import 'dart:math';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

import 'callback.dart';
import 'printing.dart';
import 'printing_info.dart';
import 'raster.dart';

class PdfPreview extends StatefulWidget {
  const PdfPreview({
    Key key,
    @required this.build,
    this.initialPageFormat,
    this.allowPrinting = true,
    this.allowSharing = true,
    this.maxPageWidth,
    this.canChangePageFormat = true,
    this.actions,
    this.pageFormats,
    this.onError,
    this.onPrinted,
    this.onShared,
  }) : super(key: key);

  final LayoutCallback build;

  final PdfPageFormat initialPageFormat;

  final bool allowPrinting;

  final bool allowSharing;

  final double maxPageWidth;

  final bool canChangePageFormat;

  final List<PdfPreviewAction> actions;

  final Map<String, PdfPageFormat> pageFormats;

  final Widget Function(BuildContext context) onError;

  final void Function(BuildContext context) onPrinted;

  final void Function(BuildContext context) onShared;

  @override
  _PdfPreviewState createState() => _PdfPreviewState();
}

class _PdfPreviewState extends State<PdfPreview> {
  final GlobalKey<State<StatefulWidget>> shareWidget = GlobalKey();
  final GlobalKey<State<StatefulWidget>> listView = GlobalKey();

  final List<_PdfPreviewPage> pages = <_PdfPreviewPage>[];

  PdfPageFormat pageFormat;

  PrintingInfo info = PrintingInfo.unavailable;
  bool infoLoaded = false;

  double dpi = 10;

  dynamic error;

  static const Map<String, PdfPageFormat> defaultPageFormats =
      <String, PdfPageFormat>{
    'A4': PdfPageFormat.a4,
    'Letter': PdfPageFormat.letter,
  };

  Future<void> _raster() async {
    Uint8List _doc;

    if (!info.canRaster) {
      return;
    }

    try {
      _doc = await widget.build(pageFormat);
    } catch (e) {
      error = e;
      return;
    }

    if (error != null) {
      setState(() {
        error = null;
      });
    }

    int pageNum = 0;
    await for (final PdfRaster page in Printing.raster(_doc, dpi: dpi)) {
      setState(() {
        if (pages.length <= pageNum) {
          pages.add(_PdfPreviewPage(page: page));
        } else {
          pages[pageNum] = _PdfPreviewPage(page: page);
        }
      });

      pageNum++;
    }

    pages.removeRange(pageNum, pages.length);
  }

  @override
  void initState() {
    final Locale locale =
        WidgetsBinding.instance.window.locale ?? const Locale('en', 'US');
    final String cc = locale.countryCode;
    if (cc == 'US' || cc == 'CA' || cc == 'MX') {
      pageFormat = widget.initialPageFormat ?? PdfPageFormat.letter;
    } else {
      pageFormat = widget.initialPageFormat ?? PdfPageFormat.a4;
    }

    super.initState();
  }

  @override
  void reassemble() {
    _raster();
    super.reassemble();
  }

  @override
  void didUpdateWidget(covariant PdfPreview oldWidget) {
    if (oldWidget.build != widget.build) {
      pages.clear();
      _raster();
    }
    super.didUpdateWidget(oldWidget);
  }

  @override
  void didChangeDependencies() {
    if (!infoLoaded) {
      Printing.info().then((PrintingInfo _info) {
        setState(() {
          infoLoaded = true;
          info = _info;
          _raster();
        });
      });
    }

    final MediaQueryData mq = MediaQuery.of(context);
    dpi = (min(mq.size.width - 16, widget.maxPageWidth)) *
        mq.devicePixelRatio /
        pageFormat.width *
        72;

    _raster();
    super.didChangeDependencies();
  }

  Widget _showError() {
    if (widget.onError != null) {
      return widget.onError(context);
    }

    return const Center(
      child: Text(
        'Unable to display the document',
        style: TextStyle(
          fontSize: 20,
        ),
      ),
    );
  }

  Widget _createPreview() {
    if (error != null) {
      Widget content = _showError();
      assert(() {
        content = ErrorWidget.withDetails(
          message: error.toString(),
        );
        return true;
      }());
      return content;
    }

    if (!info.canRaster) {
      return _showError();
    }

    if (pages.isEmpty) {
      return const Center(child: CircularProgressIndicator());
    }

    return Scrollbar(
      child: ListView.builder(
        itemCount: pages.length,
        itemBuilder: (BuildContext context, int index) => pages[index],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);

    final Widget scrollView = Container(
      decoration: BoxDecoration(
        gradient: LinearGradient(
          colors: <Color>[Colors.grey.shade400, Colors.grey.shade200],
          begin: Alignment.topCenter,
          end: Alignment.bottomCenter,
        ),
      ),
      width: double.infinity,
      alignment: Alignment.center,
      child: Container(
        constraints: widget.maxPageWidth != null
            ? BoxConstraints(maxWidth: widget.maxPageWidth)
            : null,
        child: _createPreview(),
      ),
    );

    final List<Widget> actions = <Widget>[];

    if (widget.allowPrinting && info.canPrint) {
      actions.add(
        IconButton(
          icon: const Icon(Icons.print),
          color: theme.accentIconTheme.color,
          onPressed: _print,
        ),
      );
    }

    if (widget.allowSharing && info.canShare) {
      actions.add(
        IconButton(
          key: shareWidget,
          icon: const Icon(Icons.share),
          color: theme.accentIconTheme.color,
          onPressed: _share,
        ),
      );
    }

    if (widget.canChangePageFormat) {
      final Map<String, PdfPageFormat> _pageFormats =
          widget.pageFormats ?? defaultPageFormats;
      final List<String> keys = _pageFormats.keys.toList();
      actions.add(
        DropdownButton<PdfPageFormat>(
          // style: theme.accentTextTheme.button,
          dropdownColor: Colors.grey.shade700,
          icon: Icon(
            Icons.arrow_drop_down,
            color: theme.accentIconTheme.color,
          ),
          value: pageFormat,
          items: List<DropdownMenuItem<PdfPageFormat>>.generate(
            _pageFormats.length,
            (int index) {
              final String key = keys[index];
              final PdfPageFormat val = _pageFormats[key];
              return DropdownMenuItem<PdfPageFormat>(
                child: Text(key),
                value: val,
              );
            },
          ),
          onChanged: (PdfPageFormat _pageFormat) {
            setState(() {
              pageFormat = _pageFormat;
              _raster();
            });
          },
        ),
      );
    }

    if (widget.actions != null) {
      for (final PdfPreviewAction action in widget.actions) {
        actions.add(
          IconButton(
            icon: action.icon,
            color: theme.accentIconTheme.color,
            onPressed: action.onPressed == null
                ? null
                : () => action.onPressed(
                      context,
                      widget.build,
                      pageFormat,
                    ),
          ),
        );
      }
    }

    assert(() {
      if (actions.isNotEmpty) {
        actions.add(
          Switch(
            activeColor: Colors.red,
            value: pw.Document.debug,
            onChanged: (bool value) {
              setState(
                () {
                  pw.Document.debug = value;
                  _raster();
                },
              );
            },
          ),
        );
      }

      return true;
    }());

    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Expanded(child: scrollView),
        if (actions.isNotEmpty)
          Material(
            elevation: 4,
            color: theme.primaryColor,
            child: SafeArea(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceAround,
                children: actions,
              ),
            ),
          )
      ],
    );
  }

  Future<void> _print() async {
    final bool result = await Printing.layoutPdf(onLayout: widget.build);

    if (result && widget.onPrinted != null) {
      widget.onPrinted(context);
    }
  }

  Future<void> _share() async {
    // Calculate the widget center for iPad sharing popup position
    final RenderBox referenceBox =
        shareWidget.currentContext.findRenderObject();
    final Offset topLeft =
        referenceBox.localToGlobal(referenceBox.paintBounds.topLeft);
    final Offset bottomRight =
        referenceBox.localToGlobal(referenceBox.paintBounds.bottomRight);
    final Rect bounds = Rect.fromPoints(topLeft, bottomRight);

    final Uint8List bytes = await widget.build(pageFormat);
    final bool result = await Printing.sharePdf(bytes: bytes, bounds: bounds);

    if (result && widget.onShared != null) {
      widget.onShared(context);
    }
  }
}

class _PdfPreviewPage extends StatelessWidget {
  const _PdfPreviewPage({
    Key key,
    this.page,
  }) : super(key: key);

  final PdfRaster page;

  @override
  Widget build(BuildContext context) {
    final PdfRasterImage im = PdfRasterImage(page);

    return Container(
      margin: const EdgeInsets.only(
        left: 8,
        top: 8,
        right: 8,
        bottom: 12,
      ),
      decoration: const BoxDecoration(
        color: Colors.white,
        boxShadow: <BoxShadow>[
          BoxShadow(
            offset: Offset(0, 3),
            blurRadius: 5,
            color: Color(0xFF000000),
          ),
        ],
      ),
      child: AspectRatio(
        aspectRatio: page.width / page.height,
        child: Image(
          image: im,
          fit: BoxFit.cover,
        ),
      ),
    );
  }
}

typedef OnPdfPreviewActionPressed = void Function(
  BuildContext context,
  LayoutCallback build,
  PdfPageFormat pageFormat,
);

class PdfPreviewAction {
  const PdfPreviewAction({
    @required this.icon,
    @required this.onPressed,
  }) : assert(icon != null);

  final Icon icon;
  final OnPdfPreviewActionPressed onPressed;
}