feat(stats): 주요 통계 역대 최고 기록 제공

src/main/java/com/devkor/ifive/nadab/domain/stats/application/DailyStatsService.java

@@ -1,7 +1,10 @@
 package com.devkor.ifive.nadab.domain.stats.application;
 
+import com.devkor.ifive.nadab.domain.stats.application.helper.PeakStatsTracker;
 import com.devkor.ifive.nadab.domain.stats.core.dto.daily.DailyStatsViewModel;
 import com.devkor.ifive.nadab.domain.stats.core.dto.daily.DateCountDto;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakMetric;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
 import com.devkor.ifive.nadab.domain.stats.core.repository.DailyStatsRepository;
 import com.devkor.ifive.nadab.global.shared.util.TodayDateTimeProvider;
 import lombok.RequiredArgsConstructor;
@@ -18,6 +21,7 @@
 public class DailyStatsService {
 
     private final DailyStatsRepository repo;
+    private final PeakStatsTracker peakStatsTracker;
 
     private static final ZoneId SEOUL = ZoneId.of("Asia/Seoul");
     private static final DateTimeFormatter FMT =
@@ -57,15 +61,28 @@ public DailyStatsViewModel getDailyStatsLast7Days() {
         List<Long> assignedCounts = days.stream().map(d -> assignedMap.getOrDefault(d, 0L)).toList();
         List<Long> completedCounts = days.stream().map(d -> completedMap.getOrDefault(d, 0L)).toList();
 
+        PeakStatViewModel signupPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.DAILY_SIGNUP, days, signupCounts, today
+        );
+        PeakStatViewModel assignedQuestionPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.DAILY_ASSIGNED_QUESTION, days, assignedCounts, today
+        );
+        PeakStatViewModel dauPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.DAU, days, completedCounts, today
+        );
+
         long sharedNow = repo.countSharedDailyReportsNow();
 
         return new DailyStatsViewModel(
                 labels,
                 signupCounts,
                 assignedCounts,
                 completedCounts,
+                signupPeak,
+                assignedQuestionPeak,
+                dauPeak,
                 sharedNow,
                 OffsetDateTime.now(SEOUL).format(FMT)
         );
     }
-}
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/application/MonthlyStatsService.java

@@ -1,7 +1,10 @@
 package com.devkor.ifive.nadab.domain.stats.application;
 
+import com.devkor.ifive.nadab.domain.stats.application.helper.PeakStatsTracker;
 import com.devkor.ifive.nadab.domain.stats.core.dto.daily.DateCountDto;
 import com.devkor.ifive.nadab.domain.stats.core.dto.monthly.MonthlyStatsViewModel;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakMetric;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
 import com.devkor.ifive.nadab.domain.stats.core.repository.MonthlyStatsRepository;
 import com.devkor.ifive.nadab.global.shared.util.TodayDateTimeProvider;
 import lombok.RequiredArgsConstructor;
@@ -22,6 +25,7 @@
 public class MonthlyStatsService {
 
     private final MonthlyStatsRepository repo;
+    private final PeakStatsTracker peakStatsTracker;
 
     private static final ZoneId SEOUL = ZoneId.of("Asia/Seoul");
     private static final DateTimeFormatter FMT =
@@ -74,6 +78,24 @@ public MonthlyStatsViewModel getMonthlyStatsLast5Months() {
         List<Long> completedTotalCounts = sumCounts(completedV1Counts, completedV2Counts);
         List<Long> mauCounts = months.stream().map(m -> mauMap.getOrDefault(m, 0L)).toList();
 
+        List<LocalDate> monthStarts = months.stream().map(month -> month.atDay(1)).toList();
+        LocalDate currentMonthStart = currentMonth.atDay(1);
+        PeakStatViewModel signupPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.MONTHLY_SIGNUP, monthStarts, signupCounts, currentMonthStart
+        );
+        PeakStatViewModel assignedQuestionPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.MONTHLY_ASSIGNED_QUESTION, monthStarts, assignedCounts, currentMonthStart
+        );
+        PeakStatViewModel completedDailyReportPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.MONTHLY_DAILY_REPORT, monthStarts, completedDailyCounts, currentMonthStart
+        );
+        PeakStatViewModel completedMonthlyReportPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.MONTHLY_REPORT, monthStarts, completedTotalCounts, currentMonthStart
+        );
+        PeakStatViewModel mauPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.MAU, monthStarts, mauCounts, currentMonthStart
+        );
+
         long inProgressV1Now = repo.countInProgressMonthlyReportV1Now();
         long inProgressV2Now = repo.countInProgressMonthlyReportV2Now();
         long inProgressTotalNow = inProgressV1Now + inProgressV2Now;
@@ -87,6 +109,11 @@ public MonthlyStatsViewModel getMonthlyStatsLast5Months() {
                 completedV2Counts,
                 completedTotalCounts,
                 mauCounts,
+                signupPeak,
+                assignedQuestionPeak,
+                completedDailyReportPeak,
+                completedMonthlyReportPeak,
+                mauPeak,
                 inProgressV1Now,
                 inProgressV2Now,
                 inProgressTotalNow,

src/main/java/com/devkor/ifive/nadab/domain/stats/application/PeakStatsInitializer.java

@@ -0,0 +1,29 @@
+package com.devkor.ifive.nadab.domain.stats.application;
+
+import com.devkor.ifive.nadab.domain.stats.core.repository.PeakStatsRepository;
+import com.devkor.ifive.nadab.domain.stats.core.repository.PeakStatsStore;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.boot.ApplicationArguments;
+import org.springframework.boot.ApplicationRunner;
+import org.springframework.stereotype.Component;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class PeakStatsInitializer implements ApplicationRunner {
+
+    private final PeakStatsRepository peakStatsRepository;
+    private final PeakStatsStore peakStatsStore;
+
+    @Override
+    public void run(ApplicationArguments args) {
+        try {
+            var peaks = peakStatsRepository.findAllPeakStats();
+            peaks.forEach(peakStatsStore::updateIfGreater);
+            log.info("Peak statistics initialized: {} metrics", peaks.size());
+        } catch (RuntimeException e) {
+            log.error("Failed to initialize peak statistics", e);
+        }
+    }
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/application/WeeklyStatsService.java

@@ -1,6 +1,9 @@
 package com.devkor.ifive.nadab.domain.stats.application;
 
+import com.devkor.ifive.nadab.domain.stats.application.helper.PeakStatsTracker;
 import com.devkor.ifive.nadab.domain.stats.core.dto.daily.DateCountDto;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakMetric;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
 import com.devkor.ifive.nadab.domain.stats.core.dto.weekly.WeeklyStatsViewModel;
 import com.devkor.ifive.nadab.domain.stats.core.repository.WeeklyStatsRepository;
 import com.devkor.ifive.nadab.global.shared.util.TodayDateTimeProvider;
@@ -23,6 +26,7 @@
 public class WeeklyStatsService {
 
     private final WeeklyStatsRepository repo;
+    private final PeakStatsTracker peakStatsTracker;
 
     private static final ZoneId SEOUL = ZoneId.of("Asia/Seoul");
     private static final DateTimeFormatter FMT =
@@ -68,6 +72,22 @@ public WeeklyStatsViewModel getWeeklyStatsLast7Weeks() {
         List<Long> completedCounts = weekStarts.stream().map(d -> completedMap.getOrDefault(d, 0L)).toList();
         List<Long> wauCounts = weekStarts.stream().map(d -> wauMap.getOrDefault(d, 0L)).toList();
 
+        PeakStatViewModel signupPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.WEEKLY_SIGNUP, weekStarts, signupCounts, currentWeekStart
+        );
+        PeakStatViewModel assignedQuestionPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.WEEKLY_ASSIGNED_QUESTION, weekStarts, assignedCounts, currentWeekStart
+        );
+        PeakStatViewModel completedDailyReportPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.WEEKLY_DAILY_REPORT, weekStarts, completedDailyCounts, currentWeekStart
+        );
+        PeakStatViewModel completedWeeklyReportPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.WEEKLY_REPORT, weekStarts, completedCounts, currentWeekStart
+        );
+        PeakStatViewModel wauPeak = peakStatsTracker.updateAndGet(
+                PeakMetric.WAU, weekStarts, wauCounts, currentWeekStart
+        );
+
         long inProgressNow = repo.countInProgressWeeklyReportsNow();
 
         return new WeeklyStatsViewModel(
@@ -77,6 +97,11 @@ public WeeklyStatsViewModel getWeeklyStatsLast7Weeks() {
                 completedDailyCounts,
                 completedCounts,
                 wauCounts,
+                signupPeak,
+                assignedQuestionPeak,
+                completedDailyReportPeak,
+                completedWeeklyReportPeak,
+                wauPeak,
                 inProgressNow,
                 OffsetDateTime.now(SEOUL).format(FMT)
         );

src/main/java/com/devkor/ifive/nadab/domain/stats/application/helper/PeakStatsTracker.java

@@ -0,0 +1,58 @@
+package com.devkor.ifive.nadab.domain.stats.application.helper;
+
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakMetric;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStat;
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
+import com.devkor.ifive.nadab.domain.stats.core.repository.PeakStatsStore;
+import lombok.RequiredArgsConstructor;
+import org.springframework.stereotype.Component;
+
+import java.time.LocalDate;
+import java.util.List;
+
+@Component
+@RequiredArgsConstructor
+public class PeakStatsTracker {
+
+    private final PeakStatsStore peakStatsStore;
+
+    public PeakStatViewModel updateAndGet(
+            PeakMetric metric,
+            List<LocalDate> periodStarts,
+            List<Long> values,
+            LocalDate currentPeriodStart
+    ) {
+        if (periodStarts.size() != values.size()) {
+            throw new IllegalArgumentException("periodStarts and values must have the same size");
+        }
+
+        PeakStat candidate = findPeakCandidate(periodStarts, values);
+        if (candidate != null) {
+            peakStatsStore.updateIfGreater(metric, candidate);
+        }
+
+        return peakStatsStore.find(metric)
+                .map(peak -> PeakStatViewModel.from(peak, metric.periodUnit(), currentPeriodStart))
+                .orElseGet(PeakStatViewModel::empty);
+    }
+
+    private PeakStat findPeakCandidate(List<LocalDate> periodStarts, List<Long> values) {
+        PeakStat candidate = null;
+
+        for (int i = 0; i < periodStarts.size(); i++) {
+            long value = values.get(i);
+            LocalDate periodStart = periodStarts.get(i);
+
+            if (value <= 0) {
+                continue;
+            }
+            if (candidate == null
+                    || value > candidate.value()
+                    || value == candidate.value() && periodStart.isAfter(candidate.periodStart())) {
+                candidate = new PeakStat(value, periodStart);
+            }
+        }
+
+        return candidate;
+    }
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/daily/DailyStatsViewModel.java

@@ -1,12 +1,17 @@
 package com.devkor.ifive.nadab.domain.stats.core.dto.daily;
 
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
+
 import java.util.List;
 
 public record DailyStatsViewModel(
         List<String> labels,              // yyyy-MM-dd
         List<Long> signupCounts,
         List<Long> assignedQuestionCounts,
         List<Long> completedDailyReportCounts,
+        PeakStatViewModel signupPeak,
+        PeakStatViewModel assignedQuestionPeak,
+        PeakStatViewModel dauPeak,
         long sharedDailyReportCount,
         String refreshedAt // "2026-02-27 21:34:12"
 ) {}

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/monthly/MonthlyStatsViewModel.java

@@ -1,5 +1,7 @@
 package com.devkor.ifive.nadab.domain.stats.core.dto.monthly;
 
+import com.devkor.ifive.nadab.domain.stats.core.dto.peak.PeakStatViewModel;
+
 import java.util.List;
 
 public record MonthlyStatsViewModel(
@@ -11,6 +13,11 @@ public record MonthlyStatsViewModel(
         List<Long> completedMonthlyReportV2Counts,
         List<Long> completedMonthlyReportTotalCounts,
         List<Long> mauCounts,
+        PeakStatViewModel signupPeak,
+        PeakStatViewModel assignedQuestionPeak,
+        PeakStatViewModel completedDailyReportPeak,
+        PeakStatViewModel completedMonthlyReportPeak,
+        PeakStatViewModel mauPeak,
         long inProgressMonthlyReportV1Count,
         long inProgressMonthlyReportV2Count,
         long inProgressMonthlyReportTotalCount,

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/peak/PeakMetric.java

@@ -0,0 +1,27 @@
+package com.devkor.ifive.nadab.domain.stats.core.dto.peak;
+
+public enum PeakMetric {
+    DAILY_SIGNUP(PeakPeriodUnit.DAY),
+    DAILY_ASSIGNED_QUESTION(PeakPeriodUnit.DAY),
+    DAU(PeakPeriodUnit.DAY),
+    WEEKLY_SIGNUP(PeakPeriodUnit.WEEK),
+    WEEKLY_ASSIGNED_QUESTION(PeakPeriodUnit.WEEK),
+    WEEKLY_DAILY_REPORT(PeakPeriodUnit.WEEK),
+    WEEKLY_REPORT(PeakPeriodUnit.WEEK),
+    WAU(PeakPeriodUnit.WEEK),
+    MONTHLY_SIGNUP(PeakPeriodUnit.MONTH),
+    MONTHLY_ASSIGNED_QUESTION(PeakPeriodUnit.MONTH),
+    MONTHLY_DAILY_REPORT(PeakPeriodUnit.MONTH),
+    MONTHLY_REPORT(PeakPeriodUnit.MONTH),
+    MAU(PeakPeriodUnit.MONTH);
+
+    private final PeakPeriodUnit periodUnit;
+
+    PeakMetric(PeakPeriodUnit periodUnit) {
+        this.periodUnit = periodUnit;
+    }
+
+    public PeakPeriodUnit periodUnit() {
+        return periodUnit;
+    }
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/peak/PeakPeriodUnit.java

@@ -0,0 +1,7 @@
+package com.devkor.ifive.nadab.domain.stats.core.dto.peak;
+
+public enum PeakPeriodUnit {
+    DAY,
+    WEEK,
+    MONTH
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/peak/PeakStat.java

@@ -0,0 +1,17 @@
+package com.devkor.ifive.nadab.domain.stats.core.dto.peak;
+
+import java.time.LocalDate;
+import java.util.Objects;
+
+public record PeakStat(
+        long value,
+        LocalDate periodStart
+) {
+
+    public PeakStat {
+        if (value < 0) {
+            throw new IllegalArgumentException("Peak value must not be negative");
+        }
+        Objects.requireNonNull(periodStart, "periodStart must not be null");
+    }
+}

src/main/java/com/devkor/ifive/nadab/domain/stats/core/dto/peak/PeakStatViewModel.java

@@ -0,0 +1,41 @@
+package com.devkor.ifive.nadab.domain.stats.core.dto.peak;
+
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+
+public record PeakStatViewModel(
+        boolean available,
+        long value,
+        String periodStart,
+        String periodLabel,
+        boolean currentPeriod
+) {
+
+    private static final DateTimeFormatter MONTH_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM");
+
+    public static PeakStatViewModel from(
+            PeakStat peak,
+            PeakPeriodUnit periodUnit,
+            LocalDate currentPeriodStart
+    ) {
+        return new PeakStatViewModel(
+                true,
+                peak.value(),
+                peak.periodStart().toString(),
+                formatPeriodLabel(peak.periodStart(), periodUnit),
+                peak.periodStart().equals(currentPeriodStart)
+        );
+    }
+
+    public static PeakStatViewModel empty() {
+        return new PeakStatViewModel(false, 0L, "", "", false);
+    }
+
+    private static String formatPeriodLabel(LocalDate periodStart, PeakPeriodUnit periodUnit) {
+        return switch (periodUnit) {
+            case DAY -> periodStart.toString();
+            case WEEK -> periodStart + " ~ " + periodStart.plusDays(6);
+            case MONTH -> MONTH_FORMATTER.format(periodStart);
+        };
+    }
+}