using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using DCIT.Core.Models;
using DCIT.Core.Utilities;
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using W = DocumentFormat.OpenXml.Wordprocessing;

namespace DCIT.Core.Services
{
    public class WordTextExtractionService
    {
        private readonly IDocConversionService _docConversionService;

        public WordTextExtractionService()
            : this(new OfficeDocConversionService())
        {
        }

        public WordTextExtractionService(IDocConversionService docConversionService)
        {
            _docConversionService = docConversionService;
        }

        public ExtractedDocumentText ExtractVisibleText(string filePath)
        {
            var workingPath = filePath;
            string temporaryDocxPath = null;

            try
            {
                var extension = Path.GetExtension(filePath) ?? string.Empty;
                if (extension.Equals(".doc", StringComparison.OrdinalIgnoreCase))
                {
                    if (_docConversionService == null)
                    {
                        throw new NotSupportedException("当前环境未配置 .doc 转换服务。");
                    }

                    temporaryDocxPath = Path.Combine(
                        Path.GetTempPath(),
                        "DCIT",
                        "extract",
                        Guid.NewGuid().ToString("N") + ".docx");
                    Directory.CreateDirectory(Path.GetDirectoryName(temporaryDocxPath) ?? Path.GetTempPath());
                    _docConversionService.Convert(filePath, temporaryDocxPath);
                    workingPath = temporaryDocxPath;
                }

                using (var document = WordprocessingDocument.Open(workingPath, false))
                {
                    var builder = new StringBuilder();
                    var rootElements = GetRelevantRootElements(document);
                    foreach (var root in rootElements)
                    {
                        AppendVisibleText(root, builder);
                        if (builder.Length > 0 && builder[builder.Length - 1] != '\n')
                        {
                            builder.AppendLine();
                        }
                    }

                    return new ExtractedDocumentText
                    {
                        FilePath = filePath,
                        VisibleText = builder.ToString(),
                    };
                }
            }
            finally
            {
                TryDelete(temporaryDocxPath);
            }
        }

        private static IEnumerable<OpenXmlPartRootElement> GetRelevantRootElements(WordprocessingDocument document)
        {
            var result = new List<KeyValuePair<string, OpenXmlPartRootElement>>();
            var partQueue = new Queue<OpenXmlPartContainer>();
            partQueue.Enqueue(document.MainDocumentPart);
            var visited = new HashSet<OpenXmlPart>();

            while (partQueue.Count > 0)
            {
                var container = partQueue.Dequeue();
                foreach (var pair in container.Parts)
                {
                    var part = pair.OpenXmlPart;
                    if (part == null || !visited.Add(part))
                    {
                        continue;
                    }

                    if (part.RootElement != null && IsRelevantPart(part))
                    {
                        result.Add(new KeyValuePair<string, OpenXmlPartRootElement>(GetStablePartKey(part), part.RootElement));
                    }

                    partQueue.Enqueue(part);
                }
            }

            var ordered = result
                .OrderBy(item => item.Key, StringComparer.OrdinalIgnoreCase)
                .Select(item => item.Value)
                .ToList();

            if (document.MainDocumentPart != null && document.MainDocumentPart.Document != null)
            {
                ordered.Insert(0, document.MainDocumentPart.Document);
            }

            return ordered;
        }

        private static bool IsRelevantPart(OpenXmlPart part)
        {
            return part is HeaderPart
                || part is FooterPart
                || part is WordprocessingCommentsPart
                || part is FootnotesPart
                || part is EndnotesPart
                || part.GetType().Name.IndexOf("ChartPart", StringComparison.OrdinalIgnoreCase) >= 0;
        }

        private static string GetStablePartKey(OpenXmlPart part)
        {
            return part == null || part.Uri == null
                ? string.Empty
                : part.Uri.ToString();
        }

        private static void AppendVisibleText(OpenXmlElement root, StringBuilder builder)
        {
            foreach (var element in root.Descendants())
            {
                var leaf = element as OpenXmlLeafTextElement;
                if (leaf != null)
                {
                    if (!IsVisibleLeaf(leaf))
                    {
                        continue;
                    }

                    var text = leaf.Text;
                    if (string.IsNullOrWhiteSpace(text))
                    {
                        continue;
                    }

                    builder.Append(text);
                    builder.Append(' ');
                    continue;
                }

                if (!VmlTextMetadataUtility.IsVmlShapeElement(element))
                {
                    continue;
                }

                foreach (var binding in VmlTextMetadataUtility.CreateBindings(element))
                {
                    if (string.IsNullOrWhiteSpace(binding.Text))
                    {
                        continue;
                    }

                    builder.Append(binding.Text);
                    builder.Append(' ');
                }
            }
        }

        private static bool IsVisibleLeaf(OpenXmlLeafTextElement leaf)
        {
            if (leaf is W.FieldCode || leaf is W.DeletedText)
            {
                return false;
            }

            if (leaf.Ancestors<W.DeletedRun>().Any())
            {
                return false;
            }

            var run = leaf.Ancestors<W.Run>().FirstOrDefault();
            if (run != null && run.RunProperties != null && run.RunProperties.Vanish != null)
            {
                return false;
            }

            return true;
        }

        private static void TryDelete(string path)
        {
            try
            {
                if (!string.IsNullOrWhiteSpace(path) && File.Exists(path))
                {
                    File.Delete(path);
                }
            }
            catch
            {
            }
        }
    }
}