/**
 * 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);
}