Draft generation of valid AI movements

.drone.yml

@@ -16,7 +16,7 @@ steps:
   - name: test
     image: rust:1.67
     commands:
-      - cargo test
+      - cargo test --all-features
     volumes:
       - name: cargo-cache
         path: /cache/cargo

board-shared/Cargo.toml

@@ -7,4 +7,8 @@ edition = "2021"
 
 [dependencies]
 enum-map = "2.4.2"
+itertools = { version = "0.10.5", optional = true }
 rand = "0.8.5"
+
+[features]
+ai = ["itertools"]

board-shared/src/ai.rs

@@ -0,0 +1,81 @@
+use crate::expr::are_valid_expressions;
+use crate::game::Hand;
+use crate::lexer::lexer;
+use crate::parser::parse;
+use crate::tile::{Digit, Operator, Tile};
+use itertools::Itertools;
+
+fn merge_expression(
+    numbers: &[&Digit],
+    operators: &[&Operator],
+    equals_idx: usize,
+    buf: &mut Vec<Tile>,
+) {
+    let mut op_it = operators.iter();
+    for (i, &number) in numbers.iter().enumerate() {
+        buf.push(Tile::Digit(*number));
+        if i == equals_idx {
+            buf.push(Tile::Equals);
+        } else if let Some(&&operator) = op_it.next() {
+            buf.push(Tile::Operator(operator));
+        }
+    }
+}
+
+pub fn generate_valid_combinations(hand: &Hand) -> Vec<Vec<Tile>> {
+    let mut combinations = Vec::new();
+
+    // Separate numbers and operators
+    let mut numbers = Vec::new();
+    let mut operators = Vec::new();
+    for &tile in &hand.tiles {
+        match tile {
+            Tile::Digit(digit) => numbers.push(digit),
+            Tile::Operator(operator) => operators.push(operator),
+            _ => (),
+        }
+    }
+
+    let mut trial: Vec<Tile> = Vec::with_capacity(numbers.len() + operators.len() + 1);
+
+    // Generate all possible permutations, with an increasing number of tiles
+    for nb_digits in 2..=numbers.len() {
+        for digits in numbers.iter().permutations(nb_digits) {
+            // Then try to place the equals sign at each possible position
+            // Since equality is commutative, we only need to try half of the positions
+            for equals_idx in 0..(nb_digits / 2) {
+                for operators in operators.iter().permutations(nb_digits - 2) {
+                    merge_expression(&digits, &operators, equals_idx, &mut trial);
+                    if let Ok(tokens) = lexer(&trial) {
+                        if let Ok(expressions) = parse(&tokens) {
+                            if are_valid_expressions(&expressions) {
+                                combinations.push(trial.clone());
+                            }
+                        }
+                    }
+                    trial.clear();
+                }
+            }
+        }
+    }
+    combinations
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::tile::{Digit, Operator};
+
+    #[test]
+    fn generate_combinations() {
+        let hand = Hand::new(vec![
+            Tile::Digit(Digit::new(1)),
+            Tile::Digit(Digit::new(3)),
+            Tile::Digit(Digit::new(4)),
+            Tile::Operator(Operator::Add),
+            Tile::Operator(Operator::Subtract),
+        ]);
+        let combinations = generate_valid_combinations(&hand);
+        assert_eq!(combinations.len(), 4);
+    }
+}

board-shared/src/deck.rs

@@ -1,7 +1,7 @@
-use std::error::Error;
 use crate::tile::Operator;
 use enum_map::EnumMap;
 use rand::{thread_rng, Rng};
+use std::error::Error;
 
 type DeckSize = u16;
 type DigitDeck = [DeckSize; 19];

board-shared/src/game.rs

@@ -14,6 +14,10 @@ pub struct Hand {
 }
 
 impl Hand {
+    pub fn new(tiles: Vec<Tile>) -> Self {
+        Self { tiles }
+    }
+
     pub fn count_missing_operators(&self) -> usize {
         4usize.saturating_sub(
             self.tiles
@@ -38,8 +42,9 @@ impl Hand {
                 .push(Tile::Operator(deck.rand_operator().ok_or(EmptyDeckError)?));
         }
         for _ in 0..self.count_missing_numbers() {
-            self.tiles
-                .push(Tile::Digit(Digit::new(deck.rand_digit().ok_or(EmptyDeckError)?)));
+            self.tiles.push(Tile::Digit(Digit::new(
+                deck.rand_digit().ok_or(EmptyDeckError)?,
+            )));
         }
         Ok(())
     }
@@ -51,4 +56,8 @@ impl Hand {
             None
         }
     }
+
+    pub fn iter(&self) -> impl Iterator<Item = &Tile> {
+        self.tiles.iter()
+    }
 }

board-shared/src/lib.rs

@@ -1,3 +1,5 @@
+#[cfg(feature = "ai")]
+pub mod ai;
 pub mod board;
 pub mod deck;
 pub mod expr;

board-shared/src/parser.rs

@@ -1,5 +1,6 @@
 use crate::lexer::Token;
 use crate::tile::Operator;
+use std::fmt;
 use std::iter::Peekable;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -9,6 +10,18 @@ pub enum Expression {
     Binary(Operator, Box<Expression>, Box<Expression>),
 }
 
+impl fmt::Display for Expression {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Expression::Digit(value) => write!(f, "{}", value),
+            Expression::Parentheses(expr) => write!(f, "({})", expr),
+            Expression::Binary(operator, left, right) => {
+                write!(f, "{} {} {}", left, operator, right)
+            }
+        }
+    }
+}
+
 pub type Expressions = Vec<Expression>;
 
 pub fn parse(tokens: &[Token]) -> Result<Expressions, ()> {