reimport this PoC

4 files changed, 332 insertions, 0 deletions

diff --git a/internal/metrics/generator.go b/internal/metrics/generator.go
new file mode 100644
index 0000000..c85906a
--- /dev/null
+++ b/internal/metrics/generator.go
@@ -0,0 +1,85 @@
+package metrics
+
+import (
+	"math/rand"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const (
+	minTemperature = 15.0
+	maxTemperature = 35.0
+	maxConnections = 100
+	maxRequests    = 10
+)
+
+var (
+	jobTypes = []string{"email", "report", "backup"}
+	statuses = []string{"success", "failed"}
+)
+
+// Collectors holds Prometheus metric collectors for realtime mode
+type Collectors struct {
+	RequestsTotal      prometheus.Counter
+	ActiveConnections  prometheus.Gauge
+	TemperatureCelsius prometheus.Gauge
+	RequestDuration    prometheus.Histogram
+	JobsProcessed      *prometheus.CounterVec
+}
+
+// NewCollectors creates new Prometheus metric collectors for testing.
+// All metrics are prefixed with "epimetheus_test_" to clearly indicate
+// they are generated by the prometheus-pusher test/demo functionality.
+func NewCollectors() Collectors {
+	return Collectors{
+		RequestsTotal: prometheus.NewCounter(
+			prometheus.CounterOpts{
+				Name: "epimetheus_test_requests_total",
+				Help: "Total number of requests processed (test metric)",
+			},
+		),
+		ActiveConnections: prometheus.NewGauge(
+			prometheus.GaugeOpts{
+				Name: "epimetheus_test_active_connections",
+				Help: "Number of currently active connections (test metric)",
+			},
+		),
+		TemperatureCelsius: prometheus.NewGauge(
+			prometheus.GaugeOpts{
+				Name: "epimetheus_test_temperature_celsius",
+				Help: "Current temperature in Celsius (test metric)",
+			},
+		),
+		RequestDuration: prometheus.NewHistogram(
+			prometheus.HistogramOpts{
+				Name:    "epimetheus_test_request_duration_seconds",
+				Help:    "Histogram of request duration in seconds (test metric)",
+				Buckets: prometheus.DefBuckets,
+			},
+		),
+		JobsProcessed: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "epimetheus_test_jobs_processed_total",
+				Help: "Total number of jobs processed by type (test metric)",
+			},
+			[]string{"job_type", "status"},
+		),
+	}
+}
+
+// Simulate generates random metric values for the collectors
+func (c Collectors) Simulate() {
+	c.RequestsTotal.Add(float64(rand.Intn(maxRequests) + 1))
+	c.ActiveConnections.Set(float64(rand.Intn(maxConnections)))
+	c.TemperatureCelsius.Set(minTemperature + rand.Float64()*(maxTemperature-minTemperature))
+
+	for i := 0; i < rand.Intn(5)+1; i++ {
+		duration := rand.Float64() * 2
+		c.RequestDuration.Observe(duration)
+	}
+
+	for _, jobType := range jobTypes {
+		status := statuses[rand.Intn(len(statuses))]
+		c.JobsProcessed.WithLabelValues(jobType, status).Add(float64(rand.Intn(5)))
+	}
+}
diff --git a/internal/metrics/generator_test.go b/internal/metrics/generator_test.go
new file mode 100644
index 0000000..69395eb
--- /dev/null
+++ b/internal/metrics/generator_test.go
@@ -0,0 +1,53 @@
+package metrics
+
+import (
+	"testing"
+)
+
+func TestNewCollectors(t *testing.T) {
+	collectors := NewCollectors()
+
+	if collectors.RequestsTotal == nil {
+		t.Error("RequestsTotal should not be nil")
+	}
+	if collectors.ActiveConnections == nil {
+		t.Error("ActiveConnections should not be nil")
+	}
+	if collectors.TemperatureCelsius == nil {
+		t.Error("TemperatureCelsius should not be nil")
+	}
+	if collectors.RequestDuration == nil {
+		t.Error("RequestDuration should not be nil")
+	}
+	if collectors.JobsProcessed == nil {
+		t.Error("JobsProcessed should not be nil")
+	}
+}
+
+func TestCollectors_Simulate(t *testing.T) {
+	collectors := NewCollectors()
+
+	// Should not panic
+	collectors.Simulate()
+
+	// Run multiple times to test randomness
+	for i := 0; i < 10; i++ {
+		collectors.Simulate()
+	}
+}
+
+func TestCollectors_SimulateMetrics(t *testing.T) {
+	collectors := NewCollectors()
+
+	// Test that metrics get values after simulation
+	collectors.Simulate()
+
+	// We can't easily inspect the values without the prometheus client,
+	// but we can verify the collectors were created properly
+	if collectors.RequestsTotal == nil {
+		t.Error("RequestsTotal not initialized")
+	}
+	if collectors.JobsProcessed == nil {
+		t.Error("JobsProcessed not initialized")
+	}
+}
diff --git a/internal/metrics/sample.go b/internal/metrics/sample.go
new file mode 100644
index 0000000..04360f5
--- /dev/null
+++ b/internal/metrics/sample.go
@@ -0,0 +1,34 @@
+package metrics
+
+import "time"
+
+// Sample represents a single metric sample with timestamp
+type Sample struct {
+	MetricName string
+	Labels     map[string]string
+	Value      float64
+	Timestamp  time.Time
+}
+
+// NewSample creates a new Sample
+func NewSample(name string, labels map[string]string, value float64, timestamp time.Time) Sample {
+	if labels == nil {
+		labels = make(map[string]string)
+	}
+	return Sample{
+		MetricName: name,
+		Labels:     labels,
+		Value:      value,
+		Timestamp:  timestamp,
+	}
+}
+
+// Age returns how old the sample is
+func (s Sample) Age() time.Duration {
+	return time.Since(s.Timestamp)
+}
+
+// IsRecent returns true if the sample is recent enough for realtime ingestion
+func (s Sample) IsRecent(threshold time.Duration) bool {
+	return s.Age() < threshold
+}
diff --git a/internal/metrics/sample_test.go b/internal/metrics/sample_test.go
new file mode 100644
index 0000000..2ffd78b
--- /dev/null
+++ b/internal/metrics/sample_test.go
@@ -0,0 +1,160 @@
+package metrics
+
+import (
+	"testing"
+	"time"
+)
+
+func TestNewSample(t *testing.T) {
+	tests := []struct {
+		name      string
+		metric    string
+		labels    map[string]string
+		value     float64
+		timestamp time.Time
+		wantNil   bool
+	}{
+		{
+			name:      "with labels",
+			metric:    "test_metric",
+			labels:    map[string]string{"env": "prod", "host": "server1"},
+			value:     42.5,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+		{
+			name:      "nil labels initialized",
+			metric:    "test_metric",
+			labels:    nil,
+			value:     100,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+		{
+			name:      "empty labels",
+			metric:    "test_metric",
+			labels:    map[string]string{},
+			value:     0,
+			timestamp: time.Now(),
+			wantNil:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sample := NewSample(tt.metric, tt.labels, tt.value, tt.timestamp)
+
+			if sample.MetricName != tt.metric {
+				t.Errorf("MetricName = %v, want %v", sample.MetricName, tt.metric)
+			}
+			if sample.Value != tt.value {
+				t.Errorf("Value = %v, want %v", sample.Value, tt.value)
+			}
+			if sample.Labels == nil {
+				t.Error("Labels should never be nil")
+			}
+			if !sample.Timestamp.Equal(tt.timestamp) {
+				t.Errorf("Timestamp = %v, want %v", sample.Timestamp, tt.timestamp)
+			}
+		})
+	}
+}
+
+func TestSample_Age(t *testing.T) {
+	tests := []struct {
+		name     string
+		sample   Sample
+		wantNear time.Duration
+	}{
+		{
+			name: "recent sample",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-5 * time.Minute),
+			},
+			wantNear: 5 * time.Minute,
+		},
+		{
+			name: "old sample",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-1 * time.Hour),
+			},
+			wantNear: 1 * time.Hour,
+		},
+		{
+			name: "very recent",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Second),
+			},
+			wantNear: 10 * time.Second,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			age := tt.sample.Age()
+			// Allow 1 second tolerance for test execution time
+			if age < tt.wantNear-time.Second || age > tt.wantNear+time.Second {
+				t.Errorf("Age() = %v, want near %v", age, tt.wantNear)
+			}
+		})
+	}
+}
+
+func TestSample_IsRecent(t *testing.T) {
+	threshold := 5 * time.Minute
+
+	tests := []struct {
+		name      string
+		sample    Sample
+		threshold time.Duration
+		want      bool
+	}{
+		{
+			name: "within threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-2 * time.Minute),
+			},
+			threshold: threshold,
+			want:      true,
+		},
+		{
+			name: "beyond threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Minute),
+			},
+			threshold: threshold,
+			want:      false,
+		},
+		{
+			name: "exactly at threshold",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-5 * time.Minute),
+			},
+			threshold: threshold,
+			want:      false,
+		},
+		{
+			name: "very recent",
+			sample: Sample{
+				MetricName: "test",
+				Timestamp:  time.Now().Add(-10 * time.Second),
+			},
+			threshold: threshold,
+			want:      true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.sample.IsRecent(tt.threshold); got != tt.want {
+				t.Errorf("IsRecent() = %v, want %v (age: %v)", got, tt.want, tt.sample.Age())
+			}
+		})
+	}
+}