From b23ff24ebcca480449fbcf6286d81e7e4429b2a8 Mon Sep 17 00:00:00 2001
From: eth-p <32112321+eth-p@users.noreply.github.com>
Date: Mon, 10 Sep 2018 18:11:59 -0700
Subject: [PATCH] Added tab expansion preprocessing step.

---
 src/app.rs          | 18 ++++++++++++++++++
 src/main.rs         |  1 +
 src/preprocessor.rs | 35 +++++++++++++++++++++++++++++++++++
 src/printer.rs      | 11 ++++++++++-
 4 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 src/preprocessor.rs

diff --git a/src/app.rs b/src/app.rs
index a9ac691e..f2e2a84c 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -41,6 +41,9 @@ pub struct Config<'a> {
     /// The character width of the terminal
     pub term_width: usize,
 
+    /// The width of tab characters.
+    pub tab_width: usize,
+
     /// Whether or not to simply loop through all input (`cat` mode)
     pub loop_through: bool,
 
@@ -276,6 +279,15 @@ impl App {
                          'unbuffered'). The output is always unbuffered - this option \
                          is simply ignored.",
                     ),
+            ).arg(
+                Arg::with_name("tabs")
+                    .long("tabs")
+                    .short("t")
+                    .takes_value(true)
+                    .value_name("width")
+                    .help("Sets the tab width.")
+                    .long_help("Sets the tab width. Use a width of 0 to pass tabs through \
+                        directly"),
             ).arg(
                 Arg::with_name("terminal-width")
                     .long("terminal-width")
@@ -393,6 +405,12 @@ impl App {
                 || self.matches.value_of("color") == Some("always")
                 || self.matches.value_of("decorations") == Some("always")),
             files,
+            tab_width: self
+                .matches
+                .value_of("tabs")
+                .and_then(|w| w.parse().ok())
+                .or_else(|| env::var("BAT_TABS").ok().and_then(|w| w.parse().ok()))
+                .unwrap_or(8),
             theme: self
                 .matches
                 .value_of("theme")
diff --git a/src/main.rs b/src/main.rs
index ff87f9b8..bc3d11aa 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,6 +24,7 @@ mod decorations;
 mod diff;
 mod line_range;
 mod output;
+mod preprocessor;
 mod printer;
 mod style;
 mod terminal;
diff --git a/src/preprocessor.rs b/src/preprocessor.rs
new file mode 100644
index 00000000..5d266abf
--- /dev/null
+++ b/src/preprocessor.rs
@@ -0,0 +1,35 @@
+use console::AnsiCodeIterator;
+
+/// Expand tabs like an ANSI-enabled expand(1).
+pub fn expand(line: &str, width: usize) -> String {
+    let mut buffer = String::with_capacity(line.len() * 2);
+    let mut cursor = 0;
+
+    for chunk in AnsiCodeIterator::new(line) {
+        match chunk {
+            (text, true) => buffer.push_str(text),
+            (mut text, false) => {
+                while let Some(index) = text.find('\t') {
+                    // Add previous text.
+                    if index > 0 {
+                        cursor += index;
+                        buffer.push_str(&text[0..index]);
+                    }
+
+                    // Add tab.
+                    let spaces = width - (cursor % width);
+                    cursor += spaces;
+                    buffer.push_str(&*" ".repeat(spaces));
+
+                    // Next.
+                    text = &text[index + 1..text.len()];
+                }
+
+                cursor += text.len();
+                buffer.push_str(text);
+            }
+        }
+    }
+
+    buffer
+}
diff --git a/src/printer.rs b/src/printer.rs
index afa2ac8b..dc0137da 100644
--- a/src/printer.rs
+++ b/src/printer.rs
@@ -16,6 +16,7 @@ use decorations::{Decoration, GridBorderDecoration, LineChangesDecoration, LineN
 use diff::get_git_diff;
 use diff::LineChanges;
 use errors::*;
+use preprocessor::expand;
 use style::OutputWrap;
 use terminal::{as_terminal_escaped, to_ansi_color};
 
@@ -200,9 +201,17 @@ impl<'a> Printer for InteractivePrinter<'a> {
         line_number: usize,
         line_buffer: &[u8],
     ) -> Result<()> {
-        let line = String::from_utf8_lossy(&line_buffer);
+        let mut line = String::from_utf8_lossy(&line_buffer).to_string();
+
+        // Preprocess.
+        if self.config.tab_width > 0 {
+            line = expand(&line, self.config.tab_width);
+        }
+
+        // Highlight.
         let regions = self.highlighter.highlight(line.as_ref());
 
+        // Print.
         if out_of_range {
             return Ok(());
         }