first textarea implementation

canvas/src/textarea/provider.rs

@@ -0,0 +1,113 @@
+// src/textarea/provider.rs
+use crate::DataProvider;
+
+#[derive(Debug, Clone)]
+pub struct TextAreaProvider {
+    lines: Vec<String>,
+    name: String,
+}
+
+impl Default for TextAreaProvider {
+    fn default() -> Self {
+        Self {
+            lines: vec![String::new()],
+            name: "Text".to_string(),
+        }
+    }
+}
+
+impl TextAreaProvider {
+    pub fn from_text<S: Into<String>>(text: S) -> Self {
+        let text = text.into();
+        let mut lines: Vec<String> =
+            text.split('\n').map(|s| s.to_string()).collect();
+        if lines.is_empty() {
+            lines.push(String::new());
+        }
+        Self {
+            lines,
+            name: "Text".to_string(),
+        }
+    }
+
+    pub fn to_text(&self) -> String {
+        self.lines.join("\n")
+    }
+
+    pub fn set_text<S: Into<String>>(&mut self, text: S) {
+        let text = text.into();
+        self.lines = text.split('\n').map(|s| s.to_string()).collect();
+        if self.lines.is_empty() {
+            self.lines.push(String::new());
+        }
+    }
+
+    pub fn line_count(&self) -> usize {
+        self.lines.len()
+    }
+
+    #[inline]
+    fn char_to_byte_index(s: &str, char_idx: usize) -> usize {
+        s.char_indices()
+            .nth(char_idx)
+            .map(|(i, _)| i)
+            .unwrap_or_else(|| s.len())
+    }
+
+    pub fn split_line_at(&mut self, line_idx: usize, at_char: usize) -> usize {
+        if line_idx >= self.lines.len() {
+            return self.lines.len().saturating_sub(1);
+        }
+        let line = &mut self.lines[line_idx];
+        let byte_idx = Self::char_to_byte_index(line, at_char);
+        let right = line[byte_idx..].to_string();
+        line.truncate(byte_idx);
+        let insert_at = line_idx + 1;
+        self.lines.insert(insert_at, right);
+        insert_at
+    }
+
+    pub fn join_with_next(&mut self, line_idx: usize) -> Option<usize> {
+        if line_idx + 1 >= self.lines.len() {
+            return None;
+        }
+        let left_len = self.lines[line_idx].chars().count();
+        let right = self.lines.remove(line_idx + 1);
+        self.lines[line_idx].push_str(&right);
+        Some(left_len)
+    }
+
+    pub fn join_with_prev(
+        &mut self,
+        line_idx: usize,
+    ) -> Option<(usize, usize)> {
+        if line_idx == 0 || line_idx >= self.lines.len() {
+            return None;
+        }
+        let prev_idx = line_idx - 1;
+        let prev_len = self.lines[prev_idx].chars().count();
+        let curr = self.lines.remove(line_idx);
+        self.lines[prev_idx].push_str(&curr);
+        Some((prev_idx, prev_len))
+    }
+}
+
+impl DataProvider for TextAreaProvider {
+    fn field_count(&self) -> usize {
+        self.lines.len()
+    }
+
+    fn field_name(&self, _index: usize) -> &str {
+        &self.name
+    }
+
+    fn field_value(&self, index: usize) -> &str {
+        self.lines.get(index).map(|s| s.as_str()).unwrap_or("")
+    }
+
+    fn set_field_value(&mut self, index: usize, value: String) {
+        if index < self.lines.len() {
+            self.lines[index] = value;
+        }
+    }
+}