Added commands and metaflac file

mfbatch/metaflac.py

@@ -0,0 +1,69 @@
+# metaflac.py 
+# mfbatch
+
+from subprocess import run
+from re import match
+from io import StringIO
+
+from typing import Dict 
+
+METAFLAC_PATH = '/opt/homebrew/bin/metaflac'
+
+FlacMetadata = Dict[str, str]
+
+
+def sanatize_key(k: str) -> str:
+    """
+    Enforces the VORBIS_COMMENT spec with regard to keys
+    """
+    k = k.upper()
+    rval = ''
+    for c in k:
+        v = ord(c)
+        if 0x20 <= v <= 0x7D and v != 0x3D:
+            rval = rval + c
+        else:
+            rval = rval + '_'
+
+    return rval
+
+
+def sanatize_value(v: str) -> str: 
+    """
+    Enforces the VORBIS_COMMENT spec with regard to values. Also removes 
+    newlines, which are not supported by this tool.
+    """
+
+    return v.translate(str.maketrans('\n',' '))
+
+
+def read_metadata(path: str, metaflac_path=METAFLAC_PATH) -> FlacMetadata:
+    metaflac_command = [metaflac_path, '--list']
+    result = run(metaflac_command + [path], capture_output=True)
+    result.check_returncode()
+
+    file_metadata = {}
+    for line in result.stdout.decode('utf-8').splitlines():
+        m = match(r'^\s+comment\[\d\]: ([A-Za-z]+)=(.*)$', line)
+        if m is not None:
+            file_metadata[m[1]] = m[2]
+
+    return file_metadata
+
+
+def write_metadata(path: str, data: FlacMetadata, 
+                   metaflac_path=METAFLAC_PATH):
+    remove_job = run([metaflac_path, '--remove-all-tags', path])
+    remove_job.check_returncode()
+
+    metadatum_f = "" 
+
+    for k in data.keys():
+        key = sanatize_key(k)
+        val = sanatize_value(data[k])
+        metadatum_f  = metadatum_f + f"{key}={val}\n"
+
+    insert_job = run([metaflac_path, "--import-tags-from=-", path], 
+                     input=metadatum_f.encode('utf-8'))
+    insert_job.check_returncode()
+