WIP: map-line-numbersline-map

8 files changed, 73 insertions, 3 deletions

diff --git a/src/cli.rs b/src/cli.rs
index e1e47503..8743dbb8 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -697,6 +697,15 @@ pub struct Opt {
     /// An example is --map-styles='bold purple => red "#eeeeee", bold cyan => syntax "#eeeeee"'
     pub map_styles: Option<String>,
 
+    #[arg(long = "map-line-numbers")]
+    /// Output a line numbers map instead of the usual delta output.
+    ///
+    /// The output is a JSON document attempting to identify, for each file, for
+    /// each line in the old version of the file, the number of the
+    /// corresponding line in the new version of the file, if there is a
+    /// corresponding line.
+    pub map_line_numbers: bool,
+
     #[arg(long = "max-line-distance", default_value = "0.6", value_name = "DIST")]
     /// Maximum line pair distance parameter in within-line diff algorithm.
     ///
diff --git a/src/config.rs b/src/config.rs
index cab21eb7..da4ac16c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -94,6 +94,7 @@ pub struct Config {
     pub line_numbers_zero_style: Style,
     pub line_numbers: bool,
     pub styles_map: Option<HashMap<style::AnsiTermStyleEqualityKey, Style>>,
+    pub map_line_numbers: bool,
     pub max_line_distance_for_naively_paired_lines: f64,
     pub max_line_distance: f64,
     pub max_line_length: usize,
@@ -345,7 +346,8 @@ impl From<cli::Opt> for Config {
             } else {
                 line_fill_method
             },
-            line_numbers: opt.line_numbers && !handlers::hunk::is_word_diff(),
+            line_numbers: (opt.line_numbers || opt.map_line_numbers)
+                && !handlers::hunk::is_word_diff(),
             line_numbers_format: LeftRight::new(
                 opt.line_numbers_left_format,
                 opt.line_numbers_right_format,
@@ -360,6 +362,7 @@ impl From<cli::Opt> for Config {
             ),
             line_numbers_zero_style: styles["line-numbers-zero-style"],
             line_buffer_size: opt.line_buffer_size,
+            map_line_numbers: opt.map_line_numbers,
             max_line_distance: opt.max_line_distance,
             max_line_distance_for_naively_paired_lines,
             max_line_length: if opt.side_by_side {
@@ -395,7 +398,8 @@ impl From<cli::Opt> for Config {
             git_plus_style: styles["git-plus-style"],
             relative_paths: opt.relative_paths,
             show_themes: opt.show_themes,
-            side_by_side: opt.side_by_side && !handlers::hunk::is_word_diff(),
+            side_by_side: (opt.side_by_side || opt.map_line_numbers)
+                && !handlers::hunk::is_word_diff(),
             side_by_side_data,
             styles_map,
             syntax_dummy_theme: SyntaxTheme::default(),
diff --git a/src/features/line_numbers.rs b/src/features/line_numbers.rs
index 1c674b0f..f6498f96 100644
--- a/src/features/line_numbers.rs
+++ b/src/features/line_numbers.rs
@@ -120,6 +120,12 @@ pub fn format_and_paint_line_numbers<'a>(
     };
 
     if emit_left {
+        if config.map_line_numbers {
+            assert!(config.side_by_side && config.wrap_config.max_lines == 1);
+            if let Some(n) = line_numbers[Minus] {
+                print!("{},{}", line_numbers_data.plus_file, n)
+            }
+        }
         formatted_numbers.extend(format_and_paint_line_number_field(
             line_numbers_data,
             Minus,
@@ -130,6 +136,15 @@ pub fn format_and_paint_line_numbers<'a>(
     }
 
     if emit_right {
+        if config.map_line_numbers && line_numbers[Minus].is_some() {
+            println!(
+                ",{}",
+                line_numbers[Plus]
+                    .map(|n| n.to_string())
+                    .as_deref()
+                    .unwrap_or("null")
+            )
+        }
         formatted_numbers.extend(format_and_paint_line_number_field(
             line_numbers_data,
             Plus,
diff --git a/src/main.rs b/src/main.rs
index caf94cac..413ded4b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -112,6 +112,7 @@ fn run_app() -> std::io::Result<i32> {
     };
 
     let _show_config = opt.show_config;
+    let _map_line_numbers = opt.map_line_numbers;
     let config = config::Config::from(opt);
 
     if _show_config {
@@ -119,6 +120,9 @@ fn run_app() -> std::io::Result<i32> {
         let mut stdout = stdout.lock();
         subcommands::show_config::show_config(&config, &mut stdout)?;
         return Ok(0);
+    } else if _map_line_numbers {
+        subcommands::map_line_numbers::map_line_numbers(&config)?;
+        return Ok(0);
     }
 
     let mut output_type =
diff --git a/src/options/set.rs b/src/options/set.rs
index 732806a7..e0026aa8 100644
--- a/src/options/set.rs
+++ b/src/options/set.rs
@@ -170,6 +170,7 @@ pub fn set_options(
             inspect_raw_lines,
             keep_plus_minus_markers,
             line_buffer_size,
+            map_line_numbers,
             map_styles,
             max_line_distance,
             max_line_length,
diff --git a/src/subcommands/map_line_numbers.rs b/src/subcommands/map_line_numbers.rs
new file mode 100644
index 00000000..8b3f272e
--- /dev/null
+++ b/src/subcommands/map_line_numbers.rs
@@ -0,0 +1,32 @@
+use crate::config::Config;
+use crate::delta::delta;
+use bytelines::ByteLinesReader;
+use std::io::{self, ErrorKind, Write};
+
+#[cfg(not(tarpaulin_include))]
+pub fn map_line_numbers(config: &Config) -> std::io::Result<()> {
+    let mut writer = NullWriter {};
+    if let Err(error) = delta(io::stdin().lock().byte_lines(), &mut writer, &config) {
+        match error.kind() {
+            ErrorKind::BrokenPipe => return Ok(()),
+            _ => eprintln!("{error}"),
+        }
+    };
+    Ok(())
+}
+
+struct NullWriter {}
+
+impl Write for NullWriter {
+    fn write(&mut self, _buf: &[u8]) -> io::Result<usize> {
+        Ok(0)
+    }
+
+    fn write_all(&mut self, mut _buf: &[u8]) -> io::Result<()> {
+        Ok(())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
diff --git a/src/subcommands/mod.rs b/src/subcommands/mod.rs
index 26f04233..901ddb98 100644
--- a/src/subcommands/mod.rs
+++ b/src/subcommands/mod.rs
@@ -1,5 +1,6 @@
 pub mod diff;
 pub mod list_syntax_themes;
+pub mod map_line_numbers;
 pub mod parse_ansi;
 mod sample_diff;
 pub mod show_colors;
diff --git a/src/wrapping.rs b/src/wrapping.rs
index 40eff4f2..c327fb00 100644
--- a/src/wrapping.rs
+++ b/src/wrapping.rs
@@ -59,7 +59,11 @@ impl WrapConfig {
                     fatal("Invalid value for wrap-right-percent, not between 0 and 100.")
                 }
             },
-            max_lines: adapt_wrap_max_lines_argument(opt.wrap_max_lines.clone()),
+            max_lines: adapt_wrap_max_lines_argument(if opt.map_line_numbers {
+                "0".to_string()
+            } else {
+                opt.wrap_max_lines.clone()
+            }),
             inline_hint_syntect_style: SyntectStyle::from_delta_style(inline_hint_style),
         }
     }