CASAN/packages/casan-harness/adapters/claude-code/claude_hook.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Claude Code adapter for the CASAN agentic bridge (Plan-20, Wave 1).

Thin renderer only: it translates Claude Code lifecycle hook JSON (on stdin) into
the client-agnostic bridge contract, calls the core bridge, and renders the bridge
response back into Claude-native hook output. The core bridge stays ignorant of
Claude's JSON shape (Plan-20 §4 "Hook response renderer tách theo adapter").

Wire-up in `.claude/settings.json` (see settings.template.json in this folder):

    UserPromptSubmit -> claude_hook.py --event UserPromptSubmit
    PreToolUse       -> claude_hook.py --event PreToolUse
    PostToolUse      -> claude_hook.py --event PostToolUse
    Stop             -> claude_hook.py --event Stop

The event may also be taken from the `hook_event_name` field Claude includes in
the payload, so `--event` is optional.

Claude hook contracts honored here:
  * UserPromptSubmit: `{"decision":"block","reason":...}` blocks the prompt;
    `hookSpecificOutput.additionalContext` injects extra context on allow.
  * PreToolUse: `hookSpecificOutput.permissionDecision` = allow|deny|ask.
  * PostToolUse / Stop: observational; Stop finalizes exactly once and guards
    against the stop-hook loop via `stop_hook_active`.
"""

from __future__ import annotations

import argparse
import hashlib
import json
import os
import sys

# Import the core bridge as a module so the adapter reuses its state layout,
# hashing and op handlers without duplicating path logic or shelling out.
_ADAPTER_DIR = os.path.dirname(os.path.abspath(__file__))
_BRIDGE_DIR = os.path.abspath(os.path.join(_ADAPTER_DIR, "..", "..", "scripts", "python"))
if _BRIDGE_DIR not in sys.path:
    sys.path.insert(0, _BRIDGE_DIR)

import agentic_bridge as bridge  # noqa: E402

ADAPTER_VERSION = "20.1.0-claude"


def integration_mode():
    return os.environ.get("CASAN_AGENTIC_INTEGRATION_MODE", "project_hook")


def _ptr_path(session):
    h = hashlib.sha256(("claude:" + (session or "nosession")).encode("utf-8")).hexdigest()[:24]
    return os.path.join(bridge.sessions_dir(), "ptr-%s.json" % h)


def store_pointer(session, admission_id, trace_id):
    bridge.atomic_write_json(_ptr_path(session), {
        "admission_id": admission_id, "trace_id": trace_id})


def load_pointer(session):
    path = _ptr_path(session)
    if not os.path.exists(path):
        return None
    try:
        with open(path, "r", encoding="utf-8") as fh:
            return json.load(fh)
    except (OSError, ValueError):
        return None


def clear_pointer(session):
    try:
        os.unlink(_ptr_path(session))
    except OSError:
        pass


def _emit(obj):
    sys.stdout.write(json.dumps(obj, ensure_ascii=False))
    sys.stdout.write("\n")


def handle_user_prompt_submit(payload):
    session = payload.get("session_id")
    resp = bridge.op_begin({
        "op": "begin",
        "client": "claude-code",
        "client_version": payload.get("client_version") or os.environ.get("CASAN_CLIENT_VERSION"),
        "adapter_version": ADAPTER_VERSION,
        "project": payload.get("cwd") or payload.get("project_dir"),
        "session": session,
        "turn": payload.get("prompt_id") or payload.get("turn_id"),
        "prompt": payload.get("prompt", ""),
        "integration_mode": integration_mode(),
    })
    if resp.get("admission_id") and resp.get("decision") != "block":
        store_pointer(session, resp["admission_id"], resp.get("trace_id"))

    if resp.get("decision") == "block":
        _emit({
            "decision": "block",
            "reason": "CASAN blocked this prompt: %s" % (resp.get("reason") or "policy"),
        })
        return 0

    ctx = "[CASAN] %s" % (resp.get("context") or "admission open")
    if resp.get("warnings"):
        ctx += " | " + "; ".join(resp["warnings"])
    _emit({
        "hookSpecificOutput": {
            "hookEventName": "UserPromptSubmit",
            "additionalContext": ctx,
        }
    })
    return 0


def handle_pre_tool_use(payload):
    session = payload.get("session_id")
    ptr = load_pointer(session)
    admission_id = ptr.get("admission_id") if ptr else None
    resp = bridge.op_pre_tool({
        "op": "pre-tool",
        "admission_id": admission_id or "",
        "tool": payload.get("tool_name", ""),
        "tool_input": payload.get("tool_input"),
        "project": payload.get("cwd"),
    })
    decision = "allow" if resp.get("decision") == "allow" else "deny"
    _emit({
        "hookSpecificOutput": {
            "hookEventName": "PreToolUse",
            "permissionDecision": decision,
            "permissionDecisionReason": "CASAN: %s" % (resp.get("reason") or decision),
        }
    })
    return 0


def handle_post_tool_use(payload):
    session = payload.get("session_id")
    ptr = load_pointer(session)
    if not ptr:
        _emit({"hookSpecificOutput": {"hookEventName": "PostToolUse"}})
        return 0
    resp = payload.get("tool_response") or {}
    status = "success"
    if isinstance(resp, dict):
        if resp.get("error") or resp.get("is_error") or resp.get("success") is False:
            status = "error"
    bridge.op_post_tool({
        "op": "post-tool",
        "admission_id": ptr.get("admission_id"),
        "tool": payload.get("tool_name", ""),
        "status": status,
        "duration_ms": payload.get("duration_ms"),
        "result": resp if isinstance(resp, (str, int, float)) else None,
    })
    _emit({"hookSpecificOutput": {"hookEventName": "PostToolUse"}})
    return 0


def handle_stop(payload):
    # Guard against the stop-hook loop: if a prior Stop hook is already active,
    # do nothing (bridge finalize is also idempotent as a second line of defense).
    if payload.get("stop_hook_active"):
        _emit({})
        return 0
    session = payload.get("session_id")
    ptr = load_pointer(session)
    if not ptr:
        _emit({})
        return 0
    resp = bridge.op_finalize({
        "op": "finalize",
        "admission_id": ptr.get("admission_id"),
        "stop_reason": "completed",
        "assistant_summary": payload.get("last_assistant_message") or payload.get("assistant_summary"),
    })
    clear_pointer(session)
    _emit({"systemMessage": bridge.format_receipt(resp)})
    return 0


HANDLERS = {
    "UserPromptSubmit": handle_user_prompt_submit,
    "PreToolUse": handle_pre_tool_use,
    "PostToolUse": handle_post_tool_use,
    "Stop": handle_stop,
    "SubagentStop": handle_stop,
}


def main(argv=None):
    parser = argparse.ArgumentParser(description="CASAN Claude Code hook adapter")
    parser.add_argument("--event", help="Claude hook event name (else read from payload)")
    args = parser.parse_args(argv)

    try:
        payload = json.loads(sys.stdin.read() or "{}")
    except ValueError:
        payload = {}

    event = args.event or payload.get("hook_event_name")
    handler = HANDLERS.get(event)
    if handler is None:
        # Unknown event: never block the client turn — emit a no-op.
        _emit({})
        return 0
    try:
        return handler(payload)
    except Exception as exc:  # noqa: BLE001
        # Fail safe for the client turn. For PreToolUse we default to deny so a
        # crash cannot silently allow a side effect; other events no-op.
        if event == "PreToolUse":
            _emit({"hookSpecificOutput": {
                "hookEventName": "PreToolUse",
                "permissionDecision": "deny",
                "permissionDecisionReason": "CASAN adapter error: %s" % exc,
            }})
        else:
            _emit({})
        return 0


if __name__ == "__main__":
    sys.exit(main())