88 lines
1.5 KiB
Go
88 lines
1.5 KiB
Go
package tariff
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import (
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"errors"
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"fmt"
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"time"
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"github.com/traefik/yaegi/interp"
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"github.com/traefik/yaegi/stdlib"
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)
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type embed struct {
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Charges float64 `mapstructure:"charges"`
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Tax float64 `mapstructure:"tax"`
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Formula string `mapstructure:"formula"`
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calc func(float64, time.Time) (float64, error)
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}
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func (t *embed) init() (err error) {
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defer func() {
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if r := recover(); r != nil && err == nil {
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err = fmt.Errorf("panic: %v", r)
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}
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}()
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if t.Formula == "" {
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return nil
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}
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vm := interp.New(interp.Options{})
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if err := vm.Use(stdlib.Symbols); err != nil {
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return err
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}
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if _, err := vm.Eval(fmt.Sprintf(`
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import (
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"math"
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"time"
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)
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var (
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price float64
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charges float64 = %f
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tax float64 = %f
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ts time.Time
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)`, t.Charges, t.Tax)); err != nil {
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return err
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}
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prg, err := vm.Compile(t.Formula)
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if err != nil {
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return err
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}
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t.calc = func(price float64, ts time.Time) (float64, error) {
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if _, err := vm.Eval(fmt.Sprintf(`
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price = %f
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ts = time.Unix(%d, 0).Local()
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`, price, ts.Unix())); err != nil {
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return 0, err
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}
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res, err := vm.Execute(prg)
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if err != nil {
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return 0, err
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}
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if !res.CanFloat() {
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return 0, errors.New("formula did not return a float value")
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}
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return res.Float(), nil
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}
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// test the formula
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_, err = t.calc(0, time.Now())
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return err
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}
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func (t *embed) totalPrice(price float64, ts time.Time) float64 {
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if t.calc != nil {
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res, _ := t.calc(price, ts)
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return res
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}
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return (price + t.Charges) * (1 + t.Tax)
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}
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