Add minimal REPL host and tests

src/context_compiler/repl.py

@@ -0,0 +1,30 @@
+import json
+import sys
+from typing import TextIO
+
+from . import create_engine
+from .engine import Decision
+
+
+def format_decision(decision: Decision) -> str:
+    return json.dumps(decision, sort_keys=True, separators=(",", ":"))
+
+
+def run_repl(in_stream: TextIO, out_stream: TextIO) -> None:
+    engine = create_engine()
+
+    for line in in_stream:
+        user_input = line.rstrip("\n")
+        if user_input.strip().lower() in {"exit", "quit"}:
+            return
+        decision = engine.step(user_input)
+        print(format_decision(decision), file=out_stream)
+
+
+def main() -> int:
+    run_repl(sys.stdin, sys.stdout)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

tests/test_repl.py

@@ -0,0 +1,57 @@
+import json
+from io import StringIO
+
+from context_compiler.repl import run_repl
+
+
+def _run_session(text: str) -> list[dict[str, object]]:
+    out = StringIO()
+    run_repl(StringIO(text), out)
+    lines = [line for line in out.getvalue().splitlines() if line.strip()]
+    return [json.loads(line) for line in lines]
+
+
+def test_repl_update_flow() -> None:
+    decisions = _run_session("use Nord Stage 4\nquit\n")
+
+    assert len(decisions) == 1
+    assert decisions[0]["kind"] == "update"
+    assert decisions[0]["state"] == {
+        "facts": {"focus.device": "Nord Stage 4"},
+        "policies": {"prohibit": []},
+        "version": 1,
+    }
+
+
+def test_repl_clarify_flow() -> None:
+    decisions = _run_session("no use docker\nquit\n")
+
+    assert len(decisions) == 1
+    assert decisions[0]["kind"] == "clarify"
+    assert decisions[0]["state"] is None
+
+
+def test_repl_state_persists_across_turns() -> None:
+    decisions = _run_session("avoid docker\nallow docker\nquit\n")
+
+    assert len(decisions) == 2
+    assert decisions[0]["kind"] == "update"
+    assert decisions[0]["state"] == {
+        "facts": {"focus.device": None},
+        "policies": {"prohibit": ["docker"]},
+        "version": 1,
+    }
+    assert decisions[1]["kind"] == "update"
+    assert decisions[1]["state"] == {
+        "facts": {"focus.device": None},
+        "policies": {"prohibit": []},
+        "version": 1,
+    }
+
+
+def test_repl_exit_and_quit_terminate_session() -> None:
+    decisions_exit = _run_session("exit\nuse Nord Stage 4\n")
+    decisions_quit = _run_session("quit\nuse Nord Stage 4\n")
+
+    assert decisions_exit == []
+    assert decisions_quit == []