Rearrange some code, adds pm av

db/available.go

@@ -0,0 +1,113 @@
+package db
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"github.com/pkg/errors"
+	"mcquay.me/fs"
+	"mcquay.me/pm"
+)
+
+const an = "var/lib/pm/available.json"
+
+// Pull updates the available package database.
+func Pull(root string) error {
+	db, err := load(root)
+	if err != nil {
+		return errors.Wrap(err, "loading db")
+	}
+
+	o := pm.Available{}
+
+	// Order here is important: the guarantee made is that any packages that
+	// exist in multiple remotes will be fetched by the first configured
+	// remote, which is why we traverse the database in reverse.
+	//
+	// TODO (sm): make this concurrent
+	for i := range db {
+		u := db[len(db)-i-1]
+		resp, err := http.Get(u.String() + "/available.json")
+		if err != nil {
+			return errors.Wrap(err, "http get")
+		}
+
+		a := pm.Available{}
+		if err := json.NewDecoder(resp.Body).Decode(&a); err != nil {
+			return errors.Wrap(err, "decode remote available")
+		}
+		a.SetRemote(u)
+		o.Update(a)
+	}
+	if err := saveAvailable(root, o); err != nil {
+		return errors.Wrap(err, "saving available db")
+	}
+	return nil
+}
+
+// ListAvailable prints all installable packages
+func ListAvailable(root string, w io.Writer) error {
+	db, err := loadAvailable(root)
+	if err != nil {
+		return errors.Wrap(err, "loading")
+	}
+	names := pm.Names{}
+	nvs := map[pm.Name]pm.Versions{}
+	for n, vers := range db {
+		names = append(names, n)
+		for v := range vers {
+			nvs[n] = append(nvs[n], v)
+		}
+		sort.Sort(nvs[n])
+	}
+	sort.Sort(names)
+
+	for _, n := range names {
+		for _, v := range nvs[n] {
+			m := db[n][v]
+			fmt.Fprintf(w, "%v\t%v\t%v\n", m.Name, m.Version, m.Remote.String())
+		}
+	}
+	return nil
+}
+
+func loadAvailable(root string) (pm.Available, error) {
+	r := pm.Available{}
+	dbn := filepath.Join(root, rn)
+
+	if !fs.Exists(dbn) {
+		return r, nil
+	}
+
+	f, err := os.Open(filepath.Join(root, an))
+	if err != nil {
+		return r, errors.Wrap(err, "open")
+	}
+
+	if err := json.NewDecoder(f).Decode(&r); err != nil {
+		return r, errors.Wrap(err, "decoding db")
+	}
+
+	return r, nil
+}
+
+func saveAvailable(root string, db pm.Available) error {
+	f, err := os.Create(filepath.Join(root, an))
+	if err != nil {
+		return errors.Wrap(err, "create")
+	}
+	enc := json.NewEncoder(f)
+	enc.SetIndent("", "\t")
+	if err := enc.Encode(&db); err != nil {
+		return errors.Wrap(err, "decoding db")
+	}
+	if err := f.Close(); err != nil {
+		return errors.Wrap(err, "close db")
+	}
+	return nil
+}