Updates: when a release may install by itself, as a state machine

Issue #52: once a newer release is known, wait for a quiet moment, ask
for 30 seconds, and install unless the answer is no. The caller says
what busy and idle are. Host-tested.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

lib/release/src/auto_update.h

@@ -0,0 +1,80 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace roro::release {
+
+// Installing a release without being asked to (issue #52): once a newer one is known, wait for a
+// quiet moment (nothing recording, nothing written, no key for a while), then say so on the
+// screen for 30 seconds. Unless someone answers no, it is installed. Host-tested; the caller says
+// what "quiet" is and does the installing.
+class AutoUpdate {
+   public:
+    static constexpr uint32_t kIdleMs = 120000;  // no key for this long: nobody is using the device
+    static constexpr uint32_t kAskMs = 30000;    // how long the question stays before it answers itself
+
+    enum class Action : uint8_t {
+        None,
+        Ask,      // the question goes up
+        Dismiss,  // the question comes down, nothing is installed
+        Install,  // the question comes down, install tag()
+    };
+
+    // A newer release is known. A second offer while one is waiting or asked replaces its tag.
+    void offer(const std::string& tag) {
+        tag_ = tag;
+        if (state_ == State::Idle) state_ = State::Waiting;
+    }
+    // The setting went off, or the release is no longer wanted.
+    void withdraw() { withdrawn_ = true; }
+    // The user's answer to the question.
+    void answer(bool install) {
+        if (state_ != State::Asking) return;
+        answered_ = true;
+        accepted_ = install;
+    }
+
+    // Call often. `busy`: something is recording or being written, and a restart would cut it.
+    // `idleMs`: how long since the last key.
+    Action step(uint32_t nowMs, bool busy, uint32_t idleMs) {
+        bool withdrawn = withdrawn_;
+        withdrawn_ = false;
+        switch (state_) {
+            case State::Idle: return Action::None;
+            case State::Waiting:
+                if (withdrawn) return state_ = State::Idle, Action::None;
+                if (busy || idleMs < kIdleMs) return Action::None;
+                state_ = State::Asking;
+                askedMs_ = nowMs;
+                answered_ = false;
+                return Action::Ask;
+            case State::Asking:
+                if (withdrawn) return state_ = State::Idle, Action::Dismiss;
+                if (answered_) return state_ = State::Idle, accepted_ ? Action::Install : Action::Dismiss;
+                // Something started meanwhile (a Track from a console): the question goes, and comes back later.
+                if (busy) return state_ = State::Waiting, Action::Dismiss;
+                if (nowMs - askedMs_ >= kAskMs) return state_ = State::Idle, Action::Install;
+                return Action::None;
+        }
+        return Action::None;
+    }
+
+    bool waiting() const { return state_ == State::Waiting; }
+    bool asking() const { return state_ == State::Asking; }
+    const std::string& tag() const { return tag_; }
+    // Whole seconds until the question answers itself, rounded up.
+    int secondsLeft(uint32_t nowMs) const {
+        uint32_t gone = nowMs - askedMs_;
+        return !asking() || gone >= kAskMs ? 0 : static_cast<int>((kAskMs - gone + 999) / 1000);
+    }
+
+   private:
+    enum class State : uint8_t { Idle, Waiting, Asking };
+    State state_ = State::Idle;
+    std::string tag_;
+    uint32_t askedMs_ = 0;
+    bool answered_ = false, accepted_ = false, withdrawn_ = false;
+};
+
+}  // namespace roro::release

lib/release/src/update_check.h

@@ -24,6 +24,12 @@ inline bool shouldAnnounce(const Release& latest, const std::string& running, co
     return isNewer(latest, running) && latest.tag != failed && latest.tag != announced;
 }
 
+// Should the background check offer to install it by itself (issue #52)? Any newer release, each
+// day it is still the newest; never a version that rolled back on this device.
+inline bool shouldInstall(const Release& latest, const std::string& running, const std::string& failed) {
+    return isNewer(latest, running) && latest.tag != failed;
+}
+
 // Is `url` a download this device takes from the project's server, for this repository? Whatever
 // the API says, the device only fetches from where it asked (a redirected or rewritten answer
 // can't send it elsewhere).