Add Avisynth video encoding workflow

tools/executables.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import os
+import sys
+from pathlib import Path
+from shutil import which
+
+from tools.console import prompt_input
+
+
+def require_executable(name: str) -> str:
+    executable = which(name)
+    if executable:
+        return executable
+    fallback = _windows_default_executable(name)
+    if fallback is not None:
+        print(f"\n{name} was not found on PATH; using {fallback}.")
+        return str(fallback)
+    if not sys.stdin.isatty():
+        raise RuntimeError(_missing_tool_message(name))
+
+    print(f"\n{name} was not found on PATH.")
+    while True:
+        answer = prompt_input(
+            f"Absolute path to {name} for this run (blank = cancel): "
+        ).strip().strip('"')
+        if not answer:
+            raise RuntimeError(_missing_tool_message(name))
+        path = Path(answer).expanduser()
+        if not path.is_absolute():
+            print("Please enter an absolute path.")
+        elif not path.is_file():
+            print(f"File not found: {path}")
+        else:
+            return str(path.resolve())
+
+
+def _missing_tool_message(name: str) -> str:
+    return (
+        f"{name} was not found on PATH. Install it and make sure the "
+        f"'{name}' command works before running this script."
+    )
+
+
+def _windows_default_executable(name: str) -> Path | None:
+    if os.name != "nt" or name.casefold().removesuffix(".exe") != "mkvmerge":
+        return None
+
+    path = Path(r"C:\Program Files\MKVToolNix\mkvmerge.exe")
+    return path.resolve() if path.is_file() else None