Add duplicate detection with fuzzy matching and fix artist metadata extraction

lib/fuzzyMatch.ts

@@ -0,0 +1,97 @@
+/**
+ * Fuzzy string matching utility for duplicate detection
+ * Uses Levenshtein distance to compare strings with tolerance for formatting variations
+ */
+
+/**
+ * Normalize a string for comparison
+ * - Converts to lowercase
+ * - Removes special characters
+ * - Normalizes whitespace
+ */
+function normalizeString(str: string): string {
+    return str
+        .toLowerCase()
+        .replace(/[^a-z0-9\s]/g, '') // Remove special chars
+        .replace(/\s+/g, ' ')         // Normalize whitespace
+        .trim();
+}
+
+/**
+ * Calculate Levenshtein distance between two strings
+ * Returns the minimum number of single-character edits needed to change one string into the other
+ */
+function levenshteinDistance(a: string, b: string): number {
+    if (a.length === 0) return b.length;
+    if (b.length === 0) return a.length;
+
+    const matrix: number[][] = [];
+
+    // Initialize first column
+    for (let i = 0; i <= b.length; i++) {
+        matrix[i] = [i];
+    }
+
+    // Initialize first row
+    for (let j = 0; j <= a.length; j++) {
+        matrix[0][j] = j;
+    }
+
+    // Fill in the rest of the matrix
+    for (let i = 1; i <= b.length; i++) {
+        for (let j = 1; j <= a.length; j++) {
+            if (b.charAt(i - 1) === a.charAt(j - 1)) {
+                matrix[i][j] = matrix[i - 1][j - 1];
+            } else {
+                matrix[i][j] = Math.min(
+                    matrix[i - 1][j - 1] + 1, // substitution
+                    matrix[i][j - 1] + 1,     // insertion
+                    matrix[i - 1][j] + 1      // deletion
+                );
+            }
+        }
+    }
+
+    return matrix[b.length][a.length];
+}
+
+/**
+ * Check if two strings are similar based on Levenshtein distance
+ * @param str1 First string to compare
+ * @param str2 Second string to compare
+ * @param threshold Similarity threshold (0-1), default 0.85
+ * @returns true if strings are similar enough
+ */
+export function isSimilar(str1: string, str2: string, threshold = 0.85): boolean {
+    if (!str1 || !str2) return false;
+
+    const norm1 = normalizeString(str1);
+    const norm2 = normalizeString(str2);
+
+    // Exact match after normalization
+    if (norm1 === norm2) return true;
+
+    const distance = levenshteinDistance(norm1, norm2);
+    const maxLen = Math.max(norm1.length, norm2.length);
+
+    // Avoid division by zero
+    if (maxLen === 0) return true;
+
+    const similarity = 1 - (distance / maxLen);
+
+    return similarity >= threshold;
+}
+
+/**
+ * Check if a song (artist + title) is a duplicate of another
+ * Both artist AND title must be similar for a match
+ */
+export function isDuplicateSong(
+    artist1: string,
+    title1: string,
+    artist2: string,
+    title2: string,
+    threshold = 0.85
+): boolean {
+    return isSimilar(artist1, artist2, threshold) && isSimilar(title1, title2, threshold);
+}