Merge pull request #157 from saljam/arabic

Further improvements to the Arabic analyzer

analysis/language/ar/analyzer_ar.go

@@ -14,6 +14,7 @@ import (
 	"github.com/blevesearch/bleve/registry"
 
 	"github.com/blevesearch/bleve/analysis/token_filters/lower_case_filter"
+	"github.com/blevesearch/bleve/analysis/token_filters/unicode_normalize"
 	"github.com/blevesearch/bleve/analysis/tokenizers/unicode"
 )
 
@@ -28,6 +29,7 @@ func AnalyzerConstructor(config map[string]interface{}, cache *registry.Cache) (
 	if err != nil {
 		return nil, err
 	}
+	normalizeFilter := unicode_normalize.MustNewUnicodeNormalizeFilter(unicode_normalize.NFKC)
 	stopArFilter, err := cache.TokenFilterNamed(StopName)
 	if err != nil {
 		return nil, err
@@ -44,6 +46,7 @@ func AnalyzerConstructor(config map[string]interface{}, cache *registry.Cache) (
 		Tokenizer: tokenizer,
 		TokenFilters: []analysis.TokenFilter{
 			toLowerFilter,
+			normalizeFilter,
 			stopArFilter,
 			normalizeArFilter,
 			stemmerArFilter,

analysis/language/ar/analyzer_ar_test.go

@@ -150,6 +150,18 @@ func TestArabicAnalyzer(t *testing.T) {
 				},
 			},
 		},
+		// presentation form normalization
+		{
+			input: []byte("ﺍﻟﺴﻼﻢ"),
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term:     []byte("سلام"),
+					Position: 1,
+					Start:    0,
+					End:      15,
+				},
+			},
+		},
 	}
 
 	cache := registry.NewCache()

analysis/language/ar/stemmer_ar.go

@@ -19,26 +19,26 @@ import (
 const StemmerName = "stemmer_ar"
 
 // These were obtained from org.apache.lucene.analysis.ar.ArabicStemmer
-var prefixes = [][]byte{
+var prefixes = [][]rune{
-	[]byte("ال"),
+	[]rune("ال"),
-	[]byte("وال"),
+	[]rune("وال"),
-	[]byte("بال"),
+	[]rune("بال"),
-	[]byte("كال"),
+	[]rune("كال"),
-	[]byte("فال"),
+	[]rune("فال"),
-	[]byte("لل"),
+	[]rune("لل"),
-	[]byte("و"),
+	[]rune("و"),
 }
-var suffixes = [][]byte{
+var suffixes = [][]rune{
-	[]byte("ها"),
+	[]rune("ها"),
-	[]byte("ان"),
+	[]rune("ان"),
-	[]byte("ات"),
+	[]rune("ات"),
-	[]byte("ون"),
+	[]rune("ون"),
-	[]byte("ين"),
+	[]rune("ين"),
-	[]byte("يه"),
+	[]rune("يه"),
-	[]byte("ية"),
+	[]rune("ية"),
-	[]byte("ه"),
+	[]rune("ه"),
-	[]byte("ة"),
+	[]rune("ة"),
-	[]byte("ي"),
+	[]rune("ي"),
 }
 
 type ArabicStemmerFilter struct{}
@@ -55,21 +55,53 @@ func (s *ArabicStemmerFilter) Filter(input analysis.TokenStream) analysis.TokenS
 	return input
 }
 
+func canStemPrefix(input, prefix []rune) bool {
+	// Wa- prefix requires at least 3 characters.
+	if len(prefix) == 1 && len(input) < 4 {
+		return false
+	}
+	// Other prefixes require only 2.
+	if len(input)-len(prefix) < 2 {
+		return false
+	}
+	for i := range prefix {
+		if prefix[i] != input[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func canStemSuffix(input, suffix []rune) bool {
+	// All suffixes require at least 2 characters after stemming.
+	if len(input)-len(suffix) < 2 {
+		return false
+	}
+	stemEnd := len(input) - len(suffix)
+	for i := range suffix {
+		if suffix[i] != input[stemEnd+i] {
+			return false
+		}
+	}
+	return true
+}
+
 func stem(input []byte) []byte {
+	runes := bytes.Runes(input)
 	// Strip a single prefix.
 	for _, p := range prefixes {
-		if bytes.HasPrefix(input, p) {
+		if canStemPrefix(runes, p) {
-			input = input[len(p):]
+			runes = runes[len(p):]
 			break
 		}
 	}
 	// Strip off multiple suffixes, in their order in the suffixes array.
 	for _, s := range suffixes {
-		if bytes.HasSuffix(input, s) {
+		if canStemSuffix(runes, s) {
-			input = input[:len(input)-len(s)]
+			runes = runes[:len(runes)-len(s)]
 		}
 	}
-	return input
+	return analysis.BuildTermFromRunes(runes)
 }
 
 func StemmerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {

analysis/language/ar/stemmer_ar_test.go

@@ -21,6 +21,279 @@ func TestArabicStemmerFilter(t *testing.T) {
 		input  analysis.TokenStream
 		output analysis.TokenStream
 	}{
+		// AlPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("الحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// WalPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("والحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// BalPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("بالحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// KalPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("كالحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// FalPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("فالحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// LlPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("للاخر"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("اخر"),
+				},
+			},
+		},
+		// WaPrefix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("وحسن"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("حسن"),
+				},
+			},
+		},
+		// AhSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("زوجها"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("زوج"),
+				},
+			},
+		},
+		// AnSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدان"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// AtSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدات"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// WnSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدون"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// YnSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدين"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// YhSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهديه"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// YpSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدية"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// HSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهده"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// PSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدة"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// YSuffix
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدي"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// ComboPrefSuf
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("وساهدون"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// ComboSuf
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهدهات"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("ساهد"),
+				},
+			},
+		},
+		// ShouldntStem
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("الو"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("الو"),
+				},
+			},
+		},
+		// NonArabic
+		{
+			input: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("English"),
+				},
+			},
+			output: analysis.TokenStream{
+				&analysis.Token{
+					Term: []byte("English"),
+				},
+			},
+		},
 		{
 			input: analysis.TokenStream{
 				&analysis.Token{
@@ -93,7 +366,7 @@ func TestArabicStemmerFilter(t *testing.T) {
 				},
 			},
 		},
-		// empty
+		// Empty
 		{
 			input: analysis.TokenStream{
 				&analysis.Token{