"""Provider-agnostic LLM client.

Every chat call in the app goes through this module. The backend is picked by
app.llm.resolver (LLM_PROVIDER=auto: Ollama when reachable, otherwise the
first cloud API key found, otherwise a clear configure-me error) and the call
dispatches to either local Ollama (native API — keeps tag resolution and
keep_alive semantics) or any OpenAI-compatible cloud API. OpenAI, Anthropic,
Google Gemini, xAI (Grok) and DeepSeek all expose the OpenAI chat-completions
protocol, so a single HTTP implementation covers all of them; "custom" lets
the user point LLM_BASE_URL at anything else that speaks the same protocol
(OpenRouter, vLLM, llama.cpp server, ...).

Callers say what KIND of call they make via ``role`` ("chat", "classifier",
"vlm") instead of naming a model, so the right model is used whichever
backend is active; an explicit ``model`` argument still overrides.

Message format: callers build Ollama-style messages (optional base64 `images`
list on a message). The OpenAI path converts those to content arrays with
data: URIs, so call sites never care which provider is active.
"""

import json
from typing import AsyncIterator, Optional

import httpx

from app.api.errors import ModelUnavailable
from app.core.config import settings
from app.core.logging import get_logger
from app.llm import ollama_client, resolver
from app.llm.resolver import LLMTarget

logger = get_logger(__name__)

# Cloud inference can be slow on long prompts, but nowhere near local-26B slow.
_CLOUD_TIMEOUT = httpx.Timeout(connect=15.0, read=600.0, write=30.0, pool=10.0)


def _headers(target: LLMTarget) -> dict:
    # The resolver guarantees a key for known cloud providers; "custom"
    # endpoints (local vLLM, llama.cpp) may legitimately run keyless.
    headers = {"Content-Type": "application/json"}
    if target.api_key:
        headers["Authorization"] = f"Bearer {target.api_key}"
    return headers


def _b64_mime(b64: str) -> str:
    """Sniff the image type from base64 magic-byte prefixes."""
    if b64.startswith("iVBOR"):
        return "image/png"
    if b64.startswith("/9j/"):
        return "image/jpeg"
    if b64.startswith("R0lGOD"):
        return "image/gif"
    if b64.startswith("UklGR"):
        return "image/webp"
    return "image/png"


def _to_openai_messages(messages: list[dict]) -> list[dict]:
    """Convert Ollama-style messages (base64 `images` on the message) to the
    OpenAI content-array format with data: URIs."""
    out = []
    for m in messages:
        images = m.get("images")
        if not images:
            out.append({"role": m["role"], "content": m.get("content", "")})
            continue
        content: list[dict] = [{"type": "text", "text": m.get("content", "")}]
        for b64 in images:
            content.append({
                "type": "image_url",
                "image_url": {"url": f"data:{_b64_mime(b64)};base64,{b64}"},
            })
        out.append({"role": m["role"], "content": content})
    return out


def _is_reasoning_model(model: str) -> bool:
    """Heuristic: OpenAI reasoning model names start with 'o' + digit."""
    base = model.split("/")[-1]
    return len(base) >= 2 and base[0] == "o" and base[1].isdigit()


def _reasoning_effort_for(target: LLMTarget, resolved_model: str) -> Optional[str]:
    """Return a ``reasoning_effort`` value when cloud thinking mode is
    enabled and the resolved model looks like an OpenAI reasoning model."""
    if not settings.cloud_thinking_mode:
        return None
    if target.provider == "ollama":
        return None
    if not _is_reasoning_model(resolved_model):
        return None
    return "medium"


def _openai_payload(
    messages: list[dict],
    *,
    model: str,
    temperature: float,
    max_tokens: Optional[int],
    stream: bool,
    reasoning_effort: Optional[str] = None,
) -> dict:
    payload: dict = {
        "model": model,
        "messages": _to_openai_messages(messages),
        "temperature": temperature,
        "stream": stream,
    }
    if max_tokens:
        payload["max_tokens"] = max_tokens
    if reasoning_effort:
        payload["reasoning_effort"] = reasoning_effort
    return payload


# ─────────────────────────────────────────────────────────────────────────────
# Async chat (FastAPI request path)
# ─────────────────────────────────────────────────────────────────────────────

async def chat(
    messages: list[dict],
    *,
    model: Optional[str] = None,
    role: str = "chat",
    temperature: float = 0.7,
    num_predict: Optional[int] = None,
    keep_alive: Optional[str] = None,
) -> dict:
    """Provider-dispatched chat completion. Same return shape as
    ollama_client.chat: {content, model, prompt_tokens, completion_tokens}."""
    target = await resolver.resolve_llm()
    resolved = model or target.model_for_role(role)
    if target.provider == "ollama":
        return await ollama_client.chat(
            messages, model=resolved, temperature=temperature,
            num_predict=num_predict, keep_alive=keep_alive,
        )

    cap = num_predict if num_predict is not None else (settings.chat_num_predict or None)
    payload = _openai_payload(
        messages, model=resolved, temperature=temperature, max_tokens=cap, stream=False,
        reasoning_effort=_reasoning_effort_for(target, resolved),
    )
    url = f"{target.base_url}/chat/completions"
    async with httpx.AsyncClient(timeout=_CLOUD_TIMEOUT) as client:
        try:
            response = await client.post(url, json=payload, headers=_headers(target))
            response.raise_for_status()
        except httpx.HTTPStatusError as e:
            body = e.response.text[:500]
            logger.error(f"{target.provider} chat HTTP {e.response.status_code}: {body}")
            raise ModelUnavailable(f"{resolved} ({e.response.status_code}: {body})")
        except httpx.RequestError as e:
            raise ModelUnavailable(f"{resolved} (network error: {e})")
        data = response.json()

    choice = (data.get("choices") or [{}])[0]
    usage = data.get("usage") or {}
    return {
        "content": (choice.get("message") or {}).get("content") or "",
        "model": data.get("model") or resolved,
        "prompt_tokens": usage.get("prompt_tokens"),
        "completion_tokens": usage.get("completion_tokens"),
    }


async def stream_chat(
    messages: list[dict],
    *,
    model: Optional[str] = None,
    role: str = "chat",
    temperature: float = 0.7,
    num_predict: Optional[int] = None,
    keep_alive: Optional[str] = None,
) -> AsyncIterator[dict]:
    """Provider-dispatched streaming chat.

    Yields ``{"type": "token", "text": ...}`` per token, then a final
    ``{"type": "done", "content", "model", "prompt_tokens", "completion_tokens"}``.
    """
    target = await resolver.resolve_llm()
    resolved = model or target.model_for_role(role)
    if target.provider == "ollama":
        async for event in ollama_client.stream_chat(
            messages, model=resolved, temperature=temperature,
            num_predict=num_predict, keep_alive=keep_alive,
        ):
            yield event
        return

    cap = num_predict if num_predict is not None else (settings.chat_num_predict or None)
    payload = _openai_payload(
        messages, model=resolved, temperature=temperature, max_tokens=cap, stream=True,
        reasoning_effort=_reasoning_effort_for(target, resolved),
    )
    url = f"{target.base_url}/chat/completions"
    content_parts: list[str] = []
    final_model = resolved
    async with httpx.AsyncClient(timeout=_CLOUD_TIMEOUT) as client:
        try:
            async with client.stream("POST", url, json=payload, headers=_headers(target)) as response:
                if response.status_code >= 400:
                    body = (await response.aread()).decode("utf-8", "replace")[:500]
                    logger.error(f"{target.provider} stream HTTP {response.status_code}: {body}")
                    raise ModelUnavailable(f"{resolved} ({response.status_code}: {body})")
                async for line in response.aiter_lines():
                    line = line.strip()
                    if not line.startswith("data:"):
                        continue
                    data_str = line[5:].strip()
                    if data_str == "[DONE]":
                        break
                    try:
                        data = json.loads(data_str)
                    except ValueError:
                        continue
                    final_model = data.get("model") or final_model
                    delta = ((data.get("choices") or [{}])[0].get("delta")) or {}
                    token = delta.get("content") or ""
                    if token:
                        content_parts.append(token)
                        yield {"type": "token", "text": token}
        except httpx.RequestError as e:
            raise ModelUnavailable(f"{resolved} (network error: {e})")

    yield {
        "type": "done",
        "content": "".join(content_parts),
        "model": final_model,
        "prompt_tokens": None,
        "completion_tokens": None,
    }


async def is_available() -> bool:
    """Reachability check for the active provider (used by /health)."""
    try:
        target = await resolver.resolve_llm()
    except ModelUnavailable:
        return False
    if target.provider == "ollama":
        return await ollama_client.is_available()
    try:
        async with httpx.AsyncClient(timeout=10.0) as client:
            resp = await client.get(f"{target.base_url}/models", headers=_headers(target))
            return resp.status_code == 200
    except Exception:
        return False


# ─────────────────────────────────────────────────────────────────────────────
# Sync chat (Celery workers: summaries, figure descriptions)
# ─────────────────────────────────────────────────────────────────────────────

def chat_sync(
    messages: list[dict],
    *,
    model: Optional[str] = None,
    role: str = "chat",
    temperature: float = 0.3,
    images: Optional[list[str]] = None,
) -> dict:
    """Provider-dispatched synchronous chat for Celery workers."""
    target = resolver.resolve_llm_sync()
    resolved = model or target.model_for_role(role)
    if target.provider == "ollama":
        return ollama_client.chat_sync(
            messages, model=resolved, temperature=temperature, images=images,
        )

    final_messages = list(messages)
    if images and final_messages and final_messages[-1].get("role") == "user":
        final_messages[-1] = {**final_messages[-1], "images": images}

    payload = _openai_payload(
        final_messages, model=resolved, temperature=temperature, max_tokens=None, stream=False,
        reasoning_effort=_reasoning_effort_for(target, resolved),
    )
    url = f"{target.base_url}/chat/completions"
    with httpx.Client(timeout=300.0) as client:
        try:
            response = client.post(url, json=payload, headers=_headers(target))
            response.raise_for_status()
        except httpx.HTTPStatusError as e:
            body = e.response.text[:500]
            logger.error(f"[sync] {target.provider} chat HTTP {e.response.status_code}: {body}")
            raise ModelUnavailable(f"{resolved} ({e.response.status_code}: {body})")
        except httpx.RequestError as e:
            raise ModelUnavailable(f"{resolved} (network error: {e})")
        data = response.json()

    choice = (data.get("choices") or [{}])[0]
    usage = data.get("usage") or {}
    return {
        "content": (choice.get("message") or {}).get("content") or "",
        "model": data.get("model") or resolved,
        "prompt_tokens": usage.get("prompt_tokens"),
        "completion_tokens": usage.get("completion_tokens"),
    }