From dc000eb40f535c8ce20230bc4474bf1735848436 Mon Sep 17 00:00:00 2001
From: Jian Han <jianhan@mail.com>
Date: Sat, 6 Jan 2018 15:55:04 +1000
Subject: [PATCH] another package of fetchers

---
 .../divide_and_conquer/divide_and_conquer.go  |  8 ++
 concurrency/subtasks/fetchers/fetchers.go     | 91 +++++++++++++++++++
 concurrency/subtasks/main.go                  | 13 +--
 3 files changed, 102 insertions(+), 10 deletions(-)

diff --git a/concurrency/subtasks/divide_and_conquer/divide_and_conquer.go b/concurrency/subtasks/divide_and_conquer/divide_and_conquer.go
index 0c60ae5..a222445 100644
--- a/concurrency/subtasks/divide_and_conquer/divide_and_conquer.go
+++ b/concurrency/subtasks/divide_and_conquer/divide_and_conquer.go
@@ -9,6 +9,14 @@ import (
 	"github.com/davecgh/go-spew/spew"
 )
 
+// https://medium.com/capital-one-developers/buffered-channels-in-go-what-are-they-good-for-43703871828
+
+// One common pattern for goroutines is fan-out. When you want to apply the same data to multiple algorithms,
+// you can launch a goroutine for each subtask, and then gather the data back in when they are done.
+// For example, you might want to process the same data via multiple scoring algorithms and return back
+// all of the scores or pull data from multiple microservices to compose a single page. A buffered channel is an
+// ideal way to gather the data back from your subtasks.
+
 func RunDivideAndConquer() {
 	type in struct {
 		a int
diff --git a/concurrency/subtasks/fetchers/fetchers.go b/concurrency/subtasks/fetchers/fetchers.go
index cf1c9f0..4f04567 100644
--- a/concurrency/subtasks/fetchers/fetchers.go
+++ b/concurrency/subtasks/fetchers/fetchers.go
@@ -1 +1,92 @@
 package fetchers
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/davecgh/go-spew/spew"
+)
+
+type Fetcher interface {
+	Fetch(url string) (string, error)
+	GetName() string
+}
+
+type GoogleFetcher struct {
+	Name string
+}
+
+func (g *GoogleFetcher) Fetch(url string) (string, error) {
+	return fmt.Sprintf("%s is fetching %s", g.Name, url), nil
+}
+
+func (g *GoogleFetcher) GetName() string {
+	return g.Name
+}
+
+func NewGoogleFetcher(name string) *GoogleFetcher {
+	return &GoogleFetcher{Name: name}
+}
+
+type BingFetcher struct {
+	Name string
+}
+
+func (b *BingFetcher) Fetch(url string) (string, error) {
+	return fmt.Sprintf("%s is fetching %s", b.Name, url), nil
+}
+
+func (b *BingFetcher) GetName() string {
+	return b.Name
+}
+
+func NewBingFetcher(name string) *BingFetcher {
+	return &BingFetcher{Name: name}
+}
+
+type DuckDuckGoFetcher struct {
+	Name string
+}
+
+func (d *DuckDuckGoFetcher) Fetch(url string) (string, error) {
+	return fmt.Sprintf("%s is fetching %s", d.Name, url), nil
+}
+
+func (d *DuckDuckGoFetcher) GetName() string {
+	return d.Name
+}
+
+func NewDuckDuckGoFetcherFetcher(name string) *DuckDuckGoFetcher {
+	return &DuckDuckGoFetcher{Name: name}
+}
+func FetchResults(url string, fetchers []Fetcher, timeout time.Duration) ([]string, []error) {
+	chStr := make(chan string)
+	chErr := make(chan error)
+	for _, f := range fetchers {
+		go func(f Fetcher) {
+			s, err := f.Fetch(url)
+			if err != nil {
+				chErr <- err
+			} else {
+				chStr <- s
+			}
+		}(f)
+	}
+	stringResults := []string{}
+	errorResults := []error{}
+	for range fetchers {
+		select {
+		case s := <-chStr:
+			stringResults = append(stringResults, s)
+		case e := <-chErr:
+			errorResults = append(errorResults, e)
+		}
+	}
+	return stringResults, errorResults
+}
+
+func RunFetchers() {
+	fetchers := []Fetcher{NewGoogleFetcher("Google"), NewGoogleFetcher("Bing"), NewGoogleFetcher("Duck Duck Go")}
+	r, e := FetchResults("http://www.abc.com", fetchers, time.Millisecond*100)
+	spew.Dump(r, e)
+}
diff --git a/concurrency/subtasks/main.go b/concurrency/subtasks/main.go
index 13d1ef6..ab8f7d2 100644
--- a/concurrency/subtasks/main.go
+++ b/concurrency/subtasks/main.go
@@ -1,15 +1,8 @@
 package main
 
-import "github.com/jianhan/go-patterns/concurrency/subtasks/divide_and_conquer"
-
-// https://medium.com/capital-one-developers/buffered-channels-in-go-what-are-they-good-for-43703871828
-
-// One common pattern for goroutines is fan-out. When you want to apply the same data to multiple algorithms,
-// you can launch a goroutine for each subtask, and then gather the data back in when they are done.
-// For example, you might want to process the same data via multiple scoring algorithms and return back
-// all of the scores or pull data from multiple microservices to compose a single page. A buffered channel is an
-// ideal way to gather the data back from your subtasks.
+import "github.com/jianhan/go-patterns/concurrency/subtasks/fetchers"
 
 func main() {
-	divide_and_conquer.RunDivideAndConquer()
+	// divide_and_conquer.RunDivideAndConquer()
+	fetchers.RunFetchers()
 }