fix: ansi output resetting on newlines

We reset the terminal colors to write the line header. The problem is we
were processing the whole file, which has spans covering multiple lines.

Now just write directly to stdout and put the pen backdown.

fixes: #2

Author: jtmcdole

packages/lcov_format/lib/src/ansi_format.dart

@@ -1,4 +1,3 @@
-import 'dart:convert';
 import 'dart:io';
 
 import 'package:ansicolor/ansicolor.dart';
@@ -27,44 +26,55 @@ ansiFormat(
   }
 
   printFile(TextSpan fileSpan, LcovRecord node, String fullPath) {
-    final sb = StringBuffer();
-    SpanVisitor(
-      (span, depth) {
-        if (span.text == null) return;
-        var text = span.text!;
-
-        final argb = span.style?.foreground.argb ?? 0xFFFFFFFF;
-        final pen = ansiScopes[argb] ??= AnsiPen()
-          ..rgb(
-              r: ((argb & 0xFF0000) >> 16) / 255,
-              g: ((argb & 0xFF00) >> 8) / 255,
-              b: (argb & 0xFF) / 255);
-
-        sb.write(pen(text));
-      },
-    ).visit(fileSpan);
-
     final zero = AnsiPen()
       ..red(bg: true)
-      ..white();
+      ..black();
     final cover = AnsiPen()
       ..green(bg: true)
-      ..white();
+      ..black();
     stdout.writeln('');
     stdout.writeln(
         '────┤ $fullPath [${node.linesHit} / ${node.linesFound}] = ${node.percent.toStringAsFixed(2)}% ├────');
+
     int lineNumber = 1;
-    for (final line in LineSplitter.split('$sb')) {
+    writeLineHeader() {
       var hits = node.lines[lineNumber];
       if (hits == null) {
-        stdout.writeln('$ansiDefault${' ' * 8} | $line');
+        stdout.write('$ansiDefault${' ' * 8} | ');
       } else if (hits == 0) {
-        stdout.writeln('$ansiDefault${zero('$hits'.padLeft(8, ' '))} | $line');
+        stdout.write('$ansiDefault${zero('$hits'.padLeft(8, ' '))} | ');
       } else {
-        stdout.writeln('$ansiDefault${cover('$hits'.padLeft(8, ' '))} | $line');
+        stdout.write('$ansiDefault${cover('$hits'.padLeft(8, ' '))} | ');
       }
-      lineNumber++;
     }
+
+    writeLineHeader();
+    SpanVisitor(
+      (span, depth) {
+        if (span.text == null) {
+          return;
+        }
+        var text = span.text!;
+
+        final argb = span.style?.foreground.argb ?? 0xFFFFFFFF;
+        final pen = ansiScopes[argb] ??= AnsiPen()
+          ..rgb(
+              r: ((argb & 0xFF0000) >> 16) / 255,
+              g: ((argb & 0xFF00) >> 8) / 255,
+              b: (argb & 0xFF) / 255);
+
+        stdout.write(pen.down);
+        for (int i = 0; i < text.length; i++) {
+          final char = text[i];
+          stdout.write(char);
+          if (char == '\n') {
+            lineNumber++;
+            writeLineHeader();
+            stdout.write(pen.down);
+          }
+        }
+      },
+    ).visit(fileSpan);
   }
 
   for (var child in node.children.values) {