internal/rosa: release monitoring via Anitya

This is much more sustainable than manual package flagging.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/all.go

@@ -1,6 +1,11 @@
 package rosa
 
 import (
+	"context"
+	"encoding/json"
+	"errors"
+	"net/http"
+	"strconv"
 	"sync"
 
 	"hakurei.app/internal/pkg"
@@ -152,11 +157,57 @@ type Metadata struct {
 	Description string `json:"description"`
 	// Project home page.
 	Website string `json:"website,omitempty"`
+
+	// Project identifier on [Anitya].
+	//
+	// [Anitya]: https://release-monitoring.org/
+	ID int `json:"-"`
 }
 
 // Unversioned denotes an unversioned [PArtifact].
 const Unversioned = "\x00"
 
+// UnpopulatedIDError is returned by [Metadata.GetLatest] for an instance of
+// [Metadata] where ID is not populated.
+type UnpopulatedIDError struct{}
+
+func (UnpopulatedIDError) Unwrap() error { return errors.ErrUnsupported }
+func (UnpopulatedIDError) Error() string { return "Anitya ID is not populated" }
+
+// Versions are package versions returned by Anitya.
+type Versions struct {
+	// The latest version for the project, as determined by the version sorting algorithm.
+	Latest string `json:"latest_version"`
+	// List of all versions that aren’t flagged as pre-release.
+	Stable []string `json:"stable_versions"`
+	// List of all versions stored, sorted from newest to oldest.
+	All []string `json:"versions"`
+}
+
+// GetVersions returns versions fetched from Anitya.
+func (meta *Metadata) GetVersions(ctx context.Context) (*Versions, error) {
+	if meta.ID == 0 {
+		return nil, UnpopulatedIDError{}
+	}
+
+	var resp *http.Response
+	if req, err := http.NewRequestWithContext(
+		ctx,
+		http.MethodGet,
+		"https://release-monitoring.org/api/v2/versions/?project_id="+
+			strconv.Itoa(meta.ID),
+		nil,
+	); err != nil {
+		return nil, err
+	} else if resp, err = http.DefaultClient.Do(req); err != nil {
+		return nil, err
+	}
+
+	var v Versions
+	err := json.NewDecoder(resp.Body).Decode(&v)
+	return &v, errors.Join(err, resp.Body.Close())
+}
+
 var (
 	// artifactsM is an array of [PArtifact] metadata.
 	artifactsM [PresetEnd]Metadata