Add Avisynth video encoding workflow

tools/avisynth_runner.py

@@ -0,0 +1,110 @@
+from __future__ import annotations
+
+import os
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+
+
+@dataclass(frozen=True)
+class AvisynthRunnerSet:
+    default: Path
+    runner64: Path | None = None
+    runner32: Path | None = None
+
+    def for_script(self, script: Path) -> Path:
+        if sys.platform != "win32":
+            return self.default
+        if script_requests_32bit(script):
+            if self.runner32 is None:
+                raise RuntimeError(
+                    f"{script} requests 32-bit AviSynth with a trailing #32bit "
+                    "marker, but no 32-bit runner was found. Set "
+                    "MBT_AVS_RUNNER32 or provide tools/avisynth_runner/"
+                    "mbt_avs_runner32.exe."
+                )
+            return self.runner32
+        return self.default
+
+
+def bundled_runner_path(name: str | None = None) -> Path | None:
+    if name is None:
+        name = "mbt_avs_runner.exe" if sys.platform == "win32" else "mbt_avs_runner"
+    runner = _runner_dir() / name
+    return runner if runner.is_file() else None
+
+
+def runner_path_from_env_or_bundled() -> Path | None:
+    runners = runner_set_from_env_or_bundled()
+    return runners.default if runners is not None else None
+
+
+def runner_set_from_env_or_bundled() -> AvisynthRunnerSet | None:
+    if sys.platform == "win32":
+        return _windows_runner_set_from_env_or_bundled()
+
+    env_path = os.environ.get("MBT_AVS_RUNNER", "").strip()
+    if env_path:
+        runner = validate_runner_path(env_path)
+        return AvisynthRunnerSet(default=runner, runner64=runner)
+    bundled = bundled_runner_path()
+    if bundled is not None:
+        return AvisynthRunnerSet(default=bundled, runner64=bundled)
+    return None
+
+
+def _windows_runner_set_from_env_or_bundled() -> AvisynthRunnerSet | None:
+    runner64 = _optional_runner_from_env("MBT_AVS_RUNNER64")
+    if runner64 is None:
+        runner64 = _optional_runner_from_env("MBT_AVS_RUNNER")
+    if runner64 is None:
+        runner64 = bundled_runner_path("mbt_avs_runner.exe")
+
+    runner32 = _optional_runner_from_env("MBT_AVS_RUNNER32")
+    if runner32 is None:
+        runner32 = bundled_runner_path("mbt_avs_runner32.exe")
+
+    default = runner64 or runner32
+    if default is None:
+        return None
+    return AvisynthRunnerSet(default=default, runner64=runner64, runner32=runner32)
+
+
+def _optional_runner_from_env(name: str) -> Path | None:
+    raw = os.environ.get(name, "").strip()
+    if not raw:
+        return None
+    return validate_runner_path(raw)
+
+
+def validate_runner_path(raw_path: str) -> Path:
+    runner_path = Path(raw_path.strip().strip('"')).expanduser()
+    for candidate in _runner_candidates(runner_path):
+        if candidate.is_file():
+            return candidate.resolve()
+    raise RuntimeError(
+        f"Avisynth runner file not found: {runner_path}. "
+        "Use the full path, set MBT_AVS_RUNNER, or leave blank to use the "
+        "bundled runner when present."
+    )
+
+
+def _runner_candidates(path: Path) -> list[Path]:
+    candidates = [path]
+    if len(path.parts) == 1:
+        candidates.append(_runner_dir() / path.name)
+    return candidates
+
+
+def _runner_dir() -> Path:
+    return Path(__file__).resolve().parent / "avisynth_runner"
+
+
+def script_requests_32bit(script: Path) -> bool:
+    lines = script.read_text(encoding="utf-8").splitlines()
+    while lines and not lines[-1].strip():
+        lines.pop()
+    if not lines:
+        return False
+    normalized = "".join(lines[-1].split()).lower()
+    return normalized in {"#32bit", "#32-bit"}