cache npmjs package lookups in a local file

npm.go

@@ -101,6 +101,7 @@ func (n *NPMLookup) ReadPackagesFromFile(filename string) error {
 // Returns a slice of strings with any npm packages not in the public npm package repository
 func (n *NPMLookup) PackagesNotInPublic() []string {
 	notavail := []string{}
+	avail := readMap("/tmp/confused-npm-avail")
 	for _, pkg := range n.Packages {
 		if n.localReference(pkg.Version) || n.urlReference(pkg.Version) || n.gitReference(pkg.Version) {
 			continue
@@ -113,10 +114,13 @@ func (n *NPMLookup) PackagesNotInPublic() []string {
 				continue
 			}
 		}
-		if !n.isAvailableInPublic(pkg.Name, 0) {
+		if !avail[pkg.Name] && !n.isAvailableInPublic(pkg.Name, 0) {
 			notavail = append(notavail, pkg.Name)
+		} else {
+			avail[pkg.Name] = true
 		}
 	}
+	writeMap(avail, "/tmp/confused-npm-avail")
 	return notavail
 }
 

util.go

@@ -1,6 +1,11 @@
 package main
 
-import "strings"
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
 
 func inSlice(what rune, where []rune) bool {
 	for _, r := range where {
@@ -14,3 +19,31 @@ func inSlice(what rune, where []rune) bool {
 func countLeadingSpaces(line string) int {
 	return len(line) - len(strings.TrimLeft(line, " "))
 }
+
+// reads line-delimited contents of a file into a map of strings
+func readMap(path string) map[string]bool {
+	file, err := os.Open(path)
+	if err != nil {
+		return map[string]bool{}
+	}
+	defer file.Close()
+
+	avail := map[string]bool{}
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		avail[scanner.Text()] = true
+	}
+	return avail
+}
+
+// writes a map of strings to a line-delimited file
+func writeMap(lines map[string]bool, path string) {
+	file, _ := os.Create(path)
+	defer file.Close()
+
+	writer := bufio.NewWriter(file)
+	for key, _ := range lines {
+		fmt.Fprintln(writer, key)
+	}
+	writer.Flush()
+}