feat: implement caldav search

vendor/github.com/dolanor/caldav-go/icalendar/reflect.go

@@ -0,0 +1,78 @@
+package icalendar
+
+import (
+	"fmt"
+	"github.com/dolanor/caldav-go/icalendar/properties"
+	"github.com/dolanor/caldav-go/utils"
+	"log"
+	"reflect"
+	"strings"
+)
+
+var _ = log.Print
+
+func isInvalidOrEmptyValue(v reflect.Value) bool {
+	if !v.IsValid() {
+		return true
+	}
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	}
+	return false
+}
+
+func newValue(in reflect.Value) (out reflect.Value, isArrayElement bool) {
+
+	typ := in.Type()
+	kind := typ.Kind()
+
+	for {
+		if kind == reflect.Array || kind == reflect.Slice {
+			isArrayElement = true
+		} else if kind != reflect.Ptr {
+			break
+		}
+		typ = typ.Elem()
+		kind = typ.Kind()
+	}
+
+	out = reflect.New(typ)
+	return
+
+}
+
+func dereferencePointerValue(v reflect.Value) reflect.Value {
+	for (v.Kind() == reflect.Interface || v.Kind() == reflect.Ptr) && v.Elem().IsValid() {
+		v = v.Elem()
+	}
+	return v
+}
+
+func extractTagFromValue(v reflect.Value) (string, error) {
+
+	vdref := dereferencePointerValue(v)
+	vtemp, _ := newValue(vdref)
+
+	if encoder, ok := vtemp.Interface().(properties.CanEncodeTag); ok {
+		if tag, err := encoder.EncodeICalTag(); err != nil {
+			return "", utils.NewError(extractTagFromValue, "unable to extract tag from interface", v.Interface(), err)
+		} else {
+			return strings.ToUpper(tag), nil
+		}
+	} else {
+		typ := vtemp.Elem().Type()
+		return strings.ToUpper(fmt.Sprintf("v%s", typ.Name())), nil
+	}
+
+}