add theme option (#95)

closes #89

src/app.rs

@@ -85,6 +85,17 @@ impl App {
                     .long("list-languages")
                     .help("Displays supported languages"),
             )
+            .arg(
+                Arg::with_name("theme")
+                    .long("theme")
+                    .takes_value(true)
+                    .help("Set the theme for highlighting"),
+            )
+            .arg(
+                Arg::with_name("list-themes")
+                    .long("list-themes")
+                    .help("Displays supported themes"),
+            )
             .subcommand(
                 SubCommand::with_name("cache")
                     .about("Modify the syntax-definition and theme cache")
@@ -143,6 +154,7 @@ impl App {
             },
             term_width: Term::stdout().size().1 as usize,
             files,
+            theme: self.matches.value_of("theme"),
         })
     }
 
@@ -185,6 +197,7 @@ pub struct Config<'a> {
     pub paging: bool,
     pub term_width: usize,
     pub files: Vec<Option<&'a str>>,
+    pub theme: Option<&'a str>,
 }
 
 fn is_truecolor_terminal() -> bool {

src/assets.rs

@@ -126,11 +126,13 @@ impl HighlightingAssets {
         Ok(())
     }
 
-    pub fn default_theme(&self) -> Result<&Theme> {
+    pub fn get_theme(&self, theme: &str) -> Result<&Theme> {
-        Ok(self.theme_set
+        Ok(self.theme_set.themes.get(theme).ok_or_else(|| {
-            .themes
+            io::Error::new(
-            .get("Default")
+                io::ErrorKind::Other,
-            .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "Could not find 'Default' theme"))?)
+                format!("Could not find '{}' theme", theme),
+            )
+        })?)
     }
 }
 

src/main.rs

@@ -223,7 +223,7 @@ fn run() -> Result<()> {
             let config = app.config()?;
 
             let assets = HighlightingAssets::new();
-            let theme = assets.default_theme()?;
+            let theme = assets.get_theme(config.theme.unwrap_or("Default"))?;
 
             if app.matches.is_present("list-languages") {
                 let languages = assets.syntax_set.syntaxes();
@@ -269,6 +269,14 @@ fn run() -> Result<()> {
                 return Ok(());
             }
 
+            if app.matches.is_present("list-themes") {
+                let themes = &assets.theme_set.themes;
+                for (theme, _) in themes.iter() {
+                    println!("{}", theme);
+                }
+                return Ok(());
+            }
+
             let mut output_type = get_output_type(config.paging);
             let handle = output_type.handle()?;
             let mut printer = Printer::new(handle, &config);