From 44bf996941552c6caf2fe1298bfb458a3925be6b Mon Sep 17 00:00:00 2001
From: rhysd <lin90162@yahoo.co.jp>
Date: Mon, 11 Jul 2022 02:48:33 +0900
Subject: [PATCH] separate implementation for highlighting to
 `src/highlight.rs`

---
 src/highlight.rs | 166 +++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs       |   2 +
 src/textarea.rs  | 145 ++++-------------------------------------
 src/util.rs      |   8 +++
 4 files changed, 188 insertions(+), 133 deletions(-)
 create mode 100644 src/highlight.rs
 create mode 100644 src/util.rs

diff --git a/src/highlight.rs b/src/highlight.rs
new file mode 100644
index 0000000..8fac916
--- /dev/null
+++ b/src/highlight.rs
@@ -0,0 +1,166 @@
+use crate::util::{num_digits, spaces};
+use std::borrow::Cow;
+use std::cmp::Ordering;
+use tui::style::Style;
+use tui::text::{Span, Spans};
+
+enum Boundary {
+    Cursor(Style),
+    #[cfg(feature = "search")]
+    Search(Style),
+    End,
+}
+
+impl Boundary {
+    fn cmp(&self, other: &Boundary) -> Ordering {
+        fn rank(b: &Boundary) -> u8 {
+            match b {
+                Boundary::Cursor(_) => 2,
+                #[cfg(feature = "search")]
+                Boundary::Search(_) => 1,
+                Boundary::End => 0,
+            }
+        }
+        rank(self).cmp(&rank(other))
+    }
+
+    fn style(&self) -> Option<Style> {
+        match self {
+            Boundary::Cursor(s) => Some(*s),
+            #[cfg(feature = "search")]
+            Boundary::Search(s) => Some(*s),
+            Boundary::End => None,
+        }
+    }
+}
+
+fn replace_tabs(s: &str, tab_len: u8) -> Cow<'_, str> {
+    let tab = spaces(tab_len);
+    let mut buf = String::new();
+    for (i, c) in s.char_indices() {
+        if buf.is_empty() {
+            if c == '\t' {
+                buf.reserve(s.len());
+                buf.push_str(&s[..i]);
+                buf.push_str(tab);
+            }
+        } else if c == '\t' {
+            buf.push_str(tab);
+        } else {
+            buf.push(c);
+        }
+    }
+    if buf.is_empty() {
+        Cow::Borrowed(s)
+    } else {
+        Cow::Owned(buf)
+    }
+}
+
+pub struct LineHighlighter<'a> {
+    line: &'a str,
+    spans: Vec<Span<'a>>,
+    boundaries: Vec<(Boundary, usize)>, // TODO: Consider smallvec
+    style_begin: Style,
+    cursor_at_end: bool,
+    cursor_style: Style,
+    tab_len: u8,
+}
+
+impl<'a> LineHighlighter<'a> {
+    pub fn new(line: &'a str, cursor_style: Style, tab_len: u8) -> Self {
+        Self {
+            line,
+            spans: vec![],
+            boundaries: vec![],
+            style_begin: Style::default(),
+            cursor_at_end: false,
+            cursor_style,
+            tab_len,
+        }
+    }
+
+    pub fn line_number(&mut self, row: usize, lnum_len: u8, style: Style) {
+        let pad = spaces(lnum_len - num_digits(row + 1) + 1);
+        self.spans
+            .push(Span::styled(format!("{}{} ", pad, row + 1), style));
+    }
+
+    pub fn cursor_line(&mut self, cursor_col: usize, style: Style) {
+        if let Some((start, c)) = self.line.char_indices().nth(cursor_col) {
+            self.boundaries
+                .push((Boundary::Cursor(self.cursor_style), start));
+            self.boundaries.push((Boundary::End, start + c.len_utf8()));
+        } else {
+            self.cursor_at_end = true;
+        }
+        self.style_begin = style;
+    }
+
+    #[cfg(feature = "search")]
+    pub fn search(&mut self, matches: impl Iterator<Item = (usize, usize)>, style: Style) {
+        for (start, end) in matches {
+            if start != end {
+                self.boundaries.push((Boundary::Search(style), start));
+                self.boundaries.push((Boundary::End, end));
+            }
+        }
+    }
+
+    pub fn into_spans(self) -> Spans<'a> {
+        let Self {
+            line,
+            mut spans,
+            mut boundaries,
+            tab_len,
+            style_begin,
+            cursor_style,
+            cursor_at_end,
+        } = self;
+
+        if boundaries.is_empty() {
+            spans.push(Span::styled(replace_tabs(line, tab_len), style_begin));
+            if cursor_at_end {
+                spans.push(Span::styled(" ", cursor_style));
+            }
+            return Spans::from(spans);
+        }
+
+        boundaries.sort_unstable_by(|(l, i), (r, j)| match i.cmp(j) {
+            Ordering::Equal => l.cmp(r),
+            o => o,
+        });
+
+        let mut boundaries = boundaries.into_iter();
+        let mut style = style_begin;
+        let mut start = 0;
+        let mut stack = vec![];
+
+        loop {
+            if let Some((next_boundary, end)) = boundaries.next() {
+                if start < end {
+                    spans.push(Span::styled(
+                        replace_tabs(&line[start..end], tab_len),
+                        style,
+                    ));
+                }
+
+                style = if let Some(s) = next_boundary.style() {
+                    stack.push(style);
+                    s
+                } else {
+                    stack.pop().unwrap_or(style_begin)
+                };
+                start = end;
+            } else {
+                if start != line.len() {
+                    spans.push(Span::styled(replace_tabs(&line[start..], tab_len), style));
+                }
+                if cursor_at_end {
+                    spans.push(Span::styled(" ", cursor_style));
+                }
+                return Spans::from(spans);
+            }
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 882bcf5..ba9bce9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,11 +4,13 @@
 #![doc = include_str!("../README.md")]
 
 mod cursor;
+mod highlight;
 mod history;
 mod input;
 #[cfg(feature = "search")]
 mod search;
 mod textarea;
+mod util;
 mod word;
 
 pub use cursor::CursorMove;
diff --git a/src/textarea.rs b/src/textarea.rs
index 877d210..1ad431f 100644
--- a/src/textarea.rs
+++ b/src/textarea.rs
@@ -1,58 +1,18 @@
 use crate::cursor::CursorMove;
+use crate::highlight::LineHighlighter;
 use crate::history::{Edit, EditKind, History};
 use crate::input::{Input, Key};
 #[cfg(feature = "search")]
 use crate::search::Search;
+use crate::util::{num_digits, spaces};
 use crate::word::{find_word_end_forward, find_word_start_backward};
-use std::borrow::Cow;
-use std::cmp;
 use std::sync::atomic::{AtomicU16, Ordering};
 use tui::buffer::Buffer;
 use tui::layout::Rect;
 use tui::style::{Modifier, Style};
-use tui::text::{Span, Spans, Text};
+use tui::text::{Spans, Text};
 use tui::widgets::{Block, Paragraph, Widget};
 
-fn spaces(size: u8) -> &'static str {
-    const SPACES: &str = "                                                                                                                                                                                                                                                                ";
-    &SPACES[..size as usize]
-}
-
-fn num_digits(i: usize) -> u8 {
-    f64::log10(i as f64) as u8 + 1
-}
-
-// Highlight boundary in line
-enum Boundary {
-    Cursor(Style),
-    #[cfg(feature = "search")]
-    Search(Style),
-    End,
-}
-
-impl Boundary {
-    fn cmp(&self, other: &Boundary) -> cmp::Ordering {
-        fn rank(b: &Boundary) -> u8 {
-            match b {
-                Boundary::Cursor(_) => 2,
-                #[cfg(feature = "search")]
-                Boundary::Search(_) => 1,
-                Boundary::End => 0,
-            }
-        }
-        rank(self).cmp(&rank(other))
-    }
-
-    fn style(&self) -> Option<Style> {
-        match self {
-            Boundary::Cursor(s) => Some(*s),
-            #[cfg(feature = "search")]
-            Boundary::Search(s) => Some(*s),
-            Boundary::End => None,
-        }
-    }
-}
-
 /// A type to manage state of textarea.
 ///
 /// [`TextArea::default`] creates an empty textarea. [`TextArea::new`] creates a textarea with given text lines.
@@ -956,103 +916,23 @@ impl<'a> TextArea<'a> {
         }
     }
 
-    fn replace_tabs<'b>(&self, s: &'b str) -> Cow<'b, str> {
-        let tab = spaces(self.tab_len);
-        let mut buf = String::new();
-        for (i, c) in s.char_indices() {
-            if buf.is_empty() {
-                if c == '\t' {
-                    buf.reserve(s.len());
-                    buf.push_str(&s[..i]);
-                    buf.push_str(tab);
-                }
-            } else if c == '\t' {
-                buf.push_str(tab);
-            } else {
-                buf.push(c);
-            }
-        }
-        if buf.is_empty() {
-            Cow::Borrowed(s)
-        } else {
-            Cow::Owned(buf)
-        }
-    }
-
-    fn line_spans<'b>(&'b self, line: &'b str, row: usize, lnum_len: u8) -> Vec<Span<'b>> {
-        let mut spans = vec![];
+    fn line_spans<'b>(&'b self, line: &'b str, row: usize, lnum_len: u8) -> Spans<'b> {
+        let mut hl = LineHighlighter::new(line, self.cursor_style, self.tab_len);
 
         if let Some(style) = self.line_number_style {
-            let pad = spaces(lnum_len - num_digits(row + 1) + 1);
-            spans.push(Span::styled(format!("{}{} ", pad, row + 1), style));
+            hl.line_number(row, lnum_len, style);
         }
 
-        let mut boundaries = vec![]; // TODO: Consider smallvec
-        let mut cursor_at_end = false;
-
-        let style_begin = if row == self.cursor.0 {
-            if let Some((start, c)) = line.char_indices().nth(self.cursor.1) {
-                boundaries.push((Boundary::Cursor(self.cursor_style), start));
-                boundaries.push((Boundary::End, start + c.len_utf8()));
-            } else {
-                cursor_at_end = true;
-            }
-            self.cursor_line_style
-        } else {
-            Style::default()
-        };
+        if row == self.cursor.0 {
+            hl.cursor_line(self.cursor.1, self.cursor_line_style);
+        }
 
         #[cfg(feature = "search")]
         if let Some(matches) = self.search.matches(line) {
-            for (start, end) in matches {
-                if start != end {
-                    boundaries.push((Boundary::Search(self.search.style), start));
-                    boundaries.push((Boundary::End, end));
-                }
-            }
+            hl.search(matches, self.search.style);
         }
 
-        if boundaries.is_empty() {
-            spans.push(Span::styled(self.replace_tabs(line), style_begin));
-            if cursor_at_end {
-                spans.push(Span::styled(" ", self.cursor_style));
-            }
-            return spans;
-        }
-
-        boundaries.sort_unstable_by(|(l, i), (r, j)| match i.cmp(j) {
-            cmp::Ordering::Equal => l.cmp(r),
-            o => o,
-        });
-
-        let mut boundaries = boundaries.into_iter();
-        let mut style = style_begin;
-        let mut start = 0;
-        let mut stack = vec![];
-
-        loop {
-            if let Some((next_boundary, end)) = boundaries.next() {
-                if start < end {
-                    spans.push(Span::styled(self.replace_tabs(&line[start..end]), style));
-                }
-
-                style = if let Some(s) = next_boundary.style() {
-                    stack.push(style);
-                    s
-                } else {
-                    stack.pop().unwrap_or(style_begin)
-                };
-                start = end;
-            } else {
-                if start != line.len() {
-                    spans.push(Span::styled(self.replace_tabs(&line[start..]), style));
-                }
-                if cursor_at_end {
-                    spans.push(Span::styled(" ", self.cursor_style));
-                }
-                return spans;
-            }
-        }
+        hl.into_spans()
     }
 
     /// Build a tui-rs widget to render the current state of the textarea. The widget instance returned from this
@@ -1085,8 +965,7 @@ impl<'a> TextArea<'a> {
         let mut lines = Vec::with_capacity(self.lines.len());
         let lnum_len = num_digits(self.lines.len());
         for (i, l) in self.lines.iter().map(String::as_str).enumerate() {
-            let spans = self.line_spans(l, i, lnum_len);
-            lines.push(Spans::from(spans));
+            lines.push(self.line_spans(l, i, lnum_len));
         }
 
         let inner = Paragraph::new(Text::from(lines)).style(self.style);
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..f0e90e0
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,8 @@
+pub fn spaces(size: u8) -> &'static str {
+    const SPACES: &str = "                                                                                                                                                                                                                                                                ";
+    &SPACES[..size as usize]
+}
+
+pub fn num_digits(i: usize) -> u8 {
+    f64::log10(i as f64) as u8 + 1
+}