import asyncio
import logging
import os
import signal
import subprocess
from config import settings
import event_bus

logger = logging.getLogger(__name__)

# Track active Gemini process group IDs so we can kill them on shutdown
_active_pgroups: set[int] = set()


def _register_pgroup(pid: int) -> None:
    _active_pgroups.add(pid)


def _unregister_pgroup(pid: int) -> None:
    _active_pgroups.discard(pid)


async def cleanup() -> None:
    """Kill any lingering Gemini process groups. Call from lifespan shutdown."""
    for pid in list(_active_pgroups):
        try:
            os.killpg(pid, signal.SIGKILL)
            logger.info("Shutdown: killed Gemini process group %d", pid)
        except ProcessLookupError:
            pass
    _active_pgroups.clear()


# Map from registry model type → dispatch function key
_TYPE_TO_BACKEND = {
    "claude_cli":   "claude",
    "gemini_cli":   "gemini",
    "gemini_api":   "gemini",   # gemini_api falls back to CLI in this context
    "local_openai": "local",
}

# Explicit UI toggle values (kept for backward compat)
_EXPLICIT_BACKENDS = ("claude", "gemini", "local")
_FALLBACK = {"claude": "gemini", "gemini": "claude", "local": "claude"}


async def complete(
    system_prompt: str,
    messages: list[dict],
    model: str | None = None,
    role: str = "chat",
    max_tokens: int = 2048,
) -> tuple[str, str]:
    """
    Returns (response_text, actual_backend_used).

    model: explicit backend override ("claude" | "gemini" | "local") from UI toggle.
           None = resolve via model registry for the given role.
    role:  registry role used when model is None (default: "chat").
    """
    import model_registry as _reg
    from persona import _user

    username = _user.get()
    resolved_cfg: dict | None = None

    if model in _EXPLICIT_BACKENDS:
        # User explicitly selected a backend in the UI
        if model == "local":
            resolved_cfg = _reg.get_best_local_model(username, role)
            if not resolved_cfg:
                raise RuntimeError("No local model configured — add one at /settings/models")
        primary = model
    else:
        # Role-based routing via model registry
        resolved = _reg.get_model_for_role(username, role)
        if resolved:
            resolved_cfg = resolved
            primary = _TYPE_TO_BACKEND.get(resolved["type"], "claude")
        else:
            primary = settings.primary_backend

    fallback = _FALLBACK.get(primary, "claude")

    try:
        response = await _dispatch(primary, system_prompt, messages, resolved_cfg)
        return response, primary
    except Exception as e:
        err_str = str(e)
        logger.warning("%s failed (%s) — falling back to %s", primary, e, fallback)
        if primary == "claude" and any(k in err_str for k in ("401", "authenticate", "expired", "OAuth")):
            await event_bus.publish({"type": "claude_auth_expired"})
        response = await _dispatch(fallback, system_prompt, messages, None)
        return response, fallback


async def _dispatch(
    backend: str,
    system_prompt: str,
    messages: list[dict],
    model_cfg: dict | None,
) -> str:
    if backend == "gemini":
        return await _gemini(system_prompt, messages)
    if backend == "local":
        return await _local(system_prompt, messages, model_cfg)
    return await _claude(system_prompt, messages, model_cfg)


def _fresh_claude_token() -> str | None:
    """Read the current OAuth access token from the Claude credentials file.

    The token in the systemd .env goes stale (it rotates on each login).
    Reading directly from ~/.claude/.credentials.json always gets the latest.
    """
    import json as _json
    creds_path = os.path.expanduser("~/.claude/.credentials.json")
    try:
        with open(creds_path) as f:
            data = _json.load(f)
        return data["claudeAiOauth"]["accessToken"]
    except Exception as e:
        logger.debug("Could not read Claude credentials file: %s", e)
        return None


async def _claude(system_prompt: str, messages: list[dict], model_cfg: dict | None) -> str:
    model_name = (model_cfg or {}).get("model_name") if model_cfg else None
    cmd = [
        "claude", "--print",
        "--no-session-persistence",
        "--output-format", "text",
    ]
    # Only pass --model if it's a real model name (not a backend type string)
    if model_name and model_name not in ("claude", "gemini", "local", ""):
        cmd.extend(["--model", model_name])
    if system_prompt:
        cmd.extend(["--system-prompt", system_prompt])
    cmd.append(_build_conversation(messages))

    # Always use the freshest token from the credentials file so the systemd
    # service doesn't break when the env-var token rotates after a login.
    env = os.environ.copy()
    token = _fresh_claude_token()
    if token:
        env["CLAUDE_CODE_OAUTH_TOKEN"] = token
        env.pop("ANTHROPIC_API_KEY", None)  # never let a stale API key override OAuth

    return await _run(cmd, timeout=settings.timeout_claude, env=env)


async def _local(system_prompt: str, messages: list[dict], model_cfg: dict | None = None) -> str:
    """OpenAI-compatible backend — Open WebUI / Ollama.

    model_cfg is pre-resolved by complete() via model_registry.
    Falls back to registry lookup if not provided.
    """
    import httpx

    cfg = model_cfg
    if not cfg:
        # Fallback: resolve directly from registry
        import model_registry as _reg
        from persona import _user
        cfg = _reg.get_best_local_model(_user.get())
    if not cfg:
        raise RuntimeError("No local model configured — add one at /settings/models")

    api_url = cfg["api_url"]
    api_key = cfg["api_key"]
    model   = cfg["model_name"]

    if not api_url:
        raise RuntimeError("local_api_url not configured — set LOCAL_API_URL in .env or add a host at /settings/local")
    if not model:
        raise RuntimeError("local_model not configured — add a model at /settings/local")

    host_type = cfg.get("host_type", "openwebui")
    # "openwebui" uses Open WebUI/Ollama path layout; "openai" uses standard OpenAI layout
    chat_path = "/chat/completions" if host_type == "openai" else "/api/chat/completions"
    logger.info("local backend (%s): %s @ %s", host_type, model, api_url)

    msgs: list[dict] = []
    if system_prompt:
        msgs.append({"role": "system", "content": system_prompt})
    msgs.extend(messages)

    url = api_url.rstrip("/") + chat_path
    headers: dict[str, str] = {}
    if api_key:
        headers["Authorization"] = f"Bearer {api_key}"

    payload = {"model": model, "messages": msgs}

    async with httpx.AsyncClient(timeout=settings.timeout_local) as client:
        resp = await client.post(url, json=payload, headers=headers)
        resp.raise_for_status()
        data = resp.json()

    text = data["choices"][0]["message"]["content"]
    if not text or not text.strip():
        raise RuntimeError("Local model returned an empty response")
    return text.strip()


async def _gemini(system_prompt: str, messages: list[dict]) -> str:
    # Gemini CLI spawns MCP child processes that keep stdout pipes open after responding.
    # start_new_session=True puts the whole tree in its own process group so
    # os.killpg kills everything at once on timeout.
    cmd = [
        "gemini",
        "--output-format", "text",
        "--extensions", "",   # disable all extensions — prevents MCP child processes
        "-p", _build_prompt(system_prompt, messages),
    ]

    try:
        proc = await asyncio.create_subprocess_exec(
            *cmd,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.PIPE,
            start_new_session=True,
        )
    except FileNotFoundError:
        raise RuntimeError("gemini not found in PATH")

    _register_pgroup(proc.pid)
    timeout = settings.timeout_gemini
    try:
        stdout_bytes, _ = await asyncio.wait_for(proc.communicate(), timeout=timeout)
        raw = stdout_bytes.decode()
    except asyncio.TimeoutError:
        try:
            os.killpg(proc.pid, signal.SIGKILL)
        except ProcessLookupError:
            pass
        raise RuntimeError(f"Gemini timed out after {timeout}s")
    except asyncio.CancelledError:
        try:
            os.killpg(proc.pid, signal.SIGKILL)
        except ProcessLookupError:
            pass
        raise
    finally:
        _unregister_pgroup(proc.pid)

    clean = _clean_gemini_output(raw)
    if not clean:
        raise RuntimeError("Gemini returned an empty response")
    return clean


# Lines Gemini CLI writes to stdout that are not part of the actual response
_GEMINI_NOISE = (
    "Loaded cached credentials",
    "Loading extension:",
    "Server '",
    "Listening for",
    "Model is overloaded",
    "High demand",
    "Retrying",
    "retrying",
    "429",
    "quota",
)


def _clean_gemini_output(text: str) -> str:
    lines = [
        line for line in text.splitlines()
        if not any(line.strip().startswith(p) for p in _GEMINI_NOISE)
    ]
    return "\n".join(lines).strip()


async def _run(cmd: list[str], timeout: int = 60, env: dict | None = None) -> str:
    loop = asyncio.get_running_loop()
    result = await loop.run_in_executor(
        None,
        lambda: subprocess.run(cmd, capture_output=True, text=True, timeout=timeout, env=env),
    )
    if result.returncode != 0:
        detail = result.stderr.strip() or result.stdout.strip() or f"exit code {result.returncode}"
        raise RuntimeError(f"{cmd[0]} failed: {detail}")
    return result.stdout.strip()


def _build_conversation(messages: list[dict]) -> str:
    """Conversation only — used for Claude (system prompt passed separately)."""
    parts = []
    prior = messages[:-1]
    if prior:
        history_lines = []
        for msg in prior:
            label = settings.user_name if msg["role"] == "user" else settings.agent_name
            history_lines.append(f"{label}: {msg['content']}")
        parts.append("<conversation>\n" + "\n\n".join(history_lines) + "\n</conversation>")
    parts.append(messages[-1]["content"] if messages else "")
    return "\n\n".join(parts)


def _build_prompt(system_prompt: str, messages: list[dict]) -> str:
    """Full prompt with system context embedded — used for Gemini."""
    parts = []
    if system_prompt:
        parts.append(f"<system>\n{system_prompt}\n</system>")
    parts.append(_build_conversation(messages))
    return "\n\n".join(parts)