Extract history UI operation planning

src/app_core/history_ui.h

@@ -0,0 +1,110 @@
+#pragma once
+
+#include "foundation/result.h"
+
+namespace pp::app {
+
+enum class HistoryUiOperation {
+    undo,
+    redo,
+    clear,
+};
+
+struct HistoryUiPlan {
+    HistoryUiOperation operation = HistoryUiOperation::undo;
+    int undo_count = 0;
+    int redo_count = 0;
+    int memory_bytes = 0;
+    bool invokes_undo = false;
+    bool invokes_redo = false;
+    bool clears_history = false;
+    bool updates_memory_label = false;
+    bool updates_title = false;
+    bool no_op = false;
+};
+
+[[nodiscard]] inline pp::foundation::Status validate_history_metric(int value, const char* message) noexcept
+{
+    if (value < 0) {
+        return pp::foundation::Status::out_of_range(message);
+    }
+
+    return pp::foundation::Status::success();
+}
+
+[[nodiscard]] inline pp::foundation::Result<HistoryUiPlan> plan_history_undo(int undo_count)
+{
+    const auto count_status = validate_history_metric(undo_count, "undo action count must not be negative");
+    if (!count_status.ok()) {
+        return pp::foundation::Result<HistoryUiPlan>::failure(count_status);
+    }
+
+    HistoryUiPlan plan;
+    plan.operation = HistoryUiOperation::undo;
+    plan.undo_count = undo_count;
+    if (undo_count == 0) {
+        plan.no_op = true;
+        return pp::foundation::Result<HistoryUiPlan>::success(plan);
+    }
+
+    plan.invokes_undo = true;
+    plan.updates_memory_label = true;
+    plan.updates_title = true;
+    return pp::foundation::Result<HistoryUiPlan>::success(plan);
+}
+
+[[nodiscard]] inline pp::foundation::Result<HistoryUiPlan> plan_history_redo(int redo_count)
+{
+    const auto count_status = validate_history_metric(redo_count, "redo action count must not be negative");
+    if (!count_status.ok()) {
+        return pp::foundation::Result<HistoryUiPlan>::failure(count_status);
+    }
+
+    HistoryUiPlan plan;
+    plan.operation = HistoryUiOperation::redo;
+    plan.redo_count = redo_count;
+    if (redo_count == 0) {
+        plan.no_op = true;
+        return pp::foundation::Result<HistoryUiPlan>::success(plan);
+    }
+
+    plan.invokes_redo = true;
+    plan.updates_memory_label = true;
+    plan.updates_title = true;
+    return pp::foundation::Result<HistoryUiPlan>::success(plan);
+}
+
+[[nodiscard]] inline pp::foundation::Result<HistoryUiPlan> plan_history_clear(
+    int undo_count,
+    int redo_count,
+    int memory_bytes)
+{
+    const auto undo_status = validate_history_metric(undo_count, "undo action count must not be negative");
+    if (!undo_status.ok()) {
+        return pp::foundation::Result<HistoryUiPlan>::failure(undo_status);
+    }
+    const auto redo_status = validate_history_metric(redo_count, "redo action count must not be negative");
+    if (!redo_status.ok()) {
+        return pp::foundation::Result<HistoryUiPlan>::failure(redo_status);
+    }
+    const auto memory_status = validate_history_metric(memory_bytes, "history memory bytes must not be negative");
+    if (!memory_status.ok()) {
+        return pp::foundation::Result<HistoryUiPlan>::failure(memory_status);
+    }
+
+    HistoryUiPlan plan;
+    plan.operation = HistoryUiOperation::clear;
+    plan.undo_count = undo_count;
+    plan.redo_count = redo_count;
+    plan.memory_bytes = memory_bytes;
+    if (undo_count == 0 && redo_count == 0 && memory_bytes == 0) {
+        plan.no_op = true;
+        return pp::foundation::Result<HistoryUiPlan>::success(plan);
+    }
+
+    plan.clears_history = true;
+    plan.updates_memory_label = true;
+    return pp::foundation::Result<HistoryUiPlan>::success(plan);
+}
+
+} // namespace pp::app