1 files changed, 177 insertions, 0 deletions
diff --git a/webmap-cgi b/webmap-cgi
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+++ b/webmap-cgi
@@ -0,0 +1,177 @@
+#!/usr/bin/python3
+
+#----------------------------------------------------------------------
+# Webmap CGI (Common Gateway Interface) for the Klimatanalys Norr project
+# Copyright © 2025 Guilhem Moulin <info@guilhem.se>
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or (at
+# your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero
+# General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#----------------------------------------------------------------------
+
+# pylint: disable=invalid-name, missing-module-docstring, fixme
+# pylint: enable=invalid-name
+
+import sys
+from os import path as os_path
+from json import load as json_load, JSONDecodeError
+import logging
+from typing import Final, Iterator
+import atexit
+
+from psycopg import connect, Cursor # pylint: disable=import-error
+
+import common
+
+def get_table_map() -> dict[tuple[str, str], str]:
+    """Get mapping of pairs (MVT group name, layername) to table name."""
+    ret = {}
+    config = common.load_config()
+    layer_groups = config.get('layer-groups', {})
+    layers = config.get('layers', {})
+    layernames = set(layers.keys())
+    for groupname, patterns in layer_groups.items():
+        for layername in common.layers_in_group(groupname, patterns, layernames):
+            exportdef = layers[layername].get('publish', None)
+            if exportdef is None:
+                continue
+            if isinstance(exportdef, str):
+                exportdef = [ exportdef ]
+            for layername_mvt in exportdef:
+                k = (groupname, layername_mvt)
+                if k in ret:
+                    raise RuntimeError(f'Duplicate key {k}')
+                ret[k] = layername
+    return ret
+
+SCHEMA_NAME : Final[str] = 'postgis'
+def get_query(layername : str) -> bytes:
+    """Get GeoJSON-producing query for the given layer."""
+    # TODO don't hardcode geometry column name
+    # TODO[trixie]id_column => 'ogc_fid' (but don't hardcode either)
+    query = 'SELECT convert_to(ST_AsGeoJSON(m.*,'
+    query +=                                'geom_column=>\'wkb_geometry\','
+    query +=                                'pretty_bool=>\'f\'),'
+    query +=                   '\'UTF8\') AS "GeoJSON" '
+    query +=  'FROM ('
+    query +=    'SELECT l.* '
+    query +=      'FROM ' + common.escape_identifier(SCHEMA_NAME)
+    query +=            '.' + common.escape_identifier(layername) + ' l '
+    query +=      'WHERE l.ogc_fid = %s'
+    query +=  ') m'
+    return query.encode('utf-8')
+
+
+STATUS_OK : Final[str] = '200 OK'
+STATUS_BAD_REQUEST : Final[str] = '400 Bad Request'
+STATUS_NOT_ALLOWED : Final[str] = '405 Method Not Allowed'
+STATUS_INTERNAL_SERVER_ERROR : Final[str] = '500 Internal Server Error'
+
+EMPTY_RESPONSE_HEADERS : Final[list[tuple[str,str]]] = [
+    ('Content-Type', 'text/plain'),
+    ('Content-Length', '0'),
+]
+CONTENT_TYPE_JSON : Final[tuple[str,str]] = ('Content-Type', 'application/json; charset=UTF-8')
+
+MAX_FEATURE_COUNT : Final[int] = 500
+def application(env, start_response) -> Iterator[bytes]:
+    """Main application."""
+    if env['REQUEST_METHOD'].upper() != 'POST':
+        logging.error('Invalid request method %s', env['REQUEST_METHOD'])
+        start_response(STATUS_NOT_ALLOWED, EMPTY_RESPONSE_HEADERS)
+        return
+
+    content_type = env.get('CONTENT_TYPE', '').lower()
+    if content_type != 'application/json' and not content_type.startswith('application/json;'):
+        logging.error('Invalid Content-Type: %s', content_type)
+        start_response(STATUS_BAD_REQUEST, EMPTY_RESPONSE_HEADERS)
+        return
+
+    first = True
+    try:
+        body = json_load(env['wsgi.input'])
+        if not isinstance(body, dict):
+            raise ValueError
+
+        start_response(STATUS_OK, [CONTENT_TYPE_JSON])
+        # pylint: disable-next=no-member
+        with PG_CONN.cursor(binary=True, scrollable=False, withhold=False) as cur:
+            if not isinstance(body, dict):
+                raise ValueError
+            mvt = body.get('mvt', None)
+            layername = body.get('layer', None)
+            if not isinstance(mvt, str) or not isinstance(layername, str):
+                raise ValueError
+            query = QUERY_MAP[TABLE_MAP[(mvt, layername)]]
+            fid = body.get('fid', None)
+            if not isinstance(fid, int):
+                raise ValueError
+            cur.execute(query, params=(fid,))
+            resp = cur.fetchone()
+            if resp is not None:
+                yield resp[0]
+
+    except (JSONDecodeError, LookupError, UnicodeDecodeError, ValueError) as exc:
+        logging.exception('Invalid request body')
+        # start_response(,,sys.exc_info()) should work here, but doesn't
+        # because of https://github.com/unbit/uwsgi/issues/2278
+        if first:
+            start_response(STATUS_BAD_REQUEST, EMPTY_RESPONSE_HEADERS)
+        else:
+            # headers already sent, can't do better; the client will get a 200 status
+            # code, but fail to parse the payload as JSON anyway
+            exc_info = sys.exc_info()
+            raise exc_info[1].with_traceback(exc_info[2]) from exc
+    except Exception as exc: # pylint: disable=broad-exception-caught
+        logging.exception('Internal Server Error')
+        if first:
+            start_response(STATUS_INTERNAL_SERVER_ERROR, EMPTY_RESPONSE_HEADERS)
+        else:
+            exc_info = sys.exc_info()
+            raise exc_info[1].with_traceback(exc_info[2]) from exc
+
+# We could use a psycopg_pool.ConnectionPool() but that would be
+# overkill since we only have 2 workers and no threads.  So each worker
+# simply opens a (single) connection to PostgreSQL at launch time.
+# Use autocommit to avoid starting a transaction, cf.
+# https://www.psycopg.org/psycopg3/docs/basic/transactions.html#autocommit-transactions
+PG_CONN = connect('postgresql://webmap_guest@/webmap',
+                  autocommit=True,
+                  prepare_threshold=0,
+                  # TODO[trixie] use cursor_factory=RawCursor
+                  # https://www.psycopg.org/psycopg3/docs/advanced/cursors.html#cursor-types
+                  cursor_factory=Cursor)
+
+@atexit.register
+def handler():
+    """Gracefully close the connection before terminating the worker"""
+    # avoid "AttributeError: 'NoneType' object has no attribute 'connection_summary'"
+    # when destructing the object
+    # TODO[trixie] reevaluate, possibly related to https://github.com/psycopg/psycopg/issues/591
+    PG_CONN.close() # pylint: disable=no-member
+
+common.init_logger(app=os_path.basename(__file__), level=logging.INFO)
+TABLE_MAP : Final[dict[tuple[str, str], str]] = get_table_map()
+QUERY_MAP : Final[dict[str,bytes]] = { lyr:get_query(lyr) for lyr in set(TABLE_MAP.values()) }
+
+PG_CONN.execute( # pylint: disable=no-member
+    'SET search_path TO ' + common.escape_identifier(SCHEMA_NAME) + ',public',
+    prepare=False)
+PG_CONN.execute( # pylint: disable=no-member
+    'SET statement_timeout TO 15000', # 15s
+    prepare=False)
+
+del sys.modules['common']
+del common
+del get_query
+del get_table_map
+del os_path