float.go

package null

import (
	"database/sql"
	"encoding/json"
	"encoding/xml"
	"fmt"
	"math/rand"
	"reflect"
	"strconv"

	"gopkg.in/mgo.v2/bson"
)

// Float is a nullable float64.
// It does not consider zero values to be null.
// It will decode to null, not zero, if null.
type Float struct {
	sql.NullFloat64
}

// NewFloat creates a new Float
func NewFloat(f float64, valid bool) Float {
	return Float{
		NullFloat64: sql.NullFloat64{
			Float64: f,
			Valid:   valid,
		},
	}
}

// FloatFrom creates a new Float that will always be valid.
func FloatFrom(f float64) Float {
	return NewFloat(f, true)
}

// FloatFromPtr creates a new Float that be null if f is nil.
func FloatFromPtr(f *float64) Float {
	if f == nil {
		return NewFloat(0, false)
	}
	return NewFloat(*f, true)
}

// UnmarshalJSON implements json.Unmarshaler.
// It supports number and null input.
// 0 will not be considered a null Float.
// It also supports unmarshalling a sql.NullFloat64.
func (f *Float) UnmarshalJSON(data []byte) error {
	var err error
	var v interface{}
	if err = json.Unmarshal(data, &v); err != nil {
		return err
	}
	switch x := v.(type) {
	case float64:
		f.Float64 = float64(x)
	case map[string]interface{}:
		err = json.Unmarshal(data, &f.NullFloat64)
	case nil:
		f.Valid = false
		return nil
	default:
		err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.Float", reflect.TypeOf(v).Name())
	}
	f.Valid = err == nil
	return err
}

// UnmarshalText implements encoding.TextUnmarshaler.
// It will unmarshal to a null Float if the input is a blank or not an integer.
// It will return an error if the input is not an integer, blank, or "null".
func (f *Float) UnmarshalText(text []byte) error {
	str := string(text)
	if str == "" || str == "null" {
		f.Valid = false
		return nil
	}
	var err error
	f.Float64, err = strconv.ParseFloat(string(text), 64)
	f.Valid = err == nil
	return err
}

// MarshalJSON implements json.Marshaler.
// It will encode null if this Float is null.
func (f Float) MarshalJSON() ([]byte, error) {
	if !f.Valid {
		return []byte("null"), nil
	}
	return []byte(strconv.FormatFloat(f.Float64, 'f', -1, 64)), nil
}

// MarshalText implements encoding.TextMarshaler.
// It will encode a blank string if this Float is null.
func (f Float) MarshalText() ([]byte, error) {
	if !f.Valid {
		return []byte{}, nil
	}
	return []byte(strconv.FormatFloat(f.Float64, 'f', -1, 64)), nil
}

// MarshalXML implements the xml.Marshaler interface
func (f Float) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if f.Valid {
		return e.EncodeElement(f.Float64, start)
	}
	return e.EncodeElement(nil, start)
}

// UnmarshalXML implments the xml.Unmarshaler interface
func (f *Float) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {

	var x *float64
	if err := d.DecodeElement(&x, &start); err != nil {
		return err
	}
	if x != nil {
		f.Valid = true
		f.Float64 = *x
	} else {
		f.Valid = false
	}
	return nil
}

// GetBSON implements bson.Getter.
func (f Float) GetBSON() (interface{}, error) {
	if f.Valid {
		return f.Float64, nil
	}
	// TODO: do we need a nil pointer to a string?
	return nil, nil
}

// SetBSON implements bson.Setter.
func (f *Float) SetBSON(raw bson.Raw) error {
	var ff float64
	err := raw.Unmarshal(&ff)

	if err == nil {
		*f = Float{sql.NullFloat64{Float64: ff, Valid: true}}
	} else {
		*f = Float{sql.NullFloat64{Valid: false}}
	}
	return nil
}

// GetValue implements the compare.Valuable interface
func (f Float) GetValue() reflect.Value {
	if f.Valid {
		return reflect.ValueOf(f.Float64)
	}
	// or just nil?
	return reflect.ValueOf(nil)
}

// LoremDecode implements lorem.Decoder
func (f *Float) LoremDecode(tag, example string) error {
	f.SetValid(rand.Float64())
	return nil
}

// SetValid changes this Float's value and also sets it to be non-null.
func (f *Float) SetValid(n float64) {
	f.Float64 = n
	f.Valid = true
}

// Ptr returns a pointer to this Float's value, or a nil pointer if this Float is null.
func (f Float) Ptr() *float64 {
	if !f.Valid {
		return nil
	}
	return &f.Float64
}

// IsZero returns true for invalid Floats, for future omitempty support (Go 1.4?)
// A non-null Float with a 0 value will not be considered zero.
func (f Float) IsZero() bool {
	return !f.Valid
}