Input parsing for day 6

2 files changed, 79 insertions, 6 deletions

diff --git a/src/bin/day_5.rs b/src/bin/day_5.rs
index e7539e1..a3cf869 100644
--- a/src/bin/day_5.rs
+++ b/src/bin/day_5.rs
@@ -11,17 +11,13 @@ use structopt::StructOpt;
 type Intcode = i32;
 
 #[derive(Debug, StructOpt)]
-#[structopt(name = "Day 2: 1202 Program Alarm")]
+#[structopt(name = "Day 5: Sunny with a Chance of Asteroids")]
 /// Executes an Intcode program
 ///
 /// The program is read from stdin as a series of comma-separated
 /// values. Newlines are ignored.
 ///
-/// If an output is provided, all possible inputs are tried to find
-/// the input that results in the desired output. In this case, the
-/// inputs are returned in the format (noun, verb).
-///
-///See https://adventofcode.com/2019/day/5 for details.
+/// See https://adventofcode.com/2019/day/5 for details.
 struct Opt {
     #[structopt(short = "i", long = "input")]
     input: Vec<Intcode>,
diff --git a/src/bin/day_6.rs b/src/bin/day_6.rs
new file mode 100644
index 0000000..a305a90
--- /dev/null
+++ b/src/bin/day_6.rs
@@ -0,0 +1,77 @@
+use std::fmt;
+use std::io;
+use std::io::prelude::*;
+use std::process;
+use std::str::FromStr;
+use structopt::StructOpt;
+
+#[derive(Debug, StructOpt)]
+#[structopt(name = "Day 6: Universal Orbit Map")]
+/// Counts the total number of direct and indirect orbits between planets.
+///
+/// Input is read from stdin, one direct orbit per line, in the format
+/// `A)B` (B is orbiting A).
+///
+/// See https://adventofcode.com/2019/day/6 for details.
+struct Opt {}
+
+fn main() {
+    let stdin = io::stdin();
+    let opt = Opt::from_args();
+
+    let orbits = stdin
+        .lock()
+        .lines()
+        .map(|x| exit_on_failed_assertion(x, "Error reading input"))
+        .map(|x| exit_on_failed_assertion(x.parse::<Orbit>(), "Input was not a valid orbit"));
+
+    println!("{}", count_orbits(orbits));
+}
+
+fn exit_on_failed_assertion<A, E: std::error::Error>(data: Result<A, E>, message: &str) -> A {
+    match data {
+        Ok(data) => data,
+        Err(e) => {
+            eprintln!("{}: {}", message, e);
+            process::exit(1);
+        }
+    }
+}
+
+#[derive(Debug)]
+struct StrError {
+    str: String,
+}
+
+impl fmt::Display for StrError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.str)
+    }
+}
+impl std::error::Error for StrError {}
+
+struct Orbit {
+    a: String,
+    b: String,
+}
+
+impl FromStr for Orbit {
+    type Err = StrError;
+
+    fn from_str(s: &str) -> Result<Self, StrError> {
+        match s.split(')').collect::<Vec<_>>()[..] {
+            [a, b] => Ok(Orbit {
+                a: a.to_string(),
+                b: b.to_string(),
+            }),
+            _ => Err(StrError {
+                str: format!("{} is not a valid orbit description", s),
+            }),
+        }
+    }
+}
+
+fn count_orbits(it: impl Iterator<Item = Orbit>) -> usize {
+    // TODO
+    0
+}