New option to map raw styles encountered in input

Fixes #72

src/cli.rs

@@ -429,6 +429,12 @@ pub struct Opt {
     /// (underline), 'ol' (overline), or the combination 'ul ol'.
     pub hunk_header_decoration_style: String,
 
+    #[structopt(long = "map-styles")]
+    /// A string specifying a mapping styles encountered in raw input to desired
+    /// output styles. An example is --map-styles='black cyan => white magenta,
+    /// red cyan => white blue'
+    pub map_styles: Option<String>,
+
     /// Format string for git blame commit metadata. Available placeholders are
     /// "{timestamp}", "{author}", and "{commit}".
     #[structopt(

src/config.rs

@@ -20,6 +20,7 @@ use crate::git_config::{GitConfig, GitConfigEntry};
 use crate::minusplus::MinusPlus;
 use crate::paint::BgFillMethod;
 use crate::parse_styles;
+use crate::style;
 use crate::style::Style;
 use crate::tests::TESTING;
 use crate::utils::bat::output::PagingMode;
@@ -105,6 +106,7 @@ pub struct Config {
     pub line_numbers_style_minusplus: MinusPlus<Style>,
     pub line_numbers_zero_style: Style,
     pub line_numbers: bool,
+    pub styles_map: Option<HashMap<style::AnsiTermStyleEqualityKey, ansi_term::Style>>,
     pub max_line_distance_for_naively_paired_lines: f64,
     pub max_line_distance: f64,
     pub max_line_length: usize,
@@ -157,6 +159,7 @@ impl Config {
 impl From<cli::Opt> for Config {
     fn from(opt: cli::Opt) -> Self {
         let styles = parse_styles::parse_styles(&opt);
+        let styles_map = make_styles_map(&opt);
 
         let max_line_distance_for_naively_paired_lines =
             env::get_env_var("DELTA_EXPERIMENTAL_MAX_LINE_DISTANCE_FOR_NAIVELY_PAIRED_LINES")
@@ -297,6 +300,7 @@ impl From<cli::Opt> for Config {
             ),
             line_numbers_zero_style: styles["line-numbers-zero-style"],
             line_buffer_size: opt.line_buffer_size,
+            styles_map,
             max_line_distance: opt.max_line_distance,
             max_line_distance_for_naively_paired_lines,
             max_line_length: match (opt.side_by_side, wrap_max_lines_plus1) {
@@ -396,6 +400,31 @@ fn make_blame_palette(blame_palette: Option<String>, is_light_mode: bool) -> Vec
     }
 }
 
+fn make_styles_map(
+    opt: &cli::Opt,
+) -> Option<HashMap<style::AnsiTermStyleEqualityKey, ansi_term::Style>> {
+    if let Some(styles_map_str) = &opt.map_styles {
+        let mut styles_map = HashMap::new();
+        for pair_str in styles_map_str.split(",") {
+            let mut style_strs = pair_str.split("=>").map(|s| s.trim());
+            if let (Some(from_str), Some(to_str)) = (style_strs.next(), style_strs.next()) {
+                let key = style::ansi_term_style_equality_key(
+                    Style::from_str(from_str, None, None, true, opt.git_config.as_ref())
+                        .ansi_term_style,
+                );
+                styles_map.insert(
+                    key,
+                    Style::from_str(to_str, None, None, true, opt.git_config.as_ref())
+                        .ansi_term_style,
+                );
+            }
+        }
+        Some(styles_map)
+    } else {
+        None
+    }
+}
+
 /// Did the user supply `option` on the command line?
 pub fn user_supplied_option(option: &str, arg_matches: &clap::ArgMatches) -> bool {
     arg_matches.occurrences_of(option) > 0

src/options/set.rs

@@ -157,6 +157,7 @@ pub fn set_options(
             inspect_raw_lines,
             keep_plus_minus_markers,
             line_buffer_size,
+            map_styles,
             max_line_distance,
             max_line_length,
             // Hack: minus-style must come before minus-*emph-style because the latter default

src/paint.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::io::Write;
 
 use itertools::Itertools;
@@ -6,7 +7,6 @@ use syntect::highlighting::Style as SyntectStyle;
 use syntect::parsing::{SyntaxReference, SyntaxSet};
 use unicode_segmentation::UnicodeSegmentation;
 
-use crate::ansi;
 use crate::config::{self, delta_unreachable, Config};
 use crate::delta::State;
 use crate::edits;
@@ -18,6 +18,7 @@ use crate::minusplus::*;
 use crate::paint::superimpose_style_sections::superimpose_style_sections;
 use crate::style::Style;
 use crate::wrapping::wrap_minusplus_block;
+use crate::{ansi, style};
 
 pub struct Painter<'p> {
     pub minus_lines: Vec<(String, State)>,
@@ -138,7 +139,7 @@ impl<'p> Painter<'p> {
     /// ANSI escape sequences.
     pub fn prepare_raw_line(&self, line: &str) -> String {
         ansi::ansi_preserving_slice(
-            &self.expand_tabs(line.graphemes(true)),
+            &self.expand_tabs(self.map_styles(line).graphemes(true)),
             if self.config.keep_plus_minus_markers {
                 0
             } else {
@@ -147,6 +148,23 @@ impl<'p> Painter<'p> {
         )
     }
 
+    fn map_styles<'a>(&self, line: &'a str) -> Cow<'a, str> {
+        if let Some(styles_map) = &self.config.styles_map {
+            let transformed_line = ansi::parse_style_sections(line)
+                .iter()
+                .map(|(original_style, s)| {
+                    match styles_map.get(&style::ansi_term_style_equality_key(*original_style)) {
+                        Some(mapped_style) => mapped_style.paint(*s),
+                        None => original_style.paint(*s),
+                    }
+                })
+                .join("");
+            Cow::from(transformed_line)
+        } else {
+            Cow::from(line)
+        }
+    }
+
     /// Expand tabs as spaces.
     /// tab_width = 0 is documented to mean do not replace tabs.
     pub fn expand_tabs<'a, I>(&self, line: I) -> String

src/style.rs

@@ -1,5 +1,6 @@
 use std::borrow::Cow;
 use std::fmt;
+use std::hash::{Hash, Hasher};
 
 use lazy_static::lazy_static;
 
@@ -210,6 +211,60 @@ pub fn ansi_term_style_equality(a: ansi_term::Style, b: ansi_term::Style) -> boo
     }
 }
 
+// TODO: The equality methods were implemented first, and the equality_key
+// methods later. The former should be re-implemented in terms of the latter.
+// But why did the former not address equality of ansi_term::Color::RGB values?
+pub struct AnsiTermStyleEqualityKey {
+    attrs_key: (bool, bool, bool, bool, bool, bool, bool, bool),
+    foreground_key: Option<(u8, u8, u8, u8)>,
+    background_key: Option<(u8, u8, u8, u8)>,
+}
+
+impl PartialEq for AnsiTermStyleEqualityKey {
+    fn eq(&self, other: &Self) -> bool {
+        let option_eq = |opt_a, opt_b| match (opt_a, opt_b) {
+            (Some(a), Some(b)) => a == b,
+            (None, None) => true,
+            _ => false,
+        };
+
+        if self.attrs_key != other.attrs_key {
+            false
+        } else {
+            option_eq(self.foreground_key, other.foreground_key)
+                && option_eq(self.background_key, other.background_key)
+        }
+    }
+}
+
+impl Eq for AnsiTermStyleEqualityKey {}
+
+impl Hash for AnsiTermStyleEqualityKey {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.attrs_key.hash(state);
+        self.foreground_key.hash(state);
+        self.background_key.hash(state);
+    }
+}
+
+pub fn ansi_term_style_equality_key(style: ansi_term::Style) -> AnsiTermStyleEqualityKey {
+    let attrs_key = (
+        style.is_bold,
+        style.is_dimmed,
+        style.is_italic,
+        style.is_underline,
+        style.is_blink,
+        style.is_reverse,
+        style.is_hidden,
+        style.is_strikethrough,
+    );
+    AnsiTermStyleEqualityKey {
+        attrs_key,
+        foreground_key: style.foreground.map(ansi_term_color_equality_key),
+        background_key: style.background.map(ansi_term_color_equality_key),
+    }
+}
+
 fn ansi_term_color_equality(a: Option<ansi_term::Color>, b: Option<ansi_term::Color>) -> bool {
     match (a, b) {
         (None, None) => true,
@@ -239,6 +294,26 @@ fn ansi_term_16_color_equality(a: ansi_term::Color, b: ansi_term::Color) -> bool
     )
 }
 
+fn ansi_term_color_equality_key(color: ansi_term::Color) -> (u8, u8, u8, u8) {
+    // Same (r, g, b, a) encoding as in utils::bat::terminal::to_ansi_color.
+    // When a = 0xFF, then a 256-color number is stored in the red channel, and
+    // the green and blue channels are meaningless. But a=0 signifies an RGB
+    // color.
+    let default = 0xFF;
+    match color {
+        ansi_term::Color::Fixed(0) | ansi_term::Color::Black => (0, default, default, default),
+        ansi_term::Color::Fixed(1) | ansi_term::Color::Red => (1, default, default, default),
+        ansi_term::Color::Fixed(2) | ansi_term::Color::Green => (2, default, default, default),
+        ansi_term::Color::Fixed(3) | ansi_term::Color::Yellow => (3, default, default, default),
+        ansi_term::Color::Fixed(4) | ansi_term::Color::Blue => (4, default, default, default),
+        ansi_term::Color::Fixed(5) | ansi_term::Color::Purple => (5, default, default, default),
+        ansi_term::Color::Fixed(6) | ansi_term::Color::Cyan => (6, default, default, default),
+        ansi_term::Color::Fixed(7) | ansi_term::Color::White => (7, default, default, default),
+        ansi_term::Color::Fixed(n) => (n, default, default, default),
+        ansi_term::Color::RGB(r, g, b) => (r, g, b, 0),
+    }
+}
+
 lazy_static! {
     pub static ref GIT_DEFAULT_MINUS_STYLE: Style = Style {
         ansi_term_style: ansi_term::Color::Red.normal(),