feat: initial implementation

src/cap2geojson/__init__.py

@@ -0,0 +1,24 @@
+###############################################################################
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+###############################################################################
+
+from .convert import Converter
+
+__version__ = '0.1.0-dev1'

src/cap2geojson/convert.py

@@ -0,0 +1,132 @@
+import math
+import xmltodict
+
+
+def get_properties(alert):
+    """Creates the properties object for the GeoJSON Feature object from the CAP alert.
+
+    Args:
+        alert (dict): The extracted CAP alert object.
+
+    Returns:
+        dict: The formatted properties object.
+    """
+    info = alert["cap:info"]
+    return {
+        "identifier": alert["cap:identifier"],
+        "sender": alert["cap:sender"],
+        "sent": alert["cap:sent"],
+        "status": alert["cap:status"],
+        "msgType": alert["cap:msgType"],
+        "scope": alert["cap:scope"],
+        "category": info["cap:category"],
+        "event": info["cap:event"],
+        "urgency": info["cap:urgency"],
+        "severity": info["cap:severity"],
+        "certainty": info["cap:certainty"],
+        "effective": info["cap:effective"],
+        "onset": info["cap:onset"],
+        "expires": info["cap:expires"],
+        "senderName": info["cap:senderName"],
+        "headline": info["cap:headline"],
+        "description": info["cap:description"],
+        "instruction": info["cap:instruction"],
+        "web": info["cap:web"],
+        "contact": info["cap:contact"],
+        "areaDesc": get_area_desc(info["cap:area"]),
+    }
+
+
+def get_area_desc(area):
+    """Formats the area description for the GeoJSON properties object.
+
+    Args:
+        area (dict): The area information of the CAP alert.
+
+    Returns:
+        str: The formatted area description.
+    """
+    if isinstance(area, dict):
+        return area["cap:areaDesc"]
+    return ", ".join([a["cap:areaDesc"] for a in area])
+
+
+def get_circle_coord(theta, x_center, y_center, radius):
+    """Calculates the x and y coordinates of a point on a circle.
+
+    Args:
+        theta (_type_): _description_
+        x_center (_type_): _description_
+        y_center (_type_): _description_
+        radius (_type_): _description_
+
+    Returns:
+        tuple: The x and y coordinates of the point, rounded to 5dp.
+    """
+    x = radius * math.cos(theta) + x_center
+    y = radius * math.sin(theta) + y_center
+    return (round(x, 5), round(y, 5))
+
+
+def get_all_circle_coords(x_center, y_center, radius, n_points):
+    """
+    Estimate the n coordinates of a circle with a given center and radius.
+
+    Args:
+        x_center (_type_): _description_
+        y_center (_type_): _description_
+        radius (_type_): _description_
+        n_points (_type_): _description_
+
+    Returns:
+        list: The n estimated coordinates of the circle.
+    """
+    thetas = [i / n_points * math.tau for i in range(n_points)]
+    circle_coords = [
+        get_circle_coord(theta, x_center, y_center, radius) for theta in thetas
+    ]
+    return circle_coords
+
+
+def get_multi_coordinates(area):
+    """Formats the coordinates for the GeoJSON MultiPolygon object.
+
+    Args:
+        area (dict): The area information of the CAP alert.
+
+    Returns:
+        list: The formatted multi-polygon coordinates.
+    """
+    # Idea: loop over each area object and check if it's "cap:circle" or "cap:polygon"
+    # If it's a circle, calculate the circle coordinates and add them to the list
+    # If it's a polygon, add the polygon coordinates to the list
+
+
+def to_geojson(xml):
+    """Takes the CAP alert XML and converts it to a GeoJSON.
+
+    Args:
+        xml (bytes): The CAP XML byte string.
+
+    Returns:
+        dict: The final GeoJSON object.
+    """
+    data = xmltodict.parse(xml)
+    alert = data["cap:alert"]
+
+    alert_properties = get_properties(alert)
+    multi_polygon_coordinates = get_multi_coordinates(alert)
+
+    return {
+        "type": "FeatureCollection",
+        "features": [
+            {
+                "type": "Feature",
+                "properties": alert_properties,
+                "geometry": {
+                    "type": "MultiPolygon",
+                    "coordinates": [multi_polygon_coordinates],
+                },
+            }
+        ],
+    }

tests/data/sc.xml

@@ -0,0 +1,71 @@
+<?xml version='1.0' encoding='utf-8'?>
+<?xml-stylesheet type="text/xsl" href="https://www.meteo.sc/cap-alert-style.xsl"?>
+<alert xmlns="urn:oasis:names:tc:emergency:cap:1.2">
+    <identifier>urn:oid:2.49.0.0.690.0.2024.5.19.13.18.0</identifier>
+    <sender>[email protected]</sender>
+    <sent>2024-05-19T17:18:00+04:00</sent>
+    <status>Actual</status>
+    <msgType>Alert</msgType>
+    <scope>Public</scope>
+    <info>
+        <language>en</language>
+        <category>Met</category>
+        <event>Strong Winds</event>
+        <urgency>Immediate</urgency>
+        <severity>Moderate</severity>
+        <certainty>Observed</certainty>
+        <audience>General Public</audience>
+        <effective>2024-05-19T17:30:00+04:00</effective>
+        <onset>2024-05-19T17:30:00+04:00</onset>
+        <expires>2024-05-19T23:30:00+04:00</expires>
+        <senderName>Seychelles Meteorological Authority</senderName>
+        <headline>Moderate to strong south-easterly winds over Aldabra area</headline>
+        <description>Moderate to strong south-easterly winds over Aldabra area associated with a severe tropical storm Ialy on 19th May 2024 from 5pm to 11pm</description>
+        <instruction>Beware of strong south-easterly winds of 40km/hr gusting to 60km/hr causing rough seas. Mariners are advised to take extra precautions when navigating these areas</instruction>
+        <web>https://www.meteo.sc/alerts/severe-tropical-storm-ialy-is-expected-to-cause-moderate-to-strong-south-easterly-winds-over-aldabra-area-on-19th-may-2024/</web>
+        <contact>[email protected]</contact>
+        <area>
+            <areaDesc>Aldabra area</areaDesc>
+            <polygon>-9.186965,46.078276 -9.336746,45.936002 -9.57065,45.983427 -9.748309,46.116216 -9.897844,46.249006 -10.000609,46.42922 -9.953902,46.694799 -9.692216,46.770679 -9.467752,46.770679 -9.327387,46.742224 -9.186965,46.694799 -9.140146,46.533555 -9.121416,46.362825 -9.186965,46.078276</polygon>
+        </area>
+    </info>
+    <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
+        <ds:SignedInfo>
+            <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2006/12/xml-c14n11"/>
+            <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/>
+            <ds:Reference URI="">
+                <ds:Transforms>
+                    <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
+                    <ds:Transform Algorithm="http://www.w3.org/2006/12/xml-c14n11"/>
+                </ds:Transforms>
+                <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
+                <ds:DigestValue>s9RKcAph3khDLX4nOQQDZ7c23uVZqCDJziRZznnh3nA=</ds:DigestValue>
+            </ds:Reference>
+        </ds:SignedInfo>
+        <ds:SignatureValue>liScT3sHEpNO1TXEDY1nMC5FoBnQruioH/xkU1rNRKfK8Y3y4/lRz64ueJfoWGYB/N3NWLkMhQ6V0X4lHGPyfA==</ds:SignatureValue>
+        <ds:KeyInfo>
+            <ds:X509Data>
+                <ds:X509Certificate>MIIDeTCCAv6gAwIBAgISA7FZkY9qfwdIeZgOZUlggQr+MAoGCCqGSM49BAMDMDIx
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+1ZEDJBb2AKxTZpWdVdtfRErY5BxHuACOm9SlXGE=
+</ds:X509Certificate>
+            </ds:X509Data>
+        </ds:KeyInfo>
+    </ds:Signature>
+</alert>