Add web product Phase 1 skeleton

internal/httpapi/response.go

@@ -0,0 +1,58 @@
+package httpapi
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"ai-workflow-skill/internal/store"
+)
+
+type errorEnvelope struct {
+	Error errorPayload `json:"error"`
+}
+
+type errorPayload struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+func writeJSON(w http.ResponseWriter, status int, payload any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	_ = enc.Encode(payload)
+}
+
+func writeError(w http.ResponseWriter, err error) {
+	status, code := classifyError(err)
+	writeJSON(w, status, errorEnvelope{
+		Error: errorPayload{
+			Code:    code,
+			Message: errorMessage(err),
+		},
+	})
+}
+
+func classifyError(err error) (int, string) {
+	switch {
+	case errors.Is(err, store.ErrInvalidInput):
+		return http.StatusBadRequest, "invalid_input"
+	case errors.Is(err, store.ErrRunNotFound), errors.Is(err, store.ErrTaskNotFound), errors.Is(err, store.ErrThreadNotFound):
+		return http.StatusNotFound, "not_found"
+	case errors.Is(err, store.ErrInvalidState):
+		return http.StatusConflict, "invalid_state"
+	default:
+		return http.StatusInternalServerError, "internal_error"
+	}
+}
+
+func errorMessage(err error) string {
+	if err == nil {
+		return "unknown error"
+	}
+	return fmt.Sprintf("%v", err)
+}