subwrite/lib/highlighter.dart

import 'package:flutter/material.dart';
import 'package:subwrite/sourcelink.dart';
import 'package:subwrite/theme.dart';

import 'annotation.dart';
import 'line_info.dart';

class LineDecoration {
  int start = 0;
  int end = 0;
  Color color = Colors.white;
  Color background = Colors.white;
  bool underline = false;
  bool italic = false;
  bool bold = false;

  SourceLink? message;
}

class Highlighter {
  Highlighter() {}

  List<InlineSpan> run(BuildContext context, String text, int line, bool highlightRisk, TextStyle style, List<LineAnnotation>? insights, int? cursorStart, int? cursorEnd, bool lineSelected,
      int maxCharsBeforeWrapping) {
    TextStyle defaultStyle = style.copyWith(fontFamily: 'Iosevka', fontSize: fontSize, color: foreground, height: 1.2);
    List<InlineSpan> res = <InlineSpan>[];
    List<LineDecoration> decors = <LineDecoration>[];

    insights
        ?.where(
      (element) => element.annotationType == AnnotationType.highlight,
    )
        .forEach((element) {
      LineDecoration d = LineDecoration();
      //print("${element.sourceLink.colStart} ${element.sourceLink.colEnd}");
      d.start = element.sourceLink.colStart! - 1;
      d.end = element.sourceLink.colEnd! - 2;
      d.background = Colors.transparent;
      switch (element.type) {
        case "header":
          d.color = header;
          break;
        case "bold":
          d.color = keyword;
          d.bold = true;
          break;
        case "code":
          d.color = function;
          break;
        case "spellcheck":
          d.color = variable;
          d.underline = true;
      }

      decors.add(d);
    });

    // Assume that decorators do not overlap...
    decors.sort((a, b) {
      return a.start.compareTo(b.start);
    });

    text += ' ';

    for (int i = 0; i < text.length; i++) {
      String current = text[i];
      TextStyle style = defaultStyle.copyWith();

      // decorate
      for (var d in decors) {
        // if we are in this decoration...
        if (i >= d.start && i <= d.end) {
          style = style.copyWith(color: d.color);
          if (d.bold = true) {
            style = style.copyWith(fontWeight: FontWeight.bold);
          }
          if (d.underline = true) {
            style = style.copyWith(fontStyle: FontStyle.italic);
          }
        }
      }

      // is within selection
      if (lineSelected) {
        style = style.copyWith(backgroundColor: selection);
      } else if (cursorStart != null && cursorEnd != null) {
        if (i >= cursorStart && i < cursorEnd) {
          style = style.copyWith(backgroundColor: selection);
        }
      } else if (cursorStart != null && cursorEnd == null) {
        if (i >= cursorStart) {
          style = style.copyWith(backgroundColor: selection);
        }
      } else if (cursorStart == null && cursorEnd != null) {
        if (i < cursorEnd) {
          style = style.copyWith(backgroundColor: selection);
        }
      }

      if (highlightRisk) {
        style = style.copyWith(
          backgroundColor: risk.withOpacity(0.50),
        );
      }

      if (current == " ") {
        // NOTE: This is really annoying
        // Ideally we could put a non breaking space here and force richtext to just do the thing we want and fill all available space...
        // however richtext really doesn't want to do that...
        // if this is a space of any kind (even full-width non-breaking spaces), richtext will invisibly drop the space...
        // the space happens if this is a size block.
        // HOWEVER: if this is an printable char other than a space the algorithm works as expected....EXCEPT
        // if we try to change the color to hide that fact the renderer freaks out on lines with more than ~87-90 words and will cause
        // the line to shake...

        // so we first add the space...
        res.add(TextSpan(text: ' \u200B', style: style, mouseCursor: SystemMouseCursors.text));
        // and then if we are going to drop the space...
        if (i % maxCharsBeforeWrapping == 0) {
          // add another space...that we definitely won't drop...
          res.add(TextSpan(text: '_\u200B', style: style.copyWith(color: style.backgroundColor), mouseCursor: SystemMouseCursors.text));
        }
      } else {
        // we need to add a '\ufeff' (Zero Width No-Break Space) here to avoid RichText doing ridiculous
        // breaking logic with hyphens / slashes etc.
        res.add(TextSpan(text: '$current\u200B', style: style, mouseCursor: SystemMouseCursors.text));
      }
    }
    return res;
  }
}