Implement paging and refactor stores to match new store interface with paging

storage/store/memory/util.go

@@ -0,0 +1,86 @@
+package memory
+
+import (
+	"github.com/TwinProduction/gatus/core"
+	"github.com/TwinProduction/gatus/storage/store/paging"
+)
+
+// ShallowCopyServiceStatus returns a shallow copy of a ServiceStatus with only the results
+// within the range defined by the page and pageSize parameters
+func ShallowCopyServiceStatus(ss *core.ServiceStatus, params *paging.ServiceStatusParams) *core.ServiceStatus {
+	shallowCopy := &core.ServiceStatus{
+		Name:   ss.Name,
+		Group:  ss.Group,
+		Key:    ss.Key,
+		Uptime: core.NewUptime(),
+	}
+	numberOfResults := len(ss.Results)
+	resultsStart, resultsEnd := getStartAndEndIndex(numberOfResults, params.ResultsPage, params.ResultsPageSize)
+	if resultsStart < 0 || resultsEnd < 0 {
+		shallowCopy.Results = []*core.Result{}
+	} else {
+		shallowCopy.Results = ss.Results[resultsStart:resultsEnd]
+	}
+	numberOfEvents := len(ss.Events)
+	eventsStart, eventsEnd := getStartAndEndIndex(numberOfEvents, params.EventsPage, params.EventsPageSize)
+	if eventsStart < 0 || eventsEnd < 0 {
+		shallowCopy.Events = []*core.Event{}
+	} else {
+		shallowCopy.Events = ss.Events[eventsStart:eventsEnd]
+	}
+	if params.IncludeUptime {
+		shallowCopy.Uptime.LastHour = ss.Uptime.LastHour
+		shallowCopy.Uptime.LastTwentyFourHours = ss.Uptime.LastTwentyFourHours
+		shallowCopy.Uptime.LastSevenDays = ss.Uptime.LastSevenDays
+	}
+	return shallowCopy
+}
+
+func getStartAndEndIndex(numberOfResults int, page, pageSize int) (int, int) {
+	start := numberOfResults - (page * pageSize)
+	end := numberOfResults - ((page - 1) * pageSize)
+	if start > numberOfResults {
+		start = -1
+	} else if start < 0 {
+		start = 0
+	}
+	if end > numberOfResults {
+		end = numberOfResults
+	}
+	return start, end
+}
+
+// AddResult adds a Result to ServiceStatus.Results and makes sure that there are
+// no more than MaximumNumberOfResults results in the Results slice
+func AddResult(ss *core.ServiceStatus, result *core.Result) {
+	if ss == nil {
+		return
+	}
+	if len(ss.Results) > 0 {
+		// Check if there's any change since the last result
+		// OR there's only 1 event, which only happens when there's a start event
+		if ss.Results[len(ss.Results)-1].Success != result.Success || len(ss.Events) == 1 {
+			event := &core.Event{Timestamp: result.Timestamp}
+			if result.Success {
+				event.Type = core.EventHealthy
+			} else {
+				event.Type = core.EventUnhealthy
+			}
+			ss.Events = append(ss.Events, event)
+			if len(ss.Events) > core.MaximumNumberOfEvents {
+				// Doing ss.Events[1:] would usually be sufficient, but in the case where for some reason, the slice has
+				// more than one extra element, we can get rid of all of them at once and thus returning the slice to a
+				// length of MaximumNumberOfEvents by using ss.Events[len(ss.Events)-MaximumNumberOfEvents:] instead
+				ss.Events = ss.Events[len(ss.Events)-core.MaximumNumberOfEvents:]
+			}
+		}
+	}
+	ss.Results = append(ss.Results, result)
+	if len(ss.Results) > core.MaximumNumberOfResults {
+		// Doing ss.Results[1:] would usually be sufficient, but in the case where for some reason, the slice has more
+		// than one extra element, we can get rid of all of them at once and thus returning the slice to a length of
+		// MaximumNumberOfResults by using ss.Results[len(ss.Results)-MaximumNumberOfResults:] instead
+		ss.Results = ss.Results[len(ss.Results)-core.MaximumNumberOfResults:]
+	}
+	processUptimeAfterResult(ss.Uptime, result)
+}