"""LLM client for MindFlow reproduction.

Backbone-substitution: the paper does not state its backbone LLM; per the ICML
challenge's backend-substitution clause we use open models served via Hugging
Face Inference Providers (hosted inference). All calls go through a disk cache so
runs are cheap, reproducible and resumable.
"""
from __future__ import annotations
import os, json, time, hashlib, threading, re
from dataclasses import dataclass, field
from concurrent.futures import ThreadPoolExecutor, as_completed
from huggingface_hub import InferenceClient

CACHE_DIR = os.environ.get("MINDFLOW_CACHE", os.path.join(os.path.dirname(__file__), "..", "..", "llm_cache"))
os.makedirs(CACHE_DIR, exist_ok=True)

# Inference backend. Primary path: a self-hosted vLLM OpenAI-compatible endpoint on a
# Vast.ai GPU (HF Jobs AND HF Inference Providers both return 402 / no credit).
# Set MINDFLOW_LLM_BASE=http://<ip>:<port>/v1 to route all calls to the served model.
LLM_BASE = os.environ.get("MINDFLOW_LLM_BASE", "").strip() or None
SERVED_MODEL = os.environ.get("MINDFLOW_LLM_MODEL", "qwen")

# Logical model roster (used for cache separation + emulated judge panel). When
# LLM_BASE is set every logical name maps to the single SERVED_MODEL; a 3-judge
# panel is emulated by distinct seeds + order randomization + judge temperature>0.
GEN_MODEL = os.environ.get("MINDFLOW_GEN_MODEL", "Qwen/Qwen2.5-72B-Instruct")
JUDGE_MODELS = os.environ.get(
    "MINDFLOW_JUDGE_MODELS",
    "Qwen/Qwen2.5-72B-Instruct,meta-llama/Llama-3.3-70B-Instruct,Qwen/Qwen2.5-32B-Instruct",
).split(",")

_stats_lock = threading.Lock()
STATS = {"calls": 0, "cache_hits": 0, "prompt_tokens": 0, "completion_tokens": 0, "errors": 0}


def _key(model, messages, temperature, max_tokens, seed):
    h = hashlib.sha256(
        json.dumps([model, messages, temperature, max_tokens, seed], sort_keys=True).encode()
    ).hexdigest()
    return h


def _cache_path(k):
    return os.path.join(CACHE_DIR, k + ".json")


_clients = {}
_clients_lock = threading.Lock()


def _client(model):
    key = "__served__" if LLM_BASE else model
    with _clients_lock:
        if key not in _clients:
            if LLM_BASE:
                _clients[key] = InferenceClient(base_url=LLM_BASE, api_key="EMPTY", timeout=180)
            else:
                _clients[key] = InferenceClient(model=model, token=os.environ.get("HF_TOKEN") or None, timeout=180)
        return _clients[key]


def chat(messages, model=None, temperature=0.7, max_tokens=1200, seed=None, retries=4):
    """Single chat completion with disk cache + retry. Returns text."""
    model = model or GEN_MODEL
    # cache key keeps the *logical* model name (so emulated judges cache separately)
    k = _key(model, messages, temperature, max_tokens, seed)
    p = _cache_path(k)
    if os.path.exists(p):
        with _stats_lock:
            STATS["cache_hits"] += 1
        return json.load(open(p))["content"]
    api_model = SERVED_MODEL if LLM_BASE else model
    last = None
    for attempt in range(retries):
        try:
            cli = _client(model)
            kwargs = dict(model=api_model, messages=messages, temperature=temperature, max_tokens=max_tokens)
            if seed is not None:
                kwargs["seed"] = seed
            r = cli.chat_completion(**kwargs)
            content = r.choices[0].message.content or ""
            usage = getattr(r, "usage", None)
            with _stats_lock:
                STATS["calls"] += 1
                if usage:
                    STATS["prompt_tokens"] += getattr(usage, "prompt_tokens", 0) or 0
                    STATS["completion_tokens"] += getattr(usage, "completion_tokens", 0) or 0
            json.dump({"model": model, "content": content}, open(p, "w"))
            return content
        except Exception as e:  # noqa
            last = e
            with _stats_lock:
                STATS["errors"] += 1
            time.sleep(min(2 ** attempt, 20) + 0.5)
    raise RuntimeError(f"chat failed for {model}: {last}")


def chat_json(messages, model=None, temperature=0.5, max_tokens=1200, seed=None, retries=4):
    """Chat that must return JSON. Retries with a repair nudge; returns dict."""
    out = chat(messages, model=model, temperature=temperature, max_tokens=max_tokens, seed=seed, retries=retries)
    obj = extract_json(out)
    if obj is None:
        # one repair attempt (non-cached temp bump)
        rep = messages + [
            {"role": "assistant", "content": out[:500]},
            {"role": "user", "content": "Your reply was not valid JSON. Reply with ONLY the JSON object, no prose, no code fences."},
        ]
        out = chat(rep, model=model, temperature=0.2, max_tokens=max_tokens, seed=(seed or 0) + 1)
        obj = extract_json(out)
    return obj if obj is not None else {}


def extract_json(text):
    if not text:
        return None
    text = text.strip()
    # strip code fences
    m = re.search(r"```(?:json)?\s*(.*?)```", text, re.DOTALL)
    if m:
        text = m.group(1).strip()
    # find first balanced { ... }
    start = text.find("{")
    if start == -1:
        return None
    depth = 0
    for i in range(start, len(text)):
        c = text[i]
        if c == "{":
            depth += 1
        elif c == "}":
            depth -= 1
            if depth == 0:
                cand = text[start : i + 1]
                try:
                    return json.loads(cand)
                except Exception:
                    try:
                        return json.loads(cand.replace("\n", " "))
                    except Exception:
                        return None
    return None


def parallel_map(fn, items, workers=8):
    """Run fn over items concurrently, preserving order."""
    results = [None] * len(items)
    with ThreadPoolExecutor(max_workers=workers) as ex:
        futs = {ex.submit(fn, it): i for i, it in enumerate(items)}
        for f in as_completed(futs):
            results[futs[f]] = f.result()
    return results


def reset_stats():
    with _stats_lock:
        for k in STATS:
            STATS[k] = 0


def get_stats():
    with _stats_lock:
        return dict(STATS)