Don't allow matches from shows only matching 'the'

categorize/match/match.go

@@ -2,6 +2,8 @@ package match
 
 import (
 	"errors"
+	"strings"
+	"unicode"
 
 	"github.com/agnivade/levenshtein"
 )
@@ -17,10 +19,12 @@ type match struct {
 func FindBestMatch(candidate string, index []string) (string, error) {
 	haveCommonPrefix := []string{}
 	for _, indexEntry := range index {
-		prefix := getLongestCommonPrefix(candidate, indexEntry)
-		// Single character prefixes aren't that helpful.
-		// I don't want to get into threshold territory by playing with a number higher than this, though
-		if len(prefix) > 1 {
+		prefix := getLongestCommonPrefix(
+			normalizeForMatch(candidate),
+			normalizeForMatch(indexEntry),
+		)
+
+		if isPrefixMeaningful(prefix) {
 			haveCommonPrefix = append(haveCommonPrefix, indexEntry)
 		}
 	}
@@ -61,3 +65,24 @@ func findMinScoreMatch(matches []match) match {
 
 	return minScorematch
 }
+
+func normalizeForMatch(target string) string {
+	return filterChars(target, func(r rune) bool {
+		return !isCharLikelySeparator(r)
+	})
+}
+
+func filterChars(target string, shouldAllowChar func(s rune) bool) string {
+	builder := strings.Builder{}
+	for _, char := range target {
+		if shouldAllowChar(char) {
+			builder.WriteRune(char)
+		}
+	}
+
+	return builder.String()
+}
+
+func isCharLikelySeparator(r rune) bool {
+	return !unicode.IsNumber(r) && !unicode.IsLetter(r)
+}

categorize/match/match_test.go

@@ -78,6 +78,13 @@ func TestFindBestMatch(t *testing.T) {
 			expectedMatch: "",
 			expectedError: ErrNoMatches,
 		},
+		{
+			// two have a common prefix of "the-a" but really there should be no match
+			candidate:     "the-amazing-gymnist",
+			index:         []string{"the-athlete", "sitting-at-home", "the-show-about-nothing"},
+			expectedMatch: "",
+			expectedError: ErrNoMatches,
+		},
 	}
 
 	for _, test := range tt {
@@ -89,7 +96,7 @@ func TestFindBestMatch(t *testing.T) {
 		t.Run(testName, func(t *testing.T) {
 			match, err := FindBestMatch(test.candidate, test.index)
 			if test.expectedError != nil {
-				assert.ErrorIs(t, err, ErrNoMatches, fmt.Sprintf("got %s", match))
+				assert.ErrorIs(t, err, ErrNoMatches, fmt.Sprintf("got match %q and error %q", match, err))
 			} else {
 				assert.Nil(t, err)
 				assert.Equal(t, test.expectedMatch, match)

categorize/match/prefix.go

@@ -1,5 +1,9 @@
 package match
 
+import (
+	"strings"
+)
+
 func getLongestCommonPrefix(a, b string) string {
 	shortestString, longestString := getShortestAndLongestString(a, b)
 	for i := range shortestString {
@@ -19,3 +23,38 @@ func getShortestAndLongestString(a, b string) (string, string) {
 		return a, b
 	}
 }
+
+// isPrefixMeaningful checks if the given of a match is truly meaningful enough to allow it to be considered a
+// good enough match to continue processing. For instance, a longest common prefix of a single letter is not really
+// all that meaningful.
+func isPrefixMeaningful(prefix string) bool {
+	// Single character prefixes aren't that helpful.
+	// I don't want to get into threshold territory by playing with a number higher than this, though
+	if len(prefix) <= 1 {
+		return false
+	}
+
+	// A match whose prefix is "the" (possibly followed by a separator) is probably not that useful of a match
+	return isPrefixMeaningfulWithoutThe(prefix)
+}
+
+// Check if the start of a given prefix is 'the', and if it is, whether removing it would still procure a
+// meaningful match
+func isPrefixMeaningfulWithoutThe(prefix string) bool {
+	if len(prefix) < 3 {
+		return false
+	}
+
+	startsWithThe := strings.ToLower(prefix[:3]) == "the"
+	if !startsWithThe {
+		return true
+	}
+
+	trimmedPrefix := strings.TrimFunc(prefix, isCharLikelySeparator)
+	if len(trimmedPrefix) <= 3 {
+		return false
+	}
+
+	prefixWithoutThe := strings.TrimFunc(trimmedPrefix[3:], isCharLikelySeparator)
+	return isPrefixMeaningful(prefixWithoutThe)
+}

categorize/match/prefix_test.go

@@ -39,3 +39,40 @@ func TestLongestCommonPrefix(t *testing.T) {
 		assert.Equal(t, test.expectedPrefix, prefix)
 	}
 }
+
+func TestIsPrefixMeaningful(t *testing.T) {
+	tt := []struct {
+		prefix   string
+		expected bool
+	}{
+		{
+			prefix:   "Brooklyn",
+			expected: true,
+		},
+		{
+			prefix:   "b",
+			expected: false,
+		},
+		{
+			prefix:   "The",
+			expected: false,
+		},
+		{
+			prefix:   "The-",
+			expected: false,
+		},
+		{
+			prefix:   "The Runner",
+			expected: true,
+		},
+		{
+			prefix:   "The R",
+			expected: false,
+		},
+	}
+
+	for _, test := range tt {
+		isMeaningful := isPrefixMeaningful(test.prefix)
+		assert.Equal(t, test.expected, isMeaningful)
+	}
+}

categorize/tv_test.go

@@ -46,15 +46,27 @@ func TestFindBestFolder(t *testing.T) {
 			"",
 			match.ErrNoMatches,
 		},
+		{
+			"A match with a non-meaningful prefix ('the') should not match",
+			"The.Amazing.Spider-Man.1977.S01.VHSRip",
+			[]string{"The-Good-Place", "The-Simpsons", "Stranger-Things", "Brooklyn-Nine-Nine", "The-IT-Crowd"},
+			"",
+			match.ErrNoMatches,
+		},
+		{
+			"A good match starting with 'the' should still match",
+			"The.Simpsons.S06.720p.DSNP.WEB-DL.DDP5.1.H.264-MZABI",
+			[]string{"The-Good-Place", "The-Simpsons", "Stranger-Things", "Brooklyn-Nine-Nine", "The-IT-Crowd"},
+			"The-Simpsons",
+			nil,
+		},
 	}
 
 	for _, test := range table {
 		t.Run(test.testName, func(t *testing.T) {
-
 			foundFolder, err := findShowFolder(test.fileName, test.folders)
-
 			if test.expectedError != nil {
-				assert.ErrorIs(t, err, test.expectedError, fmt.Sprintf("got %s", foundFolder))
+				assert.ErrorIs(t, err, test.expectedError, fmt.Sprintf("got show %q and error %q", foundFolder, err))
 			} else {
 				assert.Nil(t, err)
 				assert.Equal(t, test.expectedFolder, foundFolder)