Refactor project structure

This follows guidance from several well-known Python best practices
guides. Basically, the idea is create a package for the application
that is comprised of several re-usable modules.

See: https://docs.python-guide.org/writing/structure/
See: https://realpython.com/python-application-layouts/

dspace_statistics_api/app.py

@@ -0,0 +1,73 @@
+from .database import database_connection
+import falcon
+
+db = database_connection()
+db.set_session(readonly=True)
+
+class AllItemsResource:
+    def on_get(self, req, resp):
+        """Handles GET requests"""
+        # Return HTTPBadRequest if id parameter is not present and valid
+        limit = req.get_param_as_int("limit", min=0, max=100) or 100
+        page = req.get_param_as_int("page", min=0) or 0
+        offset = limit * page
+
+        cursor = db.cursor()
+
+        # get total number of items so we can estimate the pages
+        cursor.execute('SELECT COUNT(id) FROM items')
+        pages = round(cursor.fetchone()[0] / limit)
+
+        # get statistics, ordered by id, and use limit and offset to page through results
+        cursor.execute('SELECT id, views, downloads FROM items ORDER BY id ASC LIMIT {} OFFSET {}'.format(limit, offset))
+
+        # create a list to hold dicts of item stats
+        statistics = list()
+
+        # iterate over results and build statistics object
+        for item in cursor:
+            statistics.append({ 'id': item['id'], 'views': item['views'], 'downloads': item['downloads'] })
+
+        cursor.close()
+
+        message = {
+                'currentPage': page,
+                'totalPages': pages,
+                'limit': limit,
+                'statistics': statistics
+        }
+
+        resp.media = message
+
+class ItemResource:
+    def on_get(self, req, resp, item_id):
+        """Handles GET requests"""
+
+        cursor = db.cursor()
+        cursor.execute('SELECT views, downloads FROM items WHERE id={}'.format(item_id))
+        if cursor.rowcount == 0:
+            raise falcon.HTTPNotFound(
+                    title='Item not found',
+                    description='The item with id "{}" was not found.'.format(item_id)
+            )
+        else:
+            results = cursor.fetchone()
+
+            statistics = {
+                'id': item_id,
+                'views': results['views'],
+                'downloads': results['downloads']
+            }
+
+            resp.media = statistics
+
+        cursor.close()
+
+def on_exit(api):
+    print("Shutting down DB")
+
+api = falcon.API()
+api.add_route('/items', AllItemsResource())
+api.add_route('/item/{item_id:int}', ItemResource())
+
+# vim: set sw=4 ts=4 expandtab: