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examples/simulations/rollback-policy/simulation.hpp

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+#pragma once
+
+#include <cstddef>
+#include <optional>
+#include <set>
+#include <string>
+#include <vector>
+
+namespace ota::rollback {
+
+    enum class Phase { Idle,
+                       Assess,
+                       RestoreData,
+                       SelectPrevious,
+                       CheckPrevious,
+                       Recovered,
+                       SeparateRecovery };
+    enum class Slot { A,
+                      B };
+
+    struct Data {
+        int schema = 1;
+        std::vector<int> records{1, 2, 3, 4};
+    };
+
+    // These are assumed complete durable records, not a storage implementation.
+    struct Storage {
+        Phase phase = Phase::Idle;
+        Slot running = Slot::B;
+        std::string failed_release = "system-2";
+        std::string previous_release = "system-1";
+        std::set<std::string> blocked_releases;
+        std::string failure_reason;
+        std::string recovery_reason;
+        bool report_pending = false;
+        bool window_open = true;
+        bool target_eligible = true;
+        int attempts_left = 2;
+        int boots_requested = 0;
+        Data data;
+        std::optional<Data> backup;
+        bool backup_valid = false;
+        bool restore_authorized = false;
+        std::size_t records_lost = 0;
+        int restores = 0;
+    };
+
+    class Coordinator {
+    public:
+        explicit Coordinator(Storage &storage);
+        void start(const std::string &reason);
+        void advance(bool previous_healthy = true);
+        // Call once for an actual reset, not merely a coordinator restart.
+        void after_reset();
+
+    private:
+        Storage &storage_;
+        void stop(const std::string &reason);
+    };
+
+    bool terminal(Phase phase);
+    bool can_offer(const Storage &storage, const std::string &release);
+    const char *name(Phase phase);
+    const std::vector<std::string> &scenarios();
+    Storage run_scenario(const std::string &scenario);
+
+}// namespace ota::rollback