1 files changed, 62 insertions, 0 deletions
diff --git a/ucd/property_value_aliases.go b/ucd/property_value_aliases.go
new file mode 100644
index 0000000..c438c54
--- /dev/null
+++ b/ucd/property_value_aliases.go
@@ -0,0 +1,62 @@
+package ucd
+
+import "io"
+
+type PropertyValueAliases struct {
+	GeneralCategory             map[string]string
+	GeneralCategoryDefaultRange *CodePointRange
+	GeneralCategoryDefaultValue string
+}
+
+// ParsePropertyValueAliases parses the PropertyValueAliases.txt.
+func ParsePropertyValueAliases(r io.Reader) (*PropertyValueAliases, error) {
+	catName2Abbs := map[string]string{}
+	var defaultGCCPRange *CodePointRange
+	var defaultGCVal string
+	p := newParser(r)
+	for p.parse() {
+		// https://www.unicode.org/reports/tr44/#Property_Value_Aliases
+		// > In PropertyValueAliases.txt, the first field contains the abbreviated alias for a Unicode property,
+		// > the second field specifies an abbreviated symbolic name for a value of that property, and the third
+		// > field specifies the long symbolic name for that value of that property. These are the preferred
+		// > aliases. Additional aliases for some property values may be specified in the fourth or subsequent
+		// > fields.
+		if len(p.fields) > 0 && p.fields[0].symbol() == "gc" {
+			catNameShort := p.fields[1].normalizedSymbol()
+			catNameLong := p.fields[2].normalizedSymbol()
+			catName2Abbs[catNameShort] = catNameShort
+			catName2Abbs[catNameLong] = catNameShort
+			for _, f := range p.fields[3:] {
+				catNameOther := f.normalizedSymbol()
+				catName2Abbs[catNameOther] = catNameShort
+			}
+		}
+
+		// https://www.unicode.org/reports/tr44/#Missing_Conventions
+		// > @missing lines are also supplied for many properties in the file PropertyValueAliases.txt.
+		// > ...
+		// > there are currently two syntactic patterns used for @missing lines, as summarized schematically below:
+		// >     1. code_point_range; default_prop_val
+		// >     2. code_point_range; property_name; default_prop_val
+		// > ...
+		// > Pattern #2 is used in PropertyValueAliases.txt and in DerivedNormalizationProps.txt, both of which
+		// > contain values associated with many properties. For example:
+		// >     # @missing: 0000..10FFFF; NFD_QC; Yes
+		if len(p.defaultFields) > 0 && p.defaultFields[1].symbol() == "General_Category" {
+			var err error
+			defaultGCCPRange, err = p.defaultFields[0].codePointRange()
+			if err != nil {
+				return nil, err
+			}
+			defaultGCVal = p.defaultFields[2].normalizedSymbol()
+		}
+	}
+	if p.err != nil {
+		return nil, p.err
+	}
+	return &PropertyValueAliases{
+		GeneralCategory:             catName2Abbs,
+		GeneralCategoryDefaultRange: defaultGCCPRange,
+		GeneralCategoryDefaultValue: defaultGCVal,
+	}, nil
+}