feat: add ResolveOrExtractRAFromHeaders to internal/utils module in @observerly/skysolve

internal/utils/headers.go

@@ -0,0 +1,49 @@
+/*****************************************************************************************************************/
+
+//	@author		Michael Roberts <[email protected]>
+//	@package	@observerly/skysolve
+//	@license	Copyright © 2021-2025 observerly
+
+/*****************************************************************************************************************/
+
+package utils
+
+/*****************************************************************************************************************/
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/observerly/iris/pkg/fits"
+)
+
+/*****************************************************************************************************************/
+
+func ResolveOrExtractRAFromHeaders(value float32, header fits.FITSHeader) (float32, error) {
+	// First, pick a candidate RA (v):
+	v := value
+
+	// If the candidate RA (v) is NaN, try to get it from the header:
+	if math.IsNaN(float64(v)) {
+		ra, exists := header.Floats["RA"]
+		if !exists {
+			return float32(math.NaN()), fmt.Errorf("ra header not found in the supplied FITS file")
+		}
+		v = ra.Value
+	}
+
+	// Validate the candidate RA (v) is a valid float32:
+	if math.IsNaN(float64(v)) {
+		return float32(math.NaN()), fmt.Errorf("ra value needs to be a valid float32")
+	}
+
+	// Validate the candidate RA (v) is within the range [0, 360]:
+	if v < 0 || v > 360 {
+		return float32(math.NaN()), fmt.Errorf("ra value is out of range: %f", v)
+	}
+
+	// Return the candidate RA (v):
+	return v, nil
+}
+
+/*****************************************************************************************************************/

internal/utils/headers_test.go

@@ -0,0 +1,152 @@
+/*****************************************************************************************************************/
+
+//	@author		Michael Roberts <[email protected]>
+//	@package	@observerly/skysolve
+//	@license	Copyright © 2021-2025 observerly
+
+/*****************************************************************************************************************/
+
+package utils
+
+/*****************************************************************************************************************/
+
+import (
+	"math"
+	"testing"
+
+	"github.com/observerly/iris/pkg/fits"
+)
+
+/*****************************************************************************************************************/
+
+// newFITSHeaderWithRA is a helper that returns a fits.FITSHeader
+// populated with an RA value.
+func newFITSHeaderWithRA(ra float32) fits.FITSHeader {
+	return fits.FITSHeader{
+		Floats: map[string]fits.FITSHeaderFloat{
+			"RA": {
+				Value:   ra,
+				Comment: "Right Ascension",
+			},
+		},
+	}
+}
+
+/*****************************************************************************************************************/
+
+// newFITSHeaderNoRA is a helper that returns a fits.FITSHeader
+// with no RA entry in the Floats map.
+func newFITSHeaderNoRA() fits.FITSHeader {
+	return fits.FITSHeader{
+		Floats: map[string]fits.FITSHeaderFloat{},
+	}
+}
+
+/*****************************************************************************************************************/
+
+func TestRAValueIsNotNaNAndWithinRange(t *testing.T) {
+	value := float32(180.0)
+	header := newFITSHeaderNoRA()
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	if got != value {
+		t.Errorf("Expected %f, got %f", value, got)
+	}
+}
+
+func TestRAValueIsNotNaNAndOutOfRangeNegative(t *testing.T) {
+	value := float32(-1.0)
+	header := newFITSHeaderNoRA()
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error for negative RA, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN for out-of-range RA, got %f", got)
+	}
+}
+
+func TestRAValueIsNotNaNAndOutOfRangePositive(t *testing.T) {
+	value := float32(361.0)
+	header := newFITSHeaderNoRA()
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error for RA > 360, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN for out-of-range RA, got %f", got)
+	}
+}
+
+func TestRAValueIsNaNAndRAHeaderFoundAndValid(t *testing.T) {
+	value := float32(math.NaN())
+	header := newFITSHeaderWithRA(123.45)
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err != nil {
+		t.Fatalf("Unexpected error when RA is pulled from header: %v", err)
+	}
+	expected := float32(123.45)
+	if got != expected {
+		t.Errorf("Expected RA = %f, got %f", expected, got)
+	}
+}
+
+func TestRAValueIsNaNAndRAHeaderMissing(t *testing.T) {
+	value := float32(math.NaN())
+	header := newFITSHeaderNoRA()
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error when RA header is missing, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN when RA header is missing, got %f", got)
+	}
+}
+
+func TestRAValueIsNaNAndRAHeaderOutOfRangeNegative(t *testing.T) {
+	value := float32(math.NaN())
+	header := newFITSHeaderWithRA(-5.0)
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error for negative RA, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN for out-of-range RA, got %f", got)
+	}
+}
+
+func TestRAValueIsNaNAndRAHeaderOutOfRangePositive(t *testing.T) {
+	value := float32(math.NaN())
+	header := newFITSHeaderWithRA(400.0)
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error for RA > 360, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN for out-of-range RA, got %f", got)
+	}
+}
+
+func TestRAValueIsNaNAndRAHeaderNaN(t *testing.T) {
+	value := float32(math.NaN())
+	header := newFITSHeaderWithRA(float32(math.NaN()))
+
+	got, err := ResolveOrExtractRAFromHeaders(value, header)
+	if err == nil {
+		t.Fatalf("Expected an error for RA=NaN in header, but got none")
+	}
+	if !math.IsNaN(float64(got)) {
+		t.Errorf("Expected NaN when RA=NaN in header, got %f", got)
+	}
+}
+
+/*****************************************************************************************************************/