From e9b896004862679a78c362523ab91345b9fdbb8f Mon Sep 17 00:00:00 2001
From: Aly Raffauf <aly@aly.codes>
Date: Thu, 2 Jul 2026 21:48:41 -0400
Subject: [PATCH] api: add server and implement getBacklinksCount

---
 cmd/asterism/main.go      |  9 +++++++++
 internal/api/backlinks.go | 32 ++++++++++++++++++++++++++++++++
 internal/api/server.go    | 18 ++++++++++++++++++
 internal/api/source.go    | 27 +++++++++++++++++++++++++++
 internal/store/query.go   | 20 ++++++++++++++++++++
 5 files changed, 106 insertions(+)
 create mode 100644 internal/api/backlinks.go
 create mode 100644 internal/api/server.go
 create mode 100644 internal/api/source.go
 create mode 100644 internal/store/query.go

diff --git a/cmd/asterism/main.go b/cmd/asterism/main.go
index 8efeceb..764deeb 100644
--- a/cmd/asterism/main.go
+++ b/cmd/asterism/main.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/gorilla/websocket"
 
+	"github.com/alyraffauf/asterism/internal/api"
 	"github.com/alyraffauf/asterism/internal/firehose"
 	"github.com/alyraffauf/asterism/internal/store"
 )
@@ -50,6 +51,14 @@ func main() {
 		panic(err)
 	}
 
+	server := &api.Server{Store: linkStore}
+	go func() {
+		if err := server.Run(":8081"); err != nil {
+			panic(err)
+		}
+	}()
+	defer conn.Close()
+
 	consumer := &firehose.Consumer{
 		WantedCollections: parseCollections(*collectionsFlag),
 		Store:             linkStore,
diff --git a/internal/api/backlinks.go b/internal/api/backlinks.go
new file mode 100644
index 0000000..2820a6d
--- /dev/null
+++ b/internal/api/backlinks.go
@@ -0,0 +1,32 @@
+package api
+
+import (
+	"encoding/json"
+	"log"
+	"net/http"
+)
+
+type backlinksCountResponse struct {
+	Total uint64 `json:"total"`
+}
+
+func (s *Server) GetBacklinksCount(w http.ResponseWriter, r *http.Request) {
+	subject := r.URL.Query().Get("subject")
+	source := r.URL.Query().Get("source")
+
+	collection, path, err := parseSource(source)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	total, err := s.Store.CountBacklinks(r.Context(), subject, collection, path)
+	if err != nil {
+		log.Println("count backlinks:", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(backlinksCountResponse{Total: total})
+}
diff --git a/internal/api/server.go b/internal/api/server.go
new file mode 100644
index 0000000..6f6f1ba
--- /dev/null
+++ b/internal/api/server.go
@@ -0,0 +1,18 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/alyraffauf/asterism/internal/store"
+)
+
+type Server struct {
+	Store *store.Store
+}
+
+func (s *Server) Run(addr string) error {
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /xrpc/blue.microcosm.links.getBacklinksCount", s.GetBacklinksCount)
+
+	return http.ListenAndServe(addr, mux)
+}
diff --git a/internal/api/source.go b/internal/api/source.go
new file mode 100644
index 0000000..17f437a
--- /dev/null
+++ b/internal/api/source.go
@@ -0,0 +1,27 @@
+package api
+
+import (
+	"fmt"
+	"strings"
+)
+
+func parseSource(raw string) (collection string, path string, err error) {
+	collection, rawPath, ok := strings.Cut(raw, ":")
+	if !ok {
+		return "", "", fmt.Errorf("source must contain a ':' separator")
+	}
+	if collection == "" {
+		return "", "", fmt.Errorf("source is missing a collection before ':'")
+	}
+
+	switch {
+	case rawPath == "":
+		return "", "", fmt.Errorf("source is missing a path after ':'")
+	case rawPath == ".":
+		return collection, ".", nil
+	case strings.HasPrefix(rawPath, "."):
+		return "", "", fmt.Errorf("source path must not start with '.'")
+	default:
+		return collection, "." + rawPath, nil
+	}
+}
diff --git a/internal/store/query.go b/internal/store/query.go
new file mode 100644
index 0000000..5c00aba
--- /dev/null
+++ b/internal/store/query.go
@@ -0,0 +1,20 @@
+package store
+
+import (
+	"context"
+	"fmt"
+)
+
+func (s *Store) CountBacklinks(ctx context.Context, target, collection, fieldPath string) (uint64, error) {
+	var total uint64
+
+	err := s.db.QueryRowContext(ctx,
+		`SELECT COUNT(*) FROM links WHERE target = ? AND collection = ? AND field_path = ?`,
+		target, collection, fieldPath,
+	).Scan(&total)
+	if err != nil {
+		return 0, fmt.Errorf("count backlinks: %w", err)
+	}
+
+	return total, nil
+}
-- 
2.51.2