SpotiFLAC-Mobile/go_backend/extension_runtime_matching.go

// Package gobackend provides Track Matching API for extension runtime
package gobackend

import (
	"strings"

	"github.com/dop251/goja"
)

// ==================== Track Matching API ====================

// matchingCompareStrings compares two strings with fuzzy matching
func (r *ExtensionRuntime) matchingCompareStrings(call goja.FunctionCall) goja.Value {
	if len(call.Arguments) < 2 {
		return r.vm.ToValue(0.0)
	}

	str1 := strings.ToLower(strings.TrimSpace(call.Arguments[0].String()))
	str2 := strings.ToLower(strings.TrimSpace(call.Arguments[1].String()))

	if str1 == str2 {
		return r.vm.ToValue(1.0)
	}

	// Calculate Levenshtein distance-based similarity
	similarity := calculateStringSimilarity(str1, str2)
	return r.vm.ToValue(similarity)
}

// matchingCompareDuration compares two durations with tolerance
func (r *ExtensionRuntime) matchingCompareDuration(call goja.FunctionCall) goja.Value {
	if len(call.Arguments) < 2 {
		return r.vm.ToValue(false)
	}

	dur1 := int(call.Arguments[0].ToInteger())
	dur2 := int(call.Arguments[1].ToInteger())

	// Default tolerance: 3 seconds
	tolerance := 3000 // milliseconds
	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) {
		tolerance = int(call.Arguments[2].ToInteger())
	}

	diff := dur1 - dur2
	if diff < 0 {
		diff = -diff
	}

	return r.vm.ToValue(diff <= tolerance)
}

// matchingNormalizeString normalizes a string for comparison
func (r *ExtensionRuntime) matchingNormalizeString(call goja.FunctionCall) goja.Value {
	if len(call.Arguments) < 1 {
		return r.vm.ToValue("")
	}

	str := call.Arguments[0].String()
	normalized := normalizeStringForMatching(str)
	return r.vm.ToValue(normalized)
}

// calculateStringSimilarity calculates similarity between two strings (0-1)
func calculateStringSimilarity(s1, s2 string) float64 {
	if len(s1) == 0 && len(s2) == 0 {
		return 1.0
	}
	if len(s1) == 0 || len(s2) == 0 {
		return 0.0
	}

	// Use Levenshtein distance
	distance := levenshteinDistance(s1, s2)
	maxLen := len(s1)
	if len(s2) > maxLen {
		maxLen = len(s2)
	}

	return 1.0 - float64(distance)/float64(maxLen)
}

// levenshteinDistance calculates the Levenshtein distance between two strings
func levenshteinDistance(s1, s2 string) int {
	if len(s1) == 0 {
		return len(s2)
	}
	if len(s2) == 0 {
		return len(s1)
	}

	// Create matrix
	matrix := make([][]int, len(s1)+1)
	for i := range matrix {
		matrix[i] = make([]int, len(s2)+1)
		matrix[i][0] = i
	}
	for j := range matrix[0] {
		matrix[0][j] = j
	}

	// Fill matrix
	for i := 1; i <= len(s1); i++ {
		for j := 1; j <= len(s2); j++ {
			cost := 1
			if s1[i-1] == s2[j-1] {
				cost = 0
			}
			matrix[i][j] = min(
				matrix[i-1][j]+1,      // deletion
				matrix[i][j-1]+1,      // insertion
				matrix[i-1][j-1]+cost, // substitution
			)
		}
	}

	return matrix[len(s1)][len(s2)]
}

// normalizeStringForMatching normalizes a string for comparison
func normalizeStringForMatching(s string) string {
	// Convert to lowercase
	s = strings.ToLower(s)

	// Remove common suffixes/prefixes
	suffixes := []string{
		" (remastered)", " (remaster)", " - remastered", " - remaster",
		" (deluxe)", " (deluxe edition)", " - deluxe", " - deluxe edition",
		" (explicit)", " (clean)", " [explicit]", " [clean]",
		" (album version)", " (single version)", " (radio edit)",
		" (feat.", " (ft.", " feat.", " ft.",
	}
	for _, suffix := range suffixes {
		if idx := strings.Index(s, suffix); idx != -1 {
			s = s[:idx]
		}
	}

	// Remove special characters
	var result strings.Builder
	for _, r := range s {
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == ' ' {
			result.WriteRune(r)
		}
	}

	// Collapse multiple spaces
	s = strings.Join(strings.Fields(result.String()), " ")

	return strings.TrimSpace(s)
}