import json
import multiprocessing as mp
import os
import signal
import time

import pytest
import torch
import torch.optim as optim
from torch.utils.data import Dataset

from astrai.config import TrainConfig
from astrai.config.model_config import AutoRegressiveLMConfig
from astrai.model.transformer import AutoRegressiveLM
from astrai.parallel.signal_handler import register_signal_handlers
from astrai.trainer import Trainer
from astrai.trainer.schedule import SchedulerFactory
from astrai.trainer.train_context import TrainContext


class _PicklableDataset(Dataset):
    def __init__(self, length=200, max_length=64, vocab_size=1000):
        self.length = length
        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,)),
        }


def _build_model():
    config = AutoRegressiveLMConfig(
        vocab_size=1000,
        hidden_size=8,
        num_attention_heads=2,
        num_key_value_heads=1,
        intermediate_size=16,
        max_position_embeddings=64,
        num_hidden_layers=2,
        rms_norm_eps=1e-5,
    )
    device = "cuda" if torch.cuda.is_available() else "cpu"
    return AutoRegressiveLM(config).to(device=device)


class _ReadyCallback:
    def __init__(self, ready_file):
        self._ready_file = ready_file

    def on_train_begin(self, context):
        with open(self._ready_file, "w") as f:
            f.write("ready")
            f.flush()
            os.fsync(f.fileno())


def _inner_run(batch_per_device, ckpt_interval, ckpt_dir, log_dir, ready_file):
    dataset = _PicklableDataset()

    def model_fn():
        return _build_model()

    def optimizer_fn(m):
        return optim.AdamW(m.parameters(), lr=0.001)

    def scheduler_fn(optim):
        return SchedulerFactory.create(
            "cosine", optim, warmup_steps=10, lr_decay_steps=10, min_rate=0.05
        )

    train_config = TrainConfig(
        strategy="seq",
        model_fn=model_fn,
        dataset=dataset,
        optimizer_fn=optimizer_fn,
        scheduler_fn=scheduler_fn,
        ckpt_dir=ckpt_dir,
        log_dir=log_dir,
        n_epoch=1,
        batch_per_device=batch_per_device,
        ckpt_interval=ckpt_interval,
        grad_accum_steps=1,
        random_seed=42,
        device_type="cuda" if torch.cuda.is_available() else "cpu",
    )

    trainer = Trainer(train_config)
    trainer.callbacks.insert(0, _ReadyCallback(ready_file))
    trainer.train()


def _spawn_train_and_signal(ckpt_dir, sig, timeout=120):
    log_dir = os.path.join(ckpt_dir, "logs")
    ready_file = os.path.join(ckpt_dir, "ready.txt")

    ctx = mp.get_context("spawn")
    p = ctx.Process(
        target=_inner_run,
        args=(2, 1000, ckpt_dir, log_dir, ready_file),
    )
    p.start()

    deadline = time.time() + 30
    while time.time() < deadline:
        if os.path.exists(ready_file):
            with open(ready_file) as f:
                if f.read().strip() == "ready":
                    break
        if not p.is_alive():
            break
        time.sleep(0.5)

    assert p.is_alive(), "Training process died before becoming ready"

    os.kill(p.pid, sig)
    p.join(timeout=timeout)

    if p.is_alive():
        p.kill()
        p.join(timeout=5)

    return p.exitcode


def test_context_stop_flag():
    ctx = TrainContext()
    assert not ctx.stop_requested
    ctx.request_stop()
    assert ctx.stop_requested


def test_register_signal_handlers():
    ctx = TrainContext()
    register_signal_handlers(ctx)
    assert not ctx.stop_requested
    os.kill(os.getpid(), signal.SIGTERM)
    assert ctx.stop_requested


def test_sigterm_triggers_checkpoint_save(base_test_env):
    exitcode = _spawn_train_and_signal(base_test_env["test_dir"], signal.SIGTERM)
    assert exitcode == 0, f"Training process exited with code {exitcode} (expected 0)"

    ckpt_dir = base_test_env["test_dir"]
    meta_files = []
    for root, dirs, files in os.walk(ckpt_dir):
        for f in files:
            if f == "meta.json":
                meta_files.append(os.path.join(root, f))

    assert len(meta_files) > 0, f"No checkpoint meta.json found in {ckpt_dir}"

    with open(meta_files[-1]) as f:
        meta = json.load(f)
    assert "consumed_samples" in meta
    assert meta["consumed_samples"] >= 0


@pytest.mark.slow
def test_sigint_triggers_checkpoint_save(base_test_env):
    exitcode = _spawn_train_and_signal(base_test_env["test_dir"], signal.SIGINT)
    assert exitcode == 0, f"Training process exited with code {exitcode} (expected 0)"

    ckpt_dir = base_test_env["test_dir"]
    meta_files = []
    for root, dirs, files in os.walk(ckpt_dir):
        for f in files:
            if f == "meta.json":
                meta_files.append(os.path.join(root, f))

    assert len(meta_files) > 0, f"No checkpoint meta.json found in {ckpt_dir}"