feat: cache installed applications

cache.go

@@ -0,0 +1,50 @@
+package vin
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/skmatz/vin/cache"
+)
+
+func (v *Vin) cacheDir() (string, error) {
+	cache, err := os.UserCacheDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(cache, "vin"), nil
+}
+
+var repoReplacer = strings.NewReplacer("/", "---")
+
+func (v *Vin) AppAlreadyInstalled(app App) (bool, error) {
+	cacheDir, err := v.cacheDir()
+	if err != nil {
+		return false, err
+	}
+
+	c := cache.New(cacheDir)
+	key := repoReplacer.Replace(app.Repo)
+	value := c.GetString(key)
+	return value == *app.release.TagName, nil
+}
+
+func (v *Vin) SaveCache(app App) error {
+	cacheDir, err := v.cacheDir()
+	if err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(cacheDir, os.ModePerm); err != nil {
+		return err
+	}
+
+	c := cache.New(cacheDir)
+	key := repoReplacer.Replace(app.Repo)
+	value := *app.release.TagName
+	if err := c.SetString(key, value); err != nil {
+		return err
+	}
+	return nil
+}

cache/cache.go

@@ -0,0 +1,56 @@
+package cache
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// Cache represents a file cache.
+type Cache struct {
+	dir string
+	m   sync.RWMutex
+}
+
+func New(dir string) *Cache {
+	return &Cache{dir: dir}
+}
+
+func (c *Cache) path(key string) string {
+	return filepath.Join(c.dir, key)
+}
+
+func (c *Cache) Get(key string) []byte {
+	c.m.RLock()
+	defer c.m.RUnlock()
+
+	b, err := ioutil.ReadFile(c.path(key))
+	if err != nil {
+		return nil
+	}
+	return b
+}
+
+func (c *Cache) GetString(key string) string {
+	return string(c.Get(key))
+}
+
+func (c *Cache) Set(key string, value []byte) error {
+	if len(value) == 0 {
+		return fmt.Errorf("value is empty")
+	}
+
+	c.m.Lock()
+	defer c.m.Unlock()
+
+	if err := ioutil.WriteFile(c.path(key), value, os.ModePerm); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *Cache) SetString(key, value string) error {
+	return c.Set(key, []byte(value))
+}

cli/cli.go

@@ -99,6 +99,11 @@ func (c *CLI) Run(opt Options) error {
 	for _, app := range v.Apps {
 		app := app
 		eg.Go(func() error {
+			exists, err := v.AppAlreadyInstalled(app)
+			if err != nil || exists {
+				return err
+			}
+
 			urls := app.SuitableAssetURLs()
 			if len(urls) == 0 {
 				return fmt.Errorf("no suitable assets are found: %s", app.Repo)
@@ -115,6 +120,10 @@ func (c *CLI) Run(opt Options) error {
 			if err := app.RunCommand(); err != nil {
 				return err
 			}
+
+			if err := v.SaveCache(app); err != nil {
+				return err
+			}
 			return nil
 		})
 	}