, name);
            if (pkgPtr == IntPtr.Zero)
            {
                var err = alpm.alpm_errno(_handle.SafeAlpmHandle);
                if (err == Error.PkgNotFound)
                    return null;
                throw new AlpmException(err);
            }

            return new CachePackage(new SafeCachePackageHandle(pkgPtr, _handle), this);
        }

        [PrePrepareMethod]
        [SuppressMessage("ReSharper", "LoopCanBeConvertedToQuery")]
        public CachePackageList Search(IEnumerable<string> needles)
        {
            var result = Detail.UseStringList(needles, listPtr => alpm.alpm_db_search(_handle, listPtr));
            if (result == IntPtr.Zero)
            {
                var errNo = alpm.alpm_errno(_handle.SafeAlpmHandle);
                if (errNo != Error.OK)
                    throw new AlpmException(errNo);
            }

            return new CachePackageList(result, _handle, this);
        }
    }
}