// 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;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Windows.Documents;

using UyghurEditPP.Document;

namespace UyghurEditPP.Highlighting
{
	/// <summary>
	/// Represents a immutable piece text with highlighting information.
	/// </summary>
	public class RichText
	{
		/// <summary>
		/// The empty string without any formatting information.
		/// </summary>
		public static readonly RichText Empty = new RichText(string.Empty);

		readonly string text;
		internal readonly int[] stateChangeOffsets;
		internal readonly HighlightingColor[] stateChanges;

		/// <summary>
		/// Creates a RichText instance with the given text and RichTextModel.
		/// </summary>
		/// <param name="text">
		/// The text to use in this RichText instance.
		/// </param>
		/// <param name="model">
		/// The model that contains the formatting to use for this RichText instance.
		/// <c>model.DocumentLength</c> should correspond to <c>text.Length</c>.
		/// This parameter may be null, in which case the RichText instance just holds plain text.
		/// </param>
		public RichText(string text, RichTextModel model = null)
		{
			if (text == null)
				throw new ArgumentNullException("text");
			this.text = text;
			if (model != null) {
				var sections = model.GetHighlightedSections(0, text.Length).ToArray();
				stateChangeOffsets = new int[sections.Length];
				stateChanges = new HighlightingColor[sections.Length];
				for (int i = 0; i < sections.Length; i++) {
					stateChangeOffsets[i] = sections[i].Offset;
					stateChanges[i] = sections[i].Color;
				}
			} else {
				stateChangeOffsets = new int[] { 0 };
				stateChanges = new HighlightingColor[] { HighlightingColor.Empty };
			}
		}

		internal RichText(string text, int[] offsets, HighlightingColor[] states)
		{
			this.text = text;
			Debug.Assert(offsets[0] == 0);
			Debug.Assert(offsets.Last() <= text.Length);
			this.stateChangeOffsets = offsets;
			this.stateChanges = states;
		}

		/// <summary>
		/// Gets the text.
		/// </summary>
		public string Text {
			get { return text; }
		}

		/// <summary>
		/// Gets the text length.
		/// </summary>
		public int Length {
			get { return text.Length; }
		}

		int GetIndexForOffset(int offset)
		{
			if (offset < 0 || offset > text.Length)
				throw new ArgumentOutOfRangeException("offset");
			int index = Array.BinarySearch(stateChangeOffsets, offset);
			if (index < 0) {
				// If no color change exists directly at offset,
				// return the index of the color segment that contains offset.
				index = ~index - 1;
			}
			return index;
		}

		int GetEnd(int index)
		{
			// Gets the end of the color segment no. index.
			if (index + 1 < stateChangeOffsets.Length)
				return stateChangeOffsets[index + 1];
			else
				return text.Length;
		}

		/// <summary>
		/// Gets the HighlightingColor for the specified offset.
		/// </summary>
		public HighlightingColor GetHighlightingAt(int offset)
		{
			return stateChanges[GetIndexForOffset(offset)];
		}

		/// <summary>
		/// Retrieves the highlighted sections in the specified range.
		/// The highlighted sections will be sorted by offset, and there will not be any nested or overlapping sections.
		/// </summary>
		public IEnumerable<HighlightedSection> GetHighlightedSections(int offset, int length)
		{
			int index = GetIndexForOffset(offset);
			int pos = offset;
			int endOffset = offset + length;
			while (pos < endOffset) {
				int endPos = Math.Min(endOffset, GetEnd(index));
				yield return new HighlightedSection {
					Offset = pos,
					Length = endPos - pos,
					Color = stateChanges[index]
				};
				pos = endPos;
				index++;
			}
		}

		/// <summary>
		/// Creates a new RichTextModel with the formatting from this RichText.
		/// </summary>
		public RichTextModel ToRichTextModel()
		{
			return new RichTextModel(stateChangeOffsets, stateChanges.Select(ch => ch.Clone()).ToArray());
		}

		/// <summary>
		/// Gets the text.
		/// </summary>
		public override string ToString()
		{
			return text;
		}

		/// <summary>
		/// Creates WPF Run instances that can be used for TextBlock.Inlines.
		/// </summary>
		public Run[] CreateRuns()
		{
			Run[] runs = new Run[stateChanges.Length];
			for (int i = 0; i < runs.Length; i++) {
				int startOffset = stateChangeOffsets[i];
				int endOffset = i + 1 < stateChangeOffsets.Length ? stateChangeOffsets[i + 1] : text.Length;
				Run r = new Run(text.Substring(startOffset, endOffset - startOffset));
				HighlightingColor state = stateChanges[i];
				ApplyColorToTextElement(r, state);
				runs[i] = r;
			}
			return runs;
		}

		internal static void ApplyColorToTextElement(TextElement r, HighlightingColor state)
		{
			if (state.Foreground != null)
				r.Foreground = state.Foreground.GetBrush(null);
			if (state.Background != null)
				r.Background = state.Background.GetBrush(null);
			if (state.FontWeight != null)
				r.FontWeight = state.FontWeight.Value;
			if (state.FontStyle != null)
				r.FontStyle = state.FontStyle.Value;
		}

		/// <summary>
		/// Produces HTML code for the line, with &lt;span style="..."&gt; tags.
		/// </summary>
		public string ToHtml(HtmlOptions options = null)
		{
			StringWriter stringWriter = new StringWriter(CultureInfo.InvariantCulture);
			using (var htmlWriter = new HtmlRichTextWriter(stringWriter, options)) {
				htmlWriter.Write(this);
			}
			return stringWriter.ToString();
		}

		/// <summary>
		/// Produces HTML code for a section of the line, with &lt;span style="..."&gt; tags.
		/// </summary>
		public string ToHtml(int offset, int length, HtmlOptions options = null)
		{
			StringWriter stringWriter = new StringWriter(CultureInfo.InvariantCulture);
			using (var htmlWriter = new HtmlRichTextWriter(stringWriter, options)) {
				htmlWriter.Write(this, offset, length);
			}
			return stringWriter.ToString();
		}

		/// <summary>
		/// Creates a substring of this rich text.
		/// </summary>
		public RichText Substring(int offset, int length)
		{
			if (offset == 0 && length == this.Length)
				return this;
			string newText = text.Substring(offset, length);
			RichTextModel model = ToRichTextModel();
			OffsetChangeMap map = new OffsetChangeMap(2);
			map.Add(new OffsetChangeMapEntry(offset + length, text.Length - offset - length, 0));
			map.Add(new OffsetChangeMapEntry(0, offset, 0));
			model.UpdateOffsets(map);
			return new RichText(newText, model);
		}

		/// <summary>
		/// Concatenates the specified rich texts.
		/// </summary>
		public static RichText Concat(params RichText[] texts)
		{
			if (texts == null || texts.Length == 0)
				return Empty;
			else if (texts.Length == 1)
				return texts[0];
			string newText = string.Concat(texts.Select(txt => txt.text));
			RichTextModel model = texts[0].ToRichTextModel();
			int offset = texts[0].Length;
			for (int i = 1; i < texts.Length; i++) {
				model.Append(offset, texts[i].stateChangeOffsets, texts[i].stateChanges);
				offset += texts[i].Length;
			}
			return new RichText(newText, model);
		}

		/// <summary>
		/// Concatenates the specified rich texts.
		/// </summary>
		public static RichText operator +(RichText a, RichText b)
		{
			return RichText.Concat(a, b);
		}

		/// <summary>
		/// Implicit conversion from string to RichText.
		/// </summary>
		public static implicit operator RichText(string text)
		{
			if (text != null)
				return new RichText(text);
			else
				return null;
		}
	}
}
