Add line number width calculation

3 files changed, 154 insertions, 3 deletions

diff --git a/src/features/line_numbers.rs b/src/features/line_numbers.rs
index 2ac0de01..c8570ad2 100644
--- a/src/features/line_numbers.rs
+++ b/src/features/line_numbers.rs
@@ -136,7 +136,7 @@ lazy_static! {
     static ref LINE_NUMBERS_PLACEHOLDER_REGEX: Regex = format::make_placeholder_regex(&["nm", "np"]);
 }
 
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct LineNumbersData<'a> {
     pub format_data: PlusMinus<format::FormatStringData<'a>>,
     pub line_number: PlusMinus<usize>,
@@ -144,6 +144,8 @@ pub struct LineNumbersData<'a> {
     pub plus_file: String,
 }
 
+pub type SideBySideLineWidth = PlusMinus<usize>;
+
 // Although it's probably unusual, a single format string can contain multiple placeholders. E.g.
 // line-numbers-right-format = "{nm} {np}|"
 impl<'a> LineNumbersData<'a> {
@@ -170,6 +172,32 @@ impl<'a> LineNumbersData<'a> {
             1 + (hunk_max_line_number as f64).log10().floor() as usize;
         self.plus_file = plus_file;
     }
+
+    pub fn formatted_width(&self) -> SideBySideLineWidth {
+        let format_data_width = |format_data: &format::FormatStringData<'a>| {
+            // Provide each Placeholder with the max_line_number_width to calculate the
+            // actual width. Only use prefix and suffix of the last element, otherwise
+            // only the prefix (as the suffix also contains the following prefix).
+            format_data
+                .last()
+                .map(|last| {
+                    let (prefix_width, suffix_width) = last.width(self.hunk_max_line_number_width);
+                    format_data
+                        .iter()
+                        .rev()
+                        .skip(1)
+                        .map(|p| p.width(self.hunk_max_line_number_width).0)
+                        .sum::<usize>()
+                        + prefix_width
+                        + suffix_width
+                })
+                .unwrap_or(0)
+        };
+        PlusMinus::new(
+            format_data_width(&self.format_data[Left]),
+            format_data_width(&self.format_data[Right]),
+        )
+    }
 }
 
 #[allow(clippy::too_many_arguments)]
@@ -258,6 +286,8 @@ pub mod tests {
                 alignment_spec: None,
                 width: None,
                 suffix: "",
+                prefix_len: 0,
+                suffix_len: 0,
             }]
         )
     }
@@ -272,6 +302,8 @@ pub mod tests {
                 alignment_spec: None,
                 width: Some(4),
                 suffix: "",
+                prefix_len: 0,
+                suffix_len: 0,
             }]
         )
     }
@@ -286,6 +318,8 @@ pub mod tests {
                 alignment_spec: Some(">"),
                 width: Some(4),
                 suffix: "",
+                prefix_len: 0,
+                suffix_len: 0,
             }]
         )
     }
@@ -300,6 +334,8 @@ pub mod tests {
                 alignment_spec: Some(">"),
                 width: Some(4),
                 suffix: "",
+                prefix_len: 0,
+                suffix_len: 0,
             }]
         )
     }
@@ -314,6 +350,8 @@ pub mod tests {
                 alignment_spec: Some(">"),
                 width: Some(4),
                 suffix: "@@",
+                prefix_len: 2,
+                suffix_len: 2,
             }]
         )
     }
@@ -332,6 +370,8 @@ pub mod tests {
                     alignment_spec: Some("<"),
                     width: Some(3),
                     suffix: "@@---{np:_>4}**",
+                    prefix_len: 2,
+                    suffix_len: 15,
                 },
                 format::FormatStringPlaceholderData {
                     prefix: "@@---",
@@ -339,6 +379,8 @@ pub mod tests {
                     alignment_spec: Some(">"),
                     width: Some(4),
                     suffix: "**",
+                    prefix_len: 5,
+                    suffix_len: 2,
                 }
             ]
         )
@@ -354,10 +396,78 @@ pub mod tests {
                 alignment_spec: None,
                 width: None,
                 suffix: "__@@---**",
+                prefix_len: 0,
+                suffix_len: 9,
             },]
         )
     }
 
+    #[test]
+    fn test_line_number_placeholder_width_one() {
+        use format::parse_line_number_format;
+
+        let data = parse_line_number_format("", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(0), (0, 0));
+
+        let data = parse_line_number_format("", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (0, 0));
+
+        let data = parse_line_number_format("│+│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (0, 3));
+
+        let data = parse_line_number_format("{np}", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (4, 0));
+
+        let data = parse_line_number_format("│{np}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (5, 1));
+
+        let data = parse_line_number_format("│{np:2}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (5, 1));
+
+        let data = parse_line_number_format("│{np:6}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(4), (7, 1));
+    }
+
+    #[test]
+    fn test_line_number_placeholder_width_two() {
+        use format::parse_line_number_format;
+
+        let data = parse_line_number_format("│{nm}│{np}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(1), (2, 6));
+        assert_eq!(data[1].width(1), (2, 1));
+
+        let data = parse_line_number_format("│{nm:_>5}│{np:1}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(1), (6, 8));
+        assert_eq!(data[1].width(1), (2, 1));
+
+        let data = parse_line_number_format("│{nm}│{np:5}│", &LINE_NUMBERS_PLACEHOLDER_REGEX);
+        assert_eq!(data[0].width(7), (8, 8));
+        assert_eq!(data[1].width(7), (8, 1));
+    }
+
+    #[test]
+    fn test_line_numbers_data() {
+        let mut data = LineNumbersData::from_format_strings("", "");
+        data.initialize_hunk(&[(10, 11), (10000, 100001)], "a".into());
+        assert_eq!(data.formatted_width(), PlusMinus::new(0, 0));
+
+        let mut data = LineNumbersData::from_format_strings("│", "│+│");
+        data.initialize_hunk(&[(10, 11), (10000, 100001)], "a".into());
+        assert_eq!(data.formatted_width(), PlusMinus::new(1, 3));
+
+        let mut data = LineNumbersData::from_format_strings("│{nm:^3}│", "│{np:^3}│");
+        data.initialize_hunk(&[(10, 11), (10000, 100001)], "a".into());
+        assert_eq!(data.formatted_width(), PlusMinus::new(8, 8));
+
+        let mut data = LineNumbersData::from_format_strings("│{nm:^3}│ │{np:<12}│ │{nm}│", "");
+        data.initialize_hunk(&[(10, 11), (10000, 100001)], "a".into());
+        assert_eq!(data.formatted_width(), PlusMinus::new(32, 0));
+
+        let mut data = LineNumbersData::from_format_strings("│{np:^3}│ │{nm:<12}│ │{np}│", "");
+        data.initialize_hunk(&[(10, 11), (10000, 100001)], "a".into());
+        assert_eq!(data.formatted_width(), PlusMinus::new(32, 0));
+    }
+
     fn _get_capture<'a>(i: usize, j: usize, caps: &'a Vec<Captures>) -> &'a str {
         caps[i].get(j).map_or("", |m| m.as_str())
     }
diff --git a/src/features/side_by_side.rs b/src/features/side_by_side.rs
index ca493949..9b9a10f8 100644
--- a/src/features/side_by_side.rs
+++ b/src/features/side_by_side.rs
@@ -61,6 +61,23 @@ impl SideBySideData {
     }
 }
 
+pub fn available_line_width(
+    config: &Config,
+    data: &line_numbers::LineNumbersData,
+) -> line_numbers::SideBySideLineWidth {
+    let linennumbers_width = data.formatted_width();
+
+    // The width can be reduced by the line numbers and/or a possibly kept 1-wide "+/-/ " prefix.
+    let line_width = |side: PanelSide| {
+        config.side_by_side_data[side]
+            .width
+            .saturating_sub(linennumbers_width[side])
+            .saturating_sub(config.keep_plus_minus_markers as usize)
+    };
+
+    LeftRight::new(line_width(Left), line_width(Right))
+}
+
 /// Emit a sequence of minus and plus lines in side-by-side mode.
 #[allow(clippy::too_many_arguments)]
 pub fn paint_minus_and_plus_lines_side_by_side<'a>(
diff --git a/src/format.rs b/src/format.rs
index 67d1f509..1f8bfb00 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -1,4 +1,5 @@
 use regex::Regex;
+use unicode_segmentation::UnicodeSegmentation;
 
 #[derive(Debug, Default, PartialEq)]
 pub struct FormatStringPlaceholderData<'a> {
@@ -7,6 +8,23 @@ pub struct FormatStringPlaceholderData<'a> {
     pub alignment_spec: Option<&'a str>,
     pub width: Option<usize>,
     pub suffix: &'a str,
+    pub prefix_len: usize,
+    pub suffix_len: usize,
+}
+
+impl<'a> FormatStringPlaceholderData<'a> {
+    pub fn width(&self, hunk_max_line_number_width: usize) -> (usize, usize) {
+        // Only if Some(placeholder) is present will there be a number formatted
+        // by this placeholder, if not width is also None.
+        (
+            self.prefix_len
+                + std::cmp::max(
+                    self.placeholder.map_or(0, |_| hunk_max_line_number_width),
+                    self.width.unwrap_or(0),
+                ),
+            self.suffix_len,
+        )
+    }
 }
 
 pub type FormatStringData<'a> = Vec<FormatStringPlaceholderData<'a>>;
@@ -40,8 +58,10 @@ pub fn parse_line_number_format<'a>(
 
     for captures in placeholder_regex.captures_iter(format_string) {
         let _match = captures.get(0).unwrap();
+        let prefix = &format_string[offset.._match.start()];
+        let suffix = &format_string[_match.end()..];
         format_data.push(FormatStringPlaceholderData {
-            prefix: &format_string[offset.._match.start()],
+            prefix,
             placeholder: captures.get(1).map(|m| m.as_str()),
             alignment_spec: captures.get(3).map(|m| m.as_str()),
             width: captures.get(4).map(|m| {
@@ -49,7 +69,9 @@ pub fn parse_line_number_format<'a>(
                     .parse()
                     .unwrap_or_else(|_| panic!("Invalid width in format string: {}", format_string))
             }),
-            suffix: &format_string[_match.end()..],
+            suffix,
+            prefix_len: prefix.graphemes(true).count(),
+            suffix_len: suffix.graphemes(true).count(),
         });
         offset = _match.end();
     }
@@ -61,6 +83,8 @@ pub fn parse_line_number_format<'a>(
             alignment_spec: None,
             width: None,
             suffix: &format_string[0..],
+            prefix_len: 0,
+            suffix_len: format_string.graphemes(true).count(),
         })
     }
     format_data