from __future__ import annotations

import json
import os
from pathlib import Path

import torch
import torch.distributed as dist
import yaml
from datasets import load_dataset
from transformers import AutoModelForCausalLM, AutoTokenizer

import hackable  # noqa: F401
from hackable import reward_plugins as reward_plugins_mod
from hackable.utils import resolve_repo_path


THINKING_SYSTEM_PROMPT = (
    "Solve the following math problem.\n"
    "Think step-by-step inside <think>...</think> tags.\n"
    "Then output only the final answer in LaTeX boxed format.\n"
    "Do not include any words or explanations outside the tags/boxed answer.\n"
    "Output format must be exactly:\n"
    "<think>your reasoning</think>\n"
    "\\boxed{your_final_answer}\n"
)


def _load_yaml(path: str) -> dict:
    with open(path, "r", encoding="utf-8") as handle:
        return yaml.safe_load(handle)


def _dist_info() -> tuple[int, int, int]:
    rank = int(os.environ.get("RANK", "0"))
    world_size = int(os.environ.get("WORLD_SIZE", "1"))
    local_rank = int(os.environ.get("LOCAL_RANK", "0"))
    return rank, world_size, local_rank


def _init_distributed() -> tuple[int, int, int]:
    rank, world_size, local_rank = _dist_info()
    if world_size > 1 and not dist.is_initialized():
        backend = "nccl" if torch.cuda.is_available() else "gloo"
        dist.init_process_group(backend=backend, init_method="env://")
    return rank, world_size, local_rank


def _resolve_local_model_dir(base_cfg: dict, model_dir: str) -> Path:
    candidate = Path(model_dir)
    if candidate.is_absolute() and candidate.exists():
        return candidate.resolve()
    if not candidate.is_absolute() and candidate.exists():
        return candidate.resolve()

    repo_local = resolve_repo_path(model_dir)
    if repo_local.exists():
        return repo_local

    cache_root = resolve_repo_path(base_cfg.get("storage", {}).get("cache_dir", "cache"))
    prefixed = (cache_root / candidate).resolve()
    if prefixed.exists():
        return prefixed

    raise FileNotFoundError(
        f"Model directory not found locally: '{model_dir}'. "
        f"Tried '{candidate}', '{repo_local}', and '{prefixed}'."
    )


def _build_chat_prompts(
    tokenizer: AutoTokenizer, questions: list[str], system_prompt: str
) -> list[str]:
    if getattr(tokenizer, "chat_template", None) is None:
        raise RuntimeError("Tokenizer has no chat_template; cannot apply chat formatting.")

    prompts: list[str] = []
    for q in questions:
        messages = [
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": q.strip()},
        ]
        text = tokenizer.apply_chat_template(
            messages,
            tokenize=False,
            add_generation_prompt=True,
        )
        prompts.append(text)
    return prompts


def _load_math_level_rows(
    level: str,
    split: str,
    max_samples: int | None,
    cache_dir: str | None,
) -> tuple[list[str], list[str]]:
    dataset_name = "EleutherAI/hendrycks_math"
    dataset_configs = (
        "algebra",
        "counting_and_probability",
        "geometry",
        "intermediate_algebra",
        "number_theory",
        "prealgebra",
        "precalculus",
    )

    questions: list[str] = []
    references: list[str] = []

    for config_name in dataset_configs:
        rows = load_dataset(
            dataset_name,
            config_name,
            split=split,
            cache_dir=cache_dir,
        )
        for row in rows:
            row_level = str(row.get("level", "")).strip()
            if row_level != level:
                continue
            questions.append(str(row.get("problem", "")))
            references.append(str(row.get("solution", "")))
            if max_samples is not None and len(questions) >= max_samples:
                return questions[:max_samples], references[:max_samples]

    return questions, references


@torch.no_grad()
def main() -> None:
    rank, world_size, local_rank = _init_distributed()

    base_cfg = _load_yaml(str(resolve_repo_path(os.environ["BASE_CONFIG"])))
    model_dir = os.environ.get("MODEL_DIR") or os.environ.get("MODEL_PATH")
    if not model_dir:
        raise ValueError("Set MODEL_DIR or MODEL_PATH for the checkpoint to evaluate.")
    resolved_model_dir = _resolve_local_model_dir(base_cfg, model_dir)

    generation = base_cfg.get("generation", {})
    max_prompt_length = int(generation.get("max_prompt_length", 512))
    max_new_tokens = int(generation.get("max_completion_length", 256))
    max_prompt_length = int(os.environ.get("MAX_PROMPT_LENGTH", str(max_prompt_length)))
    max_new_tokens = int(os.environ.get("MAX_NEW_TOKENS", str(max_new_tokens)))

    split = os.environ.get("MATH_SPLIT", "test")
    max_samples_env = os.environ.get("MAX_SAMPLES", os.environ.get("EVAL_MAX_SAMPLES", "-1"))
    max_samples = None if int(max_samples_env) < 0 else int(max_samples_env)

    batch_size = int(os.environ.get("BATCH_SIZE", "4"))

    cache_root = resolve_repo_path(base_cfg.get("storage", {}).get("cache_dir", "cache"))
    datasets_cache = str(cache_root / "datasets")
    models_cache = str(cache_root / "models")

    tokenizer = AutoTokenizer.from_pretrained(
        str(resolved_model_dir),
        trust_remote_code=bool(base_cfg.get("model", {}).get("trust_remote_code", False)),
        cache_dir=models_cache,
        local_files_only=True,
    )
    if tokenizer.pad_token_id is None:
        tokenizer.pad_token = tokenizer.eos_token
    # Decoder-only safe.
    tokenizer.padding_side = "left"

    dtype = torch.bfloat16 if bool(base_cfg.get("trainer", {}).get("bf16", True)) else torch.float16
    model = AutoModelForCausalLM.from_pretrained(
        str(resolved_model_dir),
        trust_remote_code=bool(base_cfg.get("model", {}).get("trust_remote_code", False)),
        cache_dir=models_cache,
        torch_dtype=dtype,
        local_files_only=True,
    )
    if torch.cuda.is_available():
        torch.cuda.set_device(local_rank)
        device = torch.device(f"cuda:{local_rank}")
    else:
        device = torch.device("cpu")
    model.to(device)
    model.eval()

    questions, references = _load_math_level_rows(
        level="Level 1",
        split=split,
        max_samples=max_samples,
        cache_dir=datasets_cache,
    )

    indices = list(range(rank, len(questions), world_size))
    local_questions = [questions[i] for i in indices]
    local_refs = [references[i] for i in indices]

    chat_prompts = _build_chat_prompts(tokenizer, local_questions, THINKING_SYSTEM_PROMPT)
    completions: list[str] = []

    for start in range(0, len(chat_prompts), batch_size):
        batch_prompts = chat_prompts[start : start + batch_size]
        enc = tokenizer(
            batch_prompts,
            return_tensors="pt",
            padding=True,
            truncation=True,
            max_length=max_prompt_length,
        )
        input_ids = enc["input_ids"].to(device)
        attn = enc["attention_mask"].to(device)
        prompt_seq_len = input_ids.shape[1]

        out = model.generate(
            input_ids=input_ids,
            attention_mask=attn,
            max_new_tokens=max_new_tokens,
            do_sample=False,
            pad_token_id=tokenizer.pad_token_id,
            eos_token_id=tokenizer.eos_token_id,
        )
        for bi in range(out.size(0)):
            gen_ids = out[bi, prompt_seq_len:]
            completions.append(tokenizer.decode(gen_ids, skip_special_tokens=True))

    # Strict boxed correctness (project metric)
    strict_scores = []
    for completion, reference in zip(completions, local_refs, strict=True):
        pred_text = reward_plugins_mod._extract_predicted_answer_text(completion)
        ref_text = reward_plugins_mod._extract_reference_answer_text(reference)
        if not pred_text or not ref_text:
            strict_scores.append(0.0)
            continue
        pred_norm = reward_plugins_mod._normalize_answer_text(pred_text)
        ref_norm = reward_plugins_mod._normalize_answer_text(ref_text)
        if pred_norm and ref_norm and pred_norm == ref_norm:
            strict_scores.append(1.0)
            continue
        pred_value = reward_plugins_mod._parse_numeric(pred_text)
        ref_value = reward_plugins_mod._parse_numeric(ref_text)
        if pred_value is not None and ref_value is not None and reward_plugins_mod._is_close(pred_value, ref_value):
            strict_scores.append(1.0)
        else:
            strict_scores.append(0.0)

    # Lenient numeric correctness fallback
    lenient_scores: list[float] = []
    for completion, reference in zip(completions, local_refs, strict=True):
        ref_val = reward_plugins_mod._extract_reference_target(reference)
        boxed = reward_plugins_mod._extract_last_boxed(completion)
        if boxed:
            pred_val = reward_plugins_mod._parse_numeric(boxed)
            if pred_val is None:
                nums = reward_plugins_mod._extract_numbers(boxed)
                pred_val = nums[-1] if nums else None
        else:
            nums = reward_plugins_mod._extract_numbers(completion)
            pred_val = nums[-1] if nums else None

        if ref_val is not None and pred_val is not None and reward_plugins_mod._is_close(pred_val, ref_val):
            lenient_scores.append(1.0)
        else:
            lenient_scores.append(0.0)

    local_records: list[dict] = []
    for i, idx in enumerate(indices):
        local_records.append(
            {
                "sample_index": int(idx),
                "question": local_questions[i],
                "reference_answer": local_refs[i],
                "model_answer_raw": completions[i],
                "correctness": float(lenient_scores[i]),
                "correctness_strict_boxed": float(strict_scores[i]),
            }
        )

    if dist.is_initialized():
        gathered: list[list[dict] | None] = [None for _ in range(world_size)]
        dist.all_gather_object(gathered, local_records)
        merged: list[dict] = []
        for part in gathered:
            if part:
                merged.extend(part)
    else:
        merged = local_records

    if rank != 0:
        return

    merged.sort(key=lambda r: r["sample_index"])
    output_path = resolve_repo_path(
        os.environ.get(
            "OUTPUT_PATH",
            "artifacts/eval/math_level1_thinking_zeroshot/answers.jsonl",
        )
    )
    output_path.parent.mkdir(parents=True, exist_ok=True)
    with output_path.open("w", encoding="utf-8") as handle:
        for row in merged:
            handle.write(json.dumps(row, ensure_ascii=True) + "\n")

    acc = sum(r["correctness"] for r in merged) / len(merged) if merged else 0.0
    acc_strict = (
        sum(r["correctness_strict_boxed"] for r in merged) / len(merged)
        if merged
        else 0.0
    )
    print(f"Wrote {len(merged)} rows to {output_path}")
    print(f"Accuracy (lenient numeric): {acc:.4f}")
    print(f"Accuracy (strict boxed): {acc_strict:.4f}")


if __name__ == "__main__":
    main()