feat(tfstated): add json encoding and decoding helpers

cmd/tfstated/get.go

@@ -12,21 +12,20 @@ import (
 func handleGet(db *database.DB) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Cache-Control", "no-store, no-cache")
-		w.Header().Set("Content-Type", "application/json")
 
 		if r.URL.Path == "/" {
-			w.WriteHeader(http.StatusBadRequest)
+			_ = errorResponse(w, http.StatusBadRequest,
-			_, _ = w.Write([]byte("{\"msg\": \"No state path provided, cannot GET /\"}"))
+				fmt.Errorf("no state path provided, cannot GET /"))
 			return
 		}
 
 		if data, err := db.GetState(r.URL.Path); err != nil {
 			if errors.Is(err, sql.ErrNoRows) {
-				w.WriteHeader(http.StatusNotFound)
+				_ = errorResponse(w, http.StatusNotFound,
+					fmt.Errorf("state path not found: %s", r.URL.Path))
 			} else {
-				w.WriteHeader(http.StatusInternalServerError)
+				_ = errorResponse(w, http.StatusInternalServerError, err)
 			}
-			_, _ = w.Write([]byte(fmt.Sprintf("{\"msg\": \"%+v\"}", err)))
 		} else {
 			w.WriteHeader(http.StatusOK)
 			_, _ = w.Write(data)

cmd/tfstated/helpers.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+)
+
+func decode(r *http.Request, data any) error {
+	if err := json.NewDecoder(r.Body).Decode(&data); err != nil {
+		return fmt.Errorf("failed to decode json: %w", err)
+	}
+	return nil
+}
+
+func encode(w http.ResponseWriter, status int, data any) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(data); err != nil {
+		slog.Error("failed to encode json", "err", err)
+		return fmt.Errorf("failed to encode json: %w", err)
+	}
+	return nil
+}
+
+func errorResponse(w http.ResponseWriter, status int, err error) error {
+	type errorResponse struct {
+		Msg    string `json:"msg"`
+		Status int    `json:"status"`
+	}
+	return encode(w, status, &errorResponse{
+		Msg:    fmt.Sprintf("%+v", err),
+		Status: status,
+	})
+}

cmd/tfstated/post.go

@@ -10,21 +10,19 @@ import (
 
 func handlePost(db *database.DB) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Content-Type", "application/json")
 		if r.URL.Path == "/" {
-			w.WriteHeader(http.StatusBadRequest)
+			_ = errorResponse(w, http.StatusBadRequest,
-			_, _ = w.Write([]byte("{\"msg\": \"No state path provided, cannot POST /\"}"))
+				fmt.Errorf("no state path provided, cannot POST /"),
+			)
 			return
 		}
 		data, err := io.ReadAll(r.Body)
 		if err != nil {
-			w.WriteHeader(http.StatusBadRequest)
+			_ = errorResponse(w, http.StatusBadRequest, err)
-			_, _ = w.Write([]byte(fmt.Sprintf("{\"msg\": \"failed to read request body: %+v\"}", err)))
 			return
 		}
 		if err := db.SetState(r.URL.Path, data); err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
+			_ = errorResponse(w, http.StatusInternalServerError, err)
-			_, _ = w.Write([]byte(fmt.Sprintf("{\"msg\": \"%+v\"}", err)))
 		} else {
 			w.WriteHeader(http.StatusOK)
 		}