First, Last, and File System Repository.

asset/README.md

@@ -27,12 +27,13 @@ The information provided on this project is strictly for informational purposes
 - [type FileSystemRepository](<#FileSystemRepository>)
   - [func NewFileSystemRepository\(base string\) \*FileSystemRepository](<#NewFileSystemRepository>)
   - [func \(r \*FileSystemRepository\) Get\(name string\) \(\<\-chan \*Snapshot, error\)](<#FileSystemRepository.Get>)
+  - [func \(r \*FileSystemRepository\) LastDate\(name string\) \(time.Time, error\)](<#FileSystemRepository.LastDate>)
 - [type Repository](<#Repository>)
 - [type Snapshot](<#Snapshot>)
 
 
 <a name="FileSystemRepository"></a>
-## type [FileSystemRepository](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L16-L21>)
+## type [FileSystemRepository](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L18-L23>)
 
 FileSystemRepository stores and retrieves asset snapshots using the local file system.
 
@@ -44,7 +45,7 @@ type FileSystemRepository struct {
 ```
 
 <a name="NewFileSystemRepository"></a>
-### func [NewFileSystemRepository](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L25>)
+### func [NewFileSystemRepository](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L27>)
 
 ```go
 func NewFileSystemRepository(base string) *FileSystemRepository
@@ -53,16 +54,25 @@ func NewFileSystemRepository(base string) *FileSystemRepository
 NewFileSystemRepository initializes a file system repository with the given base directory.
 
 <a name="FileSystemRepository.Get"></a>
-### func \(\*FileSystemRepository\) [Get](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L32>)
+### func \(\*FileSystemRepository\) [Get](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L34>)
 
 ```go
 func (r *FileSystemRepository) Get(name string) (<-chan *Snapshot, error)
 ```
 
 Get attempts to return a channel of snapshots fo the asset with the given name.
 
+<a name="FileSystemRepository.LastDate"></a>
+### func \(\*FileSystemRepository\) [LastDate](<https://github.com/cinar/indicator/blob/v2/asset/file_system_repository.go#L40>)
+
+```go
+func (r *FileSystemRepository) LastDate(name string) (time.Time, error)
+```
+
+LastDate returns the date of the last snapshot for the asset with the given name.
+
 <a name="Repository"></a>
-## type [Repository](<https://github.com/cinar/indicator/blob/v2/asset/repository.go#L9-L13>)
+## type [Repository](<https://github.com/cinar/indicator/blob/v2/asset/repository.go#L11-L19>)
 
 Repository serves as a centralized storage and retrieval location for asset snapshots.
 
@@ -71,6 +81,10 @@ type Repository interface {
     // Get attempts to return a channel of snapshots for
     // the asset with the given name.
     Get(name string) (<-chan *Snapshot, error)
+
+    // LastDate returns the date of the last snapshot for
+    // the asset with the given name.
+    LastDate(name string) (time.Time, error)
 }
 ```
 

asset/file_system_repository.go

@@ -5,8 +5,10 @@
 package asset
 
 import (
+	"errors"
 	"fmt"
 	"path/filepath"
+	"time"
 
 	"github.com/cinar/indicator/helper"
 )
@@ -33,3 +35,21 @@ func (r *FileSystemRepository) Get(name string) (<-chan *Snapshot, error) {
 	file := filepath.Join(r.base, fmt.Sprintf("%s.csv", name))
 	return helper.ReadFromCsvFile[Snapshot](file, true)
 }
+
+// LastDate returns the date of the last snapshot for the asset with the given name.
+func (r *FileSystemRepository) LastDate(name string) (time.Time, error) {
+	var last time.Time
+
+	snapshots, err := r.Get(name)
+	if err != nil {
+		return last, err
+	}
+
+	snapshot := helper.ChanToSlice(helper.Last(snapshots, 1))
+
+	if len(snapshot) != 1 {
+		return last, errors.New("empty asset")
+	}
+
+	return snapshot[0].Date, nil
+}

asset/file_system_repository_test.go

@@ -6,6 +6,7 @@ package asset_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/cinar/indicator/asset"
 	"github.com/cinar/indicator/helper"
@@ -30,3 +31,36 @@ func TestFileSystemRepositoryGetNonExisting(t *testing.T) {
 		t.Fatal("expected error")
 	}
 }
+
+func TestFileSystemRepositoryLastDate(t *testing.T) {
+	expeted := time.Date(2022, 12, 30, 0, 0, 0, 0, time.UTC)
+
+	repository := asset.NewFileSystemRepository("testdata")
+
+	actual, err := repository.LastDate("brk-b")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if actual != expeted {
+		t.Fatalf("actual %v expected %v", actual, expeted)
+	}
+}
+
+func TestFileSystemRepositoryLastDateNonExisting(t *testing.T) {
+	repository := asset.NewFileSystemRepository("testdata")
+
+	_, err := repository.LastDate("brk")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}
+
+func TestFileSystemRepositoryLastDateEmpty(t *testing.T) {
+	repository := asset.NewFileSystemRepository("testdata")
+
+	_, err := repository.LastDate("empty")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}

asset/repository.go

@@ -14,7 +14,6 @@ type Repository interface {
 	Get(name string) (<-chan *Snapshot, error)
 
 	// LastDate returns the date of the last snapshot for
-	// the asset with the given name, if any. Returns an
-	// empty value if no snapshots exist.
-	LastDate(name string) time.Time
+	// the asset with the given name.
+	LastDate(name string) (time.Time, error)
 }

asset/testdata/empty.csv

@@ -0,0 +1 @@
+Date,Open,High,Low,Close,Adj Close,Volume

helper/README.md

@@ -40,10 +40,12 @@ The information provided on this project is strictly for informational purposes
 - [func Duplicate\[T any\]\(input \<\-chan T, count int\) \[\]\<\-chan T](<#Duplicate>)
 - [func Field\[T, S any\]\(c \<\-chan \*S, name string\) \(\<\-chan T, error\)](<#Field>)
 - [func Filter\[T Number\]\(c \<\-chan T, p func\(T\) bool\) \<\-chan T](<#Filter>)
+- [func First\[T any\]\(c \<\-chan T, count int\) \<\-chan T](<#First>)
 - [func Head\[T Number\]\(c \<\-chan T, count int\) \<\-chan T](<#Head>)
 - [func IncrementBy\[T Number\]\(c \<\-chan T, i T\) \<\-chan T](<#IncrementBy>)
 - [func KeepNegatives\[T Number\]\(c \<\-chan T\) \<\-chan T](<#KeepNegatives>)
 - [func KeepPositives\[T Number\]\(c \<\-chan T\) \<\-chan T](<#KeepPositives>)
+- [func Last\[T any\]\(c \<\-chan T, count int\) \<\-chan T](<#Last>)
 - [func Map\[F, T any\]\(c \<\-chan F, f func\(F\) T\) \<\-chan T](<#Map>)
 - [func Multiply\[T Number\]\(ac, bc \<\-chan T\) \<\-chan T](<#Multiply>)
 - [func MultiplyBy\[T Number\]\(c \<\-chan T, m T\) \<\-chan T](<#MultiplyBy>)
@@ -88,7 +90,9 @@ The information provided on this project is strictly for informational purposes
   - [func NewNumericReportColumn\[T Number\]\(name string, values \<\-chan T\) ReportColumn](<#NewNumericReportColumn>)
 - [type Ring](<#Ring>)
   - [func NewRing\[T any\]\(size int\) \*Ring\[T\]](<#NewRing>)
-  - [func \(r \*Ring\[T\]\) Insert\(t T\) T](<#Ring[T].Insert>)
+  - [func \(r \*Ring\[T\]\) Get\(\) \(T, bool\)](<#Ring[T].Get>)
+  - [func \(r \*Ring\[T\]\) IsEmpty\(\) bool](<#Ring[T].IsEmpty>)
+  - [func \(r \*Ring\[T\]\) Put\(t T\) T](<#Ring[T].Put>)
 
 
 ## Constants
@@ -344,6 +348,15 @@ even := helper.Filter(c, func(n int) bool {
 })
 ```
 
+<a name="First"></a>
+## func [First](<https://github.com/cinar/indicator/blob/v2/helper/first.go#L8>)
+
+```go
+func First[T any](c <-chan T, count int) <-chan T
+```
+
+First takes a channel of values and returns a new channel containing the first N values.
+
 <a name="Head"></a>
 ## func [Head](<https://github.com/cinar/indicator/blob/v2/helper/head.go#L16>)
 
@@ -412,6 +425,15 @@ positives := helper.KeepPositives(c)
 fmt.Println(helper.ChanToSlice(positives)) // [0, 20, 4, 0]
 ```
 
+<a name="Last"></a>
+## func [Last](<https://github.com/cinar/indicator/blob/v2/helper/last.go#L8>)
+
+```go
+func Last[T any](c <-chan T, count int) <-chan T
+```
+
+Last takes a channel of values and returns a new channel containing the last N values.
+
 <a name="Map"></a>
 ## func [Map](<https://github.com/cinar/indicator/blob/v2/helper/map.go#L17>)
 
@@ -950,7 +972,7 @@ func NewNumericReportColumn[T Number](name string, values <-chan T) ReportColumn
 NewNumericReportColumn returns a new instance of a numeric data column for a report.
 
 <a name="Ring"></a>
-## type [Ring](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L18-L21>)
+## type [Ring](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L18-L23>)
 
 Ring represents a ring structure that can be instantiated using the NewRing function.
 
@@ -972,21 +994,39 @@ type Ring[T any] struct {
 ```
 
 <a name="NewRing"></a>
-### func [NewRing](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L24>)
+### func [NewRing](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L26>)
 
 ```go
 func NewRing[T any](size int) *Ring[T]
 ```
 
 NewRing creates a new ring instance with the given size.
 
-<a name="Ring[T].Insert"></a>
-### func \(\*Ring\[T\]\) [Insert](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L33>)
+<a name="Ring[T].Get"></a>
+### func \(\*Ring\[T\]\) [Get](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L53>)
+
+```go
+func (r *Ring[T]) Get() (T, bool)
+```
+
+Get retrieves the available value from the ring buffer. If empty, it returns the default value \(T\) and false.
+
+<a name="Ring[T].IsEmpty"></a>
+### func \(\*Ring\[T\]\) [IsEmpty](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L71>)
+
+```go
+func (r *Ring[T]) IsEmpty() bool
+```
+
+IsEmpty checks if the current ring buffer is empty.
+
+<a name="Ring[T].Put"></a>
+### func \(\*Ring\[T\]\) [Put](<https://github.com/cinar/indicator/blob/v2/helper/ring.go#L37>)
 
 ```go
-func (r *Ring[T]) Insert(t T) T
+func (r *Ring[T]) Put(t T) T
 ```
 
-Insert function inserts the specified value into the ring and returns the value that was previously stored at that index.
+Put inserts the specified value into the ring and returns the value that was previously stored at that index.
 
 Generated by [gomarkdoc](<https://github.com/princjef/gomarkdoc>)

helper/first.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2023 Onur Cinar. All Rights Reserved.
+// The source code is provided under MIT License.
+// https://github.com/cinar/indicator
+
+package helper
+
+// First takes a channel of values and returns a new channel containing the first N values.
+func First[T any](c <-chan T, count int) <-chan T {
+	result := make(chan T, cap(c))
+
+	go func() {
+		defer close(result)
+		for i := 0; i < count; i++ {
+			n, ok := <-c
+			if !ok {
+				return
+			}
+
+			result <- n
+		}
+
+		Drain(c)
+	}()
+
+	return result
+}

helper/first_test.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2023 Onur Cinar. All Rights Reserved.
+// The source code is provided under MIT License.
+// https://github.com/cinar/indicator
+
+package helper_test
+
+import (
+	"testing"
+
+	"github.com/cinar/indicator/helper"
+)
+
+func TestFirst(t *testing.T) {
+	input := helper.SliceToChan([]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10})
+	expected := helper.SliceToChan([]int{1, 2, 3, 4})
+
+	actual := helper.First(input, 4)
+
+	err := helper.CheckEquals(actual, expected)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestFirstLessValues(t *testing.T) {
+	input := helper.SliceToChan([]int{1, 2})
+	expected := helper.SliceToChan([]int{1, 2})
+
+	actual := helper.First(input, 4)
+
+	err := helper.CheckEquals(actual, expected)
+	if err != nil {
+		t.Fatal(err)
+	}
+}

helper/last.go

@@ -8,5 +8,20 @@ package helper
 func Last[T any](c <-chan T, count int) <-chan T {
 	result := make(chan T, cap(c))
 
+	go func() {
+		defer close(result)
+
+		ring := NewRing[T](count)
+
+		for n := range c {
+			ring.Put(n)
+		}
+
+		for !ring.IsEmpty() {
+			n, _ := ring.Get()
+			result <- n
+		}
+	}()
+
 	return result
 }