feat(backend): start on fediverse auth support

backend/db/fediverse.go

@@ -0,0 +1,76 @@
+package db
+
+import (
+	"context"
+	"os"
+
+	"emperror.dev/errors"
+	"github.com/georgysavva/scany/pgxscan"
+	"github.com/jackc/pgx/v4"
+	"golang.org/x/oauth2"
+)
+
+type FediverseApp struct {
+	ID int64
+	// Instance is the instance's base API url, excluding schema
+	Instance     string
+	ClientID     string
+	ClientSecret string
+	InstanceType string
+}
+
+func (f FediverseApp) ClientConfig() *oauth2.Config {
+	// if f.MastodonCompatible() {
+	return &oauth2.Config{
+		ClientID:     f.ClientID,
+		ClientSecret: f.ClientSecret,
+		Endpoint: oauth2.Endpoint{
+			AuthURL:   "https://" + f.Instance + "/oauth/authorize",
+			TokenURL:  "https://" + f.Instance + "/oauth/token",
+			AuthStyle: oauth2.AuthStyleInParams,
+		},
+		Scopes:      []string{"read:accounts"},
+		RedirectURL: os.Getenv("BASE_URL") + "/auth/login/mastodon",
+	}
+	// }
+
+	// TODO: misskey, assuming i can even find english API documentation, that is
+}
+
+func (f FediverseApp) MastodonCompatible() bool {
+	return f.InstanceType == "mastodon" || f.InstanceType == "pleroma" || f.InstanceType == "akkoma" || f.InstanceType == "pixelfed"
+}
+
+const ErrNoInstanceApp = errors.Sentinel("instance doesn't have an app")
+
+func (db *DB) FediverseApp(ctx context.Context, instance string) (fa FediverseApp, err error) {
+	sql, args, err := sq.Select("*").From("fediverse_apps").Where("instance = ?", instance).ToSql()
+	if err != nil {
+		return fa, errors.Wrap(err, "building sql")
+	}
+
+	err = pgxscan.Get(ctx, db, &fa, sql, args...)
+	if err != nil {
+		if errors.Cause(err) == pgx.ErrNoRows {
+			return fa, ErrNoInstanceApp
+		}
+		return fa, errors.Wrap(err, "executing query")
+	}
+	return fa, nil
+}
+
+func (db *DB) CreateFediverseApp(ctx context.Context, instance, instanceType, clientID, clientSecret string) (fa FediverseApp, err error) {
+	sql, args, err := sq.Insert("fediverse_apps").
+		Columns("instance", "instance_type", "client_id", "client_secret").
+		Values(instance, instanceType, clientID, clientSecret).
+		Suffix("RETURNING *").ToSql()
+	if err != nil {
+		return fa, errors.Wrap(err, "building query")
+	}
+
+	err = pgxscan.Get(ctx, db, &fa, sql, args...)
+	if err != nil {
+		return fa, errors.Wrap(err, "executing query")
+	}
+	return fa, nil
+}