feat: show selection stats in footer

Author: uednd

src/screen/editor/context.rs

@@ -1,5 +1,8 @@
 use crate::{
-    model::{cell::CellAddress, workbook::Workbook},
+    model::{
+        cell::{CellAddress, CellValue},
+        workbook::Workbook,
+    },
     screen::ScreenCommand,
     theme::Theme,
 };
@@ -22,6 +25,14 @@ pub struct TableContext {
     pending_command: Option<ScreenCommand>,
 }
 
+/// 当前选区的统计信息。
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct SelectionStats {
+    pub average: f64,
+    pub sum: f64,
+    pub count: usize,
+}
+
 impl TableContext {
     /// 创建编辑器共享状态。
     pub fn new(theme: Theme, path: String, wb: Workbook) -> Self {
@@ -72,6 +83,52 @@ impl TableContext {
         self.selection = None;
     }
 
+    /// 统计当前多单元格矩形选区。
+    ///
+    /// `count` 统计有内容的单元格；`sum` 和 `average` 只统计数字。
+    pub fn selection_stats(&self) -> Option<SelectionStats> {
+        let selection = self.selection?;
+        let Selection::Range { .. } = selection else {
+            return None;
+        };
+
+        let (r1, r2, c1, c2) = selection.normalized_bounds(self.wb.rows, self.wb.columns);
+        if r1 == r2 && c1 == c2 {
+            return None;
+        }
+
+        let mut sum = 0.0;
+        let mut number_count = 0;
+        let mut value_count = 0;
+
+        for row in r1..=r2 {
+            for col in c1..=c2 {
+                let addr = CellAddress { row, col };
+                let Some(cell) = self.wb.get_cell(addr) else {
+                    continue;
+                };
+
+                value_count += 1;
+                if let Some(number) = cell_value_as_number(&cell.value) {
+                    sum += number;
+                    number_count += 1;
+                }
+            }
+        }
+
+        let average = if number_count == 0 {
+            0.0
+        } else {
+            sum / number_count as f64
+        };
+
+        Some(SelectionStats {
+            average,
+            sum,
+            count: value_count,
+        })
+    }
+
     /// 已复制的区域（用于渲染虚线边框）。
     ///
     /// `None` 表示没有待粘贴的复制内容。
@@ -261,3 +318,11 @@ impl TableContext {
             .unwrap_or_default()
     }
 }
+
+fn cell_value_as_number(value: &CellValue) -> Option<f64> {
+    match value {
+        CellValue::Number(n) => Some(*n),
+        CellValue::Text(text) => text.parse::<f64>().ok(),
+        CellValue::Empty | CellValue::Error(_) => None,
+    }
+}

src/screen/editor/navigation.rs

@@ -145,8 +145,28 @@ impl Mode for NavigationMode {
 
     fn footer(&self, ctx: &TableContext) -> FooterLine {
         use ratatui::text::Span;
-        FooterLine {
-            hint: Some(Line::from(vec![
+        let hint = if let Some(stats) = ctx.selection_stats() {
+            Line::from(vec![
+                Span::styled("平均值=", Style::default().fg(ctx.theme.accent)),
+                Span::styled(
+                    format!(" {}", format_number(stats.average)),
+                    Style::default().fg(ctx.theme.text_dim),
+                ),
+                Span::styled("  ", Style::default().fg(ctx.theme.text_dim)),
+                Span::styled("求和=", Style::default().fg(ctx.theme.accent)),
+                Span::styled(
+                    format!(" {}", format_number(stats.sum)),
+                    Style::default().fg(ctx.theme.text_dim),
+                ),
+                Span::styled("  ", Style::default().fg(ctx.theme.text_dim)),
+                Span::styled("计数=", Style::default().fg(ctx.theme.accent)),
+                Span::styled(
+                    format!(" {}", stats.count),
+                    Style::default().fg(ctx.theme.text_dim),
+                ),
+            ])
+        } else {
+            Line::from(vec![
                 Span::styled("Ctrl+S", Style::default().fg(ctx.theme.accent)),
                 Span::styled(" 保存", Style::default().fg(ctx.theme.text_dim)),
                 Span::styled("  ", Style::default().fg(ctx.theme.text_dim)),
@@ -155,7 +175,11 @@ impl Mode for NavigationMode {
                 Span::styled("  ", Style::default().fg(ctx.theme.text_dim)),
                 Span::styled("Enter", Style::default().fg(ctx.theme.accent)),
                 Span::styled(" 编辑", Style::default().fg(ctx.theme.text_dim)),
-            ])),
+            ])
+        };
+
+        FooterLine {
+            hint: Some(hint),
             status: Some(Line::from(vec![
                 Span::styled("[", Style::default().fg(ctx.theme.text_dim)),
                 Span::styled(
@@ -208,3 +232,18 @@ impl NavigationMode {
         }
     }
 }
+
+fn format_number(n: f64) -> String {
+    if n == 0.0 {
+        return "0".to_string();
+    }
+
+    let abs = n.abs();
+    if abs < 1e-6 || abs >= 1e12 {
+        return format!("{:.2e}", n);
+    }
+
+    let text = format!("{:.10}", n);
+    let text = text.trim_end_matches('0');
+    text.trim_end_matches('.').to_string()
+}