using System;
using System.Diagnostics;
using System.Globalization;
using LibGit2Sharp.Core;
using LibGit2Sharp.Core.Handles;

namespace LibGit2Sharp
{
    /// <summary>
    /// A reference to a <see cref="Blob"/> known by the <see cref="Index"/>.
    /// </summary>
    [DebuggerDisplay("{DebuggerDisplay,nq}")]
    public class IndexEntry : IEquatable<IndexEntry>
    {
        private static readonly LambdaEqualityHelper<IndexEntry> equalityHelper =
            new LambdaEqualityHelper<IndexEntry>(x => x.Path, x => x.Id, x => x.Mode, x => x.StageLevel);

        /// <summary>
        /// Gets the relative path to the file within the working directory.
        /// </summary>
        public virtual string Path { get; private set; }

        /// <summary>
        /// Gets the file mode.
        /// </summary>
        public virtual Mode Mode { get; private set; }

        /// <summary>
        /// Gets the stage number.
        /// </summary>
        public virtual StageLevel StageLevel { get; private set; }

        /// <summary>
        /// Whether the file is marked as assume-unchanged
        /// </summary>
        public virtual bool AssumeUnchanged { get; private set; }

        /// <summary>
        /// Gets the id of the <see cref="Blob"/> pointed at by this index entry.
        /// </summary>
        public virtual ObjectId Id { get; private set; }

        internal static IndexEntry BuildFromPtr(IndexEntrySafeHandle handle)
        {
            if (handle == null || handle.IsZero)
            {
                return null;
            }

            GitIndexEntry entry = handle.MarshalAsGitIndexEntry();

            FilePath path = LaxFilePathMarshaler.FromNative(entry.Path);

            return new IndexEntry
            {
                Path = path.Native,
                Id = entry.Id,
                StageLevel = Proxy.git_index_entry_stage(handle),
                Mode = (Mode)entry.Mode,
                AssumeUnchanged = (GitIndexEntry.GIT_IDXENTRY_VALID & entry.Flags) == GitIndexEntry.GIT_IDXENTRY_VALID
            };
        }

        /// <summary>
        /// Determines whether the specified <see cref="Object"/> is equal to the current <see cref="IndexEntry"/>.
        /// </summary>
        /// <param name="obj">The <see cref="Object"/> to compare with the current <see cref="IndexEntry"/>.</param>
        /// <returns>True if the specified <see cref="Object"/> is equal to the current <see cref="IndexEntry"/>; otherwise, false.</returns>
        public override bool Equals(object obj)
        {
            return Equals(obj as IndexEntry);
        }

        /// <summary>
        /// Determines whether the specified <see cref="IndexEntry"/> is equal to the current <see cref="IndexEntry"/>.
        /// </summary>
        /// <param name="other">The <see cref="IndexEntry"/> to compare with the current <see cref="IndexEntry"/>.</param>
        /// <returns>True if the specified <see cref="IndexEntry"/> is equal to the current <see cref="IndexEntry"/>; otherwise, false.</returns>
        public bool Equals(IndexEntry other)
        {
            return equalityHelper.Equals(this, other);
        }

        /// <summary>
        /// Returns the hash code for this instance.
        /// </summary>
        /// <returns>A 32-bit signed integer hash code.</returns>
        public override int GetHashCode()
        {
            return equalityHelper.GetHashCode(this);
        }

        /// <summary>
        /// Tests if two <see cref="IndexEntry"/> are equal.
        /// </summary>
        /// <param name="left">First <see cref="IndexEntry"/> to compare.</param>
        /// <param name="right">Second <see cref="IndexEntry"/> to compare.</param>
        /// <returns>True if the two objects are equal; false otherwise.</returns>
        public static bool operator ==(IndexEntry left, IndexEntry right)
        {
            return Equals(left, right);
        }

        /// <summary>
        /// Tests if two <see cref="IndexEntry"/> are different.
        /// </summary>
        /// <param name="left">First <see cref="IndexEntry"/> to compare.</param>
        /// <param name="right">Second <see cref="IndexEntry"/> to compare.</param>
        /// <returns>True if the two objects are different; false otherwise.</returns>
        public static bool operator !=(IndexEntry left, IndexEntry right)
        {
            return !Equals(left, right);
        }

        private string DebuggerDisplay
        {
            get
            {
                return string.Format(CultureInfo.InvariantCulture,
                                     "{0} ({1}) => \"{2}\"",
                                     Path,
                                     StageLevel,
                                     Id.ToString(7));
            }
        }
    }
}
