feat: add admin occupancy and reservation history reports

src/main/java/com/slotline/report/AdminReportController.java

@@ -0,0 +1,42 @@
+package com.slotline.report;
+
+import com.slotline.report.dto.OccupancyReport;
+import com.slotline.report.dto.ReservationHistoryEntry;
+import com.slotline.security.AuthenticatedUser;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.time.Instant;
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/admin/reports")
+@Tag(name = "Admin reports")
+public class AdminReportController {
+
+    private final AdminReportService reportService;
+
+    public AdminReportController(AdminReportService reportService) {
+        this.reportService = reportService;
+    }
+
+    @GetMapping("/resources/{resourceId}/occupancy")
+    @Operation(summary = "Occupancy of a resource over a time window (ADMIN only)")
+    public OccupancyReport occupancy(@AuthenticationPrincipal AuthenticatedUser actor, @PathVariable Long resourceId,
+                                     @RequestParam String from, @RequestParam String until) {
+        return reportService.occupancy(actor.organizationId(), resourceId, Instant.parse(from), Instant.parse(until));
+    }
+
+    @GetMapping("/resources/{resourceId}/history")
+    @Operation(summary = "Full reservation history of a resource (ADMIN only)")
+    public List<ReservationHistoryEntry> history(@AuthenticationPrincipal AuthenticatedUser actor,
+                                                 @PathVariable Long resourceId) {
+        return reportService.history(actor.organizationId(), resourceId);
+    }
+}

src/main/java/com/slotline/report/AdminReportService.java

@@ -0,0 +1,54 @@
+package com.slotline.report;
+
+import com.slotline.report.dto.OccupancyReport;
+import com.slotline.report.dto.ReservationHistoryEntry;
+import com.slotline.reservation.Reservation;
+import com.slotline.reservation.ReservationRepository;
+import com.slotline.resource.Resource;
+import com.slotline.resource.ResourceService;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.List;
+
+@Service
+public class AdminReportService {
+
+    private final ReservationRepository reservations;
+    private final ResourceService resources;
+
+    public AdminReportService(ReservationRepository reservations, ResourceService resources) {
+        this.reservations = reservations;
+        this.resources = resources;
+    }
+
+    @Transactional(readOnly = true)
+    public OccupancyReport occupancy(Long organizationId, Long resourceId, Instant from, Instant until) {
+        Resource resource = resources.require(organizationId, resourceId);
+        List<Reservation> active = reservations.findActiveForResourceBetween(resource.getId(), from, until);
+        long bookedMinutes = active.stream()
+                .mapToLong(reservation -> clampedMinutes(reservation, from, until))
+                .sum();
+        long windowMinutes = Duration.between(from, until).toMinutes();
+        double utilization = windowMinutes > 0 ? (bookedMinutes * 100.0) / windowMinutes : 0.0;
+        return new OccupancyReport(resource.getId(), resource.getName(), from, until, active.size(), bookedMinutes,
+                windowMinutes, Math.round(utilization * 100.0) / 100.0);
+    }
+
+    @Transactional(readOnly = true)
+    public List<ReservationHistoryEntry> history(Long organizationId, Long resourceId) {
+        Resource resource = resources.require(organizationId, resourceId);
+        return reservations.findByResourceIdOrderByStartTimeAsc(resource.getId()).stream()
+                .map(ReservationHistoryEntry::from)
+                .toList();
+    }
+
+    private long clampedMinutes(Reservation reservation, Instant from, Instant until) {
+        Instant start = reservation.getStartTime().isBefore(from) ? from : reservation.getStartTime();
+        Instant end = reservation.getEndTime().isAfter(until) ? until : reservation.getEndTime();
+        long minutes = Duration.between(start, end).toMinutes();
+        return Math.max(minutes, 0);
+    }
+}

src/main/java/com/slotline/report/dto/OccupancyReport.java

@@ -0,0 +1,14 @@
+package com.slotline.report.dto;
+
+import java.time.Instant;
+
+public record OccupancyReport(
+        Long resourceId,
+        String resourceName,
+        Instant from,
+        Instant until,
+        int reservationCount,
+        long bookedMinutes,
+        long windowMinutes,
+        double utilizationPercent) {
+}

src/main/java/com/slotline/report/dto/ReservationHistoryEntry.java

@@ -0,0 +1,27 @@
+package com.slotline.report.dto;
+
+import com.slotline.reservation.Reservation;
+import com.slotline.reservation.ReservationStatus;
+
+import java.time.Instant;
+
+public record ReservationHistoryEntry(
+        Long id,
+        Long userId,
+        Instant startTime,
+        Instant endTime,
+        ReservationStatus status,
+        String seriesId,
+        Instant createdAt) {
+
+    public static ReservationHistoryEntry from(Reservation reservation) {
+        return new ReservationHistoryEntry(
+                reservation.getId(),
+                reservation.getUserId(),
+                reservation.getStartTime(),
+                reservation.getEndTime(),
+                reservation.getStatus(),
+                reservation.getSeriesId(),
+                reservation.getCreatedAt());
+    }
+}