datetime

Contains various date/time related utility functionality, like parsing and formatting ISO8601 strings + converting Date and DateTime Google Common Types to/from UTC as well as different timezones/locations.

For dealing with ISO8601 formatted strings we make use of the relvacode/iso8601 library.

It also contains a "TimeProvider" which is useful for controlling the perception of time in a service, by injecting this we get a single and mockable source of the current time throughout the code base.

Install

go get github.com/dentech-floss/[email protected]

Usage

datetime

datetime.go contains a bunch of reusable utility func's for dealing with date/time to/from Time.

Here follows an example or it's usage, check out the datetime_test.go for the full monty.

package example

import (
    "testing"
    "github.com/dentech-floss/datetime/pkg/datetime"
)

func Test_ISO8601StringToTime(t *testing.T) {

    from = "2006-01-02T15:04:05-07:00"

    localTime, err = datetime.ISO8601StringToTime(from)
    if err != nil {
        t.Fatal(err)
    }
    utcTime, err = datetime.ISO8601StringToUTCTime(from)
    if err != nil {
        t.Fatal(err)
    }

    _, offsetInSeconds := localTime.Zone()
    offsetInHours := (offsetInSeconds / 60) / 60
    require.Equal(-7, offsetInHours)

    require.Equal(from, datetime.TimeToISO8601DateTimeString(localTime))
    require.Equal("2006-01-02T22:04:05Z", datetime.TimeToISO8601DateTimeString(utcTime))

    require.Equal(utcTime.In(localTime.Location()), localTime)
    require.Equal(localTime.UTC(), utcTime)
}

TimeProvider

Disadvantages of using "time.Now()" in the code? Well... are we using UTC or not? What if we use "time.Now()" somewhere when we were supposed to use "time.Now().UTC()"? What if we have time-sensitive code and want to write tests for certain times?

Inject the mockable TimeProvider and get a single source of the current time.

package example

import (
    "github.com/dentech-floss/datetime/pkg/datetime"
)

func main() {
    timeProvider := datetime.NewUTCTimeProvider() // provider of current time in UTC
    patientGatewayServiceV1 := service.NewPatientGatewayServiceV1(timeProvider) // inject it
}

package example

func (s *PatientGatewayServiceV1) FindAppointments(
    ctx context.Context,
    request *patient_gateway_service_v1.FindAppointmentsRequest,
) (*patient_gateway_service_v1.FindAppointmentsResponse, error) {

    now := s.timeProvider.Now() // Get the current time in UTC
}

Control the perception of time when testing:

package example

import (
    "testing"
    "github.com/dentech-floss/datetime/pkg/datetime"
)

func Test_FindAppointments(t *testing.T) {

    now, err := datetime.ISO8601StringToUTCTime("2022-01-02T22:04:05+07:00")
    if err != nil {
        t.Fatal(err)
    }

    timeProvider := datetime.NewFakeTimeProvider(now) // provider of current time of choice
    patientGatewayServiceV1 := service.NewPatientGatewayServiceV1(timeProvider) // inject it

    patientGatewayServiceV1.FindAppointments(...)
}