import json
import os
import shutil
import tempfile

import numpy as np
import pytest
import safetensors.torch as st
import torch
from tokenizers import pre_tokenizers
from torch.utils.data import Dataset

from astrai.config.model_config import ModelConfig
from astrai.model.transformer import Transformer
from astrai.tokenize import BpeTokenizer, BpeTrainer


class RandomDataset(Dataset):
    """Random dataset for testing purposes."""

    def __init__(self, length=None, max_length=64, vocab_size=1000):
        self.length = length or int(np.random.randint(100, 200))
        self.max_length = max_length
        self.vocab_size = vocab_size

    def __len__(self):
        return self.length

    def __getitem__(self, idx):
        return {
            "input_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
            "target_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
        }


class MultiTurnDataset(Dataset):
    """Multi-turn dataset with loss mask for SFT training tests."""

    def __init__(self, length=None, max_length=64, vocab_size=1000):
        self.length = length or int(np.random.randint(100, 200))
        self.max_length = max_length
        self.vocab_size = vocab_size

    def __len__(self):
        return self.length

    def __getitem__(self, idx):
        input_ids = torch.randint(0, self.vocab_size, (self.max_length,))
        target_ids = torch.randint(0, self.vocab_size, (self.max_length,))
        loss_mask = torch.randint(0, 1, (self.max_length,))

        return {
            "input_ids": input_ids,
            "target_ids": target_ids,
            "loss_mask": loss_mask,
        }


class EarlyStoppingDataset(Dataset):
    """Dataset that triggers early stopping after a specified number of iterations."""

    def __init__(self, length=10, stop_after=5):
        self.length = length
        self.stop_after = stop_after
        self.count = 0

    def __len__(self):
        return self.length

    def __getitem__(self, idx):
        self.count += 1
        if self.count == self.stop_after:
            raise RuntimeError("Simulated early stopping")

        return {
            "input_ids": torch.randint(0, 1000, (64,)),
            "target_ids": torch.randint(0, 1000, (64,)),
        }


@pytest.fixture
def base_test_env(request: pytest.FixtureRequest):
    """Create base test environment with randomly configured model and tokenizer"""
    func_name = request.function.__name__
    test_dir = tempfile.mkdtemp(prefix=f"{func_name}_")
    config_path = os.path.join(test_dir, "config.json")

    n_dim_choices = [8, 16, 32]
    n_head_choices = [2, 4]

    dim = int(np.random.choice(n_dim_choices))
    n_heads = int(np.random.choice(n_head_choices))
    n_kv_heads = n_heads // 2
    dim_ffn = dim * 2

    config = {
        "vocab_size": 1000,
        "dim": dim,
        "n_heads": n_heads,
        "n_kv_heads": n_kv_heads,
        "dim_ffn": dim_ffn,
        "max_len": 1024,
        "n_layers": 4,
        "norm_eps": 1e-5,
    }

    with open(config_path, "w") as f:
        json.dump(config, f)
    device = "cuda" if torch.cuda.is_available() else "cpu"
    transformer_config = ModelConfig().load(config_path)
    model = Transformer(transformer_config).to(device=device)
    tokenizer = BpeTokenizer()

    yield {
        "device": device,
        "test_dir": str(test_dir),
        "config_path": config_path,
        "transformer_config": transformer_config,
        "model": model,
        "tokenizer": tokenizer,
    }

    shutil.rmtree(test_dir)


@pytest.fixture
def random_dataset():
    dataset = RandomDataset()
    yield dataset


@pytest.fixture
def multi_turn_dataset():
    dataset = MultiTurnDataset()
    yield dataset


@pytest.fixture
def early_stopping_dataset():
    dataset = EarlyStoppingDataset()
    yield dataset


@pytest.fixture
def test_env(request: pytest.FixtureRequest):
    """Create a test environment with saved model and tokenizer files."""

    func_name = request.function.__name__
    test_dir = tempfile.mkdtemp(prefix=f"{func_name}_")
    config_path = os.path.join(test_dir, "config.json")
    tokenizer_path = os.path.join(test_dir, "tokenizer.json")
    model_path = os.path.join(test_dir, "model.safetensors")

    config = {
        "vocab_size": 1000,
        "dim": 128,
        "n_heads": 4,
        "n_kv_heads": 2,
        "dim_ffn": 256,
        "max_len": 64,
        "n_layers": 2,
        "norm_eps": 1e-5,
    }
    with open(config_path, "w") as f:
        json.dump(config, f)

    tokenizer = BpeTokenizer()
    trainer = BpeTrainer(tokenizer)
    sp_token_iter = iter(pre_tokenizers.ByteLevel.alphabet())
    trainer.train_from_iterator(sp_token_iter, config["vocab_size"], 1)
    tokenizer.save(tokenizer_path)

    transformer_config = ModelConfig().load(config_path)
    model = Transformer(transformer_config)
    st.save_file(model.state_dict(), model_path)

    yield {
        "test_dir": test_dir,
        "model": model,
        "tokenizer": tokenizer,
        "transformer_config": transformer_config,
    }

    shutil.rmtree(test_dir)