This is where it all begins...

.gitignore

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+.DS_Store
+.vscode

.goreleaser.yml

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+# This is an example goreleaser.yaml file with some sane defaults.
+# Make sure to check the documentation at http://goreleaser.com
+builds:
+- env:
+  - CGO_ENABLED=0
+archive:
+  replacements:
+    darwin: Darwin
+    linux: Linux
+    windows: Windows
+    386: i386
+    amd64: x86_64
+checksum:
+  name_template: 'checksums.txt'
+snapshot:
+  name_template: "{{ .Tag }}-next"
+changelog:
+  sort: asc
+  filters:
+    exclude:
+    - '^docs:'
+    - '^test:'

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2018 Rafiqul Hasan
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# checkr
+
+### A cli tool to check whether a package name is available on different package managers.
+
+![Screen Recording](https://raw.githubusercontent.com/shopnilsazal/checkr/master/recording.gif)

cmd/checkr/helpers.go

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+package main
+
+import (
+	"fmt"
+	"net/http"
+	"runtime"
+)
+
+// PackageResponse Type
+type PackageResponse struct {
+	packageManager string
+	statusCode     int
+}
+
+// Get status code from package manager
+func getPackageStatus(name, url string, ch chan<- PackageResponse) {
+	resp, err := http.Get(url)
+	if err != nil {
+		ch <- PackageResponse{name, 500}
+		return
+	}
+	ch <- PackageResponse{name, resp.StatusCode}
+	resp.Body.Close()
+}
+
+// Get full url of the package manager based on name
+func getFullURL(url, manager, name string) string {
+	fullURL := url + name
+	switch manager {
+	case "pip":
+		fullURL = fullURL + "/json"
+	case "gem":
+		fullURL = fullURL + ".json"
+	}
+	return fullURL
+}
+
+// Get success and error symbols
+func getSymbols() (successSym, errorSym string) {
+	if runtime.GOOS == "windows" {
+		successSym = "\u001b[32m" + "√" + "\u001b[39m"
+		errorSym = "\u001b[31m" + "×" + "\u001b[39m"
+	} else {
+		successSym = "\u001b[32m" + "✔" + "\u001b[39m"
+		errorSym = "\u001b[31m" + "✖" + "\u001b[39m"
+	}
+	return
+}
+
+// Get the message to print on console
+func getMessage(resp PackageResponse, name string) string {
+	var msg string
+	ss, es := getSymbols()
+	switch resp.statusCode {
+	case 404:
+		msg = fmt.Sprintf("%s %s is available on '%s' \n", ss, name, resp.packageManager)
+	case 200:
+		msg = fmt.Sprintf("%s %s is unavailable on '%s' \n", es, name, resp.packageManager)
+	default:
+		msg = fmt.Sprintf("%s oops! something bad happened in '%s' \n", es, resp.packageManager)
+	}
+	return msg
+}

cmd/checkr/main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/shopnilsazal/checkr/spinner"
+)
+
+var urls = map[string]string{
+	"npm":    "https://registry.npmjs.org/",
+	"pip":    "https://pypi.org/pypi/",
+	"crates": "https://crates.io/api/v1/crates/",
+	"gem":    "https://rubygems.org/api/v1/gems/",
+	"hex":    "https://hex.pm/api/packages/",
+}
+
+func main() {
+
+	name := flag.String("n", "react", "Provide a package name you want to search.")
+	managers := flag.String("m", "npm", "Provide package managers where you want to search.")
+	flag.Parse()
+
+	spin := spinner.New("%s Loading...")
+
+	ch := make(chan PackageResponse)
+	_, errorSym := getSymbols()
+
+	allManagers := strings.Split(*managers, ",")
+	if len(allManagers) == 1 {
+		manager := allManagers[0]
+		if manager == "all" {
+			spin.Start()
+			defer spin.Stop()
+
+			for key, url := range urls {
+				fullURL := getFullURL(url, key, *name)
+				go getPackageStatus(key, fullURL, ch)
+			}
+
+			for range urls {
+				res := <-ch
+				spin.Stop()
+				fmt.Printf(getMessage(res, *name))
+				spin.Start()
+			}
+
+		} else if u, ok := urls[manager]; ok {
+			spin.Start()
+			fullURL := getFullURL(u, manager, *name)
+			resp, err := http.Get(fullURL)
+			if err != nil {
+				fmt.Printf("%s oops! something bad happened in '%s' \n", errorSym, manager)
+			}
+			spin.Stop()
+			defer resp.Body.Close()
+			fmt.Printf(getMessage(PackageResponse{manager, resp.StatusCode}, *name))
+
+		} else {
+			fmt.Printf("%s '%s' is not a valid package manager.\n", errorSym, manager)
+		}
+
+	} else {
+		var validManagers []string
+		spin.Start()
+		defer spin.Stop()
+
+		for _, m := range allManagers {
+			if u, ok := urls[m]; ok {
+				fullURL := getFullURL(u, m, *name)
+				go getPackageStatus(m, fullURL, ch)
+				validManagers = append(validManagers, m)
+			} else {
+				fmt.Printf("%s '%s' is not a valid package manager.\n", errorSym, m)
+			}
+		}
+
+		for range validManagers {
+			res := <-ch
+			spin.Stop()
+			fmt.Printf(getMessage(res, *name))
+			spin.Start()
+		}
+	}
+}

spinner/spinner.go

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+package spinner
+
+import (
+	"fmt"
+	"sync/atomic"
+	"time"
+)
+
+// ClearLine go to the beggining of the line and clear it
+const ClearLine = "\r\033[K"
+
+// Spin type
+var Spin = `⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏`
+
+// Spinner main type
+type Spinner struct {
+	frames []rune
+	pos    int
+	active uint64
+	text   string
+}
+
+// New Spinner with args
+func New(text string) *Spinner {
+	s := &Spinner{
+		text: ClearLine + text,
+	}
+	s.Set(Spin)
+	return s
+}
+
+// Set frames to the given string which must not use spaces.
+func (s *Spinner) Set(frames string) {
+	s.frames = []rune(frames)
+}
+
+// Start shows the spinner.
+func (s *Spinner) Start() *Spinner {
+	if atomic.LoadUint64(&s.active) > 0 {
+		return s
+	}
+	atomic.StoreUint64(&s.active, 1)
+	go func() {
+		for atomic.LoadUint64(&s.active) > 0 {
+			fmt.Printf(s.text, s.next())
+			time.Sleep(100 * time.Millisecond)
+		}
+	}()
+	return s
+}
+
+// Stop hides the spinner.
+func (s *Spinner) Stop() bool {
+	if x := atomic.SwapUint64(&s.active, 0); x > 0 {
+		fmt.Printf(ClearLine)
+		return true
+	}
+	return false
+}
+
+func (s *Spinner) next() string {
+	r := s.frames[s.pos%len(s.frames)]
+	s.pos++
+	return string(r)
+}