1 files changed, 167 insertions, 0 deletions
diff --git a/2022/src/bin/day_2.rs b/2022/src/bin/day_2.rs
new file mode 100644
index 0000000..deb5294
--- /dev/null
+++ b/2022/src/bin/day_2.rs
@@ -0,0 +1,167 @@
+use nom::{
+    branch::alt,
+    character::complete::{char as nom_char, line_ending},
+    combinator::{map, value},
+    multi::separated_list1,
+    sequence::tuple,
+    IResult,
+};
+use std::fs;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let input = fs::read_to_string("inputs/day_2.txt")?;
+    let game_log_part_1 = GameLog::parser(&input).unwrap().1;
+    dbg!(game_log_part_1.total_score());
+
+    let game_log_part_2 = GameLog::parser_part_2(&input).unwrap().1;
+    dbg!(game_log_part_2.total_score());
+    Ok(())
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+struct GameLog {
+    moves: Vec<GameRound>,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+struct GameRound {
+    opponent: Move,
+    me: Move,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+enum Move {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+enum GameResult {
+    Win,
+    Lose,
+    Draw,
+}
+
+impl GameLog {
+    fn parser(input: &str) -> IResult<&str, GameLog> {
+        map(separated_list1(line_ending, GameRound::parser), |moves| {
+            GameLog { moves }
+        })(input)
+    }
+
+    fn parser_part_2(input: &str) -> IResult<&str, GameLog> {
+        map(
+            separated_list1(line_ending, GameRound::parser_part_2),
+            |moves| GameLog { moves },
+        )(input)
+    }
+
+    fn total_score(&self) -> u32 {
+        self.moves.iter().map(|m| m.score()).sum()
+    }
+}
+
+impl GameRound {
+    fn parser(input: &str) -> IResult<&str, GameRound> {
+        map(
+            tuple((Move::opponent_parser, nom_char(' '), Move::player_parser)),
+            |(opponent, _, me)| GameRound { opponent, me },
+        )(input)
+    }
+
+    fn parser_part_2(input: &str) -> IResult<&str, GameRound> {
+        map(
+            tuple((Move::opponent_parser, nom_char(' '), GameResult::parser)),
+            |(opponent, _, result)| {
+                use GameResult::*;
+                use Move::*;
+
+                let me = match opponent {
+                    Rock => match result {
+                        Win => Paper,
+                        Draw => Rock,
+                        Lose => Scissors,
+                    },
+                    Paper => match result {
+                        Win => Scissors,
+                        Draw => Paper,
+                        Lose => Rock,
+                    },
+                    Scissors => match result {
+                        Win => Rock,
+                        Draw => Scissors,
+                        Lose => Paper,
+                    },
+                };
+                GameRound { opponent, me }
+            },
+        )(input)
+    }
+
+    fn score(&self) -> u32 {
+        let victory_points = match self.me.beats(&self.opponent) {
+            GameResult::Lose => 0,
+            GameResult::Draw => 3,
+            GameResult::Win => 6,
+        };
+
+        let throw_points = match self.me {
+            Move::Rock => 1,
+            Move::Paper => 2,
+            Move::Scissors => 3,
+        };
+
+        victory_points + throw_points
+    }
+}
+
+impl Move {
+    fn opponent_parser(input: &str) -> IResult<&str, Move> {
+        alt((
+            value(Move::Rock, nom_char('A')),
+            value(Move::Paper, nom_char('B')),
+            value(Move::Scissors, nom_char('C')),
+        ))(input)
+    }
+
+    fn player_parser(input: &str) -> IResult<&str, Move> {
+        alt((
+            value(Move::Rock, nom_char('X')),
+            value(Move::Paper, nom_char('Y')),
+            value(Move::Scissors, nom_char('Z')),
+        ))(input)
+    }
+
+    fn beats(&self, other: &Move) -> GameResult {
+        use GameResult::*;
+        use Move::*;
+        match self {
+            Rock => match other {
+                Rock => Draw,
+                Paper => Lose,
+                Scissors => Win,
+            },
+            Paper => match other {
+                Rock => Win,
+                Paper => Draw,
+                Scissors => Lose,
+            },
+            Scissors => match other {
+                Rock => Lose,
+                Paper => Win,
+                Scissors => Draw,
+            },
+        }
+    }
+}
+
+impl GameResult {
+    fn parser(input: &str) -> IResult<&str, GameResult> {
+        alt((
+            value(GameResult::Lose, nom_char('X')),
+            value(GameResult::Draw, nom_char('Y')),
+            value(GameResult::Win, nom_char('Z')),
+        ))(input)
+    }
+}