"""
评估入口脚本

使用方式:
    # 在测试集上评估
    python scripts/evaluate.py --config configs/default_config.yaml --checkpoint checkpoints/best_model.pt

    # 指定解码策略
    python scripts/evaluate.py --checkpoint checkpoints/best_model.pt evaluation.decoding.strategy=beam_search evaluation.decoding.beam_size=10
"""

import argparse
import json
import sys
from pathlib import Path

try:
    from omegaconf import OmegaConf
except ImportError:  # pragma: no cover
    OmegaConf = None
    import yaml

sys.path.insert(0, str(Path(__file__).resolve().parent.parent / "src"))

import torch
from torch.utils.data import DataLoader

from easytranslate.data.collator import TranslationCollator
from easytranslate.data.dataset import (
    TranslationDataset,
    load_custom_dataset,
    load_opus_dataset,
    load_wmt_dataset,
)
from easytranslate.data.tokenizer import TokenizerWrapper, build_tokenizer
from easytranslate.evaluation.evaluator import Evaluator
from easytranslate.model import TransformerTranslationModel
from easytranslate.model.finetune import load_pretrained_model


def parse_args():
    parser = argparse.ArgumentParser(description="EasyTranslate Evaluation")
    parser.add_argument("--config", type=str, default="configs/default_config.yaml")
    parser.add_argument("--checkpoint", type=str, required=True, help="模型检查点路径")
    parser.add_argument("--output", type=str, default="outputs/evaluation_results.json", help="结果保存路径")
    args, unknown = parser.parse_known_args()
    return args, unknown


def _get_config(config, *keys, default=None):
    value = config
    for key in keys:
        if isinstance(value, dict):
            value = value.get(key, default)
        else:
            value = getattr(value, key, default)
        if value is default:
            break
    return value


def _load_config(path, cli_overrides=None):
    if OmegaConf is not None:
        config = OmegaConf.load(path)
        if cli_overrides:
            config = OmegaConf.merge(config, OmegaConf.from_cli(cli_overrides))
        return config

    with open(path, "r", encoding="utf-8") as fin:
        config = yaml.safe_load(fin)
    if cli_overrides:
        print("Warning: OmegaConf is not installed; CLI overrides are ignored.")
    return config


def load_test_split(config):
    dataset_name = _get_config(config, "data", "dataset_name")

    if dataset_name == "wmt":
        try:
            dataset = load_wmt_dataset(
                year=_get_config(config, "data", "wmt", "year"),
                language_pair=_get_config(config, "data", "wmt", "language_pair"),
                split="test",
            )
        except Exception:
            dataset = load_wmt_dataset(
                year=_get_config(config, "data", "wmt", "year"),
                language_pair=_get_config(config, "data", "wmt", "language_pair"),
                split="validation",
            )
        return list(dataset["src"]), list(dataset["tgt"])

    if dataset_name == "opus":
        try:
            dataset = load_opus_dataset(
                subset=_get_config(config, "data", "opus", "subset"),
                split="test",
            )
        except Exception:
            dataset = load_opus_dataset(
                subset=_get_config(config, "data", "opus", "subset"),
                split="validation",
            )
        return list(dataset["src"]), list(dataset["tgt"])

    if dataset_name == "custom":
        data = load_custom_dataset(
            train_src=_get_config(config, "data", "custom", "train_src"),
            train_tgt=_get_config(config, "data", "custom", "train_tgt"),
            val_src=_get_config(config, "data", "custom", "val_src"),
            val_tgt=_get_config(config, "data", "custom", "val_tgt"),
            test_src=_get_config(config, "data", "custom", "test_src"),
            test_tgt=_get_config(config, "data", "custom", "test_tgt"),
            preprocessing_config=_get_config(config, "data", "preprocessing"),
        )
        if "test" not in data:
            raise ValueError("Custom dataset missing test split")
        return data["test"]["src"], data["test"]["tgt"]

    raise ValueError(f"Unsupported dataset_name: {dataset_name}")


def _get_tokenizer_train_texts(config, allow_auto: bool = False) -> list[str] | None:
    dataset_name = _get_config(config, "data", "dataset_name")
    if dataset_name == "custom":
        custom = _get_config(config, "data", "custom") or {}
        data = load_custom_dataset(
            train_src=custom.get("train_src"),
            train_tgt=custom.get("train_tgt"),
            val_src=custom.get("val_src"),
            val_tgt=custom.get("val_tgt"),
            test_src=custom.get("test_src"),
            test_tgt=custom.get("test_tgt"),
            preprocessing_config=_get_config(config, "data", "preprocessing"),
        )
        return list(data["train"]["src"]) + list(data["train"]["tgt"])

    if not allow_auto:
        return None

    if dataset_name == "wmt":
        try:
            dataset = load_wmt_dataset(
                year=_get_config(config, "data", "wmt", "year"),
                language_pair=_get_config(config, "data", "wmt", "language_pair"),
                split="train",
            )
        except Exception:
            dataset = load_wmt_dataset(
                year=_get_config(config, "data", "wmt", "year"),
                language_pair=_get_config(config, "data", "wmt", "language_pair"),
                split="validation",
            )
        return list(dataset["src"]) + list(dataset["tgt"])

    if dataset_name == "opus":
        try:
            dataset = load_opus_dataset(
                subset=_get_config(config, "data", "opus", "subset"),
                split="train",
            )
        except Exception:
            dataset = load_opus_dataset(
                subset=_get_config(config, "data", "opus", "subset"),
                split="validation",
            )
        return list(dataset["src"]) + list(dataset["tgt"])

    return None


def build_model_and_tokenizer(config, device):
    model_type = _get_config(config, "model", "type")
    if model_type == "transformer_scratch":
        tokenizer_config = _get_config(config, "tokenizer") or {}
        tokenizer_path = tokenizer_config.get("path") or tokenizer_config.get("tokenizer_path")
        tokenizer_type = tokenizer_config.get("type", "bpe")
        auto_train = bool(tokenizer_config.get("auto_train", False))
        if tokenizer_type in {"bpe", "sentencepiece"} and not tokenizer_path:
            train_texts = _get_tokenizer_train_texts(config, allow_auto=auto_train)
            if train_texts is None:
                raise ValueError(
                    "BPE tokenizer requires tokenizer.path or a local custom dataset with train texts. "
                    "Automatic WMT/OPUS download is disabled by default. "
                    "Set tokenizer.auto_train=true to enable it, or provide tokenizer.path/pretrained tokenizer."
                )
            tokenizer = build_tokenizer(tokenizer_config, train_texts=train_texts)
        else:
            tokenizer = build_tokenizer(tokenizer_config)
        model = TransformerTranslationModel(
            src_vocab_size=tokenizer.vocab_size,
            tgt_vocab_size=tokenizer.vocab_size,
            d_model=_get_config(config, "model", "transformer", "d_model"),
            nhead=_get_config(config, "model", "transformer", "nhead"),
            num_encoder_layers=_get_config(config, "model", "transformer", "num_encoder_layers"),
            num_decoder_layers=_get_config(config, "model", "transformer", "num_decoder_layers"),
            dim_feedforward=_get_config(config, "model", "transformer", "dim_feedforward"),
            dropout=_get_config(config, "model", "transformer", "dropout"),
            activation=_get_config(config, "model", "transformer", "activation"),
            max_seq_len=_get_config(config, "model", "transformer", "max_seq_len"),
            use_flash_attention=_get_config(config, "model", "transformer", "use_flash_attention"),
            use_rotary_embedding=_get_config(config, "model", "transformer", "use_rotary_embedding"),
            pre_norm=_get_config(config, "model", "transformer", "pre_norm"),
            pad_id=tokenizer.pad_token_id,
        )
        return model.to(device), tokenizer

    model, hf_tokenizer = load_pretrained_model(
        config.model.pretrained.model_name,
        config.model.pretrained.src_lang,
        config.model.pretrained.tgt_lang,
        device=str(device),
    )
    tokenizer = TokenizerWrapper(
        hf_tokenizer,
        pad_token=getattr(hf_tokenizer, "pad_token", "<pad>"),
        unk_token=getattr(hf_tokenizer, "unk_token", "<unk>"),
        bos_token=getattr(hf_tokenizer, "bos_token", "<s>"),
        eos_token=getattr(hf_tokenizer, "eos_token", "</s>"),
    )
    return model, tokenizer


def load_checkpoint(model, checkpoint_path, device):
    checkpoint = torch.load(checkpoint_path, map_location=device)
    if isinstance(checkpoint, dict):
        if "model_state_dict" in checkpoint:
            model.load_state_dict(checkpoint["model_state_dict"])
        elif "state_dict" in checkpoint:
            model.load_state_dict(checkpoint["state_dict"])
        else:
            try:
                model.load_state_dict(checkpoint)
            except Exception as exc:
                raise ValueError("Checkpoint does not contain a valid model state dict") from exc
    else:
        raise ValueError("Unsupported checkpoint format")
    return model


def main():
    args, cli_overrides = parse_args()

    print("=" * 60)
    print("  EasyTranslate - Evaluation")
    print("=" * 60)

    config = _load_config(args.config, cli_overrides)
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    model, tokenizer = build_model_and_tokenizer(config, device)
    model = load_checkpoint(model, args.checkpoint, device)

    src_texts, tgt_texts = load_test_split(config)

    dataset = TranslationDataset(
        src_texts=src_texts,
        tgt_texts=tgt_texts,
        tokenizer=tokenizer,
        max_src_len=_get_config(config, "data", "preprocessing", "max_src_len"),
        max_tgt_len=_get_config(config, "data", "preprocessing", "max_tgt_len"),
    )
    collator = TranslationCollator(pad_token_id=tokenizer.pad_token_id)
    dataloader = DataLoader(
        dataset,
        batch_size=config.data.dataloader.batch_size,
        shuffle=False,
        num_workers=int(config.data.dataloader.num_workers),
        pin_memory=bool(config.data.dataloader.pin_memory),
        collate_fn=collator,
    )

    evaluator = Evaluator(model, tokenizer, config)
    results = evaluator.evaluate(dataloader, src_texts=src_texts, ref_texts=tgt_texts)

    output_path = Path(args.output)
    output_path.parent.mkdir(parents=True, exist_ok=True)
    with output_path.open("w", encoding="utf-8") as fout:
        json.dump(results, fout, ensure_ascii=False, indent=2)

    print(json.dumps(results, ensure_ascii=False, indent=2))


if __name__ == "__main__":
    main()