Initial

backend/internal/rest/response.go

@@ -0,0 +1,66 @@
+package rest
+
+import (
+	"encoding/json"
+	"io"
+	"log/slog"
+	"net/http"
+	"strconv"
+)
+
+const (
+	maxRequestBody = 1 << 20
+	defaultLimit   = 50
+	maxLimit       = 200
+)
+
+type errorResponse struct {
+	Error string `json:"error"`
+}
+
+func writeJson(w http.ResponseWriter, status int, value any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+	if value == nil {
+		return
+	}
+	if err := json.NewEncoder(w).Encode(value); err != nil {
+		slog.Error("encode response", slog.String("op", "rest.writeJson"), slog.Any("error", err))
+	}
+}
+
+func writeError(w http.ResponseWriter, status int, message string) {
+	writeJson(w, status, errorResponse{Error: message})
+}
+
+func writeNoContent(w http.ResponseWriter) {
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func decodeJson(r *http.Request, dst any) error {
+	decoder := json.NewDecoder(io.LimitReader(r.Body, maxRequestBody))
+	decoder.DisallowUnknownFields()
+	return decoder.Decode(dst)
+}
+
+func pagination(r *http.Request) (limit, offset int64) {
+	limit = defaultLimit
+	query := r.URL.Query()
+
+	if value := query.Get("limit"); value != "" {
+		if parsed, err := strconv.ParseInt(value, 10, 64); err == nil && parsed > 0 {
+			limit = parsed
+		}
+	}
+	if limit > maxLimit {
+		limit = maxLimit
+	}
+
+	if value := query.Get("offset"); value != "" {
+		if parsed, err := strconv.ParseInt(value, 10, 64); err == nil && parsed >= 0 {
+			offset = parsed
+		}
+	}
+
+	return limit, offset
+}