feat: add configio module for comment-preserving YAML round-trip writes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_configio.py

@@ -0,0 +1,157 @@
+import glob
+import os
+import pytest
+from hbd.server import configio
+
+SAMPLE_YAML = """\
+# Server configuration
+hbd_port: 50004  # HTTP API port
+interval: 20
+users:
+  alice:
+    full_name: Alice Smith
+    admin: true
+notification_channels:
+  pushover_ops:
+    type: pushover
+    token: abc123
+"""
+
+
+def test_read_roundtrip_loads_values(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    assert data["hbd_port"] == 50004
+    assert data["interval"] == 20
+    assert data["users"]["alice"]["full_name"] == "Alice Smith"
+
+
+def test_write_config_creates_backup(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    data["interval"] = 30
+    configio.write_config(str(f), data)
+    backups = configio.list_backups(str(f))
+    assert len(backups) == 1
+    assert ".bak." in backups[0]
+
+
+def test_write_config_preserves_comments(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    data["interval"] = 30
+    configio.write_config(str(f), data)
+    content = f.read_text()
+    assert "# Server configuration" in content
+    assert "# HTTP API port" in content
+
+
+def test_write_config_atomically_replaces_file(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    data["interval"] = 99
+    configio.write_config(str(f), data)
+    assert not (tmp_path / ".hb.yaml.tmp").exists()
+    data2 = configio.read_roundtrip(str(f))
+    assert data2["interval"] == 99
+
+
+def test_write_config_backup_rotation(tmp_path):
+    cfg = tmp_path / ".hb.yaml"
+    cfg.write_text(SAMPLE_YAML)
+    # Pre-create 10 existing backups with old timestamps
+    for i in range(10):
+        (tmp_path / f".hb.yaml.bak.20260101-{i:06d}").write_text("old")
+    data = configio.read_roundtrip(str(cfg))
+    configio.write_config(str(cfg), data)
+    backups = configio.list_backups(str(cfg))
+    assert len(backups) == 10
+    assert not (tmp_path / ".hb.yaml.bak.20260101-000000").exists()
+
+
+def test_list_backups_newest_first(tmp_path):
+    cfg = tmp_path / ".hb.yaml"
+    cfg.write_text(SAMPLE_YAML)
+    for i in range(3):
+        (tmp_path / f".hb.yaml.bak.20260101-{i:02d}0000").write_text("b")
+    backups = configio.list_backups(str(cfg))
+    assert len(backups) == 3
+    assert backups == sorted(backups, reverse=True)
+
+
+def test_apply_structured_section_server_updates_keys(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    configio.apply_structured_section(data, "server", {"interval": 60, "hbd_port": 8080})
+    assert data["interval"] == 60
+    assert data["hbd_port"] == 8080
+
+
+def test_apply_structured_section_server_ignores_unknown_keys(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    configio.apply_structured_section(data, "server", {"interval": 60, "not_a_key": "x"})
+    assert "not_a_key" not in data
+
+
+def test_apply_structured_section_users_replaces_dict(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    new_users = {"bob": {"full_name": "Bob Jones", "admin": False}}
+    configio.apply_structured_section(data, "users", new_users)
+    assert "alice" not in data["users"]
+    assert data["users"]["bob"]["full_name"] == "Bob Jones"
+
+
+def test_apply_yaml_section_notification_channels(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    new_yaml = "email_ops:\n  type: email\n  recipients: [ops@example.com]\n"
+    configio.apply_yaml_section(data, "notification_channels", new_yaml)
+    assert "email_ops" in data["notification_channels"]
+    assert "pushover_ops" not in data["notification_channels"]
+
+
+def test_apply_yaml_section_thresholds_maps_to_threshold_configs(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    configio.apply_yaml_section(data, "thresholds", "default:\n  cpu: 80\n")
+    assert "threshold_configs" in data
+    assert data["threshold_configs"]["default"]["cpu"] == 80
+
+
+def test_apply_yaml_section_dns_replaces_each_key(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    configio.apply_yaml_section(
+        data, "dns",
+        "nsupdate_bin: /usr/bin/nsupdate\ndyndomains: [dyn.example.com]\n"
+    )
+    assert data["nsupdate_bin"] == "/usr/bin/nsupdate"
+    assert data["dyndomains"] == ["dyn.example.com"]
+
+
+def test_apply_yaml_section_unknown_raises(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    with pytest.raises(ValueError, match="Unknown YAML section"):
+        configio.apply_yaml_section(data, "nope", "x: 1\n")
+
+
+def test_apply_structured_section_unknown_raises(tmp_path):
+    f = tmp_path / ".hb.yaml"
+    f.write_text(SAMPLE_YAML)
+    data = configio.read_roundtrip(str(f))
+    with pytest.raises(ValueError, match="Unknown structured section"):
+        configio.apply_structured_section(data, "nope", {"x": 1})