Make a handlebars helper that uses prlink to generate a link from a file

src/bin/generate_readme.rs

@@ -7,13 +7,15 @@
 // README.md.
 
 extern crate handlebars;
+extern crate prlink;
 #[macro_use]
 extern crate serde_json;
 
-use handlebars::Handlebars;
+use handlebars::{Handlebars, Helper, RenderContext, RenderError};
 
 use std::fs::File;
 use std::io::prelude::*;
+use std::path::PathBuf;
 
 fn main() {
     let template = include_str!("../../README-template.hbs");
@@ -23,7 +25,9 @@ order to make changes here rather than committing the changes directly.";
 
     let mut generated_readme = File::create("README.md").unwrap();
 
-    let hbs = Handlebars::new();
+    let mut hbs = Handlebars::new();
+    hbs.register_helper("playground_link", Box::new(playground_link_helper));
+
     write!(
         generated_readme,
         "{}",
@@ -33,3 +37,10 @@ order to make changes here rather than committing the changes directly.";
         ).unwrap()
     ).unwrap();
 }
+
+fn playground_link_helper(h: &Helper, _: &Handlebars, rc: &mut RenderContext) -> Result<(), RenderError> {
+    let filename = PathBuf::from(h.param(0).unwrap().value().as_str().unwrap());
+    let link = prlink::linkify_file(&filename);
+    rc.writer.write(link.into_bytes().as_ref())?;
+    Ok(())
+}