Tests for scrabble-score's optional extensions

exercises/scrabble-score/example.rs

@@ -1,40 +1,35 @@
-use std::collections::HashMap;
-
 pub fn score(word: &str) -> u16 {
-    let values = dictionary();
-    word.to_lowercase()
-        .chars()
-        .map(|c| values.get(&c).clone())
-        .fold(0, |score, v| score + v.unwrap_or(&0))
+    let mut score: u16 = 0;
+    let mut previous_char_value: u16 = 0;
+
+    // normalise the word to lowercase, for case-insensitivity, also, for easier iteration,
+    // reduce the multi-character value multipliers :double and :triple to a single char.
+    let tokenised_word = word.to_lowercase().replace(":double", "2").replace(":triple", "3");
+
+    for a_char in tokenised_word.chars() {
+        let value = char_value(a_char, previous_char_value);
+        score += value;
+        previous_char_value = value;
+    }
+
+    score
 }
 
-fn dictionary() -> HashMap<char, u16> {
-    let mut values = HashMap::new();
-    values.insert('a', 1);
-    values.insert('b', 3);
-    values.insert('c', 3);
-    values.insert('d', 2);
-    values.insert('e', 1);
-    values.insert('f', 4);
-    values.insert('g', 2);
-    values.insert('h', 4);
-    values.insert('i', 1);
-    values.insert('j', 8);
-    values.insert('k', 5);
-    values.insert('l', 1);
-    values.insert('m', 3);
-    values.insert('n', 1);
-    values.insert('o', 1);
-    values.insert('p', 3);
-    values.insert('q', 10);
-    values.insert('r', 1);
-    values.insert('s', 1);
-    values.insert('t', 1);
-    values.insert('u', 1);
-    values.insert('v', 4);
-    values.insert('w', 4);
-    values.insert('x', 8);
-    values.insert('y', 4);
-    values.insert('z', 10);
-    values
+/// Calculates the value of the current character.
+///
+/// The previous characters' value is required in case the current
+/// token is a multiplier, which affects the score of the previous char.
+fn char_value(the_char: char, prev_value: u16) -> u16 {
+    match the_char {
+        'a'|'e'|'i'|'o'|'u'|'l'|'n'|'r'|'s'|'t' => 1,
+        'd'|'g' => 2,
+        'b'|'c'|'m'|'p' => 3,
+        'f'|'h'|'v'|'w'|'y' => 4,
+        'k' => 5,
+        'j'|'x' => 8,
+        'q'|'z' => 10,
+        '2' =>   prev_value, // repeat the previous value, effectively doubling the previous value
+        '3' => 2*prev_value, // repeat the previous value twice, effectively multiplying it by 3x
+        _   => 0, // 'funny' characters, such as accented ones or foreign alphabets, count for 0
+    }
 }

exercises/scrabble-score/tests/scrabble-score.rs

@@ -61,3 +61,71 @@ fn non_english_scrabble_letters_do_not_score() {
 fn empty_words_are_worth_zero() {
     assert_eq!(score(""), 0);
 }
+
+// =============================================
+//  Extensions
+//
+//  The tests below correspond to the optional
+//  extensions described in the README
+// =============================================
+
+#[test]
+#[ignore]
+fn single_letter_double_score() {
+    assert_eq!(score("a:double"), 2);
+}
+
+#[test]
+#[ignore]
+fn other_single_letter_double_score() {
+    assert_eq!(score("g:double"), 4);
+}
+
+#[test]
+#[ignore]
+fn double_scoring_letter_in_a_word() {
+    assert_eq!(score("zo:doubleo"), 13);
+}
+
+#[test]
+#[ignore]
+fn double_letters_at_word_boundary() {
+    assert_eq!(score("fabulous"), 13);
+    assert_eq!(score("f:doubleabulous"), 17);
+    assert_eq!(score("fabulous:double"), 14);
+}
+
+#[test]
+#[ignore]
+fn single_letter_triple_score() {
+    assert_eq!(score("a:triple"), 3);
+}
+
+#[test]
+#[ignore]
+fn other_single_letter_triple_score() {
+    assert_eq!(score("g:triple"), 6);
+}
+
+#[test]
+#[ignore]
+fn triple_scoring_letter_in_a_word() {
+    assert_eq!(score("zo:tripleo"), 14);
+}
+
+#[test]
+#[ignore]
+fn triple_letters_at_word_boundary() {
+    assert_eq!(score("fabulous"), 13);
+    assert_eq!(score("f:tripleabulous"), 21);
+    assert_eq!(score("fabulous:triple"), 15);
+}
+
+#[test]
+#[ignore]
+fn zero_scoring_letters_not_multiplied() {
+    assert_eq!(score("pinata"), 8);
+    assert_eq!(score("piñata"), 7);
+    assert_eq!(score("piñ:doubleata"), 7);
+    assert_eq!(score("piñ:tripleata"), 7);
+}