Add format support

src/format/fixed.rs

@@ -0,0 +1,54 @@
+use unicode_segmentation::UnicodeSegmentation;
+
+pub struct FixedFormatter {
+    length: usize,
+    keep_original: bool,
+}
+
+impl FixedFormatter {
+    pub fn new(length: usize, keep_original: bool) -> Self {
+        FixedFormatter {
+            length,
+            keep_original,
+        }
+    }
+
+    pub fn format(&self, message: &str) -> String {
+        let mut result = String::new();
+        let vec: Vec<_> = UnicodeSegmentation::graphemes(message, true).collect();
+        let mut current_length = 0;
+        for grapheme in vec {
+            if grapheme == "\n" {
+                if self.keep_original {
+                    result.push('\n');
+                    current_length = 0;
+                }
+                continue;
+            }
+            if current_length >= self.length {
+                result.push('\n');
+                current_length = 0;
+            }
+            result.push_str(grapheme);
+            current_length += 1;
+        }
+        return result;
+    }
+}
+
+#[test]
+fn test_format() {
+    let formatter = FixedFormatter::new(10, false);
+    let message = "This is a test message.\nThis is another line.";
+    let formatted_message = formatter.format(message);
+    assert_eq!(
+        formatted_message,
+        "This is a \ntest messa\nge.This is\n another l\nine."
+    );
+    assert_eq!(formatter.format("● This is a test."), "● This is \na test.");
+    let fommater2 = FixedFormatter::new(10, true);
+    assert_eq!(
+        fommater2.format("● Th\nis is a test."),
+        "● Th\nis is a te\nst."
+    );
+}