/* DocumentWriter.cs
 * part of zaaReloaded2
 * 
 * Copyright 2015-2017 Daniel Kraus
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Office.Interop.Word;
using System.Text.RegularExpressions;
using System.Collections.ObjectModel;

namespace zaaReloaded2.Formatter
{
    /// <summary>
    /// Helper class that serves to write text to a Word document or
    /// to a linked DocumentWriter. Provides a buffer that can be
    /// appended or prepended to, which facilitates conditional output
    /// depending on whether there is text in the buffer or not.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Linking several DocumentWriters permits a cascading work flow
    /// with several buffers.
    /// </para>
    /// <para>
    /// Markup support: The DocumentWriter supports basic markup to control
    /// the text styles in the Word document.
    /// </para>
    /// <list type="unordered">
    ///     <item>&lt;b&gt; and &lt;/b&gt; - bold/unbold</item>
    ///     <item>&lt;style:NAME&gt; - set the paragraph or character style</item>
    ///     <item>&lt;/style&gt; - remove *character* style</item>
    /// </list>
    /// </remarks>
    class DocumentWriter
    {
        #region Properties

        /// <summary>
        /// Gets the Document associated with this DocumentWriter,
        /// or null if there is no associated Document.
        /// </summary>
        public Document Document { get; set; }

        /// <summary>
        /// Gets the parent DocumentWriter (if any).
        /// </summary>
        public DocumentWriter Parent { get; set; }

        /// <summary>
        /// Returns true if there is text in the buffer.
        /// </summary>
        public bool HasBufferedText { get { return _buffer.Length > 0; } }

        /// <summary>
        /// Returns text without markup from the buffer.
        /// </summary>
        public string Text
        {
            get
            {
                if (!HasBufferedText)
                    throw new InvalidOperationException("This DocumentWriter does not have any text.");

                return _markupRegex.Replace(_buffer.ToString(), String.Empty);
            }
        }

        #endregion

        #region Constructors

        public DocumentWriter()
        {
            _buffer = new StringBuilder();
        }

        /// <summary>
        /// Creates a new DocumentWriter instance that is associated
        /// with a Word Document.
        /// </summary>
        /// <param name="document"></param>
        public DocumentWriter(Document document)
            : this()
        {
            Document = document;
        }

        /// <summary>
        /// Creates a new DocumentWriter instance that is associated
        /// with a parent DocumentWriter.
        /// </summary>
        /// <param name="parent"></param>
        public DocumentWriter(DocumentWriter parent)
            : this()
        {
            Parent = parent;
        }

        #endregion

        #region Overrides

        public override string ToString()
        {
            return _buffer.ToString();
        }

        #endregion

        #region Public methods

        /// <summary>
        /// Flushes the buffer to the associated Word document and/or the
        /// parent DocumentWriter.
        /// </summary>
        public void Flush()
        {
            if (!HasBufferedText) return;

            if (Document == null && Parent == null)
            {
                throw new InvalidOperationException(
                    "No document and no parent buffer to flush into.");
            }

            if (Document != null)
            {
                Selection s = Document.ActiveWindow.Selection;
                s.ClearCharacterDirectFormatting();
                s.ClearParagraphDirectFormatting();
                MarkupToDocument(_buffer.ToString());
            }
            if (Parent != null)
            {
                Parent.Write(_buffer.ToString());
            }

            _buffer.Clear();
        }

        /// <summary>
        /// Writes text to the buffer.
        /// </summary>
        /// <param name="text">Text to write to the buffer.</param>
        public void Write(string text)
        {
            _buffer.Append(text);
        }

        /// <summary>
        /// Appends a line of text to the buffer.
        /// </summary>
        /// <param name="text">Text to append.</param>
        public void WriteLine(string text)
        {
            _buffer.AppendLine(text);
        }

        /// <summary>
        /// Appends a newline to the buffer.
        /// </summary>
        public void WriteLine()
        {
            _buffer.AppendLine();
        }

        /// <summary>
        /// Inserts text at the start of the buffer.
        /// </summary>
        /// <param name="text">Text to insert at the start of the
        /// buffer.</param>
        public void Prepend(string text)
        {
            _buffer.Insert(0, text);
        }

        #endregion

        #region Private methods

        /// <summary>
        /// Parses a string containing markup (e.g., "&lt;b&gt;", "&lt;/b&gt;")
        /// and writes formatted text to the current Document.
        /// </summary>
        void MarkupToDocument(string text)
        {
            string[] substrings = _markupRegex.Split(text);
            Selection sel = Document.ActiveWindow.Selection;
            Highlights hightlights = new Highlights();
            foreach (string substring in substrings)
            {
                switch (substring)
                {
                    case "<b>":
                        sel.Font.Bold = 1;
                        break;
                    case "</b>":
                        sel.Font.Bold = 0;
                        break;
                    case "<i>":
                        sel.Font.Italic = 1;
                        break;
                    case "</i>":
                        sel.Font.Italic = 0;
                        break;
                    case "<u>":
                        sel.Font.Underline = WdUnderline.wdUnderlineSingle;
                        break;
                    case "</u>":
                        sel.Font.Underline = WdUnderline.wdUnderlineNone;
                        break;
                    case "<highlight>":
                        hightlights.Start(sel.Range);
                        break;
                    case "</highlight>":
                        hightlights.Stop(sel.Range);
                        break;
                    case "</style>":
                        sel.ClearCharacterStyle();
                        break;
                    default:
                        Match styleMatch = _styleRegex.Match(substring);
                        if (styleMatch.Success)
                        {
                            sel.set_Style(styleMatch.Groups["style"].Value);
                        }
                        else
                        {
                            sel.TypeText(substring);
                        }
                        break;
                }
            }
            hightlights.ApplyHighlights();
        }

        #endregion

        #region Fields

        StringBuilder _buffer;
        // Put pattern in parentheses so they will not be discarded by Regex.Split
        // The splitting pattern must not contain subgroups!
        static readonly Regex _markupRegex = new Regex(@"(<[^ >]+>)");
        static readonly Regex _styleRegex = new Regex(@"<style:(?<style>[^>]+)>");

        #endregion

        #region Helper class for highlighting

        /// <summary>
        /// Embedded helper class to manage highlights.
        /// </summary>
        class Highlights
        {
            public void Start(Range start)
            {
                if (_currentHighlight == null)
                {
                    _currentHighlight = start;
                    _highlights.Add(_currentHighlight);
                }
            }

            public void Stop(Range stop)
            {
                if (_currentHighlight != null)
                {
                    _currentHighlight.End = stop.End;
                    _currentHighlight = null;
                }
            }

            public void ApplyHighlights()
            {
                foreach (Range r in _highlights)
                {
                    r.HighlightColorIndex = WdColorIndex.wdYellow;
                }
            }

            public Highlights()
            {
                _highlights = new Collection<Range>();
                _currentHighlight = null;
            }

            Collection<Range> _highlights;
            Range _currentHighlight;
        }
        
        #endregion
    }
}