rework error handling

anyhow!() ftw.

2 files changed, 103 insertions, 53 deletions

diff --git a/Cargo.toml b/Cargo.toml
index a076bb5..afd808f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,3 +22,4 @@ doc         = false
 [dependencies]
 clap        = "2.33"
 libc        = "0.2"
+anyhow      = "1.0"
diff --git a/src/vtcol.rs b/src/vtcol.rs
index e0ff6cb..6a51b49 100644
--- a/src/vtcol.rs
+++ b/src/vtcol.rs
@@ -1,4 +1,6 @@
+use anyhow::{anyhow, Result};
 use std::{fmt,
+          io::Error,
           path::{Path, PathBuf},
           sync::atomic::{AtomicBool, Ordering}};
 
@@ -119,18 +121,23 @@ impl<'a> fmt::Display for Scheme
 /* struct Job -- Runtime parameters.
  */
 #[derive(Debug)]
-struct Job
+enum Job
 {
-    scheme: Scheme, /* The color scheme to switch to. */
+    /** List available schemes. */
+    List,
+    /** Dump a scheme. */
+    Dump(Scheme),
+    /** The color scheme to switch to. */
+    Set(Scheme),
 }
 
 impl<'a> Job
 {
-    pub fn from_argv() -> Job
+    pub fn from_argv() -> Result<Job>
     {
         use clap::{App, Arg};
 
-        let matches = App::new(clap::crate_name!())
+        let app = App::new(clap::crate_name!())
             .version(clap::crate_version!())
             .author(clap::crate_authors!())
             .about(clap::crate_description!())
@@ -171,35 +178,34 @@ impl<'a> Job
                     .long("list")
                     .help("list available color schemes")
                     .takes_value(false),
-            )
-            .get_matches();
+            );
 
-        if matches.is_present("v") {
+        let matches = app.get_matches();
+
+        if matches.is_present("verbose") {
             VERBOSITY.store(true, Ordering::SeqCst);
         }
 
-        if matches.is_present("l") {
-            Job::schemes();
-            std::process::exit(0);
+        if matches.is_present("list") {
+            return Ok(Self::List);
         };
 
         if let Some(name) = matches.value_of("dump") {
-            let scm = Job::pick_scheme(name);
-            Job::dump(scm);
-            std::process::exit(0);
+            let scm = Self::pick_scheme(name);
+            return Ok(Self::Dump(scm));
         }
 
         let scheme = match matches.value_of("file") {
-            Some("-") => Job::scheme_from_stdin(),
+            Some("-") => Self::scheme_from_stdin(),
             Some(fname) => Scheme::Custom(Some(PathBuf::from(fname))),
             None =>
                 match matches.value_of("scheme") {
-                    Some("-") | None => Job::scheme_from_stdin(),
-                    Some(name) => Job::pick_scheme(name),
+                    Some("-") | None => Self::scheme_from_stdin(),
+                    Some(name) => Self::pick_scheme(name),
                 },
         };
 
-        Job { scheme }
+        Ok(Self::Set(scheme))
     }
 
     fn pick_scheme(name: &str) -> Scheme
@@ -226,22 +232,56 @@ impl<'a> Job
     {
         vrb!("Dumping color scheme {}", scm);
         match scm {
-            Scheme::Default => Job::dump_scheme(&DEFAULT_COLORS),
-            Scheme::SolarizedDark => Job::dump_scheme(&SOLARIZED_COLORS_DARK),
-            Scheme::SolarizedLight => Job::dump_scheme(&SOLARIZED_COLORS_LIGHT),
-            Scheme::Custom(None) => Job::dump_palette(Palette::from_stdin()),
+            Scheme::Default => Self::dump_scheme(&DEFAULT_COLORS),
+            Scheme::SolarizedDark => Self::dump_scheme(&SOLARIZED_COLORS_DARK),
+            Scheme::SolarizedLight =>
+                Self::dump_scheme(&SOLARIZED_COLORS_LIGHT),
+            Scheme::Custom(None) => Self::dump_palette(Palette::from_stdin()),
             Scheme::Custom(Some(fname)) =>
-                Job::dump_palette(Palette::from_file(&fname)),
+                Self::dump_palette(Palette::from_file(&fname)),
         }
     }
 
     fn dump_scheme(colors: &[&str; PALETTE_SIZE])
     {
         let pal: Palette = Palette::new(colors);
-        pal.dump()
+        pal.dump();
     }
 
     fn dump_palette(pal: Palette) { pal.dump() }
+
+    fn run(self) -> Result<()>
+    {
+        match self {
+            Self::Dump(scm) => Self::dump(scm),
+            Self::List => Self::schemes(),
+            Self::Set(scm) => Self::set_scheme(scm)?,
+        }
+
+        Ok(())
+    }
+
+    fn set_scheme(scheme: Scheme) -> Result<()>
+    {
+        let pal: Palette = match scheme {
+            Scheme::Default => Palette::new(&DEFAULT_COLORS),
+            Scheme::SolarizedDark => Palette::new(&SOLARIZED_COLORS_DARK),
+            Scheme::SolarizedLight => Palette::new(&SOLARIZED_COLORS_LIGHT),
+            Scheme::Custom(None) => Palette::from_stdin(),
+            Scheme::Custom(Some(ref fname)) => Palette::from_file(fname),
+        };
+        vrb!("Using palette:");
+        vrb!("{}", pal);
+        let fd = get_console_fd()?;
+        vrb!("fd: {}", fd);
+
+        ioctl_pio_cmap(fd, &pal)?;
+
+        clear_term(fd)?;
+        vrb!("successfully enabled scheme {:?}", scheme);
+        /* It’s fine to leak the fd, the kernel will clean up anyways. */
+        Ok(())
+    }
 } /* [impl Job] */
 
 /* Rust appears to come with two wrappers for ``ioctl(2)``, but neither can be utilized for our
@@ -519,54 +559,63 @@ fn fd_of_path(path: &std::path::Path) -> Option<Fd>
     }
 }
 
-fn get_console_fd() -> Option<Fd>
+fn get_console_fd() -> Result<Fd>
 {
     for path in CONSOLE_PATHS.iter() {
         vrb!("trying path: {:?}", path);
         let path = std::path::Path::new(path);
         if let Some(fd) = fd_of_path(path) {
             vrb!(" * Success!");
-            return Some(fd);
+            return Ok(fd);
         }
     }
-    vrb!("could not retrieve fd for any of the search paths");
-    None
+    Err(anyhow!("could not retrieve fd for any of the search paths"))
 }
 
-fn write_to_term(fd: Fd, buf: &str)
+fn write_to_term(fd: Fd, buf: &str) -> Result<()>
 {
     let len = buf.len() as libc::size_t;
-    let raw = std::ffi::CString::new(buf.as_bytes()).unwrap();
-    unsafe { libc::write(fd, raw.as_ptr() as *const libc::c_void, len) };
+
+    if unsafe { libc::write(fd, buf.as_ptr() as *const libc::c_void, len) }
+        != len as isize
+    {
+        Err(anyhow!(
+            "failed to write {} B to fd {}: {}",
+            len,
+            fd,
+            Error::last_os_error()
+        ))
+    } else {
+        Ok(())
+    }
+}
+
+fn clear_term(fd: Fd) -> Result<()>
+{
+    let clear = "\x1b[2J";
+    let cursor = "\x1b[1;1H";
+    write_to_term(fd, clear)?;
+    write_to_term(fd, cursor)?;
+
+    Ok(())
 }
 
-fn clear_term(fd: Fd)
+fn ioctl_pio_cmap(fd: Fd, pal: &Palette) -> Result<()>
 {
-    let clear: &str = "\x1b[2J";
-    let cursor: &str = "\x1b[1;1H";
-    write_to_term(fd, clear);
-    write_to_term(fd, cursor);
+    if unsafe { ioctl(fd, PIO_CMAP, std::mem::transmute(pal)) } < 0 {
+        Err(anyhow!(
+            "PIO_CMAP, ioctl failed to insert new palette: {}",
+            Error::last_os_error()
+        ))
+    } else {
+        Ok(())
+    }
 }
 
-fn main()
+fn main() -> Result<()>
 {
-    let job = Job::from_argv();
+    let job = Job::from_argv()?;
     vrb!("job parms: {:?}", job);
-    let mut pal: Palette = match job.scheme {
-        Scheme::Default => Palette::new(&DEFAULT_COLORS),
-        Scheme::SolarizedDark => Palette::new(&SOLARIZED_COLORS_DARK),
-        Scheme::SolarizedLight => Palette::new(&SOLARIZED_COLORS_LIGHT),
-        Scheme::Custom(None) => Palette::from_stdin(),
-        Scheme::Custom(Some(ref fname)) => Palette::from_file(fname),
-    };
-    vrb!("Using palette:");
-    vrb!("{}", pal);
-    let fd = get_console_fd().unwrap();
-    vrb!("fd: {}", fd);
 
-    if unsafe { ioctl(fd, PIO_CMAP, std::mem::transmute(&mut pal)) } < 0 {
-        panic!("PIO_CMAP, ioctl failed to insert new palette")
-    }
-    clear_term(fd);
-    vrb!("terminated from job {:?}", job);
+    job.run()
 }