Add printer

This adds a separate struct that handles printing of the different
tokens.

src/printer.rs

@@ -0,0 +1,145 @@
+use ansi_term::Style;
+use console::Term;
+use errors::*;
+use std::io::Write;
+use syntect::highlighting;
+use terminal::as_terminal_escaped;
+use {Colors, LineChange, LineChanges, Options, OptionsStyle};
+
+const PANEL_WIDTH: usize = 7;
+
+pub struct Printer<'a> {
+    handle: &'a mut Write,
+    colors: Colors,
+    term_width: usize,
+    options: &'a Options<'a>,
+    pub line_changes: Option<LineChanges>,
+}
+
+impl<'a> Printer<'a> {
+    pub fn new(handle: &'a mut Write, options: &'a Options) -> Self {
+        let (_, term_width) = Term::stdout().size();
+        let term_width = term_width as usize;
+
+        let colors = if options.colored_output {
+            Colors::colored()
+        } else {
+            Colors::plain()
+        };
+
+        Printer {
+            handle,
+            colors,
+            term_width,
+            options,
+            line_changes: None,
+        }
+    }
+
+    pub fn print_header(&mut self, filename: &str) -> Result<()> {
+        match self.options.style {
+            OptionsStyle::Full => {}
+            _ => return Ok(()),
+        }
+
+        self.print_horizontal_line('┬')?;
+
+        writeln!(
+            self.handle,
+            "{}{} File {}",
+            " ".repeat(PANEL_WIDTH),
+            self.colors.grid.paint("│"),
+            self.colors.filename.paint(filename)
+        )?;
+
+        self.print_horizontal_line('┼')
+    }
+
+    pub fn print_footer(&mut self) -> Result<()> {
+        if let OptionsStyle::Full = self.options.style {
+            self.print_horizontal_line('┴')
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn print_line(
+        &mut self,
+        line_number: usize,
+        regions: &[(highlighting::Style, &str)],
+    ) -> Result<()> {
+        let decorations = vec![
+            self.print_line_number(line_number),
+            self.print_git_marker(line_number),
+            self.print_line_border(),
+            Some(as_terminal_escaped(
+                &regions,
+                self.options.true_color,
+                self.options.colored_output,
+            )),
+        ];
+
+        write!(
+            self.handle,
+            "{}",
+            decorations
+                .into_iter()
+                .filter_map(|dec| dec)
+                .collect::<Vec<_>>()
+                .join(" ")
+        )?;
+
+        Ok(())
+    }
+
+    fn print_line_number(&self, line_number: usize) -> Option<String> {
+        if let OptionsStyle::Plain = self.options.style {
+            return None;
+        }
+
+        Some(
+            self.colors
+                .line_number
+                .paint(format!("{:4}", line_number))
+                .to_string(),
+        )
+    }
+
+    fn print_git_marker(&self, line_number: usize) -> Option<String> {
+        match self.options.style {
+            OptionsStyle::Full => {}
+            _ => return None,
+        }
+
+        let marker = if let Some(ref changes) = self.line_changes {
+            match changes.get(&(line_number as u32)) {
+                Some(&LineChange::Added) => self.colors.git_added.paint("+"),
+                Some(&LineChange::RemovedAbove) => self.colors.git_removed.paint("‾"),
+                Some(&LineChange::RemovedBelow) => self.colors.git_removed.paint("_"),
+                Some(&LineChange::Modified) => self.colors.git_modified.paint("~"),
+                _ => Style::default().paint(" "),
+            }
+        } else {
+            Style::default().paint(" ")
+        };
+
+        Some(marker.to_string())
+    }
+
+    fn print_line_border(&self) -> Option<String> {
+        if let OptionsStyle::Plain = self.options.style {
+            return None;
+        }
+
+        Some(self.colors.grid.paint("│").to_string())
+    }
+
+    fn print_horizontal_line(&mut self, grid_char: char) -> Result<()> {
+        let hline = "─".repeat(self.term_width - (PANEL_WIDTH + 1));
+        let hline = format!("{}{}{}", "─".repeat(PANEL_WIDTH), grid_char, hline);
+
+        writeln!(self.handle, "{}", self.colors.grid.paint(hline))?;
+
+        Ok(())
+    }
+}