"""
Claude CLI session manager for Echo-Core.

Wraps the Claude Code CLI to provide conversation management.
Each Discord channel maps to at most one active Claude session,
tracked in sessions/active.json.
"""

import json
import logging
import os
import shutil
import subprocess
import tempfile
from datetime import datetime, timezone
from pathlib import Path

logger = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Constants & configuration
# ---------------------------------------------------------------------------

PROJECT_ROOT = Path(__file__).resolve().parent.parent
PERSONALITY_DIR = PROJECT_ROOT / "personality"
SESSIONS_DIR = PROJECT_ROOT / "sessions"
_SESSIONS_FILE = SESSIONS_DIR / "active.json"

VALID_MODELS = {"haiku", "sonnet", "opus"}
DEFAULT_MODEL = "sonnet"
DEFAULT_TIMEOUT = 120  # seconds

CLAUDE_BIN = os.environ.get("CLAUDE_BIN", "claude")

PERSONALITY_FILES = [
    "IDENTITY.md",
    "SOUL.md",
    "USER.md",
    "AGENTS.md",
    "TOOLS.md",
    "HEARTBEAT.md",
]

# Environment variables allowed through to the Claude subprocess
_ENV_PASSTHROUGH = {
    "PATH", "HOME", "USER", "LANG", "LC_ALL", "TERM",
    "SHELL", "TMPDIR", "XDG_CONFIG_HOME", "XDG_DATA_HOME",
    "CLAUDE_CONFIG_DIR",
}

# ---------------------------------------------------------------------------
# Module-level binary check
# ---------------------------------------------------------------------------

if not shutil.which(CLAUDE_BIN):
    logger.warning(
        "Claude CLI (%s) not found on PATH. "
        "Session functions will raise FileNotFoundError.",
        CLAUDE_BIN,
    )

# ---------------------------------------------------------------------------
# Internal helpers
# ---------------------------------------------------------------------------


def _safe_env() -> dict[str, str]:
    """Return a filtered copy of os.environ for subprocess calls."""
    return {k: v for k, v in os.environ.items() if k in _ENV_PASSTHROUGH}


def _load_sessions() -> dict:
    """Load sessions from active.json. Returns {} if missing or empty."""
    try:
        text = _SESSIONS_FILE.read_text(encoding="utf-8")
        if not text.strip():
            return {}
        return json.loads(text)
    except (FileNotFoundError, json.JSONDecodeError):
        return {}


def _save_sessions(data: dict) -> None:
    """Atomically write sessions to active.json via tempfile + os.replace."""
    SESSIONS_DIR.mkdir(parents=True, exist_ok=True)
    fd, tmp_path = tempfile.mkstemp(
        dir=SESSIONS_DIR, prefix=".active_", suffix=".json"
    )
    try:
        with os.fdopen(fd, "w", encoding="utf-8") as f:
            json.dump(data, f, indent=2, ensure_ascii=False)
            f.write("\n")
        os.replace(tmp_path, _SESSIONS_FILE)
    except BaseException:
        # Clean up temp file on any failure
        try:
            os.unlink(tmp_path)
        except OSError:
            pass
        raise


def _run_claude(cmd: list[str], timeout: int) -> dict:
    """Run a Claude CLI command and return the parsed JSON output."""
    if not shutil.which(CLAUDE_BIN):
        raise FileNotFoundError(
            "Claude CLI not found. "
            "Install: https://docs.anthropic.com/en/docs/claude-code"
        )

    try:
        proc = subprocess.run(
            cmd,
            capture_output=True,
            text=True,
            timeout=timeout,
            env=_safe_env(),
            cwd=PROJECT_ROOT,
        )
    except subprocess.TimeoutExpired:
        raise TimeoutError(f"Claude CLI timed out after {timeout}s")

    if proc.returncode != 0:
        raise RuntimeError(
            f"Claude CLI error (exit {proc.returncode}): "
            f"{proc.stderr[:500]}"
        )

    try:
        data = json.loads(proc.stdout)
    except json.JSONDecodeError as exc:
        raise RuntimeError(f"Failed to parse Claude CLI output: {exc}")

    return data


# ---------------------------------------------------------------------------
# Public API
# ---------------------------------------------------------------------------


def build_system_prompt() -> str:
    """Concatenate personality/*.md files into a single system prompt."""
    if not PERSONALITY_DIR.is_dir():
        raise FileNotFoundError(
            f"Personality directory not found: {PERSONALITY_DIR}"
        )

    parts: list[str] = []
    for filename in PERSONALITY_FILES:
        filepath = PERSONALITY_DIR / filename
        if filepath.is_file():
            parts.append(filepath.read_text(encoding="utf-8"))

    return "\n\n---\n\n".join(parts)


def start_session(
    channel_id: str,
    message: str,
    model: str = DEFAULT_MODEL,
    timeout: int = DEFAULT_TIMEOUT,
) -> tuple[str, str]:
    """Start a new Claude CLI session for a channel.

    Returns (response_text, session_id).
    """
    if model not in VALID_MODELS:
        raise ValueError(
            f"Invalid model '{model}'. Must be one of: haiku, sonnet, opus"
        )

    system_prompt = build_system_prompt()

    cmd = [
        CLAUDE_BIN, "-p", message,
        "--model", model,
        "--output-format", "json",
        "--system-prompt", system_prompt,
    ]

    data = _run_claude(cmd, timeout)

    for field in ("result", "session_id"):
        if field not in data:
            raise RuntimeError(
                f"Claude CLI response missing required field: {field}"
            )

    response_text = data["result"]
    session_id = data["session_id"]

    # Save session metadata
    now = datetime.now(timezone.utc).isoformat()
    sessions = _load_sessions()
    sessions[channel_id] = {
        "session_id": session_id,
        "model": model,
        "created_at": now,
        "last_message_at": now,
        "message_count": 1,
    }
    _save_sessions(sessions)

    return response_text, session_id


def resume_session(
    session_id: str,
    message: str,
    timeout: int = DEFAULT_TIMEOUT,
) -> str:
    """Resume an existing Claude session by ID. Returns response text."""
    cmd = [
        CLAUDE_BIN, "-p", message,
        "--resume", session_id,
        "--output-format", "json",
    ]

    data = _run_claude(cmd, timeout)

    if "result" not in data:
        raise RuntimeError(
            "Claude CLI response missing required field: result"
        )

    response_text = data["result"]

    # Update session metadata
    now = datetime.now(timezone.utc).isoformat()
    sessions = _load_sessions()
    for channel_id, session in sessions.items():
        if session.get("session_id") == session_id:
            session["last_message_at"] = now
            session["message_count"] = session.get("message_count", 0) + 1
            break
    _save_sessions(sessions)

    return response_text


def send_message(
    channel_id: str,
    message: str,
    model: str = DEFAULT_MODEL,
    timeout: int = DEFAULT_TIMEOUT,
) -> str:
    """High-level convenience: auto start or resume based on channel state."""
    session = get_active_session(channel_id)
    if session is not None:
        return resume_session(session["session_id"], message, timeout)
    response_text, _session_id = start_session(
        channel_id, message, model, timeout
    )
    return response_text


def clear_session(channel_id: str) -> bool:
    """Remove a channel's session entry. Returns True if removed."""
    sessions = _load_sessions()
    if channel_id not in sessions:
        return False
    del sessions[channel_id]
    _save_sessions(sessions)
    return True


def get_active_session(channel_id: str) -> dict | None:
    """Return session metadata for a channel, or None."""
    sessions = _load_sessions()
    return sessions.get(channel_id)


def list_sessions() -> dict:
    """Return all channel→session mappings from active.json."""
    return _load_sessions()