From 170f13636c10418b5948f4cbfd93d37d7a3ee7b0 Mon Sep 17 00:00:00 2001
From: Filip Leonarski <filip.leonarski@psi.ch>
Date: Tue, 16 Dec 2025 13:23:20 +0100
Subject: [PATCH] BraggPrediction: Add SystematicAbsence header

---
 .../bragg_integration/BraggPrediction.cpp     | 52 +------------------
 .../bragg_integration/CMakeLists.txt          |  1 +
 .../bragg_integration/SystematicAbsence.h     | 26 ++++++++++
 3 files changed, 29 insertions(+), 50 deletions(-)
 create mode 100644 image_analysis/bragg_integration/SystematicAbsence.h

diff --git a/image_analysis/bragg_integration/BraggPrediction.cpp b/image_analysis/bragg_integration/BraggPrediction.cpp
index 498f78bb..3f8ec9ad 100644
--- a/image_analysis/bragg_integration/BraggPrediction.cpp
+++ b/image_analysis/bragg_integration/BraggPrediction.cpp
@@ -2,10 +2,7 @@
 // SPDX-License-Identifier: GPL-3.0-only
 
 #include "BraggPrediction.h"
-
-inline bool odd(const int val) {
-    return (val & 1) != 0;
-}
+#include "SystematicAbsence.h"
 
 BraggPrediction::BraggPrediction(int max_reflections)
     : max_reflections(max_reflections), reflections(max_reflections) {}
@@ -55,52 +52,7 @@ int BraggPrediction::Calc(const DiffractionExperiment &experiment, const Crystal
             const float AhBk_z = Ah_z + Bstar.z * k;
 
             for (int l = -settings.max_hkl; l < settings.max_hkl; l++) {
-                bool absent = false;
-                // (000) is not too interesting
-                if (h == 0 && k == 0 && l == 0)
-                    absent = true;
-
-                switch (settings.centering) {
-                    case 'I':
-                        // Body-centered: h + k + l must be even
-                        if (odd(h + k + l))
-                            absent = true;
-                        break;
-                    case 'A':
-                        // A-centered: k + l must be even
-                        if (odd(k + l))
-                            absent = true;
-                        break;
-                    case 'B':
-                        // B-centered: h + l must be even
-                        if (odd(h + l))
-                            absent = true;
-                        break;
-                    case 'C':
-                        // C-centered: h + k must be even
-                        if (odd(h + k))
-                            absent = true;
-                        break;
-                    case 'F': { // Face-centered: h, k, l all even or all odd
-                        if (odd(h+k) || odd(h+l) || odd(k+l))
-                            absent = true;
-                        break;
-                    }
-                    case 'R': {
-                        // Rhombohedral in hexagonal setting (hR, a_h=b_h, γ=120°):
-                        // Reflection condition: -h + k + l = 3n  (equivalently h - k + l = 3n)
-                        int mod = (-h + k + l) % 3;
-                        if (mod < 0) mod += 3;
-                        if (mod != 0)
-                            absent = true;
-                        break;
-                    }
-                    default:
-                        // P or unspecified: no systematic absences
-                        break;
-                }
-
-                if (absent)
+                if (systematic_absence(h, k, l, settings.centering))
                     continue;
 
                 if (i >= max_reflections)
diff --git a/image_analysis/bragg_integration/CMakeLists.txt b/image_analysis/bragg_integration/CMakeLists.txt
index 95b9e4f4..3ff89fb2 100644
--- a/image_analysis/bragg_integration/CMakeLists.txt
+++ b/image_analysis/bragg_integration/CMakeLists.txt
@@ -8,6 +8,7 @@ ADD_LIBRARY(JFJochBraggIntegration STATIC
         CalcISigma.h
         BraggPredictionFactory.cpp
         BraggPredictionFactory.h
+        SystematicAbsence.h
 )
 
 TARGET_LINK_LIBRARIES(JFJochBraggIntegration JFJochCommon)
diff --git a/image_analysis/bragg_integration/SystematicAbsence.h b/image_analysis/bragg_integration/SystematicAbsence.h
new file mode 100644
index 00000000..ea27ae32
--- /dev/null
+++ b/image_analysis/bragg_integration/SystematicAbsence.h
@@ -0,0 +1,26 @@
+// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
+// SPDX-License-Identifier: GPL-3.0-only
+
+#ifndef JFJOCH_SYSTEMATICABSENCE_H
+#define JFJOCH_SYSTEMATICABSENCE_H
+
+static inline bool odd_int(int v) { return (v & 1) != 0; }
+
+static inline bool systematic_absence(int h, int k, int l, char centering) {
+    if (h == 0 && k == 0 && l == 0) return true;
+    switch (centering) {
+        case 'I': return odd_int(h + k + l);
+        case 'A': return odd_int(k + l);
+        case 'B': return odd_int(h + l);
+        case 'C': return odd_int(h + k);
+        case 'F': return (odd_int(h + k) || odd_int(h + l) || odd_int(k + l));
+        case 'R': {
+            int mod = (-h + k + l) % 3;
+            if (mod < 0) mod += 3;
+            return mod != 0;
+        }
+        default:  return false; // P
+    }
+}
+
+#endif //JFJOCH_SYSTEMATICABSENCE_H
\ No newline at end of file