using System;
using LibGit2Sharp.Core;
using LibGit2Sharp.Handlers;

namespace LibGit2Sharp
{
    /// <summary>
    ///   Class to translate libgit2 callbacks into delegates exposed by LibGit2Sharp.
    ///   Handles generating libgit2 git_remote_callbacks datastructure given a set
    ///   of LibGit2Sharp delegates and handles propagating libgit2 callbacks into
    ///   corresponding LibGit2Sharp exposed delegates.
    /// </summary>
    internal class RemoteCallbacks
    {
        internal RemoteCallbacks(ProgressHandler onProgress = null, CompletionHandler onCompletion = null, UpdateTipsHandler onUpdateTips = null)
        {
            Progress = onProgress;
            Completion = onCompletion;
            UpdateTips = onUpdateTips;
        }

        #region Delegates

        /// <summary>
        ///   Progress callback. Corresponds to libgit2 progress callback.
        /// </summary>
        private readonly ProgressHandler Progress;

        /// <summary>
        ///   UpdateTips callback. Corresponds to libgit2 update_tips callback.
        /// </summary>
        private readonly UpdateTipsHandler UpdateTips;

        /// <summary>
        ///   Completion callback. Corresponds to libgit2 Completion callback.
        /// </summary>
        private readonly CompletionHandler Completion;

        #endregion

        internal GitRemoteCallbacks GenerateCallbacks()
        {
            GitRemoteCallbacks callbacks = new GitRemoteCallbacks {version = 1};

            if (Progress != null)
            {
                callbacks.progress = GitProgressHandler;
            }

            if (UpdateTips != null)
            {
                callbacks.update_tips = GitUpdateTipsHandler;
            }

            if (Completion != null)
            {
                callbacks.completion = GitCompletionHandler;
            }

            return callbacks;
        }

        #region Handlers to respond to callbacks raised by libgit2

        /// <summary>
        ///   Handler for libgit2 Progress callback. Converts values
        ///   received from libgit2 callback to more suitable types
        ///   and calls delegate provided by LibGit2Sharp consumer.
        /// </summary>
        /// <param name="str">IntPtr to string from libgit2</param>
        /// <param name="len">length of string</param>
        /// <param name="data"></param>
        private void GitProgressHandler(IntPtr str, int len, IntPtr data)
        {
            ProgressHandler onProgress = Progress;

            if (onProgress != null)
            {
                string message = Utf8Marshaler.FromNative(str, len);
                onProgress(message);
            }
        }

        /// <summary>
        ///   Handler for libgit2 update_tips callback. Converts values
        ///   received from libgit2 callback to more suitable types
        ///   and calls delegate provided by LibGit2Sharp consumer.
        /// </summary>
        /// <param name="str">IntPtr to string</param>
        /// <param name="oldId">Old reference ID</param>
        /// <param name="newId">New referene ID</param>
        /// <param name="data"></param>
        /// <returns></returns>
        private int GitUpdateTipsHandler(IntPtr str, ref GitOid oldId, ref GitOid newId, IntPtr data)
        {
            UpdateTipsHandler onUpdateTips = UpdateTips;
            int result = 0;

            if (onUpdateTips != null)
            {
                string refName = Utf8Marshaler.FromNative(str);
                result = onUpdateTips(refName, oldId, newId);
            }

            return result;
        }

        /// <summary>
        ///   Handler for libgit2 completion callback. Converts values
        ///   received from libgit2 callback to more suitable types
        ///   and calls delegate provided by LibGit2Sharp consumer.
        /// </summary>
        /// <param name="remoteCompletionType"></param>
        /// <param name="data"></param>
        /// <returns></returns>
        private int GitCompletionHandler(RemoteCompletionType remoteCompletionType, IntPtr data)
        {
            CompletionHandler completion = Completion;
            int result = 0;

            if (completion != null)
            {
                result = completion(remoteCompletionType);
            }

            return result;
        }

        #endregion
    }
}