Add ability to run application from the command line.

pyproject.toml

@@ -30,3 +30,6 @@ classifiers = [
 
 [project.urls]
 "Homepage" = "https://github.com/MrCurtis/fk-graph"
+
+[project.scripts]
+fk-graph = "fk_graph.cli:main"

src/fk_graph/cli.py

@@ -0,0 +1,37 @@
+from argparse import ArgumentParser
+
+from sqlalchemy import create_engine
+
+from fk_graph import setup_data, get_graph
+from fk_graph.plotly_functions import run_app
+
+def main():
+    args = _parse_args()
+    if args.demo:
+        engine = create_engine("sqlite+pysqlite:///:memory:")
+        setup_data(engine)
+    elif args.connection_string:
+        engine = create_engine(args.connection_string)
+    graph = get_graph(engine, args.table, args.primary_key)
+    run_app(graph)
+
+def _parse_args():
+    parser = ArgumentParser(
+        prog="fk-graph",
+        description="Visualise the graphs hidden within relational databases.",
+
+    )
+    parser.add_argument("--demo", action="store_true", help="Run with the built-in demo database.")
+    parser.add_argument("--connection-string")
+    parser.add_argument("--table", required=True)
+    parser.add_argument("--primary-key", required=True)
+    args = parser.parse_args()
+    if (
+        (not args.demo and args.connection_string is None)
+        or
+        (args.demo and args.connection_string is not None)
+    ):
+        parser.error(
+            "Exactly one of --demo and --connection-string should be used."
+        )
+    return args

tests/test_cli.py

@@ -0,0 +1,66 @@
+from shlex import split as shlex_split
+from subprocess import Popen, run
+from time import sleep
+from unittest import TestCase
+
+from requests import get
+import requests
+from requests.adapters import HTTPAdapter
+from requests.packages.urllib3.util.retry import Retry
+
+import logging
+
+logging.basicConfig(level=logging.DEBUG)
+
+s = requests.Session()
+retries = Retry(total=5, backoff_factor=1, status_forcelist=[502, 503, 504])
+s.mount('http://', HTTPAdapter(max_retries=retries))
+s.mount('https://', HTTPAdapter(max_retries=retries))
+
+class TestCLI(TestCase):
+    def test_simple_case(self):
+        command = "fk-graph --demo --table=table_a --primary-key=1"
+        with Popen(shlex_split(command)) as process:
+            response = s.get("http://localhost:8050")
+            process.terminate()
+            # Because of the javascripty-nature of the app, we can
+            # only really inspect the status code.
+            self.assertEqual(response.status_code, 200)
+
+    def test_errors_if_both_demo_and_connection_string_included(self):
+        command = (
+            "fk-graph"
+            " --demo"
+            " --connection-string=\"sqlite+pysqlite:///:memory:\""
+            " --table=table_a"
+            " --primary-key=1"
+        )
+        completed_process = run(
+            shlex_split(command),
+            capture_output=True,
+            text=True,
+            timeout=5
+        )
+        self.assertEqual(completed_process.returncode, 2)
+        self.assertIn(
+            "Exactly one of --demo and --connection-string should be used.",
+            completed_process.stderr
+        )
+
+    def test_errors_if_neither_demo_or_connection_string_included(self):
+        command = (
+            "fk-graph"
+            " --table=table_a"
+            " --primary-key=1"
+        )
+        completed_process = run(
+            shlex_split(command),
+            capture_output=True,
+            text=True,
+            timeout=5
+        )
+        self.assertEqual(completed_process.returncode, 2)
+        self.assertIn(
+            "Exactly one of --demo and --connection-string should be used.",
+            completed_process.stderr
+        )