From 0f799b0d5adfc45e2306b2486555abfdb273f82f Mon Sep 17 00:00:00 2001
From: Mikhail Klementev <blame@dumpstack.io>
Date: Mon, 15 May 2023 07:29:40 +0000
Subject: [PATCH] feat: implement part of metasnap api

---
 distro/debian/snapshot/metasnap/metasnap.go   | 158 ++++++++++++++++++
 .../debian/snapshot/metasnap/metasnap_test.go |  28 ++++
 2 files changed, 186 insertions(+)
 create mode 100644 distro/debian/snapshot/metasnap/metasnap.go
 create mode 100644 distro/debian/snapshot/metasnap/metasnap_test.go

diff --git a/distro/debian/snapshot/metasnap/metasnap.go b/distro/debian/snapshot/metasnap/metasnap.go
new file mode 100644
index 0000000..596c0f5
--- /dev/null
+++ b/distro/debian/snapshot/metasnap/metasnap.go
@@ -0,0 +1,158 @@
+package metasnap
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/rs/zerolog/log"
+	"golang.org/x/time/rate"
+)
+
+const apiURL = "http://metasnap.debian.net/cgi-bin/api?"
+
+var archives = []string{
+	"debian",
+	"debian-security",
+	"debian-backports",
+	// "debian-archive",
+	// "debian-debug",
+	// "debian-ports",
+	// "debian-volatile",
+}
+
+var (
+	limiterTimeout time.Duration = time.Second
+	limiterBurst   int           = 3
+
+	Limiter = rate.NewLimiter(rate.Every(limiterTimeout), limiterBurst)
+)
+
+func lowerLimit() {
+	limiterTimeout = limiterTimeout * 2
+	log.Info().Msgf("limiter timeout set to %v", limiterTimeout)
+	Limiter.SetLimit(rate.Every(limiterTimeout))
+}
+
+// Retries in case of 5xx errors
+var Retries = 10
+
+var ErrNotFound = errors.New("404 not found")
+
+func query(q string) (result string, err error) {
+	flog := log.With().Str("url", q).Logger()
+
+	var resp *http.Response
+	for i := Retries; i > 0; i-- {
+		flog.Trace().Msg("wait")
+		Limiter.Wait(context.Background())
+
+		flog.Trace().Msg("start")
+		resp, err = http.Get(q)
+		if err != nil {
+			if strings.Contains(err.Error(), "reset by peer") {
+				flog.Debug().Err(err).Msg("")
+				lowerLimit()
+				continue
+			}
+			flog.Error().Err(err).Msg("")
+			return
+		}
+		defer resp.Body.Close()
+
+		flog.Debug().Msgf("%s", resp.Status)
+
+		if resp.StatusCode == 404 {
+			err = ErrNotFound
+			return
+		}
+
+		if resp.StatusCode < 500 {
+			break
+		}
+
+		flog.Debug().Msgf("retry (%d left)", i)
+	}
+
+	if resp.StatusCode >= 400 {
+		err = fmt.Errorf("%d (%s)", resp.StatusCode, q)
+	}
+
+	buf, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return
+	}
+
+	result = string(buf)
+	return
+}
+
+func queryAPIf(f string, s ...interface{}) (result string, err error) {
+	return query(apiURL + fmt.Sprintf(f, s...))
+}
+
+type Snapshot struct {
+	First string
+	Last  string
+}
+
+type PackageInfo struct {
+	Suite     string
+	Component string
+	Snapshot  Snapshot
+}
+
+func GetPackageInfo(pkg, arch, version string) (infos []PackageInfo, err error) {
+	var result string
+
+	for _, archive := range archives {
+		result, err = queryAPIf("archive=%s&pkg=%s&arch=%s&ver=%s",
+			archive, pkg, arch, version)
+		if err == nil {
+			break
+		}
+	}
+
+	if err != nil {
+		return
+	}
+
+	if result == "" {
+		err = ErrNotFound
+		return
+	}
+
+	for _, line := range strings.Split(result, "\n") {
+		if line == "" {
+			break
+		}
+
+		fields := strings.Split(line, " ")
+		if len(fields) != 4 {
+			err = fmt.Errorf("metasnap api returned %s", result)
+			return
+		}
+
+		info := PackageInfo{
+			Suite:     fields[0],
+			Component: fields[1],
+			Snapshot: Snapshot{
+				First: fields[2],
+				Last:  fields[3],
+			},
+		}
+
+		infos = append(infos, info)
+	}
+
+	if len(infos) == 0 {
+		err = ErrNotFound
+		return
+	}
+
+	return
+}
diff --git a/distro/debian/snapshot/metasnap/metasnap_test.go b/distro/debian/snapshot/metasnap/metasnap_test.go
new file mode 100644
index 0000000..264a3f4
--- /dev/null
+++ b/distro/debian/snapshot/metasnap/metasnap_test.go
@@ -0,0 +1,28 @@
+package metasnap
+
+import (
+	"testing"
+
+	"github.com/davecgh/go-spew/spew"
+)
+
+func TestGetPackageInfo(t *testing.T) {
+	// existing
+	infos, err := GetPackageInfo("linux-image-3.8-trunk-amd64",
+		"amd64", "3.8.2-1~experimental.1")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Log(spew.Sdump(infos))
+
+	// non-existing
+	infos, err = GetPackageInfo("meh", "amd64", "meh")
+	if err == nil {
+		t.Fatalf("should not be ok, result: %s", spew.Sdump(infos))
+	}
+
+	if err != ErrNotFound {
+		t.Fatal("wrong error type")
+	}
+}