// client2server - Metrics aggregation
//
// In-memory time-bucketed counters for events and commands. Buckets are
// 1-minute windows covering the last 24 hours (1440 buckets).

package main

import (
	"sync"
	"time"
)

const (
	bucketMinutes    = 1
	retentionBuckets = 24 * 60 // 24h
)

type metricsBucket struct {
	start         time.Time
	eventsTotal   int
	byType        map[string]int
	commandsTotal int
	commandsOK    int
	commandsFail  int
}

type Metrics struct {
	mu      sync.RWMutex
	buckets [retentionBuckets]*metricsBucket
}

var globalMetrics = &Metrics{}

func (m *Metrics) nowBucket() *metricsBucket {
	startOfMinute := time.Now().Truncate(bucketMinutes * time.Minute)
	idx := int(startOfMinute.Unix()/60) % retentionBuckets
	b := m.buckets[idx]
	if b == nil || !b.start.Equal(startOfMinute) {
		b = &metricsBucket{
			start:  startOfMinute,
			byType: make(map[string]int),
		}
		m.buckets[idx] = b
	}
	return b
}

func (m *Metrics) recordEvent(eventType string) {
	m.mu.Lock()
	defer m.mu.Unlock()
	b := m.nowBucket()
	b.eventsTotal++
	b.byType[eventType]++
}

func (m *Metrics) recordCommand(success bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	b := m.nowBucket()
	b.commandsTotal++
	if success {
		b.commandsOK++
	} else {
		b.commandsFail++
	}
}

// snapshot returns a list of buckets covering the last `since` minutes.
func (m *Metrics) snapshot(since time.Duration) []map[string]interface{} {
	m.mu.RLock()
	defer m.mu.RUnlock()

	cutoff := time.Now().Add(-since).Truncate(bucketMinutes * time.Minute)
	out := []map[string]interface{}{}

	// Walk buckets; for each one, check if its start >= cutoff
	for _, b := range m.buckets {
		if b == nil {
			continue
		}
		if b.start.Before(cutoff) {
			continue
		}
		out = append(out, map[string]interface{}{
			"ts":            b.start.Format(time.RFC3339),
			"events_total":  b.eventsTotal,
			"commands_total": b.commandsTotal,
			"commands_ok":   b.commandsOK,
			"commands_fail": b.commandsFail,
			"events_by_type": b.byType,
		})
	}
	return out
}

func (m *Metrics) summary() map[string]interface{} {
	m.mu.RLock()
	defer m.mu.RUnlock()
	b := m.nowBucket()
	// Aggregate events from this minute and previous 5 minutes for a more
	// meaningful "recent" number.
	total := b.eventsTotal
	for i := 1; i < 6; i++ {
		idx := (int(time.Now().Unix()/60) - i) % retentionBuckets
		if idx < 0 {
			idx += retentionBuckets
		}
		if prev := m.buckets[idx]; prev != nil {
			total += prev.eventsTotal
		}
	}
	return map[string]interface{}{
		"events_last_5min":  total,
		"events_this_min":   b.eventsTotal,
		"commands_this_min": b.commandsTotal,
	}
}