Refactor coordinates

Author: dyve

src/euring/coordinates.py

@@ -0,0 +1,96 @@
+from euring.exceptions import EuringConstraintException
+
+
+def lat_lng_to_euring_coordinates(lat: float, lng: float) -> str:
+    """Format latitude and longitude as EURING geographical coordinates."""
+    return f"{_lat_to_euring_coordinate(lat)}{_lng_to_euring_coordinate(lng)}"
+
+
+def euring_coordinates_to_lat_lng(value: str) -> dict[str, float]:
+    """Parse EURING geographical coordinates into latitude/longitude decimals."""
+    lat_str = value[:7]
+    lng_str = value[7:]
+    return dict(lat=_euring_coordinate_to_decimal(lat_str), lng=_euring_coordinate_to_decimal(lng_str))
+
+
+def _euring_coordinate_to_decimal(value: str) -> float:
+    """Convert EURING geographical coordinate string to decimal coordinate."""
+    try:
+        seconds = value[-2:]
+        minutes = value[-4:-2]
+        degrees = value[:-4]
+        result = float(degrees)
+        negative = result < 0
+        result = abs(result) + (float(minutes) / 60) + (float(seconds) / 3600)
+        if negative:
+            result = -result
+    except (IndexError, ValueError):
+        raise EuringConstraintException('Could not parse coordinate "{value}" to decimal.')
+    return result
+
+
+def _decimal_to_euring_coordinate(value: float, degrees_pos: int) -> str:
+    """Format a decimal coordinate into EURING DMS text with fixed degree width."""
+    parts = _decimal_to_euring_coordinate_components(value)
+    return "{quadrant}{degrees}{minutes}{seconds}".format(
+        quadrant=parts["quadrant"],
+        degrees="{}".format(abs(parts["degrees"])).zfill(degrees_pos),
+        minutes="{}".format(parts["minutes"]).zfill(2),
+        seconds="{}".format(parts["seconds"]).zfill(2),
+    )
+
+
+def _lat_to_euring_coordinate(value: float) -> str:
+    """Convert a latitude in decimal degrees to a EURING coordinate string."""
+    return _decimal_to_euring_coordinate(value, degrees_pos=2)
+
+
+def _lng_to_euring_coordinate(value: float) -> str:
+    """Convert a longitude in decimal degrees to a EURING DMS coordinae string."""
+    return _decimal_to_euring_coordinate(value, degrees_pos=3)
+
+
+def _decimal_to_euring_coordinate_components(value: float) -> dict[str, int | float | str]:
+    """Convert a decimal coordinate into EURING geographical coordinate components."""
+    degrees = int(value)
+    submin = abs((value - int(value)) * 60)
+    minutes = int(submin)
+    seconds = abs((submin - int(submin)) * 60)
+    quadrant = "-" if degrees < 0 else "+"
+    seconds = int(round(seconds))
+    if seconds == 60:
+        seconds = 0
+        minutes += 1
+    if minutes == 60:
+        minutes = 0
+        degrees = degrees + 1 if degrees >= 0 else degrees - 1
+    return {"quadrant": quadrant, "degrees": degrees, "minutes": minutes, "seconds": seconds}
+
+
+def _validate_euring_coordinates(value: str | None) -> None:
+    """Validate a combined EURING latitude/longitude coordinate string."""
+    if value is None:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    if len(value) != 15:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    _validate_euring_coordinate_component(value[:7], degrees_digits=2, max_degrees=90)
+    _validate_euring_coordinate_component(value[7:], degrees_digits=3, max_degrees=180)
+
+
+def _validate_euring_coordinate_component(value: str | None, *, degrees_digits: int, max_degrees: int) -> None:
+    """Validate a single EURING coordinate component."""
+    if value is None:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    expected_length = 1 + degrees_digits + 2 + 2
+    if len(value) != expected_length:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    sign = value[0]
+    if sign not in {"+", "-"}:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    degrees = value[1 : 1 + degrees_digits]
+    minutes = value[1 + degrees_digits : 1 + degrees_digits + 2]
+    seconds = value[1 + degrees_digits + 2 :]
+    if not (degrees.isdigit() and minutes.isdigit() and seconds.isdigit()):
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')
+    if int(degrees) > max_degrees or int(minutes) > 59 or int(seconds) > 59:
+        raise EuringConstraintException(f'Value "{value}" is not a valid set of coordinates.')

tests/test_coordinates.py

@@ -0,0 +1,42 @@
+"""Tests for EURING coordinate utilities."""
+
+import pytest
+
+from euring import EuringConstraintException
+from euring.coordinates import (
+    _decimal_to_euring_coordinate_components,
+    _euring_coordinate_to_decimal,
+    _lat_to_euring_coordinate,
+    _lng_to_euring_coordinate,
+    euring_coordinates_to_lat_lng,
+    lat_lng_to_euring_coordinates,
+)
+
+
+def test_coordinate_conversion():
+    lat_decimal = _euring_coordinate_to_decimal("+420500")
+    lng_decimal = _euring_coordinate_to_decimal("-0100203")
+    assert abs(lat_decimal - 42.083333) < 1e-5
+    assert abs(lng_decimal - (-10.034167)) < 1e-5
+
+    assert _lat_to_euring_coordinate(lat_decimal) == "+420500"
+    assert _lng_to_euring_coordinate(lng_decimal) == "-0100203"
+
+    dms = _decimal_to_euring_coordinate_components(12.25)
+    assert dms["quadrant"] == "+"
+    assert dms["degrees"] == 12
+    assert dms["minutes"] == 15
+    assert dms["seconds"] == 0.0
+
+
+def test_coordinates_round_trip():
+    value = "+420500-0100203"
+    parsed = euring_coordinates_to_lat_lng(value)
+    assert parsed["lat"] == pytest.approx(42.083333333333336)
+    assert parsed["lng"] == pytest.approx(-10.034166666666666)
+    assert lat_lng_to_euring_coordinates(parsed["lat"], parsed["lng"]) == value
+
+
+def test_coordinate_conversion_invalid():
+    with pytest.raises(EuringConstraintException):
+        _euring_coordinate_to_decimal("bogus")