from __future__ import annotations

import csv
import json
import os
import re
from pathlib import Path

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

import hackable  # noqa: F401
from hackable.data_plugins import GSM8KProvider
from hackable.paths import resolve_storage_path, storage_layout
from hackable.reward_plugins import gsm8k_correctness_reward
from hackable.utils import resolve_repo_path

THINK_RE = re.compile(r"<think>(.*?)</think>", re.DOTALL)


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


def _cot_word_len(completion: str) -> int:
    match = THINK_RE.search(completion)
    text = match.group(1).strip() if match else ""
    return len(text.split()) if text else 0


def _model_dtype(cfg: dict):
    return torch.bfloat16 if bool(cfg.get("trainer", {}).get("bf16", True)) else torch.float16


def _get_cache_paths(base_cfg: dict) -> tuple[Path, Path]:
    layout = storage_layout(base_cfg.get("storage", {}).get("cache_dir", "cache"))
    return layout.datasets, layout.models


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 _resolve_sweep_root(base_cfg: dict, requested_sweep_root: Path) -> Path:
    candidate = resolve_storage_path(
        requested_sweep_root,
        base_cfg.get("storage", {}).get("cache_dir", "cache"),
    )
    if candidate.is_dir() and any(path.is_dir() and path.name.startswith("run_") for path in candidate.iterdir()):
        return candidate
    raise FileNotFoundError(
        "Could not resolve SWEEP_ROOT with run directories: "
        f"{candidate}"
    )


def _discover_model_dirs(sweep_root: Path) -> list[Path]:
    dirs = [
        path
        for path in sweep_root.iterdir()
        if path.is_dir() and path.name.startswith("run_")
    ]
    if not dirs:
        raise FileNotFoundError(
            f"No run directories starting with 'run_' found in {sweep_root}"
        )
    return sorted(dirs)


@torch.no_grad()
def evaluate_one_model(
    model_dir: Path,
    base_cfg: dict,
    eval_max_samples: int,
    batch_size: int,
) -> list[dict]:
    rank, world_size, local_rank = _dist_info()
    generation = base_cfg.get("generation", {})
    max_prompt_len = int(generation.get("max_prompt_length", 512))
    max_completion_len = int(generation.get("max_completion_length", 256))
    model_name_fallback = str(base_cfg["model"]["name"])
    trust_remote_code = bool(base_cfg.get("model", {}).get("trust_remote_code", False))
    dtype = _model_dtype(base_cfg)
    datasets_cache, models_cache = _get_cache_paths(base_cfg)

    provider = GSM8KProvider()
    all_samples = provider.load(
        split="test",
        max_samples=None if eval_max_samples < 0 else eval_max_samples,
        cache_dir=str(datasets_cache),
    )
    indices = list(range(rank, len(all_samples), world_size))
    local_samples = [all_samples[idx] for idx in indices]
    prompts = [sample.prompt for sample in local_samples]
    refs = [sample.target for sample in local_samples]
    metadata = [sample.metadata for sample in local_samples]

    try:
        tokenizer = AutoTokenizer.from_pretrained(
            str(model_dir),
            trust_remote_code=trust_remote_code,
            cache_dir=str(models_cache),
            local_files_only=True,
        )
    except Exception:
        tokenizer = AutoTokenizer.from_pretrained(
            model_name_fallback,
            trust_remote_code=trust_remote_code,
            cache_dir=str(models_cache),
            local_files_only=True,
        )

    model = AutoModelForCausalLM.from_pretrained(
        str(model_dir),
        trust_remote_code=trust_remote_code,
        cache_dir=str(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()

    if tokenizer.pad_token_id is None:
        tokenizer.pad_token = tokenizer.eos_token

    completions: list[str] = []
    for start in range(0, len(prompts), batch_size):
        batch_prompts = prompts[start : start + batch_size]
        enc = tokenizer(
            batch_prompts,
            return_tensors="pt",
            padding=True,
            truncation=True,
            max_length=max_prompt_len,
        )
        input_ids = enc["input_ids"].to(device)
        attn = enc["attention_mask"].to(device)
        out = model.generate(
            input_ids=input_ids,
            attention_mask=attn,
            max_new_tokens=max_completion_len,
            do_sample=False,
            pad_token_id=tokenizer.pad_token_id,
            eos_token_id=tokenizer.eos_token_id,
        )
        prompt_lens = attn.sum(dim=1).tolist()
        for idx in range(out.size(0)):
            completion_ids = out[idx, int(prompt_lens[idx]) :]
            completions.append(tokenizer.decode(completion_ids, skip_special_tokens=True))

    scores = gsm8k_correctness_reward(
        prompts=prompts,
        completions=completions,
        references=refs,
        metadata=metadata,
    )

    local_records: list[dict] = []
    for i, (prompt, reference, completion, score) in enumerate(
        zip(prompts, refs, completions, scores, strict=True)
    ):
        local_records.append(
            {
                "sample_index": int(indices[i]),
                "prompt": prompt,
                "reference": reference,
                "completion": completion,
                "correctness": float(score),
                "cot_words": int(_cot_word_len(completion)),
            }
        )

    del model
    if torch.cuda.is_available():
        torch.cuda.empty_cache()

    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

    merged.sort(key=lambda row: row["sample_index"])
    return merged


def _summarize(records: list[dict], model_dir: str) -> dict:
    if not records:
        return {
            "name": Path(model_dir).name,
            "model_dir": model_dir,
            "num_examples": 0,
            "accuracy": 0.0,
            "avg_cot_words": 0.0,
        }
    accuracy = sum(float(row["correctness"]) for row in records) / len(records)
    avg_cot = sum(float(row["cot_words"]) for row in records) / len(records)
    return {
        "name": Path(model_dir).name,
        "model_dir": model_dir,
        "num_examples": len(records),
        "accuracy": float(accuracy),
        "avg_cot_words": float(avg_cot),
    }


def _write_accuracy_svg(summaries: list[dict], path: Path) -> None:
    width = 1000
    height = 460
    left_margin = 70
    right_margin = 30
    top_margin = 70
    bottom_margin = 90
    plot_w = width - left_margin - right_margin
    plot_h = height - top_margin - bottom_margin
    y_base = top_margin + plot_h

    runs = [row["name"] for row in summaries]
    acc_vals = [float(row["accuracy"]) for row in summaries]
    vmax = max(1.0, max(acc_vals) if acc_vals else 1.0)

    bar_count = max(1, len(runs))
    slot_w = plot_w / bar_count
    bar_w = min(120, max(30, int(slot_w * 0.55)))
    palette = ["#2563eb", "#dc2626", "#16a34a", "#ca8a04", "#7c3aed", "#0891b2"]

    parts: list[str] = []
    parts.append(f'<svg xmlns="http://www.w3.org/2000/svg" width="{width}" height="{height}">')
    parts.append('<rect width="100%" height="100%" fill="#ffffff"/>')
    parts.append(
        '<text x="40" y="34" font-size="20" font-family="sans-serif">Sweep Evaluation: GSM8K Accuracy</text>'
    )
    parts.append(
        f'<line x1="{left_margin}" y1="{y_base}" x2="{left_margin + plot_w}" y2="{y_base}" stroke="#111" stroke-width="2" />'
    )
    parts.append(
        f'<line x1="{left_margin}" y1="{top_margin}" x2="{left_margin}" y2="{y_base}" stroke="#111" stroke-width="2" />'
    )

    # y-axis ticks
    for tick in [0.0, 0.25, 0.5, 0.75, 1.0]:
        y = y_base - int((tick / vmax) * plot_h) if vmax > 0 else y_base
        parts.append(
            f'<line x1="{left_margin - 6}" y1="{y}" x2="{left_margin}" y2="{y}" stroke="#111" stroke-width="1" />'
        )
        parts.append(
            f'<text x="{left_margin - 10}" y="{y + 4}" text-anchor="end" font-size="11" font-family="sans-serif">{tick:.2f}</text>'
        )

    for idx, (run_name, acc) in enumerate(zip(runs, acc_vals, strict=True)):
        center_x = left_margin + int((idx + 0.5) * slot_w)
        bar_h = int((acc / vmax) * plot_h) if vmax > 0 else 0
        x = center_x - bar_w // 2
        y = y_base - bar_h
        color = palette[idx % len(palette)]
        parts.append(f'<rect x="{x}" y="{y}" width="{bar_w}" height="{bar_h}" fill="{color}" />')
        parts.append(
            f'<text x="{center_x}" y="{y - 8}" text-anchor="middle" font-size="12" font-family="sans-serif">{acc:.3f}</text>'
        )
        parts.append(
            f'<text x="{center_x}" y="{y_base + 18}" text-anchor="middle" font-size="11" font-family="sans-serif">{run_name}</text>'
        )

    parts.append("</svg>")
    path.write_text("\n".join(parts), encoding="utf-8")


def main() -> None:
    rank, _, _ = _init_distributed()
    base_cfg = _load_yaml(str(resolve_repo_path(os.environ["BASE_CONFIG"])))
    requested_sweep_root = Path(os.environ["SWEEP_ROOT"])
    sweep_root = _resolve_sweep_root(base_cfg, requested_sweep_root)
    if "OUT_ROOT" in os.environ:
        out_root = resolve_repo_path(os.environ["OUT_ROOT"])
    else:
        out_root = (sweep_root / "eval_results").resolve()
    eval_max_samples = int(os.environ.get("EVAL_MAX_SAMPLES", "200"))
    eval_batch_size = int(os.environ.get("EVAL_BATCH_SIZE", "4"))

    model_dirs = _discover_model_dirs(sweep_root)
    resolved_model_dirs = [_resolve_local_model_dir(base_cfg, str(path)) for path in model_dirs]

    if rank == 0:
        out_root.mkdir(parents=True, exist_ok=True)
        (out_root / "outputs").mkdir(parents=True, exist_ok=True)

    if dist.is_initialized():
        dist.barrier()

    summaries: list[dict] = []
    for model_dir in resolved_model_dirs:
        records = evaluate_one_model(
            model_dir=model_dir,
            base_cfg=base_cfg,
            eval_max_samples=eval_max_samples,
            batch_size=eval_batch_size,
        )
        if rank == 0:
            output_jsonl = out_root / "outputs" / f"{model_dir.name}_outputs.jsonl"
            with output_jsonl.open("w", encoding="utf-8") as handle:
                for row in records:
                    handle.write(json.dumps(row, ensure_ascii=True) + "\n")
            summary = _summarize(records, str(model_dir))
            summary["outputs_jsonl"] = str(output_jsonl)
            summaries.append(summary)

        if dist.is_initialized():
            dist.barrier()

    if rank != 0:
        return

    json_path = out_root / "sweep_eval_summary.json"
    csv_path = out_root / "sweep_eval_summary.csv"
    svg_path = out_root / "sweep_eval_accuracy.svg"
    json_path.write_text(json.dumps(summaries, indent=2), encoding="utf-8")
    with csv_path.open("w", encoding="utf-8", newline="") as handle:
        writer = csv.DictWriter(
            handle,
            fieldnames=[
                "name",
                "model_dir",
                "num_examples",
                "accuracy",
                "avg_cot_words",
                "outputs_jsonl",
            ],
        )
        writer.writeheader()
        for row in summaries:
            writer.writerow(row)
    _write_accuracy_svg(summaries, svg_path)

    print(f"Saved summary: {json_path}")
    print(f"Saved summary: {csv_path}")
    print(f"Saved plot: {svg_path}")
    print(f"Saved outputs dir: {out_root / 'outputs'}")


if __name__ == "__main__":
    main()