using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using ExCSS;
using HtmlAgilityPack;
using Newtonsoft.Json;

namespace QADirector
{
    internal class HtmlToJsonConverter
    {
        private readonly FileInfo _inputFile;
        private readonly FileInfo _outputFile;

        /// <summary>
        /// Creates an object that can convert a QA Director HTML export to a JSON object.
        /// </summary>
        /// <param name="source">HTML report to be converted.</param>
        /// <param name="destination">JSON file name to be created</param>
        public HtmlToJsonConverter(FileInfo source, FileInfo destination)
        {
            _outputFile = destination;
            _inputFile = source;
        }

        /// <summary>
        /// Converts the HTML input file into JSON and writes the output file
        /// </summary>
        public void Convert()
        {
            var htmlDocument = ReadFileToHtmlDocument();

            var pages = GetPages(htmlDocument);
            Debug.WriteLine("Found {0} pages", pages.Count());

            var objects = ParseHtmlToObjects(pages);
            WriteJson(objects);
        }

        /// <summary>
        /// Write the object as JSON using a custom converter that
        /// correctly writes the property list as single properties
        /// and not as a list.
        /// </summary>
        /// <param name="obj">Object to be serialized</param>
        private void WriteJson(DataObject obj)
        {
            var converter = new CustomJsonConverter();
            var data = JsonConvert.SerializeObject(obj, Formatting.Indented, converter);
            File.WriteAllText(_outputFile.FullName, data);
        }

        /// <summary>
        /// Parses the HTML pages and creates an equivalent object by parsing the properties and values
        /// as well as the properties and values of the sub items
        /// </summary>
        /// <param name="pages">HTML pages to be analyzed. <see cref="GetPages"/>.</param>
        /// <returns>An object containing properties and child objects.</returns>
        private static DataObject ParseHtmlToObjects(IEnumerable<HtmlNode> pages)
        {
            var rootObject = new DataObject();
            var currentObject = rootObject;
            // Go through all pages
            foreach (var page in pages)
            {
                // Analyze all the span tags
                var steps = page.Descendants().Where(x => (x.Name == "span")).ToList();
                string key = null;
                foreach (var step in steps)
                {
                    if (!IsKey(step))
                    {
                        // If this is not a key, the key was detected before. Use it to populate the object
                        currentObject = AddProperty(currentObject, key, GetTextFromSpan(step));
                        key = null;
                    }
                    else
                    {
                        if (key != null)
                        {
                            // Special case: we detected a new key, although the old key has not been used as property yet
                            // This can happen for keys without value, so add it empty.
                            currentObject = AddProperty(currentObject, key, "");
                        }


                        key = GetKeyFromNode(step);
                        var level = GetIndentationFromNode(step);
                        if (level == currentObject.level)
                        {
                            // Still the same level.
                            // Remain at the same object in order to add more properties.
                        }
                        else if (level > currentObject.level)
                        {
                            // Decend to lower level: create a new child
                            var child = new DataObject {level = level, Parent = currentObject};
                            currentObject.Children.Add(child);
                            currentObject = child;
                        }
                        else
                        {
                            // Move up until level is equal
                            while (level < currentObject.level)
                            {
                                currentObject = currentObject.Parent;
                            }
                        }
                    }
                }
            }

            return rootObject;
        }

        /// <summary>
        /// Adds a property to an object.
        /// If that property already exists, create a new object and add the property there
        /// </summary>
        /// <param name="obj">Object to add the property to</param>
        /// <param name="key">Name of the property</param>
        /// <param name="value">Value of the property</param>
        /// <returns>The same object if the property did not exist yet, the new object if the property already existed</returns>
        private static DataObject AddProperty(DataObject obj, string key, string value)
        {
            // Special case: <Span> which contains the page information. Skip it.
            if (key == null) return obj;

            if (obj.Properties.ContainsKey(key))
            {
                // This key was already assigned, so this must be a new object on the same level
                var sibling = new DataObject {level = obj.level, Parent = obj.Parent};
                obj.Parent.Children.Add(sibling);
                obj = sibling;
            }

            obj.Properties.Add(key, value);
            return obj;
        }

        /// <summary>
        /// Gets the indentation from the HTML node.
        /// Detection is done via the left CSS style of the HTML element.
        /// </summary>
        /// <param name="step">HTML node to analyze</param>
        /// <returns>Indentation value, 0 if no left attribute was found</returns>
        private static decimal GetIndentationFromNode(HtmlNode step)
        {
            decimal thisIndent=0;
            var styleSheet = ExtractStyle(step);
            foreach (var cssAttribute in styleSheet.StyleRules[0].Declarations)
            {
                if (cssAttribute.Name != "left") continue;

                var numberFormatInfo = new NumberFormatInfo {NumberDecimalSeparator = "."};
                thisIndent = decimal.Parse(cssAttribute.Term.ToString().Replace("in", ""), numberFormatInfo);
                Debug.WriteLine("Left attribute found:" + cssAttribute.Term);
            }
            return thisIndent;
        }

        /// <summary>
        /// Check if the node contains a key and if so, return its text.
        /// </summary>
        /// <param name="span">HTML SPAN node to be analyzed</param>
        /// <returns>Text of the key if key was detected, <c>null</c> otherwise.
        /// Text is cleaned from HTML entities and has the trailing colon removed.</returns>
        private static string GetKeyFromNode(HtmlNode span)
        {
            return IsKey(span) ? GetTextFromSpan(span).Trim(':') : null;
        }

        /// <summary>
        /// Check if the node contains a key.
        /// Detection is done via the <c>font-weight="bold"</c> CSS style of the HTML element.
        /// </summary>
        /// <param name="span">HTML SPAN node to be analyzed</param>
        /// <returns><c>True</c> if font-weight was bold, <c>false</c> otherwise.</returns>
        private static bool IsKey(HtmlNode span)
        {
            var styleSheet = ExtractStyle(span);
            foreach (var cssAttribute in styleSheet.StyleRules[0].Declarations)
            {
                if (cssAttribute.Name != "font-weight" || cssAttribute.Term.ToString() != "bold") continue;
                return true;
            }
            return false;
        }

        /// <summary>
        /// Gets the text from a HTML SPAN element.
        /// This includes removal of the <c>NOBR</c> tag and decoding of HTML special characters.
        /// </summary>
        /// <param name="span">SPAN element to get the text from.</param>
        /// <returns>Inner text of the SPAN node</returns>
        private static string GetTextFromSpan(HtmlNode span)
        {
            var text = span.Descendants("nobr").First().InnerText; // There is only one <nobr>
            text = System.Net.WebUtility.HtmlDecode(text);
            return text;
        }

        /// <summary>
        /// Extracts the information of the <c>style</c> attribute
        /// </summary>
        /// <param name="element">HTML element to extract the style information from</param>
        /// <returns></returns>
        private static StyleSheet ExtractStyle(HtmlNode element)
        {
            var rawStyle = element.Attributes["style"].Value;
            var styleSheet = new Parser().Parse(String.Format(".dummy{{{0}}}", rawStyle));
            return styleSheet;
        }

        /// <summary>
        /// Gets the pages, identified by a DIV element defining the width and height
        /// inside another DIV element
        /// (the one with style="page-break-inside:avoid;page-break-after:always;")
        /// </summary>
        /// <param name="htmlDocument">HTML to analyze</param>
        /// <returns>DIV nodes corresponding to pages, using the inner of the described DIVs (the one defining width and height)</returns>
        private static IEnumerable<HtmlNode> GetPages(HtmlDocument htmlDocument)
        {
            var pages =
                htmlDocument.DocumentNode.Descendants()
                    .Where(x =>(x.Name == "div" && x.Ancestors("div").Count() == 1));
            return pages;
        }

        /// <summary>
        /// Reads the file contents from disk and converts it into a HTML document
        /// </summary>
        /// <returns>HTML document as read from disk</returns>
        private HtmlDocument ReadFileToHtmlDocument()
        {
            var source = File.ReadAllText(_inputFile.FullName);
            var html = new HtmlDocument();
            html.LoadHtml(source);
            return html;
        }
    }
}

foreach (var cssAttribute in styleSheet.StyleRules[0].Declarations)
{
    if (cssAttribute.Name != "font-weight" || cssAttribute.Term.ToString() != "bold") continue;
    return true;
}
return false;

foreach (var cssAttribute in styleSheet.StyleRules[0].Declarations)
{
    if (cssAttribute.Name == "font-weight" && cssAttribute.Term.ToString() == "bold")
    {
        return true;
    }
}
return false;

private static bool IsKey(HtmlNode span)
{
    var styleSheet = ExtractStyle(span);
    bool isKey = styleSheet.StyleRules[0].Declarations
                      .Any(cssAttribute.Name == "font-weight" && cssAttribute.Term.ToString() == "bold");

    return isKey;
}

private static DataObject ParseHtmlToObjects(IEnumerable<HtmlNode> pages)
{
    var rootObject = new DataObject();
    var currentObject = rootObject;

    foreach (var page in pages)
    {
        var steps = page.Descendants().Where(x => (x.Name == "span")).ToList();
        currentObject = AnalyzeSpanTags(steps, currentObject);
    }

    return rootObject;
}

private static DataObject AnalyzeSpanTags(IEnumerable<HtmlNode> steps, DataObject currentObject)
{
    string key = null;
    foreach (var step in steps)
    {
        if (!IsKey(step))
        {
            // If this is not a key, the key was detected before. Use it to populate the object
            currentObject = AddProperty(currentObject, key, GetTextFromSpan(step));
            key = null;
            continue;
        }

        // Special case: Maybe we detected a new key, although the old key has not been used as property yet
        // This can happen for keys without value, so add it empty.
        currentObject = AddProperty(currentObject, key, "");

        key = GetKeyFromNode(step);
        var level = GetIndentationFromNode(step);

        if (level > currentObject.level)
        {
            // Decend to lower level: create a new child
            var child = new DataObject { level = level, Parent = currentObject };
            currentObject.Children.Add(child);
            currentObject = child;
        }
        else
        {
            currentObject = EqualizeLevel(currentObject, level);
        }
    }
    return currentObject;
}

private static DataObject EqualizeLevel(DataObject obj, decimal level)
{
    while (level < obj.level)
    {
        obj = obj.Parent;
    }
    return obj;
}

// Go through all pages
foreach (var page in pages)

private static DataObject GetAddedSiblingIfKeyExists(DataObject obj, string key)
{
    if (key == null || !obj.Properties.ContainsKey(key)) { return obj; }

    var sibling = new DataObject { level = obj.level, Parent = obj.Parent };
    obj.Parent.Children.Add(sibling);
    return sibling;
}

private static DataObject AddProperty(DataObject obj, string key, string value)
{
    // Special case: <Span> which contains the page information. Skip it.
    if (key == null) return obj;

    obj.Properties.Add(key, value);
    return obj;
}

private static DataObject AnalyzeSpanTags(IEnumerable<HtmlNode> steps, DataObject currentObject)
{
    string key = null;
    foreach (var step in steps)
    {
        currentObject = GetAddedSiblingIfKeyExists(currentObject, key);

        if (!IsKey(step))
        {
        .....

/// <summary>
    /// Converts the HTML input file into JSON and writes the output file
    /// </summary>
    public void Convert()