From 161e5f7a5f5b1f7029854280bd688783ef1a8ede Mon Sep 17 00:00:00 2001
From: Joseph Montanaro <jfmontanaro@modg.org>
Date: Fri, 3 Dec 2021 10:34:31 -0800
Subject: [PATCH] add day 2

---
 2021/src/day2.rs | 78 ++++++++++++++++++++++++++++++++++++++++++++++++
 2021/src/lib.rs  |  9 +++++-
 2021/src/main.rs | 13 ++++----
 3 files changed, 93 insertions(+), 7 deletions(-)
 create mode 100644 2021/src/day2.rs

diff --git a/2021/src/day2.rs b/2021/src/day2.rs
new file mode 100644
index 0000000..fb4746d
--- /dev/null
+++ b/2021/src/day2.rs
@@ -0,0 +1,78 @@
+use std::str::FromStr;
+
+use color_eyre::eyre;
+use eyre::{eyre, ensure};
+
+use crate::lib::ParseLines;
+
+
+enum Direction {
+    Forward,
+    Up,
+    Down,
+}
+
+
+struct MoveCmd {
+    dir: Direction,
+    value: i32,
+}
+
+
+impl<'a> FromStr for MoveCmd {
+    type Err = eyre::Report;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let parts: Vec<&str> = s.split_whitespace().collect();
+        ensure!(parts.len() == 2, "Could not parse: \"{}\" (Wrong number of words)", s);
+
+        let dir = match parts[0] {
+            "forward" => Direction::Forward,
+            "up" => Direction::Up,
+            "down" => Direction::Down,
+            _ => return Err(eyre!("Could not parse: \"{}\" (invalid axis)", s)),
+        };
+
+        let value = parts[1].parse::<i32>()?;
+
+        Ok(MoveCmd{dir, value})
+    }
+}
+
+
+pub fn part1(data: &str) -> eyre::Result<()> {
+    let mut horiz = 0; // how many units forward
+    let mut vert = 0; // how many units DOWN (so flipped)
+    for res in data.parse_lines::<MoveCmd>() {
+        let cmd = res?;
+        match cmd.dir {
+            Direction::Forward => horiz += cmd.value,
+            Direction::Up => vert -= cmd.value,
+            Direction::Down => vert += cmd.value,
+        }
+    }
+
+    println!("One: {}", horiz * vert);
+    Ok(())
+}
+
+
+pub fn part2(data: &str) -> eyre::Result<()> {
+    let mut horiz = 0;
+    let mut vert = 0;
+    let mut aim = 0;
+    for res in data.parse_lines::<MoveCmd>() {
+        let cmd = res?;
+        match cmd.dir {
+            Direction::Down => aim += cmd.value, // flipped again
+            Direction::Up => aim -= cmd.value,
+            Direction::Forward => {
+                horiz += cmd.value;
+                vert +=  cmd.value * aim;
+            }
+        }
+    }
+
+    println!("Two: {}", horiz * vert);
+    Ok(())
+}
diff --git a/2021/src/lib.rs b/2021/src/lib.rs
index dbe3b59..1da8eda 100644
--- a/2021/src/lib.rs
+++ b/2021/src/lib.rs
@@ -36,7 +36,7 @@ pub trait ParseLines {
 }
 
 
-impl ParseLines for String {
+impl ParseLines for str {
     fn parse_lines<T: FromStr>(&self) -> LineParser<'_, T> {
         LineParser {
             it: self.lines(),
@@ -45,3 +45,10 @@ impl ParseLines for String {
     }
 }
 
+
+impl ParseLines for String {
+    fn parse_lines<T: FromStr>(&self) -> LineParser<'_, T> {
+        self[..].parse_lines::<T>()
+    }
+}
+
diff --git a/2021/src/main.rs b/2021/src/main.rs
index 6a867a9..6f956e7 100644
--- a/2021/src/main.rs
+++ b/2021/src/main.rs
@@ -3,13 +3,19 @@ use color_eyre::eyre;
 mod lib;
 use lib::{load, ParseLines};
 
+mod day2;
+
+
 
 
 fn main() -> eyre::Result<()> {
-    day_one()
+    let data = load("data/02.txt")?;
+    day2::part1(&data)?;
+    day2::part2(&data)
 }
 
 
+#[allow(dead_code)]
 fn day_one() -> eyre::Result<()> {
     let data = load("data/01.txt")?;
 
@@ -38,8 +44,3 @@ fn day_one() -> eyre::Result<()> {
     println!("Two: {}", window_increases);
     Ok(())
 }
-
-
-// fn day_two() -> eyre::Result<()> {
-
-// }