using System;
using System.Diagnostics;
using System.Globalization;

namespace AvalonStudio.TextEditor.Document
{
#if NREFACTORY
using ICSharpCode.NRefactory.Editor;
#endif

    /// <summary>
    ///     Represents a line inside a <see cref="TextDocument" />.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         The <see cref="TextDocument.Lines" /> collection contains one DocumentLine instance
    ///         for every line in the document. This collection is read-only to user code and is automatically
    ///         updated to reflect the current document content.
    ///     </para>
    ///     <para>
    ///         Internally, the DocumentLine instances are arranged in a binary tree that allows for both efficient updates and
    ///         lookup.
    ///         Converting between offset and line number is possible in O(lg N) time,
    ///         and the data structure also updates all offsets in O(lg N) whenever a line is inserted or removed.
    ///     </para>
    /// </remarks>
    public sealed partial class DocumentLine : IDocumentLine
    {
        #region ToString

        /// <summary>
        ///     Gets a string with debug output showing the line number and offset.
        ///     Does not include the line's text.
        /// </summary>
        public override string ToString()
        {
            if (IsDeleted)
                return "[DocumentLine deleted]";
            return string.Format(
                CultureInfo.InvariantCulture,
                "[DocumentLine Number={0} Offset={1} Length={2}]", LineNumber, Offset, Length);
        }

        #endregion ToString

        #region Constructor

#if DEBUG

        // Required for thread safety check which is done only in debug builds.
        // To save space, we don't store the document reference in release builds as we don't need it there.
        private readonly TextDocument document;

#endif

        internal bool isDeleted;

        internal DocumentLine(TextDocument document)
        {
#if DEBUG
            Debug.Assert(document != null);
            this.document = document;
#endif
        }

        [Conditional("DEBUG")]
        private void DebugVerifyAccess()
        {
#if DEBUG
            document.DebugVerifyAccess();
#endif
        }

        #endregion Constructor

        #region Events

        //		/// <summary>
        //		/// Is raised when the line is deleted.
        //		/// </summary>
        //		public event EventHandler Deleted;
        //
        //		/// <summary>
        //		/// Is raised when the line's text changes.
        //		/// </summary>
        //		public event EventHandler TextChanged;
        //
        //		/// <summary>
        //		/// Raises the Deleted or TextChanged event.
        //		/// </summary>
        //		internal void RaiseChanged()
        //		{
        //			if (IsDeleted) {
        //				if (Deleted != null)
        //					Deleted(this, EventArgs.Empty);
        //			} else {
        //				if (TextChanged != null)
        //					TextChanged(this, EventArgs.Empty);
        //			}
        //		}

        #endregion Events

        #region Properties stored in tree

        /// <summary>
        ///     Gets if this line was deleted from the document.
        /// </summary>
        public bool IsDeleted
        {
            get
            {
                DebugVerifyAccess();
                return isDeleted;
            }
        }

        /// <summary>
        ///     Gets the number of this line.
        ///     Runtime: O(log n)
        /// </summary>
        /// <exception cref="InvalidOperationException">The line was deleted.</exception>
        public int LineNumber
        {
            get
            {
                if (IsDeleted)
                    throw new InvalidOperationException();
                return DocumentLineTree.GetIndexFromNode(this) + 1;
            }
        }

        /// <summary>
        ///     Gets the starting offset of the line in the document's text.
        ///     Runtime: O(log n)
        /// </summary>
        /// <exception cref="InvalidOperationException">The line was deleted.</exception>
        public int Offset
        {
            get
            {
                if (IsDeleted)
                    throw new InvalidOperationException();
                return DocumentLineTree.GetOffsetFromNode(this);
            }
        }

        /// <summary>
        ///     Gets the end offset of the line in the document's text (the offset before the line delimiter).
        ///     Runtime: O(log n)
        /// </summary>
        /// <exception cref="InvalidOperationException">The line was deleted.</exception>
        /// <remarks>EndOffset = <see cref="Offset" /> + <see cref="Length" />.</remarks>
        public int EndOffset
        {
            get { return Offset + Length; }
        }

        #endregion Properties stored in tree

        #region Length

        private int totalLength;
        private byte delimiterLength;

        /// <summary>
        ///     Gets the length of this line. The length does not include the line delimiter. O(1)
        /// </summary>
        /// <remarks>
        ///     This property is still available even if the line was deleted;
        ///     in that case, it contains the line's length before the deletion.
        /// </remarks>
        public int Length
        {
            get
            {
                DebugVerifyAccess();
                return totalLength - delimiterLength;
            }
        }

        /// <summary>
        ///     Gets the length of this line, including the line delimiter. O(1)
        /// </summary>
        /// <remarks>
        ///     This property is still available even if the line was deleted;
        ///     in that case, it contains the line's length before the deletion.
        /// </remarks>
        public int TotalLength
        {
            get
            {
                DebugVerifyAccess();
                return totalLength;
            }
            internal set
            {
                // this is set by DocumentLineTree
                totalLength = value;
            }
        }

        /// <summary>
        ///     <para>Gets the length of the line delimiter.</para>
        ///     <para>
        ///         The value is 1 for single <c>"\r"</c> or <c>"\n"</c>, 2 for the <c>"\r\n"</c> sequence;
        ///         and 0 for the last line in the document.
        ///     </para>
        /// </summary>
        /// <remarks>
        ///     This property is still available even if the line was deleted;
        ///     in that case, it contains the line delimiter's length before the deletion.
        /// </remarks>
        public int DelimiterLength
        {
            get
            {
                DebugVerifyAccess();
                return delimiterLength;
            }
            internal set
            {
                Debug.Assert(value >= 0 && value <= 2);
                delimiterLength = (byte)value;
            }
        }

        #endregion Length

        #region Previous / Next Line

        /// <summary>
        ///     Gets the next line in the document.
        /// </summary>
        /// <returns>The line following this line, or null if this is the last line.</returns>
        public DocumentLine NextLine
        {
            get
            {
                DebugVerifyAccess();

                if (right != null)
                {
                    return right.LeftMost;
                }
                var node = this;
                DocumentLine oldNode;
                do
                {
                    oldNode = node;
                    node = node.parent;
                    // we are on the way up from the right part, don't output node again
                } while (node != null && node.right == oldNode);
                return node;
            }
        }

        /// <summary>
        ///     Gets the previous line in the document.
        /// </summary>
        /// <returns>The line before this line, or null if this is the first line.</returns>
        public DocumentLine PreviousLine
        {
            get
            {
                DebugVerifyAccess();

                if (left != null)
                {
                    return left.RightMost;
                }
                var node = this;
                DocumentLine oldNode;
                do
                {
                    oldNode = node;
                    node = node.parent;
                    // we are on the way up from the left part, don't output node again
                } while (node != null && node.left == oldNode);
                return node;
            }
        }

        IDocumentLine IDocumentLine.NextLine
        {
            get { return NextLine; }
        }

        IDocumentLine IDocumentLine.PreviousLine
        {
            get { return PreviousLine; }
        }

        #endregion Previous / Next Line
    }
}