adapter: split dynamodb.go into cohesive files (no behavior change)

adapter/dynamodb_errors.go

@@ -0,0 +1,78 @@
+package adapter
+
+import (
+	"net/http"
+
+	"github.com/cockroachdb/errors"
+	json "github.com/goccy/go-json"
+)
+
+type dynamoAPIError struct {
+	status    int
+	errorType string
+	message   string
+}
+
+func (e *dynamoAPIError) Error() string {
+	if e == nil {
+		return ""
+	}
+	if e.message != "" {
+		return e.message
+	}
+	return http.StatusText(e.status)
+}
+
+func newDynamoAPIError(status int, errorType string, message string) error {
+	return &dynamoAPIError{
+		status:    status,
+		errorType: errorType,
+		message:   message,
+	}
+}
+
+func writeDynamoErrorFromErr(w http.ResponseWriter, err error) {
+	var apiErr *dynamoAPIError
+	if errors.As(err, &apiErr) {
+		writeDynamoError(w, apiErr.status, apiErr.errorType, apiErr.message)
+		return
+	}
+	writeDynamoError(w, http.StatusInternalServerError, dynamoErrInternal, err.Error())
+}
+
+// dynamoErrIsTransient reports whether err is a transient/internal failure
+// (Pebble error, context deadline, decode failure) as opposed to a structured
+// validation/malformed-input error. A *dynamoAPIError is always a deliberate
+// validation result (it carries an HTTP status + error type), so it is NOT
+// transient; everything else — a raw wrapped store/context error — is. The
+// lease pre-pass uses this to decide whether an unresolvable item must fail
+// closed (transient) or may be skipped (validation, rejected identically by
+// the read path).
+func dynamoErrIsTransient(err error) bool {
+	if err == nil {
+		return false
+	}
+	var apiErr *dynamoAPIError
+	return !errors.As(err, &apiErr)
+}
+
+func writeDynamoError(w http.ResponseWriter, status int, errorType string, message string) {
+	if message == "" {
+		message = http.StatusText(status)
+	}
+
+	resp := map[string]string{"message": message}
+	if errorType != "" {
+		resp["__type"] = errorType
+		w.Header().Set("x-amzn-ErrorType", errorType)
+	}
+	w.Header().Set("Content-Type", "application/x-amz-json-1.0")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(resp)
+}
+
+func writeDynamoJSON(w http.ResponseWriter, payload any) {
+	w.Header().Set("Content-Type", "application/x-amz-json-1.0")
+	w.WriteHeader(http.StatusOK)
+	_ = json.NewEncoder(w).Encode(payload)
+}