Refactor memorystore

Fix issues
Add unit test
Add documentation

internal/memorystore/memorystore_test.go

@@ -0,0 +1,156 @@
+// Copyright (C) NHR@FAU, University Erlangen-Nuremberg.
+// All rights reserved. This file is part of cc-backend.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package memorystore
+
+import (
+	"testing"
+
+	"github.com/ClusterCockpit/cc-lib/schema"
+)
+
+func TestAssignAggregationStrategy(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected AggregationStrategy
+		wantErr  bool
+	}{
+		{"empty string", "", NoAggregation, false},
+		{"sum", "sum", SumAggregation, false},
+		{"avg", "avg", AvgAggregation, false},
+		{"invalid", "invalid", NoAggregation, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := AssignAggregationStrategy(tt.input)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("AssignAggregationStrategy(%q) error = %v, wantErr %v", tt.input, err, tt.wantErr)
+				return
+			}
+			if result != tt.expected {
+				t.Errorf("AssignAggregationStrategy(%q) = %v, want %v", tt.input, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestAddMetric(t *testing.T) {
+	// Reset Metrics before test
+	Metrics = make(map[string]MetricConfig)
+
+	err := AddMetric("test_metric", MetricConfig{
+		Frequency:   60,
+		Aggregation: SumAggregation,
+	})
+	if err != nil {
+		t.Errorf("AddMetric() error = %v", err)
+	}
+
+	if _, ok := Metrics["test_metric"]; !ok {
+		t.Error("AddMetric() did not add metric to Metrics map")
+	}
+
+	// Test updating with higher frequency
+	err = AddMetric("test_metric", MetricConfig{
+		Frequency:   120,
+		Aggregation: SumAggregation,
+	})
+	if err != nil {
+		t.Errorf("AddMetric() error = %v", err)
+	}
+
+	if Metrics["test_metric"].Frequency != 120 {
+		t.Errorf("AddMetric() frequency = %d, want 120", Metrics["test_metric"].Frequency)
+	}
+
+	// Test updating with lower frequency (should not update)
+	err = AddMetric("test_metric", MetricConfig{
+		Frequency:   30,
+		Aggregation: SumAggregation,
+	})
+	if err != nil {
+		t.Errorf("AddMetric() error = %v", err)
+	}
+
+	if Metrics["test_metric"].Frequency != 120 {
+		t.Errorf("AddMetric() frequency = %d, want 120 (should not downgrade)", Metrics["test_metric"].Frequency)
+	}
+}
+
+func TestGetMetricFrequency(t *testing.T) {
+	// Reset Metrics before test
+	Metrics = map[string]MetricConfig{
+		"test_metric": {
+			Frequency:   60,
+			Aggregation: SumAggregation,
+		},
+	}
+
+	freq, err := GetMetricFrequency("test_metric")
+	if err != nil {
+		t.Errorf("GetMetricFrequency() error = %v", err)
+	}
+	if freq != 60 {
+		t.Errorf("GetMetricFrequency() = %d, want 60", freq)
+	}
+
+	_, err = GetMetricFrequency("nonexistent")
+	if err == nil {
+		t.Error("GetMetricFrequency() expected error for nonexistent metric")
+	}
+}
+
+func TestBufferWrite(t *testing.T) {
+	b := newBuffer(100, 10)
+
+	// Test writing value
+	nb, err := b.write(100, schema.Float(42.0))
+	if err != nil {
+		t.Errorf("buffer.write() error = %v", err)
+	}
+	if nb != b {
+		t.Error("buffer.write() created new buffer unexpectedly")
+	}
+	if len(b.data) != 1 {
+		t.Errorf("buffer.write() len(data) = %d, want 1", len(b.data))
+	}
+	if b.data[0] != schema.Float(42.0) {
+		t.Errorf("buffer.write() data[0] = %v, want 42.0", b.data[0])
+	}
+
+	// Test writing value from past (should error)
+	_, err = b.write(50, schema.Float(10.0))
+	if err == nil {
+		t.Error("buffer.write() expected error for past timestamp")
+	}
+}
+
+func TestBufferRead(t *testing.T) {
+	b := newBuffer(100, 10)
+	
+	// Write some test data
+	b.write(100, schema.Float(1.0))
+	b.write(110, schema.Float(2.0))
+	b.write(120, schema.Float(3.0))
+
+	// Read data
+	data := make([]schema.Float, 3)
+	result, from, to, err := b.read(100, 130, data)
+	if err != nil {
+		t.Errorf("buffer.read() error = %v", err)
+	}
+	// Buffer read should return from as firstWrite (start + freq/2)
+	if from != 100 {
+		t.Errorf("buffer.read() from = %d, want 100", from)
+	}
+	if to != 130 {
+		t.Errorf("buffer.read() to = %d, want 130", to)
+	}
+	if len(result) != 3 {
+		t.Errorf("buffer.read() len(result) = %d, want 3", len(result))
+	}
+}