Support caching results

go/inquire/inquire.go

@@ -2,6 +2,7 @@ package main
import (
	"bytes"
	"encoding/gob"
	"encoding/json"
	"flag"
	"fmt"
@@ -29,17 +30,24 @@ type PageInfo struct {
}
var config = struct {
	output string
	output    string
	cachePath string
}{}
func init() {
	flag.StringVar(&config.output, "output", "text", "what format to output")
	flag.StringVar(&config.cachePath, "cache", "inquire.db", "path to the cache file")
}
func main() {
	flag.Parse()
	u := flag.Args()[0]
	if flag.NArg() != 1 {
		fmt.Fprintf(os.Stderr, "Usage: %s [flags] <url>\n", os.Args[0])
		os.Exit(1)
	}
	u := flag.Arg(0)
	url, err := url.Parse(u)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
@@ -50,12 +58,37 @@ func main() {
		u = "http://" + u
	}
	info, err := GetPageInfo(u)
	db, err := openCache(config.cachePath)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
	}
	var info *PageInfo
	cached := isCached(db, u)
	if cached {
		info, err = GetPageInfoFromCache(db, u)
	} else {
		info, err = GetPageInfo(u)
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	if !cached {
		err = storeInCache(db, u, info)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
		}
		err = writeCache(db, config.cachePath)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
		}
	}
	switch config.output {
	case "text":
		fmt.Printf("url: %s\ntitle: %s\ndescription: %s\nimage: %s\n",
@@ -90,6 +123,57 @@ func main() {
	}
}
type Cache map[string][]byte
func openCache(path string) (Cache, error) {
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return Cache{}, nil
		}
		return nil, err
	}
	dec := gob.NewDecoder(f)
	var db Cache
	err = dec.Decode(&db)
	return db, err
}
func isCached(db Cache, u string) bool {
	_, ok := db[u]
	return ok
}
func GetPageInfoFromCache(db Cache, u string) (*PageInfo, error) {
	rawInfo := db[u]
	var info *PageInfo
	err := json.Unmarshal(rawInfo, &info)
	return info, err
}
func storeInCache(db Cache, u string, info *PageInfo) error {
	rawInfo, err := json.Marshal(info)
	if err != nil {
		return err
	}
	db[u] = rawInfo
	return nil
}
func writeCache(db Cache, path string) error {
	f, err := os.Create(path)
	if err != nil {
		return err
	}
	defer f.Close()
	enc := gob.NewEncoder(f)
	err = enc.Encode(db)
	return err
}
func GetPageInfo(u string) (*PageInfo, error) {
	res, err := http.Get(u)
	if err != nil {