func (b *Backend) FieldType(typ reflect.Type, t *structs.Tag) (string, error) {
	if c := codec.FromTag(t); c != nil {
		if c.Binary || t.PipeName() != "" {
			return "BLOB", nil
		}
		return "TEXT", nil
	}
	switch typ.Kind() {
	case reflect.Bool:
		return "BOOLEAN", nil
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return "INTEGER", nil
	case reflect.Float32, reflect.Float64:
		return "REAL", nil
	case reflect.String:
		return "TEXT", nil
	case reflect.Slice:
		// []byte
		if typ.Elem().Kind() == reflect.Uint8 {
			return "BLOB", nil
		}
	case reflect.Struct:
		if typ.Name() == "Time" && typ.PkgPath() == "time" {
			return "INTEGER", nil
		}
	}
	return "", fmt.Errorf("can't map field type %v to a database type", typ)
}

// InputNamed takes a (generally) user-provided input string and parses it into the out
// parameter, which must be settable (this usually means you'll have to pass a pointer
// to this function). See the documentation on Parse() for a list of the supported types.
// If name is provided, it will be included in any error returned by this function.
// Additional constraints might be specified with the tag parameter, the ones currently
// supported are:
//  - required: Marks the field as required, will return an error if it's empty.
//  - optional: Marks the field as optional, will accept empty values.
//  - max_length: Sets the maximum length for the input.
//  - min_length: Sets the minimum length for the input.
//  - alphanumeric: Requires the input to be only letters and numbers
//
// Finally, the required parameter indicates if the value should be considered required
// or optional in absence of the "required" and "optional" tag fields.
func InputNamed(name string, input string, out interface{}, tag *structs.Tag, required bool) error {
	v, err := types.SettableValue(out)
	if err != nil {
		return err
	}
	if err := parse(input, v); err != nil {
		return err
	}
	if v.Type().Kind() != reflect.Bool && tag != nil {
		if ((required && !tag.Optional()) || tag.Required()) && input == "" {
			return RequiredInputError(name)
		}
		if maxlen, ok := tag.MaxLength(); ok && len(input) > maxlen {
			if name != "" {
				return i18n.Errorfc("form", "%s is too long (maximum length is %d)", name, maxlen)
			}
			return i18n.Errorfc("form", "too long (maximum length is %d)", maxlen)
		}
		if minlen, ok := tag.MinLength(); ok && len(input) < minlen {
			if name != "" {
				return i18n.Errorfc("form", "%s is too short (minimum length is %d)", name, minlen)
			}
			return i18n.Errorfc("form", "too short (minimum length is %d)", minlen)
		}
		if tag.Alphanumeric() && len(input) > 0 && !alphanumericRe.MatchString(input) {
			if name != "" {
				return i18n.Errorfc("form", "%s must be alphanumeric", name)
			}
			return i18n.Errorfc("form", "must be alphanumeric")
		}
	}
	return nil
}

func (d *Driver) isPrimaryKey(fields *driver.Fields, idx int, tag *structs.Tag) bool {
	if tag.Has("primary_key") {
		return true
	}
	for _, v := range fields.CompositePrimaryKey {
		if v == idx {
			return true
		}
	}
	return false
}

func (ormStructConfigurator) DecomposeField(s *structs.Struct, typ reflect.Type, tag *structs.Tag) bool {
	// Don't decompose fields with a codec
	if tag.Has("codec") {
		return false
	}
	// Avoid decomposing time.Time
	if typ.Name() == "Time" && typ.PkgPath() == "time" {
		return false
	}
	return true
}

func (b *SqlBackend) ScanByteSlice(val []byte, goVal *reflect.Value, t *structs.Tag) error {
	if goVal.Kind() == reflect.String {
		goVal.SetString(string(val))
		return nil
	}
	if len(val) > 0 && !t.Has("raw") {
		b := make([]byte, len(val))
		copy(b, val)
		val = b
	}
	goVal.Set(reflect.ValueOf(val))
	return nil
}

// returns wheter the kind defaults to nullempty option
func defaultsToNullEmpty(typ reflect.Type, t *structs.Tag) bool {
	if t.Has("references") || t.Has("codec") || (t.Has("notnull") && typ.Kind() != reflect.Bool) {
		return true
	}
	switch typ.Kind() {
	case reflect.Slice, reflect.Ptr, reflect.Interface, reflect.String:
		return true
	case reflect.Struct:
		return typ == timeType
	}
	return false
}

// FromTag returns the pipe for a given field tag.
func FromTag(t *structs.Tag) *Pipe {
	return registry[t.PipeName()]
}

// FromTag returns the pipe for a given field tag.
func FromTag(t *structs.Tag) *Codec {
	return codecs[t.CodecName()]
}

func defaultsToOmitEmpty(typ reflect.Type, t *structs.Tag) bool {
	return t.Has("auto_increment") || (t.Has("default") && typ.Kind() != reflect.Bool)
}