feature/7: Moving promise into repo (#8)

* feature/7: Moving promise into repo

* Fixing CI

go.mod

@@ -2,10 +2,7 @@ module github.com/thinkdata-works/gocache
 
 go 1.18
 
-require (
- github.com/stretchr/testify v1.8.3
- github.com/thinkdata-works/gopromise v0.1.0
-)
+require github.com/stretchr/testify v1.8.3
 
 require (
  github.com/davecgh/go-spew v1.1.1 // indirect

go.sum

@@ -4,8 +4,6 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.8.3 h1:RP3t2pwF7cMEbC1dqtB6poj3niw/9gnV4Cjg5oW5gtY=
 github.com/stretchr/testify v1.8.3/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-github.com/thinkdata-works/gopromise v0.1.0 h1:qVWnyufZfoMyeUr4DtdhQhmgXz9abFdGAHhCdipM3Pk=
-github.com/thinkdata-works/gopromise v0.1.0/go.mod h1:vec0Q1/jvqEZ7UutAfzRKYIiqEcj4/pAQOxLvnzxP3c=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

pkg/gocache/cache.go

@@ -2,17 +2,15 @@ package gocache
 
 import (
  "time"
-
- "github.com/thinkdata-works/gopromise/pkg/promise"
 )
 
 type Cache[K comparable, V any] struct {
- cache *partitionedCache[K, promise.Promise[V]]
+ cache *partitionedCache[K, Promise[V]]
 }
 
 func NewCache[K comparable, V any](partitionSize, totalPartitions int, cacheExpiry time.Duration) *Cache[K, V] {
  return &Cache[K, V]{
- cache: newPartitionedCached[K, promise.Promise[V]](
+ cache: newPartitionedCached[K, Promise[V]](
  partitionSize, totalPartitions, cacheExpiry,
  ),
  }
@@ -23,7 +21,7 @@ func (c *Cache[K, V]) HasKey(k K) (bool, error) {
 }
 
 func (c *Cache[K, V]) Get(k K, getter func() (*V, error)) (*V, error) {
- valpromise, alreadyExists := c.cache.GetOrCreate(k, promise.NewPromise[V]())
+ valpromise, alreadyExists := c.cache.GetOrCreate(k, NewPromise[V]())
  if alreadyExists {
  val, err := valpromise.Wait()
  if err != nil {

pkg/gocache/promise.go

@@ -0,0 +1,73 @@
+package gocache
+
+import (
+ "sync"
+ "time"
+)
+
+type future[V any] struct {
+ v *V
+ err error
+}
+
+type Promise[V any] struct {
+ ch chan future[V]
+ v *V
+ err error
+ mu *sync.Mutex
+ count int
+ done bool
+ start time.Time
+}
+
+func NewPromise[V any]() *Promise[V] {
+ return &Promise[V]{
+ ch: make(chan future[V]),
+ start: time.Now(),
+ mu: &sync.Mutex{},
+ done: false,
+ count: 0,
+ v: nil,
+ err: nil,
+ }
+}
+
+func (p *Promise[V]) Wait() (*V, error) {
+ p.mu.Lock()
+ if p.done {
+ p.mu.Unlock()
+ return p.v, p.err
+ }
+ p.count++
+ p.mu.Unlock()
+
+ f := <-p.ch
+ return f.v, f.err
+}
+
+func (p *Promise[V]) fulfill(v *V, err error) {
+ p.mu.Lock()
+ defer p.mu.Unlock()
+
+ if p.done {
+ // already fulfilled
+ return
+ }
+ p.done = true
+ p.v = v
+ p.err = err
+ for i := 0; i < p.count; i++ {
+ p.ch <- future[V]{
+ v: v,
+ err: err,
+ }
+ }
+}
+
+func (p *Promise[V]) Resolve(v *V) {
+ p.fulfill(v, nil)
+}
+
+func (p *Promise[V]) Reject(err error) {
+ p.fulfill(nil, err)
+}