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jumper.go
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jumper.go
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package timejumper
// https://stackoverflow.com/questions/18970265/is-there-an-easy-way-to-stub-out-time-now-globally-in-golang-during-test
import (
"errors"
"sync"
"time"
)
// Clock is an interface that allows you to a create
// different implementions for testing purposes
type Clock interface {
Now() time.Time
Since(time.Time) time.Duration
Sleep(time.Duration)
}
// RealClock implements the standard lib
// only functions relevant for this codebase
type RealClock struct{}
// Now is a proxy to time.Now
func (RealClock) Now() time.Time {
return time.Now()
}
// Since is a proxy to time.Since
func (RealClock) Since(t time.Time) time.Duration {
return time.Since(t)
}
// Sleep is a proxy to time.Sleep
func (RealClock) Sleep(d time.Duration) {
time.Sleep(d)
}
// compile-time assertion that RealClock matches Clock interface
var _ Clock = RealClock{}
// TimeMachine is a function that gets called each time Now() is called
// The default machine allows the usage of freeze, scale and jump features of
// Jumper. This allows you to completely switch out the functionality
type TimeMachine func() (newTime time.Time)
// JumperClock is a Go implementation of but does not use package globals
// https://github.com/travisjeffery/timecop
// Instantiate with New()
type JumperClock struct {
isFrozen bool
initialTime time.Time
initialTimeSetAt time.Time
scale int
activate TimeMachine
mutex sync.Mutex
}
// New returns a new instance of a TimeCopClock
func New() *JumperClock {
c := &JumperClock{
scale: 1,
}
c.Back()
c.activate = c.NewDefaultTimeMachine()
return c
}
// Now activates the TimeMachine
func (c *JumperClock) Now() time.Time {
c.mutex.Lock()
defer c.mutex.Unlock()
return c.activate()
}
// Since returns the time elapsed since t. It is shorthand for .Now().Sub(t).
func (c *JumperClock) Since(t time.Time) time.Duration {
c.mutex.Lock()
defer c.mutex.Unlock()
return c.activate().Sub(t)
}
// Sleep is similar to jump, except that it takes a duration
func (c *JumperClock) Sleep(d time.Duration) {
c.mutex.Lock()
defer c.mutex.Unlock()
now := c.activate()
// Sleep for the scaled duration
c.initialTime = now.Add(d * time.Duration(c.scale))
c.initialTimeSetAt = time.Now()
}
// compile-time assertion that RealClock matches Clock interface
var _ Clock = &JumperClock{}
// NewDefaultTimeMachine is what's used to enable scaling and freezing
func (c *JumperClock) NewDefaultTimeMachine() TimeMachine {
return func() time.Time {
if c.isFrozen {
return c.initialTime
}
diff := time.Now().Sub(c.initialTimeSetAt)
return c.initialTime.Add(diff * time.Duration(c.scale))
}
}
// Freeze ensures time doesn't progress forward
// You can still move time by freezing again with a new time
// or by using Travel
func (c *JumperClock) Freeze(t time.Time) {
c.mutex.Lock()
defer c.mutex.Unlock()
c.isFrozen = true
c.initialTime = t
c.initialTimeSetAt = time.Now()
}
// Jump sets the clock to the desired time
// Compatible with Freeze (will remain frozen if previously frozen)
func (c *JumperClock) Jump(t time.Time) {
c.mutex.Lock()
defer c.mutex.Unlock()
c.initialTime = t
c.initialTimeSetAt = time.Now()
}
// Scale sets the time scale multiplier
// If set to 0, freezes the clock instead
func (c *JumperClock) Scale(s int) error {
if s < 0 {
return errors.New("Cannot set scale to less than 0")
}
if s == 0 {
c.isFrozen = true
return nil
}
c.scale = s
return nil
}
// Back returns you to the present (future? since you started)
// Does not change the TimeMachine
func (c *JumperClock) Back() {
c.mutex.Lock()
defer c.mutex.Unlock()
now := time.Now()
c.isFrozen = false
c.initialTime = now
c.initialTimeSetAt = now
}
// SetTimeMachine sets TimeMachine, a function that controls how time works!
// It also resets the clock according to Back()
func (c *JumperClock) SetTimeMachine(t TimeMachine) {
c.Back()
c.activate = t
}