feat: add MouseReporter to create CSI for mouse events

lib/src/core/mouse/reporter.dart

@@ -0,0 +1,48 @@
+import 'package:xterm/src/core/buffer/cell_offset.dart';
+import 'package:xterm/src/core/mouse/mode.dart';
+import 'package:xterm/src/core/mouse/button.dart';
+import 'package:xterm/src/core/mouse/button_state.dart';
+
+class MouseReporter {
+  static String? report(
+    TerminalMouseButton button,
+    TerminalMouseButtonState state,
+    CellOffset position,
+    MouseReportMode reportMode,
+  ) {
+    // x and y offsets have to be incremented by 1 as the offset if 0-based,
+    // The position has to be reported using 1-based coordinates.
+    final x = position.x + 1;
+    final y = position.y + 1;
+    switch (reportMode) {
+      case MouseReportMode.normal:
+      case MouseReportMode.utf:
+        // Button ID 3 is used to signal a button release.
+        final buttonID = state == TerminalMouseButtonState.up ? 3 : button.id;
+        // The button ID is reported as shifted by 32 to produce a printable
+        // character.
+        final btn = String.fromCharCode(32 + buttonID);
+        // Normal mode only supports a maximum position of 223, while utf
+        // supports positions up to 2015. Both modes send a null byte if the
+        // position exceeds that limit.
+        final col = (reportMode == MouseReportMode.normal && x > 223) ||
+                (reportMode == MouseReportMode.utf && x > 2015)
+            ? '\x00'
+            : String.fromCharCode(32 + x);
+        final row = (reportMode == MouseReportMode.normal && y > 223) ||
+                (reportMode == MouseReportMode.utf && y > 2015)
+            ? '\x00'
+            : String.fromCharCode(32 + y + 1);
+        return "\x1b[M$btn$col$row";
+      case MouseReportMode.sgr:
+        final buttonID = button.id;
+        final upDown = state == TerminalMouseButtonState.down ? 'M' : 'm';
+        return "\x1b[<$buttonID;$x;$y$upDown";
+      case MouseReportMode.urxvt:
+        // The button ID uses the same id as to report it as in normal mode.
+        final buttonID =
+            32 + (state == TerminalMouseButtonState.up ? 3 : button.id);
+        return "\x1b[$buttonID;$x;${y}M";
+    }
+  }
+}