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package arg
import (
"encoding"
"fmt"
"reflect"
"unicode"
"unicode/utf8"
scalar "github.com/alexflint/go-scalar"
)
var textUnmarshalerType = reflect.TypeOf([]encoding.TextUnmarshaler{}).Elem()
// kind is used to track the various kinds of options:
// - regular is an ordinary option that will be parsed from a single token
// - binary is an option that will be true if present but does not expect an explicit value
// - sequence is an option that accepts multiple values and will end up in a slice
// - mapping is an option that acccepts multiple key=value strings and will end up in a map
type kind int
const (
regular kind = iota
binary
sequence
mapping
unsupported
)
func (k kind) String() string {
switch k {
case regular:
return "regular"
case binary:
return "binary"
case sequence:
return "sequence"
case mapping:
return "mapping"
case unsupported:
return "unsupported"
default:
return fmt.Sprintf("unknown(%d)", int(k))
}
}
// kindOf returns true if the type can be parsed from a string
func kindOf(t reflect.Type) (kind, error) {
if scalar.CanParse(t) {
if isBoolean(t) {
return binary, nil
} else {
return regular, nil
}
}
// look inside pointer types
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
// look inside slice and map types
switch t.Kind() {
case reflect.Slice:
if !scalar.CanParse(t.Elem()) {
return unsupported, fmt.Errorf("cannot parse into %v because we cannot parse into %v", t, t.Elem())
}
return sequence, nil
case reflect.Map:
if !scalar.CanParse(t.Key()) {
return unsupported, fmt.Errorf("cannot parse into %v because we cannot parse into the key type %v", t, t.Elem())
}
if !scalar.CanParse(t.Elem()) {
return unsupported, fmt.Errorf("cannot parse into %v because we cannot parse into the value type %v", t, t.Elem())
}
return mapping, nil
default:
return unsupported, fmt.Errorf("cannot parse into %v", t)
}
}
// isBoolean returns true if the type can be parsed from a single string
func isBoolean(t reflect.Type) bool {
switch {
case t.Implements(textUnmarshalerType):
return false
case t.Kind() == reflect.Bool:
return true
case t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Bool:
return true
default:
return false
}
}
// isExported returns true if the struct field name is exported
func isExported(field string) bool {
r, _ := utf8.DecodeRuneInString(field) // returns RuneError for empty string or invalid UTF8
return unicode.IsLetter(r) && unicode.IsUpper(r)
}
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