Implement recoding

karaokatalog/recode/recode.py

@@ -3,6 +3,36 @@ from pathlib import Path
 
 from karaokatalog.instructions.RecodeInstruction import RecodeInstruction
 
+ENCODINGS_TO_TRY = (
+    "utf-8",
+    "cp1252",
+)
+
+BOM = "\ufeff"  # Byte Order Mark, totally useless for UTF-8, still sometimes there
+
+
+def try_reading_file_with_encoding(path: Path, encoding: str) -> str:
+    with path.open("r", encoding=encoding) as f:
+        return f.read()
+
+
+def guess_encoding(path: Path) -> str:
+    for encoding_to_try in ENCODINGS_TO_TRY:
+        try:
+            content = try_reading_file_with_encoding(path, encoding_to_try)
+            if encoding_to_try == "utf-8" and content.startswith(BOM):
+                return "utf-8-sig"
+            else:
+                return encoding_to_try
+        except UnicodeDecodeError:
+            pass  # This was not the right encoding, let's try again
+
+    raise UnicodeError("Could not guess encoding.")
+
 
 def recode(paths: Sequence[Path]) -> Sequence[RecodeInstruction]:
-    raise NotImplementedError()
+    return [
+        RecodeInstruction(path, old_encoding=old_encoding, new_encoding="utf-8")
+        for path in paths
+        if (old_encoding := guess_encoding(path)) != "utf-8"
+    ]