carddav: add filtering and matching helper functions

Updates emersion/hydroxide#159.

Signed-off-by: Sebastien Binet <binet@cern.ch>
Co-authored-by: Conrad Hoffmann <ch@bitfehler.net>

carddav/match.go

@@ -0,0 +1,146 @@
+package carddav
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/emersion/go-vcard"
+)
+
+// Filter returns the filtered list of address objects matching the provided query.
+// A nil query will return the full list of address objects.
+func Filter(query *AddressBookQuery, aos []AddressObject) ([]AddressObject, error) {
+	if query == nil {
+		// FIXME: should we always return a copy of the provided slice?
+		return aos, nil
+	}
+
+	n := query.Limit
+	if n <= 0 || n > len(aos) {
+		n = len(aos)
+	}
+	out := make([]AddressObject, 0, n)
+	for _, ao := range aos {
+		ok, err := Match(query, &ao)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			continue
+		}
+
+		// TODO properties are not currently filtered even if requested
+
+		out = append(out, ao)
+		if len(out) >= n {
+			break
+		}
+	}
+	return out, nil
+}
+
+// Match reports whether the provided AddressObject matches the query.
+func Match(query *AddressBookQuery, ao *AddressObject) (matched bool, err error) {
+	if query == nil {
+		return true, nil
+	}
+
+	switch query.FilterTest {
+	default:
+		return false, fmt.Errorf("unknown query filter test %q", query.FilterTest)
+
+	case FilterAnyOf, "":
+		for _, prop := range query.PropFilters {
+			ok, err := matchPropFilter(prop, ao)
+			if err != nil {
+				return false, err
+			}
+			if ok {
+				return true, nil
+			}
+		}
+		return false, nil
+
+	case FilterAllOf:
+		for _, prop := range query.PropFilters {
+			ok, err := matchPropFilter(prop, ao)
+			if err != nil {
+				return false, err
+			}
+			if !ok {
+				return false, nil
+			}
+		}
+		return true, nil
+	}
+}
+
+func matchPropFilter(prop PropFilter, ao *AddressObject) (bool, error) {
+	// TODO: this only matches first field, there could be multiple
+	field := ao.Card.Get(prop.Name)
+	if field == nil {
+		return prop.IsNotDefined, nil
+	} else if prop.IsNotDefined {
+		return false, nil
+	}
+
+	// TODO: handle carddav.PropFilter.Params.
+	if len(prop.TextMatches) == 0 {
+		return true, nil
+	}
+
+	switch prop.Test {
+	default:
+		return false, fmt.Errorf("unknown property filter test %q", prop.Test)
+
+	case FilterAnyOf, "":
+		for _, txt := range prop.TextMatches {
+			ok, err := matchTextMatch(txt, field)
+			if err != nil {
+				return false, err
+			}
+			if ok {
+				return true, nil
+			}
+		}
+		return false, nil
+
+	case FilterAllOf:
+		for _, txt := range prop.TextMatches {
+			ok, err := matchTextMatch(txt, field)
+			if err != nil {
+				return false, err
+			}
+			if !ok {
+				return false, nil
+			}
+		}
+		return true, nil
+	}
+}
+
+func matchTextMatch(txt TextMatch, field *vcard.Field) (bool, error) {
+	// TODO: handle text-match collation attribute
+	var ok bool
+	switch txt.MatchType {
+	default:
+		return false, fmt.Errorf("unknown textmatch type %q", txt.MatchType)
+
+	case MatchEquals:
+		ok = txt.Text == field.Value
+
+	case MatchContains, "":
+		ok = strings.Contains(field.Value, txt.Text)
+
+	case MatchStartsWith:
+		ok = strings.HasPrefix(field.Value, txt.Text)
+
+	case MatchEndsWith:
+		ok = strings.HasSuffix(field.Value, txt.Text)
+	}
+
+	if txt.NegateCondition {
+		ok = !ok
+	}
+	return ok, nil
+}