﻿using System.Collections.Generic;

using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Folding;

namespace HtmlTemplate
{
    /// <summary>
    ///     Allows producing foldings from a document based on braces.
    /// </summary>
    public class BraceFoldingStrategy
    {
        /// <summary>
        ///     Creates a new BraceFoldingStrategy.
        /// </summary>
        public BraceFoldingStrategy()
        {
            OpeningBrace = '{';
            ClosingBrace = '}';
        }
        /// <summary>
        ///     Gets/Sets the opening brace. The default value is '{'.
        /// </summary>
        public char OpeningBrace { get; set; }
        /// <summary>
        ///     Gets/Sets the closing brace. The default value is '}'.
        /// </summary>
        public char ClosingBrace { get; set; }
        public void UpdateFoldings(FoldingManager manager, TextDocument document)
        {
            int firstErrorOffset;
            var newFoldings = CreateNewFoldings(document, out firstErrorOffset);
            manager.UpdateFoldings(newFoldings, firstErrorOffset);
        }
        /// <summary>
        ///     Create <see cref="NewFolding" />s for the specified document.
        /// </summary>
        public IEnumerable<NewFolding> CreateNewFoldings(TextDocument document, out int firstErrorOffset)
        {
            firstErrorOffset = -1;
            return CreateNewFoldings(document);
        }
        /// <summary>
        ///     Create <see cref="NewFolding" />s for the specified document.
        /// </summary>
        public IEnumerable<NewFolding> CreateNewFoldings(ITextSource document)
        {
            var newFoldings = new List<NewFolding>();
            var startOffsets = new Stack<int>();
            var lastNewLineOffset = 0;
            var openingBrace = OpeningBrace;
            var closingBrace = ClosingBrace;
            for (var i = 0; i < document.TextLength; i++)
            {
                var c = document.GetCharAt(i);
                if (c == openingBrace)
                {
                    startOffsets.Push(i);
                }
                else if (c == closingBrace
                         && startOffsets.Count > 0)
                {
                    var startOffset = startOffsets.Pop();
                    // don't fold if opening and closing brace are on the same line
                    if (startOffset < lastNewLineOffset)
                    {
                        newFoldings.Add(new NewFolding(startOffset, i + 1));
                    }
                }
                else if (c == '\n'
                         || c == '\r')
                {
                    lastNewLineOffset = i + 1;
                }
            }
            newFoldings.Sort((a, b) => a.StartOffset.CompareTo(b.StartOffset));
            return newFoldings;
        }
    }
}