Implement provider calculation for each providers (repository layer)

[aldy505]

It should be put on a sub-package under the repository package. The logic on how the pricing works is totally up to you.
If possible, please include unit tests.

mock-shipping-provider/repository/provider_calculation.go

Lines 5 to 10 in 68058d6

	type ProviderCalculation interface {
	// CalculateTimeOfArrival calculates the time of arrival (in hours) based on distance.
	CalculateTimeOfArrival(distance float64) int64
	// CalculatePrice price from distance, dimension, and weight combination.
	CalculatePrice(distance float64, dimension primitive.Dimension, weight float64) int64
	}

Providers are defined here:

mock-shipping-provider/primitive/provider.go

Lines 6 to 12 in 413bb3e

	const (
	ProviderUnspecified Provider = iota
	ProviderJNE
	ProviderSiCepat
	ProviderJNT
	ProviderAnterAja
	)

Example:

type JNE struct{}

func (JNE) CalculatePrice(distance float64, dimension primitive.Dimension, weight float64) int64 {
  var basePrice = 9000
  // Multiply basePrice by volume
  var volume = dimension.Width * dimension.Height * dimension.Depth
  
  // 1 hop every 200 km
  var hops float64
  if distance < 1 {
    hops = 1
  } else {
    hops = distance / 200 // division by 0 causes panic, avoid that!
  }

  return basePrice * int64(volume) * hops
}

func (JNE) CalculateTimeOfArrival(distance float64) int64 {
  return 0 // do it yourself
}

That's just an example, you don't have to follow it. Be creative.