// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
namespace Unity.CodeEditor.Document
{
/// <summary>
/// The TextAnchor class references an offset (a position between two characters).
/// It automatically updates the offset when text is inserted/removed in front of the anchor.
/// </summary>
/// <remarks>
/// <para>Use the <see cref="ITextAnchor.Offset"/> property to get the offset from a text anchor.
/// Use the <see cref="IDocument.CreateAnchor"/> method to create an anchor from an offset.
/// </para>
/// <para>
/// The document will automatically update all text anchors; and because it uses weak references to do so,
/// the garbage collector can simply collect the anchor object when you don't need it anymore.
/// </para>
/// <para>Moreover, the document is able to efficiently update a large number of anchors without having to look
/// at each anchor object individually. Updating the offsets of all anchors usually only takes time logarithmic
/// to the number of anchors. Retrieving the <see cref="ITextAnchor.Offset"/> property also runs in O(lg N).</para>
/// </remarks>
/// <example>
/// Usage:
/// <code>TextAnchor anchor = document.CreateAnchor(offset);
/// ChangeMyDocument();
/// int newOffset = anchor.Offset;
/// </code>
/// </example>
internal interface ITextAnchor
{
/// <summary>
/// Gets the text location of this anchor.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
TextLocation Location { get; }
/// <summary>
/// Gets the offset of the text anchor.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
int Offset { get; }
/// <summary>
/// Controls how the anchor moves.
/// </summary>
/// <remarks>Anchor movement is ambiguous if text is inserted exactly at the anchor's location.
/// Does the anchor stay before the inserted text, or does it move after it?
/// The property <see cref="MovementType"/> will be used to determine which of these two options the anchor will choose.
/// The default value is <see cref="AnchorMovementType.Default"/>.</remarks>
AnchorMovementType MovementType { get; set; }
/// <summary>
/// <para>
/// Specifies whether the anchor survives deletion of the text containing it.
/// </para><para>
/// <c>false</c>: The anchor is deleted when the a selection that includes the anchor is deleted.
/// <c>true</c>: The anchor is not deleted.
/// </para>
/// </summary>
/// <remarks><inheritdoc cref="IsDeleted" /></remarks>
bool SurviveDeletion { get; set; }
/// <summary>
/// Gets whether the anchor was deleted.
/// </summary>
/// <remarks>
/// <para>When a piece of text containing an anchor is removed, then that anchor will be deleted.
/// First, the <see cref="IsDeleted"/> property is set to true on all deleted anchors,
/// then the <see cref="Deleted"/> events are raised.
/// You cannot retrieve the offset from an anchor that has been deleted.</para>
/// <para>This deletion behavior might be useful when using anchors for building a bookmark feature,
/// but in other cases you want to still be able to use the anchor. For those cases, set <c><see cref="SurviveDeletion"/> = true</c>.</para>
/// </remarks>
bool IsDeleted { get; }
/// <summary>
/// Occurs after the anchor was deleted.
/// </summary>
/// <remarks>
/// <inheritdoc cref="IsDeleted" />
/// <para>Due to the 'weak reference' nature of text anchors, you will receive
/// the Deleted event only while your code holds a reference to the TextAnchor object.
/// </para>
/// </remarks>
event EventHandler Deleted;
/// <summary>
/// Gets the line number of the anchor.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
int Line { get; }
/// <summary>
/// Gets the column number of this anchor.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
int Column { get; }
}
/// <summary>
/// Defines how a text anchor moves.
/// </summary>
internal enum AnchorMovementType
{
/// <summary>
/// When text is inserted at the anchor position, the type of the insertion
/// determines where the caret moves to. For normal insertions, the anchor will move
/// after the inserted text.
/// </summary>
Default,
/// <summary>
/// Behaves like a start marker - when text is inserted at the anchor position, the anchor will stay
/// before the inserted text.
/// </summary>
BeforeInsertion,
/// <summary>
/// Behave like an end marker - when text is insered at the anchor position, the anchor will move
/// after the inserted text.
/// </summary>
AfterInsertion
}
}