Add a helper for completing authentication via the command line

src/helpers/cli.rs

@@ -0,0 +1,27 @@
+use std::io::{self, BufRead, Write};
+
+use errors::Result;
+use http_send::HttpSend;
+use registration::Registered;
+use Mastodon;
+
+/// Finishes the authentication process for the given `Registered` object,
+/// using the command-line
+pub fn authenticate<H: HttpSend>(registration: Registered<H>) -> Result<Mastodon<H>> {
+    let url = registration.authorize_url()?;
+
+    let stdout = io::stdout();
+    let stdin = io::stdin();
+
+    let mut stdout = stdout.lock();
+    let mut stdin = stdin.lock();
+
+    writeln!(&mut stdout, "Click this link to authorize: {}", url)?;
+    write!(&mut stdout, "Paste the returned authorization code: ")?;
+    stdout.flush()?;
+
+    let mut input = String::new();
+    stdin.read_line(&mut input)?;
+    let code = input.trim();
+    Ok(registration.complete(code)?)
+}

src/helpers/mod.rs

@@ -21,3 +21,6 @@ pub mod toml;
 /// features = ["json"]
 /// ```
 pub mod json;
+
+/// Helpers for working with the command line
+pub mod cli;