"""File-based state persistence.

Claude Code hooks are ephemeral processes — state must be persisted to files.
Uses $CLAUDE_PLUGIN_DATA/state/ as the storage directory.
"""

import fcntl
import json
import os
import re


def _state_dir() -> str:
    """Get the state directory, creating it if needed."""
    plugin_data = os.environ.get("CLAUDE_PLUGIN_DATA", "")
    if not plugin_data:
        # Fallback to a temp location for testing
        plugin_data = os.path.join(os.path.expanduser("~"), ".claude", "plugins", "data", "hindsight-memory")
    state_dir = os.path.join(plugin_data, "state")
    os.makedirs(state_dir, exist_ok=True)
    return state_dir


def _safe_filename(name: str) -> str:
    """Sanitize a filename to prevent path traversal.

    Strips path separators, .., and control characters. Mirrors Openclaw's
    sanitizeFilename().
    """
    # Replace path separators and dangerous patterns
    name = re.sub(r'[\\/:*?"<>|\x00-\x1f]', "_", name)
    # Collapse .. to prevent traversal
    name = name.replace("..", "_")
    # Limit length
    name = name[:200]
    return name or "state"


def _state_file(name: str) -> str:
    """Get path for a state file. Name is sanitized to prevent traversal."""
    safe = _safe_filename(name)
    path = os.path.join(_state_dir(), safe)
    # Final guard: resolved path must be inside state_dir
    resolved = os.path.realpath(path)
    expected_dir = os.path.realpath(_state_dir())
    if not resolved.startswith(expected_dir + os.sep) and resolved != expected_dir:
        raise ValueError(f"State file path escapes state directory: {name!r}")
    return path


def read_state(name: str, default=None):
    """Read a JSON state file. Returns default if not found."""
    path = _state_file(name)
    if not os.path.exists(path):
        return default
    try:
        with open(path) as f:
            return json.load(f)
    except (json.JSONDecodeError, OSError):
        return default


def write_state(name: str, data):
    """Write data to a JSON state file atomically."""
    path = _state_file(name)
    tmp_path = path + ".tmp"
    try:
        with open(tmp_path, "w") as f:
            json.dump(data, f)
        os.replace(tmp_path, path)
    except OSError:
        # Best-effort cleanup
        try:
            os.unlink(tmp_path)
        except OSError:
            pass


def get_turn_count(session_id: str) -> int:
    """Get the current turn count for a session."""
    turns = read_state("turns.json", {})
    return turns.get(session_id, 0)


def increment_turn_count(session_id: str) -> int:
    """Increment and return the turn count for a session.

    Uses flock to prevent race conditions between concurrent hook processes
    (e.g. async Stop + new UserPromptSubmit).
    """
    lock_path = _state_file("turns.lock")
    try:
        lock_fd = open(lock_path, "w")
        fcntl.flock(lock_fd, fcntl.LOCK_EX)
        try:
            turns = read_state("turns.json", {})
            turns[session_id] = turns.get(session_id, 0) + 1
            # Cap tracked sessions to prevent unbounded growth
            if len(turns) > 10000:
                sorted_keys = sorted(turns.keys())
                for k in sorted_keys[: len(sorted_keys) // 2]:
                    del turns[k]
            write_state("turns.json", turns)
            return turns[session_id]
        finally:
            fcntl.flock(lock_fd, fcntl.LOCK_UN)
            lock_fd.close()
    except OSError:
        # Fallback: proceed without lock (better than failing)
        turns = read_state("turns.json", {})
        turns[session_id] = turns.get(session_id, 0) + 1
        write_state("turns.json", turns)
        return turns[session_id]