refactor: Make internal constants and classes private

Rename module-internal constants and classes with _ prefix:
- compose.py: SINGLE_PART, PUBLISHED_TARGET_PARTS, HOST_PUBLISHED_PARTS, MIN_VOLUME_PARTS
- logs.py: DIGEST_HEX_LENGTH
- traefik.py: LIST_VALUE_KEYS, MIN_ROUTER_PARTS, MIN_SERVICE_LABEL_PARTS,
  TraefikServiceSource, TRAEFIK_CONFIG_HEADER

These items are only used within their respective modules and should
not be part of the public API.

src/compose_farm/compose.py

@@ -18,10 +18,10 @@ if TYPE_CHECKING:
     from .config import Config
 
 # Port parsing constants
-SINGLE_PART = 1
-PUBLISHED_TARGET_PARTS = 2
-HOST_PUBLISHED_PARTS = 3
-MIN_VOLUME_PARTS = 2
+_SINGLE_PART = 1
+_PUBLISHED_TARGET_PARTS = 2
+_HOST_PUBLISHED_PARTS = 3
+_MIN_VOLUME_PARTS = 2
 
 _VAR_PATTERN = re.compile(r"\$\{([A-Za-z_][A-Za-z0-9_]*)(?::-(.*?))?\}")
 
@@ -93,12 +93,16 @@ def _parse_ports(raw: Any, env: dict[str, str]) -> list[PortMapping]:  # noqa: P
             published: int | None = None
             target: int | None = None
 
-            if len(parts) == SINGLE_PART and parts[0].isdigit():
+            if len(parts) == _SINGLE_PART and parts[0].isdigit():
                 target = int(parts[0])
-            elif len(parts) == PUBLISHED_TARGET_PARTS and parts[0].isdigit() and parts[1].isdigit():
+            elif (
+                len(parts) == _PUBLISHED_TARGET_PARTS and parts[0].isdigit() and parts[1].isdigit()
+            ):
                 published = int(parts[0])
                 target = int(parts[1])
-            elif len(parts) == HOST_PUBLISHED_PARTS and parts[-2].isdigit() and parts[-1].isdigit():
+            elif (
+                len(parts) == _HOST_PUBLISHED_PARTS and parts[-2].isdigit() and parts[-1].isdigit()
+            ):
                 published = int(parts[-2])
                 target = int(parts[-1])
 
@@ -146,7 +150,7 @@ def _parse_volume_item(
     if isinstance(item, str):
         interpolated = _interpolate(item, env)
         parts = interpolated.split(":")
-        if len(parts) >= MIN_VOLUME_PARTS:
+        if len(parts) >= _MIN_VOLUME_PARTS:
             return _resolve_host_path(parts[0], compose_dir)
     elif isinstance(item, dict) and item.get("type") == "bind":
         source = item.get("source")

src/compose_farm/logs.py

@@ -20,7 +20,7 @@ if TYPE_CHECKING:
 
 
 DEFAULT_LOG_PATH = xdg_config_home() / "compose-farm" / "dockerfarm-log.toml"
-DIGEST_HEX_LENGTH = 64
+_DIGEST_HEX_LENGTH = 64
 
 
 @dataclass(frozen=True)
@@ -97,7 +97,7 @@ def _extract_image_fields(record: dict[str, Any]) -> tuple[str, str]:
         or ""
     )
 
-    if digest and not digest.startswith("sha256:") and len(digest) == DIGEST_HEX_LENGTH:
+    if digest and not digest.startswith("sha256:") and len(digest) == _DIGEST_HEX_LENGTH:
         digest = f"sha256:{digest}"
 
     return image, digest

src/compose_farm/traefik.py

@@ -26,7 +26,7 @@ if TYPE_CHECKING:
 
 
 @dataclass
-class TraefikServiceSource:
+class _TraefikServiceSource:
     """Source information to build an upstream for a Traefik service."""
 
     traefik_service: str
@@ -38,9 +38,9 @@ class TraefikServiceSource:
     scheme: str | None = None
 
 
-LIST_VALUE_KEYS = {"entrypoints", "middlewares"}
-MIN_ROUTER_PARTS = 3
-MIN_SERVICE_LABEL_PARTS = 6
+_LIST_VALUE_KEYS = {"entrypoints", "middlewares"}
+_MIN_ROUTER_PARTS = 3
+_MIN_SERVICE_LABEL_PARTS = 6
 
 
 def _parse_value(key: str, raw_value: str) -> Any:
@@ -51,7 +51,7 @@ def _parse_value(key: str, raw_value: str) -> Any:
     if value.isdigit():
         return int(value)
     last_segment = key.rsplit(".", 1)[-1]
-    if last_segment in LIST_VALUE_KEYS:
+    if last_segment in _LIST_VALUE_KEYS:
         parts = [v.strip() for v in value.split(",")] if "," in value else [value]
         return [part for part in parts if part]
     return value
@@ -102,7 +102,7 @@ def _insert(root: dict[str, Any], key_path: list[str], value: Any) -> None:  # n
             current = container_list[list_index]
 
 
-def _resolve_published_port(source: TraefikServiceSource) -> tuple[int | None, str | None]:
+def _resolve_published_port(source: _TraefikServiceSource) -> tuple[int | None, str | None]:
     """Resolve host-published port for a Traefik service.
 
     Returns (published_port, warning_message).
@@ -140,7 +140,7 @@ def _resolve_published_port(source: TraefikServiceSource) -> tuple[int | None, s
 
 def _finalize_http_services(
     dynamic: dict[str, Any],
-    sources: dict[str, TraefikServiceSource],
+    sources: dict[str, _TraefikServiceSource],
     warnings: list[str],
 ) -> None:
     for traefik_service, source in sources.items():
@@ -211,7 +211,7 @@ def _process_router_label(
     if not key_without_prefix.startswith("http.routers."):
         return
     router_parts = key_without_prefix.split(".")
-    if len(router_parts) < MIN_ROUTER_PARTS:
+    if len(router_parts) < _MIN_ROUTER_PARTS:
         return
     router_name = router_parts[2]
     router_remainder = router_parts[3:]
@@ -229,12 +229,12 @@ def _process_service_label(
     host_address: str,
     ports: list[PortMapping],
     service_names: set[str],
-    sources: dict[str, TraefikServiceSource],
+    sources: dict[str, _TraefikServiceSource],
 ) -> None:
     if not key_without_prefix.startswith("http.services."):
         return
     parts = key_without_prefix.split(".")
-    if len(parts) < MIN_SERVICE_LABEL_PARTS:
+    if len(parts) < _MIN_SERVICE_LABEL_PARTS:
         return
     traefik_service = parts[2]
     service_names.add(traefik_service)
@@ -242,7 +242,7 @@ def _process_service_label(
 
     source = sources.get(traefik_service)
     if source is None:
-        source = TraefikServiceSource(
+        source = _TraefikServiceSource(
             traefik_service=traefik_service,
             stack=stack,
             compose_service=compose_service,
@@ -267,7 +267,7 @@ def _process_service_labels(
     host_address: str,
     env: dict[str, str],
     dynamic: dict[str, Any],
-    sources: dict[str, TraefikServiceSource],
+    sources: dict[str, _TraefikServiceSource],
     warnings: list[str],
 ) -> None:
     labels = normalize_labels(definition.get("labels"), env)
@@ -328,7 +328,7 @@ def generate_traefik_config(
     """
     dynamic: dict[str, Any] = {}
     warnings: list[str] = []
-    sources: dict[str, TraefikServiceSource] = {}
+    sources: dict[str, _TraefikServiceSource] = {}
 
     # Determine Traefik's host from service assignment
     traefik_host = None
@@ -366,7 +366,7 @@ def generate_traefik_config(
     return dynamic, warnings
 
 
-TRAEFIK_CONFIG_HEADER = """\
+_TRAEFIK_CONFIG_HEADER = """\
 # Auto-generated by compose-farm
 # https://github.com/basnijholt/compose-farm
 #
@@ -382,4 +382,4 @@ TRAEFIK_CONFIG_HEADER = """\
 def render_traefik_config(dynamic: dict[str, Any]) -> str:
     """Render Traefik dynamic config as YAML with a header comment."""
     body = yaml.safe_dump(dynamic, sort_keys=False)
-    return TRAEFIK_CONFIG_HEADER + body
+    return _TRAEFIK_CONFIG_HEADER + body