Merge PR #84: feat: change history in Ustawienia

backend/README.md

@@ -22,6 +22,12 @@ Same Origin, header and JSON rules as the other writes; `Remote-User` goes on as
 `{status, message, read}`: 200 applied, 422 rejected, 409 settings unknown or changed meanwhile, 429 too soon, 502 failed (`read` is what the
 inverter holds), 400 bad body, 503 gateway unreachable or without battery commands (ADR-013).
 
+`GET /api/audit?range=7d` (`24h`, `7d` default, `30d`; 400 otherwise, 502 when InfluxDB fails) is the change history, example
+`src/test/resources/api/audit.json`: the gateway's audit rows of the heat pump (`Dom_Pompa.setpoint_audit`) and the battery
+(`electricity.deye_settings_audit`), read only, as `entries` newest first: `time`, `source` (`heat_pump`, `battery`), `what` (Polish label;
+the Deye registers are named in `DeyeSettingLabels`), `oldValue`/`newValue` (whole numbers, null when not recorded), `unit` (`°C`, `%`,
+`HHMM`, `0/1`), `who` (`Remote-User` of the request; a restore is "automatycznie (przywrócenie)") and `status` (the gateway's: APPLIED, FAILED, REJECTED, CONFLICT, INVALID).
+
 Settings are environment variables (`.env` next to `compose.yaml`); the backend refuses to start
 without the two URLs.
 Setpoint changes go only to the gateway; the user name from Traefik's `Remote-User` header (else `phone`) is sent as `X-Requested-By`.

backend/src/main/java/home/backend/Backend.java

@@ -4,8 +4,10 @@ import home.backend.adapters.config.PresetFile;
 import home.backend.adapters.gateway.GatewayHttpClient;
 import home.backend.adapters.gateway.GatewayHttpCommands;
 import home.backend.adapters.http.ApiServer;
+import home.backend.adapters.influx.InfluxAuditRepository;
 import home.backend.adapters.influx.InfluxHistoryRepository;
 import home.backend.adapters.influx.InfluxSettings;
+import home.backend.application.AuditService;
 import home.backend.application.BatteryService;
 import home.backend.application.EnergyDetailsService;
 import home.backend.application.EnergyService;
@@ -33,7 +35,8 @@ final class Backend {
      */
     static ApiServer assemble(Settings settings, Clock clock) throws IOException {
         var gateway = new GatewayHttpClient(settings.gatewayUrl(), settings.gatewayTimeout());
-        var influx = new InfluxHistoryRepository(new InfluxSettings(settings.influxUrl(), settings.influxTimeout()));
+        var influxSettings = new InfluxSettings(settings.influxUrl(), settings.influxTimeout());
+        var influx = new InfluxHistoryRepository(influxSettings);
         var commands = commands(settings);
         var setpoints = new SetpointService(commands, PresetFile.load(settings.presetsFile()));
         return new ApiServer(settings.port(),
@@ -42,7 +45,8 @@ final class Backend {
                 new EnergyDetailsService(gateway, clock),
                 new HealthService(gateway, clock, Objects.requireNonNullElse(System.getenv("VERSION"), "dev")),
                 new HistoryService(influx, clock), setpoints, new PiSensorService(gateway, clock),
-                new BatteryService(gateway, commands, clock));
+                new BatteryService(gateway, commands, clock),
+                new AuditService(new InfluxAuditRepository(influxSettings), clock));
     }
 
     /** Keeps the gateway from restoring our setpoint changes while we are up (ADR-011). */

backend/src/main/java/home/backend/adapters/http/ApiServer.java

@@ -9,6 +9,7 @@ import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import com.sun.net.httpserver.HttpExchange;
 import com.sun.net.httpserver.HttpHandler;
 import com.sun.net.httpserver.HttpServer;
+import home.backend.application.AuditService;
 import home.backend.application.BatteryService;
 import home.backend.application.EnergyDetailsService;
 import home.backend.application.EnergyService;
@@ -87,7 +88,7 @@ public class ApiServer {
     public ApiServer(int port, HeatPumpService heatPump, EnergyService energy,
             EnergyDetailsService energyDetails, HealthService health,
             HistoryService history, SetpointService setpoints, PiSensorService piSensor,
-            BatteryService battery) throws IOException {
+            BatteryService battery, AuditService audit) throws IOException {
         server = HttpServer.create(new InetSocketAddress(port), 0);
         server.setExecutor(executor);
         // Everything outside the API, with the security headers too: the web UI is the frontend's (ADR-010).
@@ -107,6 +108,7 @@ public class ApiServer {
         api("/api/pi-sensor", query -> piSensor.current());
         api("/api/health", query -> health.current());
         route("/api/history", exchange -> handleHistory(exchange, history));
+        route("/api/audit", exchange -> handleAudit(exchange, audit));
         route("/api/setpoints", exchange -> handle(exchange, Map.of(
                 "GET", () -> getSetpoints(exchange, setpoints),
                 "POST", () -> guarded(exchange, body -> postSetpoint(exchange, body, setpoints)))));
@@ -337,6 +339,19 @@ public class ApiServer {
         }));
     }
 
+    private void handleAudit(HttpExchange exchange, AuditService audit) throws IOException {
+        handle(exchange, Map.of("GET", () -> {
+            Map<String, String> query = parseQuery(exchange.getRequestURI().getRawQuery());
+            try {
+                send(exchange, 200, audit.audit(query.get("range")));
+            } catch (IllegalArgumentException e) {
+                send(exchange, 400, error(e.getMessage()));
+            } catch (IOException e) {
+                send(exchange, 502, error("audit unavailable"));
+            }
+        }));
+    }
+
     private interface Action {
         void run() throws IOException;
     }

backend/src/main/java/home/backend/adapters/influx/InfluxAuditRepository.java

@@ -0,0 +1,88 @@
+package home.backend.adapters.influx;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.application.AuditRepository;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/** The gateway's audit measurements (S3) read from InfluxDB; never written. */
+public final class InfluxAuditRepository implements AuditRepository {
+
+    private static final ObjectMapper JSON = new ObjectMapper();
+
+    private final InfluxClient influx;
+
+    public InfluxAuditRepository(InfluxSettings settings) {
+        this.influx = new InfluxClient(settings);
+    }
+
+    @Override
+    public List<Row> heatPump(Instant from, Instant to) throws IOException {
+        return rows("Dom_Pompa", "setpoint_audit", "setpoint", from, to);
+    }
+
+    @Override
+    public List<Row> battery(Instant from, Instant to) throws IOException {
+        return rows("electricity", "deye_settings_audit", "register", from, to);
+    }
+
+    private List<Row> rows(String database, String measurement, String targetTag, Instant from, Instant to)
+            throws IOException {
+        String query = "SELECT * FROM \"" + measurement + "\" WHERE time >= " + from.toEpochMilli()
+                + "ms AND time < " + to.toEpochMilli() + "ms ORDER BY time DESC";
+        var rows = new ArrayList<Row>();
+        for (JsonNode result : results(influx.query(database, query))) {
+            for (JsonNode series : result.path("series")) {
+                for (JsonNode values : series.path("values")) {
+                    rows.add(row(series.path("columns"), values, targetTag));
+                }
+            }
+        }
+        return rows;
+    }
+
+    private static JsonNode results(String body) throws IOException {
+        JsonNode root;
+        try {
+            root = JSON.readTree(body);
+        } catch (JsonProcessingException e) {
+            throw new IOException("InfluxDB returned invalid JSON: " + e.getOriginalMessage(), e);
+        }
+        failOnError(root);
+        for (JsonNode result : root.path("results")) {
+            failOnError(result);
+        }
+        return root.path("results");
+    }
+
+    private static void failOnError(JsonNode node) throws IOException {
+        if (node.hasNonNull("error")) {
+            throw new IOException("InfluxDB query failed: " + node.get("error").asText());
+        }
+    }
+
+    private static Row row(JsonNode columns, JsonNode values, String targetTag) {
+        Map<String, JsonNode> byName = new HashMap<>();
+        for (int i = 0; i < columns.size(); i++) {
+            byName.put(columns.get(i).asText(), values.get(i));
+        }
+        return new Row(Instant.ofEpochMilli(byName.get("time").asLong()), text(byName.get(targetTag)),
+                text(byName.get("requested_by")), text(byName.get("status")),
+                number(byName.get("old_value")), number(byName.get("new_value")));
+    }
+
+    private static String text(JsonNode node) {
+        return node == null || node.isNull() ? "" : node.asText();
+    }
+
+    private static Double number(JsonNode node) {
+        return node == null || !node.isNumber() ? null : node.asDouble();
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxClient.java

@@ -0,0 +1,47 @@
+package home.backend.adapters.influx;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URLEncoder;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+
+/** Read-only queries to InfluxDB 1.x over its HTTP {@code /query} endpoint; times come back in epoch ms. */
+final class InfluxClient {
+
+    private final InfluxSettings settings;
+    private final HttpClient http;
+
+    InfluxClient(InfluxSettings settings) {
+        this.settings = settings;
+        this.http = HttpClient.newBuilder().connectTimeout(settings.requestTimeout()).build();
+    }
+
+    String query(String database, String query) throws IOException {
+        HttpRequest request = HttpRequest.newBuilder(queryUri(database, query))
+                .timeout(settings.requestTimeout())
+                .GET()
+                .build();
+        try {
+            HttpResponse<String> response = http.send(request, HttpResponse.BodyHandlers.ofString());
+            if (response.statusCode() != 200) {
+                throw new IOException("InfluxDB answered HTTP " + response.statusCode());
+            }
+            return response.body();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException("InfluxDB request interrupted", e);
+        }
+    }
+
+    private URI queryUri(String database, String query) {
+        String base = settings.baseUri().toString().replaceAll("/+$", "");
+        return URI.create(base + "/query?db=" + encode(database) + "&epoch=ms&q=" + encode(query));
+    }
+
+    private static String encode(String value) {
+        return URLEncoder.encode(value, StandardCharsets.UTF_8);
+    }
+}

backend/src/main/java/home/backend/adapters/influx/InfluxHistoryRepository.java

@@ -5,12 +5,6 @@ import home.backend.domain.HistoryView.Point;
 import home.backend.domain.Series;
 
 import java.io.IOException;
-import java.net.URI;
-import java.net.URLEncoder;
-import java.net.http.HttpClient;
-import java.net.http.HttpRequest;
-import java.net.http.HttpResponse;
-import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.List;
@@ -22,12 +16,10 @@ import java.util.concurrent.Executors;
 /** History from InfluxDB 1.x over its HTTP {@code /query} endpoint (ADR-005, ADR-008). */
 public final class InfluxHistoryRepository implements HistoryRepository {
 
-    private final InfluxSettings settings;
-    private final HttpClient http;
+    private final InfluxClient influx;
 
     public InfluxHistoryRepository(InfluxSettings settings) {
-        this.settings = settings;
-        this.http = HttpClient.newBuilder().connectTimeout(settings.requestTimeout()).build();
+        this.influx = new InfluxClient(settings);
     }
 
     @Override
@@ -59,37 +51,11 @@ public final class InfluxHistoryRepository implements HistoryRepository {
 
     private Map<Long, Double> part(Source source, Instant from, Instant to, long stepMinutes) throws IOException {
         String query = source.query(from.toEpochMilli(), to.toEpochMilli(), stepMinutes);
-        return InfluxResponse.parse(fetch(source.database(), query));
+        return InfluxResponse.parse(influx.query(source.database(), query));
     }
 
     private static long stepMinutes(Instant from, Instant to, int maxPoints) {
         long stepMillis = Math.ceilDiv(Duration.between(from, to).toMillis(), maxPoints);
         return Math.max(1, Math.ceilDiv(stepMillis, Duration.ofMinutes(1).toMillis()));
     }
-
-    private String fetch(String database, String query) throws IOException {
-        HttpRequest request = HttpRequest.newBuilder(queryUri(database, query))
-                .timeout(settings.requestTimeout())
-                .GET()
-                .build();
-        try {
-            HttpResponse<String> response = http.send(request, HttpResponse.BodyHandlers.ofString());
-            if (response.statusCode() != 200) {
-                throw new IOException("InfluxDB answered HTTP " + response.statusCode());
-            }
-            return response.body();
-        } catch (InterruptedException e) {
-            Thread.currentThread().interrupt();
-            throw new IOException("InfluxDB request interrupted", e);
-        }
-    }
-
-    private URI queryUri(String database, String query) {
-        String base = settings.baseUri().toString().replaceAll("/+$", "");
-        return URI.create(base + "/query?db=" + encode(database) + "&epoch=ms&q=" + encode(query));
-    }
-
-    private static String encode(String value) {
-        return URLEncoder.encode(value, StandardCharsets.UTF_8);
-    }
 }

backend/src/main/java/home/backend/application/AuditRepository.java

@@ -0,0 +1,17 @@
+package home.backend.application;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+
+/** The gateway's audit rows in InfluxDB (S3), read only. */
+public interface AuditRepository {
+
+    /** One audited write as recorded; {@code target} is the setpoint name or the Deye register. */
+    record Row(Instant time, String target, String requestedBy, String status, Double oldValue, Double newValue) {
+    }
+
+    List<Row> heatPump(Instant from, Instant to) throws IOException;
+
+    List<Row> battery(Instant from, Instant to) throws IOException;
+}

backend/src/main/java/home/backend/application/AuditService.java

@@ -0,0 +1,70 @@
+package home.backend.application;
+
+import home.backend.application.AuditRepository.Row;
+import home.backend.domain.AuditEntry;
+import home.backend.domain.AuditView;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Comparator;
+import java.util.Map;
+import java.util.stream.Stream;
+
+/** S3: who changed what and when, from the gateway's audit rows of the heat pump and of the battery. */
+public class AuditService {
+
+    private static final String DEFAULT_RANGE = "7d";
+    private static final Map<String, Duration> RANGES =
+            Map.of("24h", Duration.ofHours(24), "7d", Duration.ofDays(7), "30d", Duration.ofDays(30));
+    private static final Map<String, String> SETPOINTS = Map.of(
+            "cwu_economy", "CWU eko", "cwu_comfort", "CWU komfort",
+            "co_economy", "CO eko", "co_comfort", "CO komfort");
+    private static final String RESTORE_USER = "restore";
+    private static final String RESTORE_LABEL = "automatycznie (przywrócenie)";
+
+    private final AuditRepository repository;
+    private final Clock clock;
+
+    public AuditService(AuditRepository repository, Clock clock) {
+        this.repository = repository;
+        this.clock = clock;
+    }
+
+    /**
+     * @param range {@code 24h}, {@code 7d} or {@code 30d}; null means 7d
+     * @throws IllegalArgumentException for an unknown range
+     */
+    public AuditView audit(String range) throws IOException {
+        Duration length = RANGES.get(range == null ? DEFAULT_RANGE : range);
+        if (length == null) {
+            throw new IllegalArgumentException("unknown range: " + range);
+        }
+        Instant to = clock.instant();
+        Instant from = to.minus(length);
+        var heatPump = repository.heatPump(from, to).stream().map(AuditService::heatPumpEntry);
+        var battery = repository.battery(from, to).stream().map(AuditService::batteryEntry);
+        return new AuditView(Stream.concat(heatPump, battery)
+                .sorted(Comparator.comparing(AuditEntry::time).reversed())
+                .toList());
+    }
+
+    private static AuditEntry heatPumpEntry(Row row) {
+        return entry(AuditEntry.HEAT_PUMP, row, SETPOINTS.getOrDefault(row.target(), row.target()), "°C");
+    }
+
+    private static AuditEntry batteryEntry(Row row) {
+        var label = DeyeSettingLabels.of(row.target());
+        return entry(AuditEntry.BATTERY, row, label.what(), label.unit());
+    }
+
+    private static AuditEntry entry(String source, Row row, String what, String unit) {
+        return new AuditEntry(row.time(), source, what, whole(row.oldValue()), whole(row.newValue()), unit,
+                RESTORE_USER.equals(row.requestedBy()) ? RESTORE_LABEL : row.requestedBy(), row.status());
+    }
+
+    private static Integer whole(Double value) {
+        return value == null ? null : (int) Math.round(value);
+    }
+}

backend/src/main/java/home/backend/application/DeyeSettingLabels.java

@@ -0,0 +1,48 @@
+package home.backend.application;
+
+import java.util.Optional;
+
+/** Polish name and unit of the Deye program registers and of the app's reserve, as the gateway audits them. */
+final class DeyeSettingLabels {
+
+    record Label(String what, String unit) {
+    }
+
+    private static final int TOU_ENABLE = 146;
+    private static final int FIRST_START = 148;
+    private static final int FIRST_SOC = 166;
+    private static final int FIRST_GRID_CHARGE = 172;
+    private static final int SLOTS = 6;
+
+    private DeyeSettingLabels() {
+    }
+
+    static Label of(String register) {
+        if ("reserve".equals(register)) {
+            return new Label("Rezerwa baterii", "%");
+        }
+        int address;
+        try {
+            address = Integer.parseInt(register);
+        } catch (NumberFormatException e) {
+            return unknown(register);
+        }
+        if (address == TOU_ENABLE) {
+            return new Label("Harmonogram baterii", "0/1");
+        }
+        return slot(address, FIRST_START, "start", "HHMM")
+                .or(() -> slot(address, FIRST_SOC, "poziom", "%"))
+                .or(() -> slot(address, FIRST_GRID_CHARGE, "ładowanie z sieci", "0/1"))
+                .orElseGet(() -> unknown(register));
+    }
+
+    private static Label unknown(String register) {
+        return new Label("Rejestr " + register, "");
+    }
+
+    private static Optional<Label> slot(int address, int first, String what, String unit) {
+        return address >= first && address < first + SLOTS
+                ? Optional.of(new Label("Przedział " + (address - first + 1) + ": " + what, unit))
+                : Optional.empty();
+    }
+}

backend/src/main/java/home/backend/domain/AuditEntry.java

@@ -0,0 +1,14 @@
+package home.backend.domain;
+
+import java.time.Instant;
+
+/**
+ * One audited write. {@code unit} is "°C", "%", "HHMM" (a clock time written as 1830) or "0/1" (off/on);
+ * the values are null when the gateway did not record them.
+ */
+public record AuditEntry(Instant time, String source, String what, Integer oldValue, Integer newValue,
+        String unit, String who, String status) {
+
+    public static final String HEAT_PUMP = "heat_pump";
+    public static final String BATTERY = "battery";
+}

backend/src/main/java/home/backend/domain/AuditView.java

@@ -0,0 +1,7 @@
+package home.backend.domain;
+
+import java.util.List;
+
+/** The audited writes of the heat pump and the battery, newest first. */
+public record AuditView(List<AuditEntry> entries) {
+}

backend/src/test/java/home/backend/adapters/http/ApiServerTest.java

@@ -2,6 +2,8 @@ package home.backend.adapters.http;
 
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import home.backend.application.AuditRepository;
+import home.backend.application.AuditService;
 import home.backend.application.BatteryService;
 import home.backend.application.EnergyDetailsService;
 import home.backend.application.EnergyService;
@@ -63,6 +65,7 @@ class ApiServerTest {
     private GatewaySnapshot snapshot;
     private boolean gatewayDown;
     private boolean historyDown;
+    private boolean auditDown;
     private RuntimeException gatewayBug;
     private final List<Command> sent = new ArrayList<>();
     private Status verdict;
@@ -178,7 +181,8 @@ class ApiServerTest {
                 new EnergyDetailsService(gateway, clock),
                 new HealthService(gateway, clock, "v1.3.0"), new HistoryService(history, clock),
                 new SetpointService(commands, PresetFile.load(null)), new PiSensorService(gateway, clock),
-                new BatteryService(gateway, batteryCommands, clock));
+                new BatteryService(gateway, batteryCommands, clock),
+                new AuditService(auditRows(), clock));
         server.start();
     }
 
@@ -187,6 +191,27 @@ class ApiServerTest {
         server.stop();
     }
 
+    private AuditRepository auditRows() {
+        return new AuditRepository() {
+            @Override
+            public List<Row> heatPump(Instant from, Instant to) throws IOException {
+                if (auditDown) {
+                    throw new IOException("influx down");
+                }
+                return List.of(
+                        new Row(Instant.parse("2026-10-24T08:00:00Z"), "cwu_economy", "restore", "APPLIED", 45.0, 8.0),
+                        new Row(Instant.parse("2026-10-23T07:00:00Z"), "co_comfort", "mariusz", "REJECTED", null, 22.0));
+            }
+
+            @Override
+            public List<Row> battery(Instant from, Instant to) {
+                return List.of(
+                        new Row(Instant.parse("2026-10-24T09:30:00Z"), "reserve", "mariusz", "APPLIED", 50.0, 60.0),
+                        new Row(Instant.parse("2026-10-23T18:00:00Z"), "174", "mariusz", "FAILED", 0.0, 1.0));
+            }
+        };
+    }
+
     private static GatewaySnapshot exampleSnapshot() {
         Map<String, Double> pump = new HashMap<>(Map.of("outdoor_temp", 4.3, "indoor_temp", 21.2,
                 "co_buffer_temp", 16.9, "cwu_temp", 13.6, "ground_in_temp", 16.0, "ground_out_temp", 14.3,
@@ -426,6 +451,24 @@ class ApiServerTest {
         assertEquals(200, get("/api/history?series=cwu_temp").statusCode());
     }
 
+    @Test
+    void auditMatchesExample() throws Exception {
+        assertMatchesExample("/api/audit?range=7d", "audit");
+    }
+
+    @Test
+    void auditRangeDefaultsAndIsChecked() throws Exception {
+        assertEquals(200, get("/api/audit").statusCode());
+        assertEquals(400, get("/api/audit?range=90d").statusCode());
+    }
+
+    @Test
+    void auditInfluxFailureIs502() throws Exception {
+        auditDown = true;
+
+        assertEquals(502, get("/api/audit?range=7d").statusCode());
+    }
+
     @Test
     void unreachableGatewayIs503WithJsonError() throws Exception {
         gatewayDown = true;

backend/src/test/java/home/backend/adapters/influx/InfluxAuditRepositoryTest.java

@@ -0,0 +1,105 @@
+package home.backend.adapters.influx;
+
+import com.sun.net.httpserver.HttpServer;
+import home.backend.application.AuditRepository.Row;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class InfluxAuditRepositoryTest {
+
+    private static final Instant FROM = Instant.parse("2026-10-17T12:00:00Z");
+    private static final Instant TO = Instant.parse("2026-10-24T12:00:00Z");
+
+    private HttpServer server;
+    private final List<String> queries = Collections.synchronizedList(new ArrayList<>());
+    private String body;
+
+    @BeforeEach
+    void startServer() throws IOException {
+        server = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+        server.createContext("/query", exchange -> {
+            queries.add(URLDecoder.decode(exchange.getRequestURI().getRawQuery(), StandardCharsets.UTF_8));
+            byte[] bytes = body.getBytes(StandardCharsets.UTF_8);
+            exchange.sendResponseHeaders(200, bytes.length);
+            exchange.getResponseBody().write(bytes);
+            exchange.close();
+        });
+        server.start();
+    }
+
+    @AfterEach
+    void stopServer() {
+        server.stop(0);
+    }
+
+    @Test
+    void readsHeatPumpRowsFromTheLegacyDatabase() throws IOException {
+        body = fixture("influx-audit-setpoints.json");
+
+        List<Row> rows = repository().heatPump(FROM, TO);
+
+        assertEquals(2, rows.size());
+        assertEquals(new Row(Instant.ofEpochMilli(1761292800000L), "cwu_economy", "restore", "APPLIED", 45.0, 8.0),
+                rows.get(0));
+        assertNull(rows.get(1).oldValue());
+        assertEquals("co_comfort", rows.get(1).target());
+        assertTrue(queries.getFirst().startsWith("db=Dom_Pompa&epoch=ms&q=SELECT * FROM \"setpoint_audit\" "
+                + "WHERE time >= " + FROM.toEpochMilli() + "ms AND time < " + TO.toEpochMilli() + "ms"),
+                queries.getFirst());
+    }
+
+    @Test
+    void readsBatteryRowsByRegisterTag() throws IOException {
+        body = fixture("influx-audit-battery.json");
+
+        List<Row> rows = repository().battery(FROM, TO);
+
+        assertEquals(List.of("reserve", "174"), rows.stream().map(Row::target).toList());
+        assertEquals(60.0, rows.getFirst().newValue());
+        assertTrue(queries.getFirst().startsWith("db=electricity&"), queries.getFirst());
+        assertTrue(queries.getFirst().contains("\"deye_settings_audit\""), queries.getFirst());
+    }
+
+    @Test
+    void noRowsIsAnEmptyList() throws IOException {
+        body = fixture("influx-query-empty.json");
+
+        assertTrue(repository().battery(FROM, TO).isEmpty());
+    }
+
+    @Test
+    void anInfluxErrorIsAnIOException() throws IOException {
+        body = fixture("influx-query-error.json");
+
+        assertThrows(IOException.class, () -> repository().heatPump(FROM, TO));
+    }
+
+    private InfluxAuditRepository repository() {
+        URI base = URI.create("http://127.0.0.1:" + server.getAddress().getPort());
+        return new InfluxAuditRepository(new InfluxSettings(base, Duration.ofSeconds(5)));
+    }
+
+    private static String fixture(String name) throws IOException {
+        return Files.readString(Path.of("src/test/resources/influx", name));
+    }
+}

backend/src/test/java/home/backend/application/AuditServiceTest.java

@@ -0,0 +1,108 @@
+package home.backend.application;
+
+import home.backend.application.AuditRepository.Row;
+import home.backend.domain.AuditEntry;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.ZoneOffset;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class AuditServiceTest {
+
+    private static final Instant NOW = Instant.parse("2026-10-24T12:00:00Z");
+    private static final Clock CLOCK = Clock.fixed(NOW, ZoneOffset.UTC);
+
+    private List<Row> heatPump = List.of();
+    private List<Row> battery = List.of();
+    private final List<Instant> asked = new ArrayList<>();
+
+    private final AuditRepository repository = new AuditRepository() {
+        @Override
+        public List<Row> heatPump(Instant from, Instant to) {
+            asked.add(from);
+            return heatPump;
+        }
+
+        @Override
+        public List<Row> battery(Instant from, Instant to) throws IOException {
+            if (battery == null) {
+                throw new IOException("influx down");
+            }
+            return battery;
+        }
+    };
+    private final AuditService service = new AuditService(repository, CLOCK);
+
+    private static Row row(String time, String target, String by, Double old, Double value) {
+        return new Row(Instant.parse(time), target, by, "APPLIED", old, value);
+    }
+
+    @Test
+    void mergesBothSourcesNewestFirst() throws IOException {
+        heatPump = List.of(row("2026-10-24T08:00:00Z", "cwu_economy", "a", 8.0, 45.0),
+                row("2026-10-22T08:00:00Z", "co_comfort", "a", 19.0, 20.0));
+        battery = List.of(row("2026-10-23T08:00:00Z", "reserve", "b", 50.0, 60.0));
+
+        var entries = service.audit(null).entries();
+
+        assertEquals(List.of("CWU eko", "Rezerwa baterii", "CO komfort"),
+                entries.stream().map(AuditEntry::what).toList());
+        assertEquals(List.of("heat_pump", "battery", "heat_pump"),
+                entries.stream().map(AuditEntry::source).toList());
+    }
+
+    @Test
+    void namesTheDeyeRegisters() throws IOException {
+        battery = List.of("146", "148", "153", "166", "171", "172", "177", "reserve", "999").stream()
+                .map(register -> row("2026-10-24T08:00:00Z", register, "a", 0.0, 1.0)).toList();
+
+        var entries = service.audit("24h").entries();
+
+        assertEquals(List.of("Harmonogram baterii/0/1", "Przedział 1: start/HHMM", "Przedział 6: start/HHMM",
+                "Przedział 1: poziom/%", "Przedział 6: poziom/%", "Przedział 1: ładowanie z sieci/0/1",
+                "Przedział 6: ładowanie z sieci/0/1", "Rezerwa baterii/%", "Rejestr 999/"),
+                entries.stream().map(e -> e.what() + "/" + e.unit()).toList());
+    }
+
+    @Test
+    void showsARestoreAsAutomaticAndKeepsMissingValuesNull() throws IOException {
+        heatPump = List.of(row("2026-10-24T08:00:00Z", "cwu_economy", "restore", null, 8.4));
+
+        var entry = service.audit("7d").entries().getFirst();
+
+        assertEquals("automatycznie (przywrócenie)", entry.who());
+        assertNull(entry.oldValue());
+        assertEquals(8, entry.newValue());
+        assertEquals("°C", entry.unit());
+    }
+
+    @Test
+    void defaultsToSevenDaysAndAllowsUpToThirty() throws IOException {
+        service.audit(null);
+        service.audit("30d");
+
+        assertEquals(List.of(NOW.minus(Duration.ofDays(7)), NOW.minus(Duration.ofDays(30))), asked);
+    }
+
+    @Test
+    void rejectsAnUnknownRange() {
+        assertThrows(IllegalArgumentException.class, () -> service.audit("90d"));
+        assertThrows(IllegalArgumentException.class, () -> service.audit(""));
+    }
+
+    @Test
+    void failsWhenOneSourceFails() {
+        battery = null;
+
+        assertThrows(IOException.class, () -> service.audit("7d"));
+    }
+}

backend/src/test/resources/api/audit.json

@@ -0,0 +1,12 @@
+{
+  "entries": [
+    { "time": "2026-10-24T09:30:00Z", "source": "battery", "what": "Rezerwa baterii", "oldValue": 50, "newValue": 60,
+      "unit": "%", "who": "mariusz", "status": "APPLIED" },
+    { "time": "2026-10-24T08:00:00Z", "source": "heat_pump", "what": "CWU eko", "oldValue": 45, "newValue": 8,
+      "unit": "°C", "who": "automatycznie (przywrócenie)", "status": "APPLIED" },
+    { "time": "2026-10-23T18:00:00Z", "source": "battery", "what": "Przedział 3: ładowanie z sieci", "oldValue": 0,
+      "newValue": 1, "unit": "0/1", "who": "mariusz", "status": "FAILED" },
+    { "time": "2026-10-23T07:00:00Z", "source": "heat_pump", "what": "CO komfort", "oldValue": null, "newValue": 22,
+      "unit": "°C", "who": "mariusz", "status": "REJECTED" }
+  ]
+}

backend/src/test/resources/influx/influx-audit-battery.json

@@ -0,0 +1 @@
+{"results":[{"statement_id":0,"series":[{"name":"deye_settings_audit","columns":["time","new_value","old_value","register","requested_by","status"],"values":[[1761298200000,60,50,"reserve","mariusz","APPLIED"],[1761242400000,1,0,"174","mariusz","FAILED"]]}]}]}

backend/src/test/resources/influx/influx-audit-setpoints.json

@@ -0,0 +1 @@
+{"results":[{"statement_id":0,"series":[{"name":"setpoint_audit","columns":["time","new_value","old_value","register","requested_by","setpoint","status"],"values":[[1761292800000,8,45,4143,"restore","cwu_economy","APPLIED"],[1761202800000,22,null,4146,"mariusz","co_comfort","REJECTED"]]}]}]}

docs/spec.md

@@ -99,7 +99,7 @@ Safety, for every write:
 
 - S1 Only allowlisted registers, each with min, max and step.
 - S2 Read back and verify after writing.
-- S3 Audit log: who, when, register, old and new value.
+- S3 Audit log: who, when, register, old and new value; shown in the app as the change history.
 - S4 Rate limit per register.
 - S5 Tests and development never write to a real device or the production database.
 - S6 The gateway accepts commands only from the backend: a shared token, and a firewall rule on

frontend/README.md

@@ -20,6 +20,8 @@ and gateway's versions in the "Wersje" card of the Stan screen.
 The Energia screen has three views, kept in the URL hash so Back works: `#energy` (Teraz), `#energy/battery` (Bateria, also
 opened by tapping the battery in the flow diagram) and `#energy/inverters` (Falowniki, the device details).
 
+Ustawienia ends with the "Historia zmian" card (`ChangeHistory.tsx`): the last 7 days of `api/audit`, 20 rows and "Pokaż więcej".
+
 In the Bateria view, `editable` from `api/battery` (the gateway takes battery changes, ADR-013) adds the reserve stepper and "Edytuj" for the
 schedule: the user confirms a summary, only changed fields are sent to `api/battery/schedule` and `api/battery/reserve`, and the UI
 checks the gateway's rules first (levels from the reserve to 100 %, starts increasing).

frontend/src/ChangeHistory.test.tsx

@@ -0,0 +1,69 @@
+import { render, screen, within } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { describe, expect, it } from "vitest";
+import { example, serve } from "./fixtures";
+import type { Audit, AuditEntry } from "./types";
+
+// A fresh module per test: the poller keeps its answers between screens, not between tests.
+const history = async () => (await import("./ChangeHistory")).ChangeHistory;
+
+const entry = (over: Partial<AuditEntry>): AuditEntry => ({
+  time: "2026-10-23T18:00:00Z", source: "battery", what: "Przedział 2: start", oldValue: 1800, newValue: 2130,
+  unit: "HHMM", who: "mariusz", status: "APPLIED", ...over,
+});
+
+describe("ChangeHistory", () => {
+  it("lists the changes with what, old and new value, who and a pill for a failed one", async () => {
+    serve({ "api/audit": example<Audit>("audit") });
+    const ChangeHistory = await history();
+    render(<ChangeHistory />);
+
+    const rows = await screen.findAllByRole("listitem");
+    expect(rows).toHaveLength(4);
+    expect(within(rows[0]).getByText("Rezerwa baterii")).toBeInTheDocument();
+    expect(rows[0]).toHaveTextContent("50 % → 60 %");
+    expect(rows[1]).toHaveTextContent("45 °C → 8 °C");
+    expect(rows[1]).toHaveTextContent("automatycznie (przywrócenie)");
+    expect(rows[2]).toHaveTextContent("nie → tak");
+    expect(within(rows[2]).getByText("nieudana")).toBeInTheDocument();
+    expect(rows[3]).toHaveTextContent("— → 22 °C");
+    expect(within(rows[3]).getByText("odrzucona")).toBeInTheDocument();
+    expect(within(rows[0]).queryByText(/nieudana|odrzucona|konflikt|nieważna/)).toBeNull();
+  });
+
+  it("shows a clock time as HH:MM", async () => {
+    serve({ "api/audit": { entries: [entry({})] } });
+    const ChangeHistory = await history();
+    render(<ChangeHistory />);
+
+    expect(await screen.findByRole("listitem")).toHaveTextContent("18:00 → 21:30");
+  });
+
+  it("says when nothing changed", async () => {
+    serve({ "api/audit": { entries: [] } });
+    const ChangeHistory = await history();
+    render(<ChangeHistory />);
+
+    expect(await screen.findByText("Brak zmian w ostatnich 7 dniach")).toBeInTheDocument();
+  });
+
+  it("shows 20 changes and the rest on request", async () => {
+    const entries = Array.from({ length: 25 }, (_, i) => entry({ time: `2026-10-23T${String(i).padStart(2, "0")}:00:00Z` }));
+    serve({ "api/audit": { entries } });
+    const ChangeHistory = await history();
+    render(<ChangeHistory />);
+
+    expect(await screen.findAllByRole("listitem")).toHaveLength(20);
+    await userEvent.click(screen.getByRole("button", { name: "Pokaż więcej (5)" }));
+    expect(screen.getAllByRole("listitem")).toHaveLength(25);
+    expect(screen.queryByRole("button", { name: /Pokaż więcej/ })).toBeNull();
+  });
+
+  it("says the history is unavailable when the backend does not answer", async () => {
+    serve({});
+    const ChangeHistory = await history();
+    render(<ChangeHistory />);
+
+    expect(await screen.findByText("Historia chwilowo niedostępna.")).toBeInTheDocument();
+  });
+});

frontend/src/ChangeHistory.tsx

@@ -0,0 +1,59 @@
+import { useState } from "react";
+import { dateTime, degrees, number, percent } from "./format";
+import { usePoll } from "./poll";
+import type { Audit, AuditEntry } from "./types";
+import { Card, Pill } from "./ui";
+
+const URL = "api/audit?range=7d";
+const PAGE = 20;
+const STATUS: Record<string, string> = {
+  FAILED: "nieudana", REJECTED: "odrzucona", CONFLICT: "konflikt", INVALID: "nieważna",
+};
+
+// 1830 is a clock time, 0/1 is off/on.
+const SHOWN: Record<string, (value: number) => string> = {
+  "°C": degrees,
+  "%": percent,
+  HHMM: (value) => `${String(Math.floor(value / 100)).padStart(2, "0")}:${String(value % 100).padStart(2, "0")}`,
+  "0/1": (value) => (value ? "tak" : "nie"),
+};
+const shown = (value: number | null, unit: string) => (value == null ? "—" : (SHOWN[unit] ?? number)(value));
+
+function Row({ entry }: { entry: AuditEntry }) {
+  const status = entry.status === "APPLIED" ? null : (STATUS[entry.status] ?? entry.status);
+  return (
+    <li className="border-t border-edge py-3 first:border-t-0 first:pt-0">
+      <div className="flex flex-wrap items-baseline justify-between gap-x-3">
+        <span className="font-semibold">{entry.what}</span>
+        <span className="text-sm text-soft">{dateTime(entry.time)}</span>
+      </div>
+      <p className="my-1">{shown(entry.oldValue, entry.unit)} → <b>{shown(entry.newValue, entry.unit)}</b></p>
+      <p className="flex flex-wrap items-center gap-2 text-sm text-soft">
+        {entry.who}
+        {status && <Pill tone="off">{status}</Pill>}
+      </p>
+    </li>
+  );
+}
+
+export function ChangeHistory() {
+  const { data, offline } = usePoll<Audit>(URL, 60000);
+  const [all, setAll] = useState(false);
+  const entries = data?.entries ?? [];
+  return (
+    <Card title="Historia zmian" aside={<span className="text-sm text-soft">ostatnie 7 dni</span>} className="mt-4">
+      {!data && <p className="my-1 text-soft">{offline ? "Historia chwilowo niedostępna." : "Wczytuję…"}</p>}
+      {data && entries.length === 0 && <p className="my-1 text-soft">Brak zmian w ostatnich 7 dniach</p>}
+      <ul className="m-0 list-none p-0">
+        {(all ? entries : entries.slice(0, PAGE)).map((entry) => (
+          <Row key={`${entry.source}${entry.time}${entry.what}`} entry={entry} />
+        ))}
+      </ul>
+      {!all && entries.length > PAGE && (
+        <button type="button" onClick={() => setAll(true)} className="mt-3 min-h-12 w-full rounded-xl border-2 border-edge font-semibold">
+          Pokaż więcej ({entries.length - PAGE})
+        </button>
+      )}
+    </Card>
+  );
+}

frontend/src/Settings.tsx

@@ -1,5 +1,6 @@
 import { useEffect, useState, type ReactNode } from "react";
 import { postJson, WriteError } from "./api";
+import { ChangeHistory } from "./ChangeHistory";
 import { dateTime, degrees, duration, localInput, withOffset } from "./format";
 import { reload, usePoll } from "./poll";
 import type { Change, CommandResult, LineStatus, Preset, RestoreOutcome, RestoreResult, Setpoint, Setpoints } from "./types";
@@ -330,6 +331,7 @@ export function Settings() {
           )}
         </Card>
       </div>
+      <ChangeHistory />
     </>
   );
 }

frontend/src/types.ts

@@ -131,6 +131,21 @@ export interface History {
   points: Point[];
 }
 
+export interface AuditEntry {
+  time: string;
+  source: "heat_pump" | "battery";
+  what: string;
+  oldValue: number | null;
+  newValue: number | null;
+  unit: string; // "°C", "%", "HHMM" (1830) or "0/1"
+  who: string;
+  status: string;
+}
+
+export interface Audit {
+  entries: AuditEntry[];
+}
+
 export interface Health {
   time: string;
   gatewayReachable: boolean;