Ocideck/lib/services/export_service.dart

import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:archive/archive.dart';
import 'package:image/image.dart' as img;
import 'package:path/path.dart' as p;
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

enum ExportFormat { pdf, pptx }

extension ExportFormatExtension on ExportFormat {
  String get label {
    switch (this) {
      case ExportFormat.pdf:
        return 'PDF';
      case ExportFormat.pptx:
        return 'PowerPoint (PPTX)';
    }
  }

  String get extension {
    switch (this) {
      case ExportFormat.pdf:
        return '.pdf';
      case ExportFormat.pptx:
        return '.pptx';
    }
  }
}

class ExportResult {
  final bool success;
  final String? outputPath;
  final String? error;

  const ExportResult._({required this.success, this.outputPath, this.error});

  factory ExportResult.ok(String path) =>
      ExportResult._(success: true, outputPath: path);
  factory ExportResult.fail(String error) =>
      ExportResult._(success: false, error: error);
}

/// Builds PDF and PPTX files from pre-rendered slide images (WYSIWYG export).
/// Slides are expected to be 16:9 PNG bytes (see [SlideRasterizer]).
class ExportService {
  // 16:9 widescreen slide size in EMU (English Metric Units): 13.333" x 7.5".
  static const int _slideWidthEmu = 12192000;
  static const int _slideHeightEmu = 6858000;

  /// JPEG quality (0–100) used when a PDF is exported in compressed mode.
  /// Low enough to shrink photo-heavy decks dramatically while keeping slides
  /// legible.
  static const int _compressedJpegQuality = 60;

  /// Slides are downscaled to this width (px) in compressed mode. The compressed
  /// PDF is meant as a screen handout, so 720p is plenty and shrinks the file
  /// further on top of JPEG encoding. Wider slides are never upscaled.
  static const int _compressedMaxWidth = 1280;

  /// Timestamp for [time] in UTC, formatted `YYYYMMDDHHMMSS` —
  /// e.g. `20260603124547`. Used as a filename prefix so exports sort
  /// chronologically and never overwrite each other.
  static String natoDtg(DateTime time) {
    final t = time.toUtc();
    String two(int n) => n.toString().padLeft(2, '0');
    return '${t.year.toString().padLeft(4, '0')}${two(t.month)}${two(t.day)}'
        '${two(t.hour)}${two(t.minute)}${two(t.second)}';
  }

  /// Write [images] to a file named after [deckPath] in the requested [format].
  ///
  /// The file name is prefixed with a UTC timestamp (see [natoDtg]),
  /// e.g. `20260603124547 deck.pdf`.
  ///
  /// The file is written to [outputDirectory] when given (created if missing);
  /// otherwise it lands next to the source deck (legacy behaviour).
  ///
  /// When [compress] is set (PDF only), each slide is re-encoded as JPEG instead
  /// of being embedded as lossless PNG, and `-compact` is appended to the file
  /// name so it never overwrites a full-quality export.
  Future<ExportResult> export(
    String deckPath,
    ExportFormat format,
    List<Uint8List> images, {
    bool compress = false,
    String? outputDirectory,
  }) async {
    if (images.isEmpty) {
      return ExportResult.fail('Geen slides om te exporteren.');
    }
    final compactSuffix = compress && format == ExportFormat.pdf
        ? '-compact'
        : '';
    final dir = (outputDirectory != null && outputDirectory.isNotEmpty)
        ? outputDirectory
        : p.dirname(deckPath);
    final prefix = '${natoDtg(DateTime.now())} ';
    final fileName =
        '$prefix${p.basenameWithoutExtension(deckPath)}$compactSuffix${format.extension}';
    final outputPath = p.join(dir, fileName);
    try {
      await Directory(dir).create(recursive: true);
      final Uint8List bytes;
      switch (format) {
        case ExportFormat.pdf:
          bytes = await _buildPdf(images, compress: compress);
        case ExportFormat.pptx:
          bytes = _buildPptx(images);
      }
      await File(outputPath).writeAsBytes(bytes, flush: true);
      return ExportResult.ok(outputPath);
    } catch (e) {
      return ExportResult.fail('Export fout: $e');
    }
  }

  // ── PDF ───────────────────────────────────────────────────────────────────

  Future<Uint8List> _buildPdf(
    List<Uint8List> images, {
    bool compress = false,
  }) async {
    final doc = pw.Document();
    // Page size in points; only the ratio matters for a full-bleed image.
    const format = PdfPageFormat(1280, 720, marginAll: 0);
    for (final png in images) {
      // MemoryImage auto-detects PNG vs JPEG from the byte header, so a
      // compressed (JPEG) slide embeds just like the lossless one.
      final image = pw.MemoryImage(compress ? _toJpeg(png) : png);
      doc.addPage(
        pw.Page(
          pageFormat: format,
          build: (_) => pw.Image(image, fit: pw.BoxFit.fill),
        ),
      );
    }
    return doc.save();
  }

  /// Downscale a rendered slide PNG to [_compressedMaxWidth] and re-encode it as
  /// JPEG at [_compressedJpegQuality]. Slides are full-bleed (no transparency),
  /// so dropping the alpha channel is safe.
  Uint8List _toJpeg(Uint8List png) {
    final decoded = img.decodePng(png);
    if (decoded == null) return png; // Unexpected; keep the original bytes.
    final resized = decoded.width > _compressedMaxWidth
        ? img.copyResize(
            decoded,
            width: _compressedMaxWidth,
            interpolation: img.Interpolation.average,
          )
        : decoded;
    return img.encodeJpg(resized, quality: _compressedJpegQuality);
  }

  // ── PPTX (Office Open XML) ─────────────────────────────────────────────────

  Uint8List _buildPptx(List<Uint8List> images) {
    final archive = Archive();
    void addText(String name, String content) {
      final data = utf8Bytes(content);
      archive.add(ArchiveFile(name, data.length, data));
    }

    final slideCount = images.length;

    addText('[Content_Types].xml', _contentTypes(slideCount));
    addText('_rels/.rels', _rootRels());
    addText('ppt/presentation.xml', _presentationXml(slideCount));
    addText('ppt/_rels/presentation.xml.rels', _presentationRels(slideCount));
    addText('ppt/presProps.xml', _presProps());
    addText('ppt/theme/theme1.xml', _theme1());
    addText('ppt/slideMasters/slideMaster1.xml', _slideMaster());
    addText('ppt/slideMasters/_rels/slideMaster1.xml.rels', _slideMasterRels());
    addText('ppt/slideLayouts/slideLayout1.xml', _slideLayout());
    addText('ppt/slideLayouts/_rels/slideLayout1.xml.rels', _slideLayoutRels());

    for (var i = 0; i < slideCount; i++) {
      final n = i + 1;
      addText('ppt/slides/slide$n.xml', _slideXml());
      addText('ppt/slides/_rels/slide$n.xml.rels', _slideRels(n));
      final png = images[i];
      archive.add(ArchiveFile('ppt/media/image$n.png', png.length, png));
    }

    return ZipEncoder().encodeBytes(archive);
  }

  static List<int> utf8Bytes(String s) => utf8.encode(s);

  String _contentTypes(int count) {
    final overrides = StringBuffer();
    for (var i = 1; i <= count; i++) {
      overrides.write(
        '<Override PartName="/ppt/slides/slide$i.xml" '
        'ContentType="application/vnd.openxmlformats-officedocument.presentationml.slide+xml"/>',
      );
    }
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">'
        '<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>'
        '<Default Extension="xml" ContentType="application/xml"/>'
        '<Default Extension="png" ContentType="image/png"/>'
        '<Override PartName="/ppt/presentation.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.presentation.main+xml"/>'
        '<Override PartName="/ppt/presProps.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.presProps+xml"/>'
        '<Override PartName="/ppt/slideMasters/slideMaster1.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.slideMaster+xml"/>'
        '<Override PartName="/ppt/slideLayouts/slideLayout1.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.slideLayout+xml"/>'
        '<Override PartName="/ppt/theme/theme1.xml" ContentType="application/vnd.openxmlformats-officedocument.theme+xml"/>'
        '$overrides'
        '</Types>';
  }

  String _rootRels() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">'
        '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="ppt/presentation.xml"/>'
        '</Relationships>';
  }

  String _presentationXml(int count) {
    final sldIds = StringBuffer();
    for (var i = 0; i < count; i++) {
      // Slide relationship ids start at rId2 (rId1 = master).
      sldIds.write('<p:sldId id="${256 + i}" r:id="rId${i + 2}"/>');
    }
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<p:presentation xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" '
        'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" '
        'xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main">'
        '<p:sldMasterIdLst><p:sldMasterId id="2147483648" r:id="rId1"/></p:sldMasterIdLst>'
        '<p:sldIdLst>$sldIds</p:sldIdLst>'
        '<p:sldSz cx="$_slideWidthEmu" cy="$_slideHeightEmu" type="screen16x9"/>'
        '<p:notesSz cx="6858000" cy="9144000"/>'
        '</p:presentation>';
  }

  String _presentationRels(int count) {
    final rels = StringBuffer();
    rels.write(
      '<Relationship Id="rId1" '
      'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideMaster" '
      'Target="slideMasters/slideMaster1.xml"/>',
    );
    for (var i = 0; i < count; i++) {
      final n = i + 1;
      rels.write(
        '<Relationship Id="rId${i + 2}" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide" '
        'Target="slides/slide$n.xml"/>',
      );
    }
    final presPropsId = 'rId${count + 2}';
    final themeId = 'rId${count + 3}';
    rels.write(
      '<Relationship Id="$presPropsId" '
      'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/presProps" '
      'Target="presProps.xml"/>',
    );
    rels.write(
      '<Relationship Id="$themeId" '
      'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/theme" '
      'Target="theme/theme1.xml"/>',
    );
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">'
        '$rels'
        '</Relationships>';
  }

  String _presProps() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<p:presentationPr xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" '
        'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" '
        'xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main"/>';
  }

  String _slideMaster() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<p:sldMaster xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" '
        'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" '
        'xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main">'
        '<p:cSld>'
        '<p:bg><p:bgRef idx="1001"><a:schemeClr val="bg1"/></p:bgRef></p:bg>'
        '${_emptySpTree()}'
        '</p:cSld>'
        '<p:clrMap bg1="lt1" tx1="dk1" bg2="lt2" tx2="dk2" accent1="accent1" '
        'accent2="accent2" accent3="accent3" accent4="accent4" accent5="accent5" '
        'accent6="accent6" hlink="hlink" folHlink="folHlink"/>'
        '<p:sldLayoutIdLst><p:sldLayoutId id="2147483649" r:id="rId1"/></p:sldLayoutIdLst>'
        '<p:txStyles><p:titleStyle/><p:bodyStyle/><p:otherStyle/></p:txStyles>'
        '</p:sldMaster>';
  }

  String _slideMasterRels() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">'
        '<Relationship Id="rId1" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideLayout" '
        'Target="../slideLayouts/slideLayout1.xml"/>'
        '<Relationship Id="rId2" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/theme" '
        'Target="../theme/theme1.xml"/>'
        '</Relationships>';
  }

  String _slideLayout() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<p:sldLayout xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" '
        'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" '
        'xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main" '
        'type="blank" preserve="1">'
        '<p:cSld name="Leeg">${_emptySpTree()}</p:cSld>'
        '<p:clrMapOvr><a:masterClrMapping/></p:clrMapOvr>'
        '</p:sldLayout>';
  }

  String _slideLayoutRels() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">'
        '<Relationship Id="rId1" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideMaster" '
        'Target="../slideMasters/slideMaster1.xml"/>'
        '</Relationships>';
  }

  String _slideXml() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<p:sld xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" '
        'xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" '
        'xmlns:p="http://schemas.openxmlformats.org/presentationml/2006/main">'
        '<p:cSld><p:spTree>'
        '<p:nvGrpSpPr><p:cNvPr id="1" name=""/><p:cNvGrpSpPr/><p:nvPr/></p:nvGrpSpPr>'
        '<p:grpSpPr><a:xfrm><a:off x="0" y="0"/><a:ext cx="0" cy="0"/>'
        '<a:chOff x="0" y="0"/><a:chExt cx="0" cy="0"/></a:xfrm></p:grpSpPr>'
        '<p:pic>'
        '<p:nvPicPr><p:cNvPr id="2" name="Slide"/>'
        '<p:cNvPicPr><a:picLocks noChangeAspect="1"/></p:cNvPicPr><p:nvPr/></p:nvPicPr>'
        '<p:blipFill><a:blip r:embed="rId2"/><a:stretch><a:fillRect/></a:stretch></p:blipFill>'
        '<p:spPr><a:xfrm><a:off x="0" y="0"/>'
        '<a:ext cx="$_slideWidthEmu" cy="$_slideHeightEmu"/></a:xfrm>'
        '<a:prstGeom prst="rect"><a:avLst/></a:prstGeom></p:spPr>'
        '</p:pic>'
        '</p:spTree></p:cSld>'
        '<p:clrMapOvr><a:masterClrMapping/></p:clrMapOvr>'
        '</p:sld>';
  }

  String _slideRels(int n) {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">'
        '<Relationship Id="rId1" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideLayout" '
        'Target="../slideLayouts/slideLayout1.xml"/>'
        '<Relationship Id="rId2" '
        'Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image" '
        'Target="../media/image$n.png"/>'
        '</Relationships>';
  }

  String _emptySpTree() {
    return '<p:spTree>'
        '<p:nvGrpSpPr><p:cNvPr id="1" name=""/><p:cNvGrpSpPr/><p:nvPr/></p:nvGrpSpPr>'
        '<p:grpSpPr><a:xfrm><a:off x="0" y="0"/><a:ext cx="0" cy="0"/>'
        '<a:chOff x="0" y="0"/><a:chExt cx="0" cy="0"/></a:xfrm></p:grpSpPr>'
        '</p:spTree>';
  }

  String _theme1() {
    return '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
        '<a:theme xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main" name="Office">'
        '<a:themeElements>'
        '<a:clrScheme name="Office">'
        '<a:dk1><a:sysClr val="windowText" lastClr="000000"/></a:dk1>'
        '<a:lt1><a:sysClr val="window" lastClr="FFFFFF"/></a:lt1>'
        '<a:dk2><a:srgbClr val="44546A"/></a:dk2>'
        '<a:lt2><a:srgbClr val="E7E6E6"/></a:lt2>'
        '<a:accent1><a:srgbClr val="4472C4"/></a:accent1>'
        '<a:accent2><a:srgbClr val="ED7D31"/></a:accent2>'
        '<a:accent3><a:srgbClr val="A5A5A5"/></a:accent3>'
        '<a:accent4><a:srgbClr val="FFC000"/></a:accent4>'
        '<a:accent5><a:srgbClr val="5B9BD5"/></a:accent5>'
        '<a:accent6><a:srgbClr val="70AD47"/></a:accent6>'
        '<a:hlink><a:srgbClr val="0563C1"/></a:hlink>'
        '<a:folHlink><a:srgbClr val="954F72"/></a:folHlink>'
        '</a:clrScheme>'
        '<a:fontScheme name="Office">'
        '<a:majorFont><a:latin typeface="Calibri Light"/><a:ea typeface=""/><a:cs typeface=""/></a:majorFont>'
        '<a:minorFont><a:latin typeface="Calibri"/><a:ea typeface=""/><a:cs typeface=""/></a:minorFont>'
        '</a:fontScheme>'
        '<a:fmtScheme name="Office">'
        '<a:fillStyleLst>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '</a:fillStyleLst>'
        '<a:lnStyleLst>'
        '<a:ln w="6350" cap="flat" cmpd="sng" algn="ctr"><a:solidFill><a:schemeClr val="phClr"/></a:solidFill><a:prstDash val="solid"/></a:ln>'
        '<a:ln w="12700" cap="flat" cmpd="sng" algn="ctr"><a:solidFill><a:schemeClr val="phClr"/></a:solidFill><a:prstDash val="solid"/></a:ln>'
        '<a:ln w="19050" cap="flat" cmpd="sng" algn="ctr"><a:solidFill><a:schemeClr val="phClr"/></a:solidFill><a:prstDash val="solid"/></a:ln>'
        '</a:lnStyleLst>'
        '<a:effectStyleLst>'
        '<a:effectStyle><a:effectLst/></a:effectStyle>'
        '<a:effectStyle><a:effectLst/></a:effectStyle>'
        '<a:effectStyle><a:effectLst/></a:effectStyle>'
        '</a:effectStyleLst>'
        '<a:bgFillStyleLst>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '<a:solidFill><a:schemeClr val="phClr"/></a:solidFill>'
        '</a:bgFillStyleLst>'
        '</a:fmtScheme>'
        '</a:themeElements>'
        '</a:theme>';
  }
}