using System.Diagnostics;
using System.IO.Compression;
using System.Runtime.InteropServices;
using System.Reflection;
using System.Text.Json;
using System.Text.RegularExpressions;
using DocumentAutomation.Shared;
using DocxWorkbench.Core;

namespace DocxWorkbench.WordInterop;

public sealed class WordNotInstalledException(string message) : InvalidOperationException(message);
public sealed class WordAutomationException(string message, Exception? inner = null) : InvalidOperationException(message, inner);

public sealed class WordDocumentService : IWordDocumentService, IDisposable
{
    private readonly StaWordQueue _queue = new();

    public Task<WordDocumentResult> BuildDocumentAsync(WordDocumentBuildRequest request, IProgress<string>? progress, CancellationToken cancellationToken)
        => _queue.Enqueue(() => BuildOnSta(request, progress, cancellationToken), cancellationToken);

    public Task<WordPreviewResult> ExportPdfAsync(string docxPath, string outputPdfPath, CancellationToken cancellationToken)
        => _queue.Enqueue(() => ExportPdfOnSta(docxPath, outputPdfPath, cancellationToken), cancellationToken);

    private static WordDocumentResult BuildOnSta(WordDocumentBuildRequest request, IProgress<string>? progress, CancellationToken token)
    {
        DocumentInputValidation.Validate(request);
        if (!request.BodyPath.EndsWith(".docx", StringComparison.OrdinalIgnoreCase) && !request.BodyPath.EndsWith(".txt", StringComparison.OrdinalIgnoreCase)) throw new UnsupportedDocumentFormatException($"Unsupported body format: {Path.GetExtension(request.BodyPath)}. Use DOCX or TXT.");
        var insertion = TemplateInsertionPointReader.Find(request.TemplatePath);
        if (insertion.Type == "None") throw new WordAutomationException("No DOC_BODY insertion point was found. Add a DOC_BODY content control, DOC_BODY bookmark, or {{DOC_BODY}} marker.");
        var started = Stopwatch.StartNew(); var temp = Path.Combine(Path.GetTempPath(), "DocumentAutomation", Guid.NewGuid().ToString("N")); Directory.CreateDirectory(temp); var workingTemplate = Path.Combine(temp, "template.docx"); var stagedOutput = Path.Combine(temp, "result.docx"); File.Copy(request.TemplatePath, workingTemplate, true);
        dynamic? application = null; dynamic? documents = null; dynamic? document = null; dynamic? range = null; var proxies = new List<object?>(); int? wordPid = null;
        try
        {
            token.ThrowIfCancellationRequested(); progress?.Report("Checking Word.Application COM registration"); var wordType = Type.GetTypeFromProgID("Word.Application", false) ?? throw new WordNotInstalledException("Microsoft Word is not installed or is not registered in COM."); application = Own(Activator.CreateInstance(wordType), proxies) ?? throw new WordAutomationException("Could not create Word.Application."); application.Visible = false; application.DisplayAlerts = 0; TrySetAutomationSecurity(application); wordPid = TryGetPid(application); progress?.Report($"Word COM started (PID {wordPid?.ToString() ?? "unknown"})");
            documents = Own(application.Documents, proxies); document = Own(documents.Open(workingTemplate, false, false, false), proxies) ?? throw new WordAutomationException("Word could not open the working template copy.");
            range = Own(FindInsertionRange(document, insertion.Type, proxies), proxies) ?? throw new WordAutomationException("The insertion point disappeared while opening the template.");
            token.ThrowIfCancellationRequested(); progress?.Report($"Inserting {Path.GetExtension(request.BodyPath).ToUpperInvariant()} body"); if (request.BodyPath.EndsWith(".txt", StringComparison.OrdinalIgnoreCase)) range.Text = File.ReadAllText(request.BodyPath).Replace("\r\n", "\r").Replace('\n', '\r'); else InsertDocxFile(range, request.BodyPath);
            token.ThrowIfCancellationRequested(); progress?.Report("Updating fields and pagination"); document.Repaginate(); document.Fields.Update(); UpdateHeadersFooters(document, proxies); document.SaveAs2(stagedOutput, 12); CommitOutput(stagedOutput, request.OutputDocxPath);
            var logPath = Path.ChangeExtension(request.OutputDocxPath, ".generation.json"); File.WriteAllText(logPath, JsonSerializer.Serialize(new { operationId = Guid.NewGuid(), template = request.TemplatePath, body = request.BodyPath, output = request.OutputDocxPath, insertionPoint = insertion.Type, wordPid, staThread = Thread.CurrentThread.ManagedThreadId, staApartment = Thread.CurrentThread.GetApartmentState().ToString(), durationMs = started.ElapsedMilliseconds, completedAtUtc = DateTime.UtcNow }, new JsonSerializerOptions { WriteIndented = true }));
            return new WordDocumentResult { OutputDocxPath = request.OutputDocxPath, LogPath = logPath, Duration = started.Elapsed, InsertionPoint = insertion.Type };
        }
        catch (WordNotInstalledException) { throw; }
        catch (WordAutomationException) { throw; }
        catch (Exception ex) when (ex is not OperationCanceledException) { throw new WordAutomationException("Word automation failed. See technical details in the operation log.", ex); }
        finally
        {
            try { if (document is not null) document.Close(0); } catch { }
            try { if (application is not null) application.Quit(0); } catch { }
            ReleaseAll(proxies); TryDeleteDirectory(temp);
        }
    }

    private static WordPreviewResult ExportPdfOnSta(string docxPath, string outputPdfPath, CancellationToken token)
    {
        if (!File.Exists(docxPath)) throw new FileNotFoundException("DOCX was not found.", docxPath); Directory.CreateDirectory(Path.GetDirectoryName(Path.GetFullPath(outputPdfPath))!); var sw = Stopwatch.StartNew(); dynamic? application = null; dynamic? documents = null; dynamic? document = null; var proxies = new List<object?>();
        try { token.ThrowIfCancellationRequested(); var wordType = Type.GetTypeFromProgID("Word.Application", false) ?? throw new WordNotInstalledException("Microsoft Word is not installed or is not registered in COM."); application = Own(Activator.CreateInstance(wordType), proxies) ?? throw new WordAutomationException("Could not create Word.Application."); application.Visible = false; application.DisplayAlerts = 0; TrySetAutomationSecurity(application); documents = Own(application.Documents, proxies); document = Own(documents.Open(docxPath, true, false, false), proxies) ?? throw new WordAutomationException("Word could not open the DOCX."); document.ExportAsFixedFormat(outputPdfPath, 17); return new WordPreviewResult { PdfPath = outputPdfPath, Duration = sw.Elapsed }; }
        catch (WordNotInstalledException) { throw; }
        catch (WordAutomationException) { throw; }
        catch (Exception ex) when (ex is not OperationCanceledException) { throw new WordAutomationException("PDF export through Word failed.", ex); }
        finally { try { if (document is not null) document.Close(0); } catch { } try { if (application is not null) application.Quit(0); } catch { } ReleaseAll(proxies); }
    }

    private static dynamic? FindInsertionRange(dynamic document, string type, List<object?> proxies)
    {
        if (type == "ContentControl") { dynamic controls = Own(document.ContentControls, proxies); for (var i = 1; i <= controls.Count; i++) { dynamic control = Own(controls[i], proxies); if (string.Equals((string?)control.Tag, "DOC_BODY", StringComparison.OrdinalIgnoreCase) || string.Equals((string?)control.Title, "DOC_BODY", StringComparison.OrdinalIgnoreCase)) return control.Range; } }
        if (type == "Bookmark") return document.Bookmarks["DOC_BODY"].Range;
        dynamic search = Own(document.Content, proxies); search.Find.ClearFormatting(); search.Find.Text = "{{DOC_BODY}}"; if (search.Find.Execute()) { search.Text = ""; return search; } return null;
    }

    private static void UpdateHeadersFooters(dynamic document, List<object?> proxies)
    {
        dynamic sections = Own(document.Sections, proxies); for (var i = 1; i <= sections.Count; i++) { dynamic section = Own(sections[i], proxies); UpdateCollection(section.Headers, proxies); UpdateCollection(section.Footers, proxies); }
        void UpdateCollection(dynamic collection, List<object?> proxies) { dynamic owned = WordDocumentService.Own(collection, proxies); for (var i = 1; i <= owned.Count; i++) { dynamic item = WordDocumentService.Own(owned[i], proxies); dynamic range = WordDocumentService.Own(item.Range, proxies); range.Fields.Update(); } }
    }

    private static void TrySetAutomationSecurity(dynamic application) { try { application.AutomationSecurity = 3; application.ScreenUpdating = false; } catch { } }
    private static void InsertDocxFile(dynamic range, string path) { range.GetType().InvokeMember("InsertFile", BindingFlags.InvokeMethod | BindingFlags.OptionalParamBinding, null, range, new object[] { path, Type.Missing, Type.Missing, Type.Missing, Type.Missing }); }
    private static int? TryGetPid(dynamic application) { try { return Process.GetProcessById((int)application.Hwnd).Id; } catch { return null; } }
    private static T? Own<T>(T? value, List<object?> proxies) where T : class { if (value is not null) proxies.Add(value); return value; }
    private static void ReleaseAll(IEnumerable<object?> proxies) { foreach (var proxy in proxies.Reverse()) try { if (proxy is not null && Marshal.IsComObject(proxy)) Marshal.FinalReleaseComObject(proxy); } catch { } }
    private static void CommitOutput(string staged, string output) { var full = Path.GetFullPath(output); if (File.Exists(full)) File.Copy(full, full + ".bak-" + DateTime.UtcNow.ToString("yyyyMMddHHmmss"), true); File.Copy(staged, full, true); }
    private static void TryDeleteDirectory(string path) { try { if (Directory.Exists(path)) Directory.Delete(path, true); } catch { } }
    public void Dispose() => _queue.Dispose();
}

internal static class TemplateInsertionPointReader
{
    public static InsertionPointInfo Find(string docxPath)
    {
        using var archive = ZipFile.OpenRead(docxPath); var entry = archive.GetEntry("word/document.xml") ?? throw new InvalidDataException("DOCX document.xml is missing."); using var reader = new StreamReader(entry.Open()); var xml = reader.ReadToEnd();
        if (Regex.IsMatch(xml, @"w:tag[^>]+w:val=""DOC_BODY""", RegexOptions.IgnoreCase)) return new InsertionPointInfo { Type = "ContentControl", Location = "word/document.xml" };
        if (Regex.IsMatch(xml, @"w:bookmarkStart[^>]+w:name=""DOC_BODY""", RegexOptions.IgnoreCase)) return new InsertionPointInfo { Type = "Bookmark", Location = "word/document.xml" };
        if (xml.Contains("{{DOC_BODY}}", StringComparison.Ordinal)) return new InsertionPointInfo { Type = "TextMarker", Location = "word/document.xml" };
        return new InsertionPointInfo { Type = "None" };
    }
}