Rewrite the kodi-scan script in Python.

The Transmission daemon image uses Alpine linux as the base which uses
busybox. realpath supports different switches in Busybox. Instead of
testing things on Alpine and Busybox, rewrite it in Python (sort of
modern Perl replacement).

.pre-commit-config.yaml

@@ -52,3 +52,48 @@ repos:
     hooks:
       - id: hadolint
       - id: docker-compose
+
+  - repo: https://github.com/ambv/black
+    rev: 20.8b1
+    hooks:
+      - id: black
+        args:
+          - |
+              --line-length=79
+
+  - repo: https://github.com/PyCQA/prospector
+    rev: 1.3.1
+    hooks:
+      - id: prospector
+        args:
+          - |-
+            --max-line-length=79
+          - |-
+            --with-tool=pyroma
+          - |-
+            --with-tool=bandit
+          - |-
+            --without-tool=pep257
+          - |-
+            --doc-warnings
+          - |-
+            --test-warnings
+          - |-
+            --full-pep8
+          - |-
+            --strictness=high
+          - |-
+            --no-autodetect
+        additional_dependencies:
+          - bandit
+          - pyroma
+
+  - repo: https://gitlab.com/pycqa/flake8.git
+    rev: 3.9.1
+    hooks:
+      - id: flake8
+        args:
+          - |-
+            --doctests
+        additional_dependencies:
+          - flake8-bugbear

daemon/Dockerfile

@@ -4,13 +4,13 @@ RUN apk add --update --no-cache --repository http://dl-cdn.alpinelinux.org/alpin
         gosu \
     && \
     apk add --update --no-cache \
-        curl \
+        python3 \
         transmission-daemon \
     && \
     mkdir -m 777 /run/transmission
 COPY --chown=root:root entrypoint /usr/local/sbin/docker-entrypoint
 COPY --chown=root:root settings.json /etc/transmission/
-COPY --chown=root:root kodi-scan /usr/local/bin/
+COPY --chown=root:root kodi_scan /usr/local/bin/
 VOLUME /var/lib/transmission
 WORKDIR /var/lib/transmission
 ENV HOME /var/lib/transmission

daemon/kodi-scan

-#!/bin/sh
-set -eu
-
-scan() {
-    case "${1:-}" in
-        audio) curl \
-                --data-binary \
-                '{ "jsonrpc": "2.0", "method": "AudioLibrary.Scan", "id": "transmission"}' \
-                -H 'content-type: application/json;' \
-                http://172.18.0.1:8080/jsonrpc ;;
-        video) curl \
-                --data-binary \
-                '{ "jsonrpc": "2.0", "method": "VideoLibrary.Scan", "id": "transmission"}' \
-                -H 'content-type: application/json;' \
-                http://172.18.0.1:8080/jsonrpc ;;
-        *) scan video; scan audio ;;
-    esac
-}
-
-starts_with() {
-    [ "${1##$2}" != "$1" ]
-}
-
-is_in_dir() {
-    ! starts_with "$(realpath --relative-base "$1" "$2")" '/'
-}
-
-if [ -z "${TR_TORRENT_DIR:-}" ]
-then
-    scan
-elif is_in_dir '/var/lib/transmission/Downloads/TV Shows' "$TR_TORRENT_DIR"
-then
-    scan video
-elif is_in_dir '/var/lib/transmission/Downloads/Movies' "$TR_TORRENT_DIR"
-then
-    scan video
-elif is_in_dir '/var/lib/transmission/Downloads/Music' "$TR_TORRENT_DIR"
-then
-    scan audio
-else
-    scan
-fi

daemon/kodi_scan

+#!/usr/bin/env python3
+"""Trigger a Kodi library update on torrent completion.
+See:
+https://github.com/transmission/transmission/wiki/Scripts#On_Torrent_Completion
+"""
+
+import json
+import pathlib
+import os
+import sys
+import urllib
+
+
+def scan(library=None):
+    """Trigger a Kodi library scan, either just audio, video or both."""
+    kodi_json_rpc_url = "http://172.18.0.1:8080/jsonrpc"
+    headers = {"content-type": "application/json"}
+    base_request_data = {"jsonrpc": "2.0", "id": "transmission"}
+    audio_request_data = base_request_data.copy()
+    audio_request_data["method"] = "AudioLibrary.Scan"
+    video_request_data = base_request_data.copy()
+    video_request_data["method"] = "VideoLibrary.Scan"
+
+    if library == "audio":
+        req = urllib.request.Request(
+            kodi_json_rpc_url,
+            headers=headers,
+            data=json.dumps(audio_request_data),
+        )
+        urllib.request.ulropen(req)
+    elif library == "video":
+        req = urllib.request.Request(
+            kodi_json_rpc_url,
+            headers=headers,
+            data=json.dumps(video_request_data),
+        )
+        urllib.request.ulropen(req)
+    else:
+        scan("video")
+        scan("audio")
+
+
+TR_DOWNLOADS_DIR = pathlib.Path("/var/lib/transmission/Downloads")
+TR_MOVIES_DIR = TR_DOWNLOADS_DIR / "Movies"
+TR_TV_SHOWS_DIR = TR_DOWNLOADS_DIR / "TV Shows"
+TR_MUSIC_DIR = TR_DOWNLOADS_DIR / "Music"
+TR_TORRENT_DIR = os.getenv("TR_TORRENT_DIR")
+
+if __name__ == "__main__":
+    if TR_TORRENT_DIR is None:
+        scan()
+        sys.exit()
+    TR_TORRENT_DIR = pathlib.Path(TR_TORRENT_DIR).resolve()
+    if (
+        TR_MOVIES_DIR in TR_TORRENT_DIR.parents
+        or TR_TV_SHOWS_DIR in TR_TORRENT_DIR.parents
+    ):
+        scan("video")
+    elif TR_MUSIC_DIR in TR_DOWNLOADS_DIR.parents:
+        scan("audio")
+    else:
+        scan()

daemon/settings.json

@@ -56,7 +56,7 @@
     "rpc-whitelist-enabled": false,
     "scrape-paused-torrents-enabled": true,
     "script-torrent-done-enabled": true,
-    "script-torrent-done-filename": "/usr/local/bin/kodi-scan",
+    "script-torrent-done-filename": "/usr/local/bin/kodi_scan",
     "seed-queue-enabled": false,
     "seed-queue-size": 10,
     "speed-limit-down": 100,