feat(stats): add v1 immersion stats dashboard (#19)

stats/src/lib/reading-utils.ts

@@ -0,0 +1,73 @@
+function isHiragana(ch: string): boolean {
+  const code = ch.charCodeAt(0);
+  return code >= 0x3040 && code <= 0x309f;
+}
+
+function isKatakana(ch: string): boolean {
+  const code = ch.charCodeAt(0);
+  return code >= 0x30a0 && code <= 0x30ff;
+}
+
+function katakanaToHiragana(text: string): string {
+  let result = '';
+  for (const ch of text) {
+    const code = ch.charCodeAt(0);
+    if (code >= 0x30a1 && code <= 0x30f6) {
+      result += String.fromCharCode(code - 0x60);
+    } else {
+      result += ch;
+    }
+  }
+  return result;
+}
+
+/**
+ * Reconstruct the full word reading from the surface form and the stored
+ * (possibly partial) reading.
+ *
+ * MeCab/Yomitan sometimes stores only the kanji portion's reading. For example,
+ * お前 (surface) with reading まえ — the stored reading covers only 前, missing
+ * the leading お. This function walks through the surface form: hiragana/katakana
+ * characters pass through as-is (converted to hiragana), and the remaining kanji
+ * portion is filled in from the stored reading.
+ */
+export function fullReading(headword: string, storedReading: string): string {
+  if (!storedReading || !headword) return storedReading || '';
+
+  const reading = katakanaToHiragana(storedReading);
+
+  const leadingKana: string[] = [];
+  const trailingKana: string[] = [];
+  const chars = [...headword];
+
+  let i = 0;
+  while (i < chars.length && (isHiragana(chars[i]) || isKatakana(chars[i]))) {
+    leadingKana.push(katakanaToHiragana(chars[i]));
+    i++;
+  }
+
+  if (i === chars.length) {
+    return reading;
+  }
+
+  let j = chars.length - 1;
+  while (j > i && (isHiragana(chars[j]) || isKatakana(chars[j]))) {
+    trailingKana.unshift(katakanaToHiragana(chars[j]));
+    j--;
+  }
+
+  // Strip matching trailing kana from the stored reading to get the core kanji reading
+  let coreReading = reading;
+  const trailStr = trailingKana.join('');
+  if (trailStr && coreReading.endsWith(trailStr)) {
+    coreReading = coreReading.slice(0, -trailStr.length);
+  }
+
+  // Strip matching leading kana from the stored reading if it already includes them
+  const leadStr = leadingKana.join('');
+  if (leadStr && coreReading.startsWith(leadStr)) {
+    return reading;
+  }
+
+  return leadStr + coreReading + trailStr;
+}