#!/usr/bin/env python3
"""UserPromptExpansion hook: run a skill TUI-side, without a model turn.

Custom slash commands in Claude Code are prompts -- typing `/x` expands skills/x/SKILL.md
and sends it to the model. For a command that is really just a local action (flip a
setting, print a state) that round trip is waste. This hook gives any skill a TUI-side
implementation: if `~/.claude/skills/<command_name>/local.py` exists, it is executed with
the command's arguments, its output is shown to you, and the expansion is blocked (exit 2),
so nothing reaches the model. Skills without a local.py expand as usual (exit 0).

Order matters: the hook fires AFTER the skill body has been expanded, so any `!` inline
commands in that SKILL.md have already run by the time this executes. A skill with a
local.py must therefore not also apply its action via `!` -- it would happen twice.

Input (stdin JSON): command_name, command_args (list), expanded_prompt, cwd, ...
Fails open: any error here means exit 0 and the normal expansion goes ahead.
"""
import json
import os
import subprocess
import sys


def main():
    try:
        data = json.load(sys.stdin)
        name = data.get("command_name") or ""
        args = data.get("command_args") or []
        if isinstance(args, str):
            args = args.split()
        if not name or "/" in name or name.startswith("."):
            return
        script = os.path.expanduser(f"~/.claude/skills/{name}/local.py")
        if not os.path.isfile(script):
            return
        r = subprocess.run(
            [sys.executable, script, *[str(a) for a in args]],
            capture_output=True, text=True, timeout=20, cwd=data.get("cwd") or None,
        )
    except Exception:
        return  # fail open: let the skill expand normally
    out = (r.stdout or "") + (r.stderr or "")
    sys.stderr.write(out.rstrip("\n") + f"\n[/{name}: handled TUI-side by skills/{name}/local.py, no model turn]\n")
    sys.exit(2)


if __name__ == "__main__":
    main()