"""Logic for the `blender` domain. Transport-agnostic (D-263).

Everything the bash wrapper decided is decided here, and every decision is a
pure function: which Blender install to use, which payload a name refers to,
which arguments are paths that need absolutising. Only `run_payload` performs.

That matters more than usual for this domain, because the thing being launched
is a 200 MB GUI application that opens files and writes GLBs. "Run it and see"
is not a test.
"""

from __future__ import annotations

import shutil
from dataclasses import dataclass
from pathlib import Path

from tooling.core import config, console, process
from tooling.core.errors import ReachError, unknown_choice

PAYLOAD_DIR = ("tooling", "scripts", "blender")

# Flatpak is checked second: a native install is faster and has no sandbox, so
# it wins when both are present. This ordering is the bash wrapper's and is
# preserved deliberately.
FLATPAK_APP = "org.blender.Blender"


@dataclass(frozen=True)
class BlenderInvocation:
    """How Blender would be launched — decided without launching it."""

    argv_prefix: list[str]
    kind: str  # "native" | "flatpak"

    @property
    def sandboxed(self) -> bool:
        """Flatpak cannot see paths outside its sandbox unless they are absolute."""
        return self.kind == "flatpak"


def resolve_blender() -> BlenderInvocation:
    """Find Blender, preferring a native install over flatpak.

    Raises rather than falling through to a bare `blender` that is not there —
    the original printed its own error and exited 1, and losing that would turn
    a missing dependency into a confusing FileNotFoundError.
    """
    native = shutil.which("blender")
    if native:
        return BlenderInvocation([native], "native")

    if shutil.which("flatpak"):
        probe = process.run(["flatpak", "info", FLATPAK_APP], check=False)
        if probe.returncode == 0:
            return BlenderInvocation(["flatpak", "run", FLATPAK_APP], "flatpak")

    raise ReachError(
        "Blender is not installed (checked PATH and flatpak)",
        fix="install Blender natively, or run: flatpak install "
        f"{FLATPAK_APP} — reach prefers the native install when both exist",
    )


def payload_dir() -> Path:
    return config.path(*PAYLOAD_DIR)


def payloads() -> list[str]:
    """Every runnable payload, by the name `run` accepts."""
    return sorted(p.stem for p in payload_dir().glob("*.py") if p.name != "__init__.py")


def resolve_payload(name: str) -> Path:
    """Map a payload name — or a path to any script — to a file to run.

    Two forms, because the bash wrapper this replaces served both: our own 35
    registered payloads BY NAME, and any other script BY PATH (the spikes and
    the glb-gen skill hand it one-off scripts of their own). A registered name
    wins; anything that resolves to an existing file is accepted as a path.

    On a miss it enumerates, because a payload name is not guessable — the 35
    names are the only place that vocabulary is written down.
    """
    stem = name[:-3] if name.endswith(".py") else name
    registered = payload_dir() / f"{stem}.py"
    if registered.is_file():
        return registered

    given = Path(name)
    if given.is_file():
        return given.resolve()

    raise unknown_choice("payload", stem, payloads())


def absolutise(args: list[str]) -> list[str]:
    """Resolve any argument that names an existing path.

    The wrapper did this for every argument, not just `--python`, because
    flatpak's sandbox resolves relative paths against a different root and the
    failure is a file-not-found from inside Blender — far from the cause. An
    argument that is not an existing path is passed through untouched, so flags
    and values survive.
    """
    return [str(Path(a).resolve()) if Path(a).exists() else a for a in args]


def run_payload(name: str, args: list[str], background: bool = True) -> None:
    """Launch a payload under Blender. The performing half."""
    payload = resolve_payload(name)
    invocation = resolve_blender()

    argv = [*invocation.argv_prefix]
    if background:
        argv.append("--background")
    argv += ["--python", str(payload)]
    if args:
        argv += ["--", *absolutise(args)]

    console.event(
        f"running {name} under {invocation.kind} Blender",
        phase="blender",
    )
    # capture=False: Blender streams its own progress, and a payload that
    # takes minutes with no output reads as a hang.
    process.run(
        argv,
        cwd=config.repo_root(),
        capture=False,
        fix=f"run `reach blender run {name}` with --no-background to watch it in the GUI",
    )
    console.verdict(f"blender: {name} finished")