Add controller airgap storage space calculation

Signed-off-by: Evans Mungai <evans@replicated.com>

Author: banjoh

pkg-new/preflights/template.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	_ "embed"
 	"fmt"
+	"math"
 	"text/template"
 
 	"github.com/replicatedhq/embedded-cluster/pkg-new/preflights/types"
@@ -44,3 +45,28 @@ func renderTemplate(spec string, data types.TemplateData) (string, error) {
 	}
 	return buf.String(), nil
 }
+
+// CalculateControllerAirgapStorageSpace calculates the required airgap storage space for controller nodes.
+// It multiplies the uncompressed size by 2, rounds up to the nearest natural number, and returns a string.
+// The quantity will be in Gi for sizes >= 1 Gi, or Mi for smaller sizes.
+func CalculateControllerAirgapStorageSpace(uncompressedSize int64) string {
+	if uncompressedSize <= 0 {
+		return ""
+	}
+
+	// Controller nodes require 2x the extracted bundle size for processing
+	requiredBytes := uncompressedSize * 2
+
+	// Convert to Gi if >= 1 Gi, otherwise use Mi
+	if requiredBytes >= 1024*1024*1024 { // 1 Gi in bytes
+		// Convert to Gi and round up to nearest natural number
+		giValue := float64(requiredBytes) / (1024 * 1024 * 1024)
+		roundedGi := math.Ceil(giValue)
+		return fmt.Sprintf("%dGi", int64(roundedGi))
+	} else {
+		// Convert to Mi and round up to nearest natural number
+		miValue := float64(requiredBytes) / (1024 * 1024)
+		roundedMi := math.Ceil(miValue)
+		return fmt.Sprintf("%dMi", int64(roundedMi))
+	}
+}