Merge pull request #149 from alexflint/parse-into-map

Add support for parsing into a map

1 files changed, 123 insertions, 0 deletions

diff --git a/sequence.go b/sequence.go
new file mode 100644
index 0000000..35a3614
--- /dev/null
+++ b/sequence.go
@@ -0,0 +1,123 @@
+package arg
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	scalar "github.com/alexflint/go-scalar"
+)
+
+// setSliceOrMap parses a sequence of strings into a slice or map. If clear is
+// true then any values already in the slice or map are first removed.
+func setSliceOrMap(dest reflect.Value, values []string, clear bool) error {
+	if !dest.CanSet() {
+		return fmt.Errorf("field is not writable")
+	}
+
+	t := dest.Type()
+	if t.Kind() == reflect.Ptr {
+		dest = dest.Elem()
+		t = t.Elem()
+	}
+
+	switch t.Kind() {
+	case reflect.Slice:
+		return setSlice(dest, values, clear)
+	case reflect.Map:
+		return setMap(dest, values, clear)
+	default:
+		return fmt.Errorf("setSliceOrMap cannot insert values into a %v", t)
+	}
+}
+
+// setSlice parses a sequence of strings and inserts them into a slice. If clear
+// is true then any values already in the slice are removed.
+func setSlice(dest reflect.Value, values []string, clear bool) error {
+	var ptr bool
+	elem := dest.Type().Elem()
+	if elem.Kind() == reflect.Ptr && !elem.Implements(textUnmarshalerType) {
+		ptr = true
+		elem = elem.Elem()
+	}
+
+	// clear the slice in case default values exist
+	if clear && !dest.IsNil() {
+		dest.SetLen(0)
+	}
+
+	// parse the values one-by-one
+	for _, s := range values {
+		v := reflect.New(elem)
+		if err := scalar.ParseValue(v.Elem(), s); err != nil {
+			return err
+		}
+		if !ptr {
+			v = v.Elem()
+		}
+		dest.Set(reflect.Append(dest, v))
+	}
+	return nil
+}
+
+// setMap parses a sequence of name=value strings and inserts them into a map.
+// If clear is true then any values already in the map are removed.
+func setMap(dest reflect.Value, values []string, clear bool) error {
+	// determine the key and value type
+	var keyIsPtr bool
+	keyType := dest.Type().Key()
+	if keyType.Kind() == reflect.Ptr && !keyType.Implements(textUnmarshalerType) {
+		keyIsPtr = true
+		keyType = keyType.Elem()
+	}
+
+	var valIsPtr bool
+	valType := dest.Type().Elem()
+	if valType.Kind() == reflect.Ptr && !valType.Implements(textUnmarshalerType) {
+		valIsPtr = true
+		valType = valType.Elem()
+	}
+
+	// clear the slice in case default values exist
+	if clear && !dest.IsNil() {
+		for _, k := range dest.MapKeys() {
+			dest.SetMapIndex(k, reflect.Value{})
+		}
+	}
+
+	// allocate the map if it is not allocated
+	if dest.IsNil() {
+		dest.Set(reflect.MakeMap(dest.Type()))
+	}
+
+	// parse the values one-by-one
+	for _, s := range values {
+		// split at the first equals sign
+		pos := strings.Index(s, "=")
+		if pos == -1 {
+			return fmt.Errorf("cannot parse %q into a map, expected format key=value", s)
+		}
+
+		// parse the key
+		k := reflect.New(keyType)
+		if err := scalar.ParseValue(k.Elem(), s[:pos]); err != nil {
+			return err
+		}
+		if !keyIsPtr {
+			k = k.Elem()
+		}
+
+		// parse the value
+		v := reflect.New(valType)
+		if err := scalar.ParseValue(v.Elem(), s[pos+1:]); err != nil {
+			return err
+		}
+		if !valIsPtr {
+			v = v.Elem()
+		}
+
+		// add it to the map
+		dest.SetMapIndex(k, v)
+	}
+	return nil
+}