import 'dart:ui' as ui;

import 'package:dartterm/assets.dart';
import 'package:dartterm/fonts.dart';
import 'package:dartterm/terminal.dart';
import 'package:flutter/material.dart';

class TerminalCustomPainter extends CustomPainter {
  Terminal t;
  double scalingFactor;

  TerminalCustomPainter(this.t, this.scalingFactor);

  @override
  bool shouldRepaint(TerminalCustomPainter oldDelegate) {
    return true;
  }

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()..filterQuality = FilterQuality.none;

    // == Fill backdrop ==
    final paint2 = Paint()
      ..color = Colors.black
      ..style = PaintingStyle.fill;
    canvas.drawRect(const Offset(0, 0) & size, paint2);

    // == Estimate dimensions for scaling ==
    var sx = size.width / Terminal.width;
    var sy = size.height / Terminal.height;
    var dpx = 0.0;
    var dpy = 0.0;
    var invScalingFactor = 1 / scalingFactor;

    for (double preferredSx in [64, 56, 48, 40, 32, 24, 16, 8]) {
      preferredSx *= invScalingFactor;
      var preferredSy = preferredSx;
      if (preferredSx < sx && preferredSy < sy) {
        sx = preferredSx.toDouble();
        sy = preferredSy.toDouble();
        dpx = ((size.width - (sx * Terminal.width)) / 2);
        dpy = ((size.height - (sy * Terminal.height)) / 2);

        dpx /= invScalingFactor;
        dpx = dpx.floorToDouble();
        dpx *= invScalingFactor;

        dpy /= invScalingFactor;
        dpy = dpy.floorToDouble();
        dpy *= invScalingFactor;

        break;
      }
    }

    for (var i = 0; i < nTiles; i++) {
      final tile = t.tiles[i];

      final (pcxDst, pcyDst) = terminal.toXY(i) ?? (0, 0);
      final (pxDst, pyDst) = (dpx + pcxDst * sx, dpy + pcyDst * sy);
      final rectDst = Rect.fromLTWH(pxDst, pyDst, sx, sy);

      var content = tile.content;
      if (content != null) {
        var source = content.sourceImage;
        var image = assets.getImageIfAvailable(source);
        if (image != null) {
          var fgRect = Rect.fromLTWH(
              content.sourceCx.toDouble() * cellW,
              content.sourceCy.toDouble() * cellH,
              cellW.toDouble(),
              cellH.toDouble());
          canvas.drawImageRect(
            image,
            fgRect,
            rectDst,
            paint,
          );
        }
      }
    }

    var todos = Todos();

    // == Draw the background and foreground of every tile ==
    for (var i = 0; i < nTiles; i++) {
      final (pcxDst, pcyDst) = terminal.toXY(i) ?? (0, 0);
      final (pxDst, pyDst) = (dpx + pcxDst * sx, dpy + pcyDst * sy);
      final rectDst = Rect.fromLTWH(pxDst, pyDst, sx, sy);

      final tile = t.tiles[i];

      var bgRect = Rect.fromLTWH(0, 0, cellW.toDouble(), cellH.toDouble());
      todos.add(Font.bg.imageName, bgRect, rectDst, tile.bg);

      var c = tile.content;
      if (c != null) {
        var fgRect = Rect.fromLTWH(c.sourceCx.toDouble() * cellW,
            c.sourceCy.toDouble() * cellH, cellW.toDouble(), cellH.toDouble());
        todos.add(c.sourceImage, fgRect, rectDst, tile.fg);
      }
    }

    for (var t in todos.imageTodos) {
      final atlas = t.atlas;
      if (atlas != null) {
        canvas.drawAtlas(atlas, t.transforms, t.rects, t.colors,
            BlendMode.modulate, null, paint);
      }
    }
  }
}

class Todos {
  List<ImageTodos> imageTodos = [];
  Map<String, int> imageTodoIx = {};

  void add(String source, Rect src, Rect dst, Color color) {
    var ix = imageTodoIx[source];
    if (ix == null) {
      ix = imageTodos.length;
      var image = assets.getImageIfAvailable(source);
      imageTodos.add(ImageTodos(image));
      imageTodoIx[source] = ix;
    }
    imageTodos[ix].add(src, dst, color);
  }
}

class ImageTodos {
  ui.Image? atlas;
  List<RSTransform> transforms = [];
  List<Rect> rects = [];
  List<Color> colors = [];

  ImageTodos(this.atlas);

  void add(Rect src, Rect dst, Color color) {
    // NOTE: Because main.dart uses aspectRatio, scaleX and scaleY should be close to the same
    var scaleX = dst.width / src.width;

    transforms.add(RSTransform.fromComponents(
      rotation: 0.0,
      scale: scaleX,
      anchorX: 0.0,
      anchorY: 0.0,
      translateX: dst.left,
      translateY: dst.top,
    ));
    rects.add(src);
    colors.add(color);
  }
}