Cleanup recite(), custom errors, fixed forking

First off, moved the giant match statements out of recite(), and into
macros in src/recite/ps.rs. There still needs to be two, since any verse
using the 'couplet' meter will need to redirect its STDOUT. Now the
recite() function returns a Result<(), Mishap>, which can be invoked
when calling the incant_ functions.

Custom errors were added in the form of 'Mishap''s. They are intended to
be returned from the incant_ functions, in the event that something goes
wrong with the Command::spawn() or Child::wait(). They each take a
String, which should be the verb or stanza that was entered by the user.

The incant_ functions separate the functionality of each type of meter
from the recite() function. They return a Result<i32, Mishap>, where
i32 is the exit code of the program that ran, and Mishap is a possible
error.

Before, the shell was cheating at forking a process to the background.
It would actually spawn a thread to wait for that process to finish.
Now, the program simply registers a handler for SIGCHLD, and uses libc's
waitpid() function to reap the child process, and print some output to
the user, indicating that it's finished.

1 files changed, 71 insertions, 0 deletions

diff --git a/src/recite/ps.rs b/src/recite/ps.rs
new file mode 100644
index 0000000..3557505
--- /dev/null
+++ b/src/recite/ps.rs
@@ -0,0 +1,71 @@
+#[macro_export]
+macro_rules! task {
+    ($verse:expr, $out:expr) => {
+        if $verse.couplet {
+            let mut child = Command::new($verse.verb())
+                .args($verse.clause())
+                .stdin(Stdio::piped())
+                .spawn()
+                .map_err(|e| match e.kind() {
+                    io::ErrorKind::PermissionDenied => Mishap::PermissionDenied($verse.verb()),
+                    _ => Mishap::Else($verse.verb()),
+                })?;
+
+            let stdin = child
+                .stdin
+                .as_mut()
+                .ok_or(Mishap::BrokenPipe($verse.verb()))?;
+            stdin
+                .write_all(&$out.as_bytes())
+                .map_err(|_| Mishap::BrokenPipe($verse.verb()))?;
+            $out.clear();
+
+            child
+        } else {
+            Command::new($verse.verb())
+                .args($verse.clause())
+                .spawn()
+                .map_err(|e| match e.kind() {
+                    io::ErrorKind::PermissionDenied => Mishap::PermissionDenied($verse.verb()),
+                    _ => Mishap::Else($verse.verb()),
+                })?
+        }
+    };
+}
+
+#[macro_export()]
+macro_rules! ctask {
+    ($verse:expr, $out:expr) => {
+        if $verse.couplet {
+            let mut child = Command::new($verse.verb())
+                .args($verse.clause())
+                .stdin(Stdio::piped())
+                .stdout(Stdio::piped())
+                .spawn()
+                .map_err(|e| match e.kind() {
+                    io::ErrorKind::PermissionDenied => Mishap::PermissionDenied($verse.verb()),
+                    _ => Mishap::Else($verse.verb()),
+                })?;
+
+            let stdin = child
+                .stdin
+                .as_mut()
+                .ok_or(Mishap::BrokenPipe($verse.verb()))?;
+            stdin
+                .write_all(&$out.as_bytes())
+                .map_err(|_| Mishap::BrokenPipe($verse.verb()))?;
+            $out.clear();
+
+            child
+        } else {
+            Command::new($verse.verb())
+                .args($verse.clause())
+                .stdout(Stdio::piped())
+                .spawn()
+                .map_err(|e| match e.kind() {
+                    io::ErrorKind::PermissionDenied => Mishap::PermissionDenied($verse.verb()),
+                    _ => Mishap::Else($verse.verb()),
+                })?
+        }
+    };
+}