feat(server): online session history with configurable stats window (#1243)

Add persisted online sessions, configurable retention and online history statistics with lifecycle, recovery, timezone and concurrency regression coverage.

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

cmd/dashboard/controller/online_history.go

@@ -0,0 +1,121 @@
+package controller
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/nezhahq/nezha/model"
+	"github.com/nezhahq/nezha/service/singleton"
+)
+
+// Get server online history
+// @Summary Get server online history
+// @Security BearerAuth
+// @Schemes
+// @Description Get online periods and aggregated uptime statistics of a specific server
+// @Tags common
+// @Param id path uint true "Server ID"
+// @Param days query int false "Query window in days (default: configured online_stats_days, clamped to it)"
+// @Produce json
+// @Success 200 {object} model.CommonResponse[model.OnlineHistoryResponse]
+// @Router /server/{id}/online-history [get]
+func getServerOnlineHistory(c *gin.Context) (*model.OnlineHistoryResponse, error) {
+	idStr := c.Param("id")
+	serverID, err := strconv.ParseUint(idStr, 10, 64)
+	if err != nil {
+		return nil, err
+	}
+
+	server, ok := singleton.ServerShared.Get(serverID)
+	if !ok || server == nil {
+		return nil, singleton.Localizer.ErrorT("server not found")
+	}
+	if !userCanViewServer(c, server) {
+		return nil, singleton.Localizer.ErrorT("unauthorized")
+	}
+	_, isMember := c.Get(model.CtxKeyAuthorizedUser)
+
+	maxDays := singleton.Conf.OnlineHistoryRetentionDays()
+	if maxDays < model.MinOnlineStatsDays || maxDays > model.MaxOnlineStatsDays {
+		maxDays = model.DefaultOnlineStatsDays
+	}
+	days := maxDays
+	if daysStr := c.Query("days"); daysStr != "" {
+		d, err := strconv.Atoi(daysStr)
+		if err != nil || d < 1 {
+			return nil, singleton.Localizer.ErrorT("invalid days parameter")
+		}
+		// 查询窗口收敛到后台设置的统计范围内
+		if d > maxDays {
+			d = maxDays
+		}
+		days = d
+	}
+
+	if !isMember && days > 1 {
+		return nil, singleton.Localizer.ErrorT("unauthorized: only 1d data available for guests")
+	}
+
+	now := time.Now()
+	windowEnd := now
+	windowStart := model.OnlineHistoryWindowStart(now, days, singleton.Loc)
+
+	sessions, err := singleton.OnlineHistoryShared.Sessions(serverID, windowStart, windowEnd)
+	if err != nil {
+		return nil, newGormError("%v", err)
+	}
+
+	periods := model.ClipOnlineSessions(sessions, windowStart, windowEnd)
+	daily := model.DailyOnlineBreakdown(periods, windowStart, windowEnd, singleton.Loc)
+	// 总时长取各日之和，与 daily[] 严格对账（每日累计原始时长后统一取整，
+	// 口径见 DailyOnlineBreakdown）
+	var totalSeconds uint64
+	for _, d := range daily {
+		totalSeconds += d.OnlineSeconds
+	}
+	windowSeconds := uint64(windowEnd.Sub(windowStart).Seconds())
+	onlineRate := 0.0
+	if windowSeconds > 0 {
+		onlineRate = float64(totalSeconds) / float64(windowSeconds) * 100
+	}
+
+	runtime := server.RuntimeSnapshot()
+	currentlyOnline := !runtime.LastActive.IsZero() && now.Sub(runtime.LastActive) <= model.OnlineActiveWindow
+	var lastActive *time.Time
+	if !runtime.LastActive.IsZero() {
+		lastActiveUTC := runtime.LastActive.UTC()
+		lastActive = &lastActiveUTC
+	}
+
+	// 响应统一以 UTC 序列化，避免窗口时间与库中读回的会话时间混用
+	// 本地偏移与 Z 两种写法（时段为值拷贝，不影响调用方）
+	utcPeriods := make([]model.OnlinePeriod, len(periods))
+	for i, p := range periods {
+		utcPeriods[i] = model.OnlinePeriod{Start: p.Start.UTC(), End: p.End.UTC(), Ongoing: p.Ongoing}
+	}
+
+	return &model.OnlineHistoryResponse{
+		ServerID:           serverID,
+		ServerName:         server.Name,
+		Days:               days,
+		MaxDays:            maxDays,
+		Timezone:           singleton.Loc.String(),
+		TzOffset:           tzOffsetSeconds(now, singleton.Loc),
+		WindowStart:        windowStart.UTC(),
+		WindowEnd:          windowEnd.UTC(),
+		TotalOnlineSeconds: totalSeconds,
+		OnlineRate:         onlineRate,
+		CurrentlyOnline:    currentlyOnline,
+		LastActive:         lastActive,
+		Periods:            utcPeriods,
+		Daily:              daily,
+	}, nil
+}
+
+// tzOffsetSeconds 返回指定时区在给定时刻相对 UTC 的偏移秒数。
+func tzOffsetSeconds(at time.Time, loc *time.Location) int {
+	_, offset := at.In(loc).Zone()
+	return offset
+}