"""
IRIS Production Training Script.
Usage: python -m iris.train_production --config iris-small --num_steps 5000
"""

import argparse, json, os, time, math
import torch
import torch.nn.functional as F
from torch.utils.data import DataLoader
from .model import IRIS
from .configs import get_model_config, CONFIGS
from .flow_matching import flow_matching_loss
from .train import SyntheticLatentDataset, CosineWarmupScheduler


def parse_args():
    p = argparse.ArgumentParser(description="Train IRIS")
    p.add_argument("--config", type=str, default="iris-small", choices=list(CONFIGS.keys()))
    p.add_argument("--num_steps", type=int, default=5000)
    p.add_argument("--batch_size", type=int, default=32)
    p.add_argument("--lr", type=float, default=2e-4)
    p.add_argument("--weight_decay", type=float, default=0.01)
    p.add_argument("--warmup_steps", type=int, default=500)
    p.add_argument("--grad_clip", type=float, default=1.0)
    p.add_argument("--num_iterations", type=int, default=4)
    p.add_argument("--num_workers", type=int, default=4)
    p.add_argument("--log_every", type=int, default=50)
    p.add_argument("--save_every", type=int, default=1000)
    p.add_argument("--output_dir", type=str, default="./iris_output")
    p.add_argument("--num_samples", type=int, default=50000)
    p.add_argument("--seed", type=int, default=42)
    p.add_argument("--resume", type=str, default=None)
    return p.parse_args()


def main():
    args = parse_args()
    torch.manual_seed(args.seed)
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
    use_amp = device.type == "cuda"
    # T4 (compute cap 7.5) reports bf16 supported but cuDNN conv kernels crash.
    # Force fp16 on GPUs below Ampere (compute cap < 8.0).
    if use_amp:
        cc = torch.cuda.get_device_capability(0)
        amp_dtype = torch.float16 if cc[0] < 8 else torch.bfloat16
    else:
        amp_dtype = torch.float32

    print(f"IRIS Training - {args.config} | Device: {device}, AMP: {amp_dtype}")
    model_cfg = get_model_config(args.config)
    model = IRIS(gradient_checkpointing=True, **model_cfg).to(device)
    counts = model.count_params()
    print(f"Model: {counts['total']:,} params ({counts['total']/1e6:.1f}M)")

    dataset = SyntheticLatentDataset(num_samples=args.num_samples, latent_channels=model_cfg["latent_channels"], latent_size=16, text_dim=model_cfg["dim"], text_length=32, seed=args.seed)
    loader = DataLoader(dataset, batch_size=args.batch_size, shuffle=True, num_workers=args.num_workers, pin_memory=(device.type=="cuda"), drop_last=True, persistent_workers=(args.num_workers>0))

    optimizer = torch.optim.AdamW(model.parameters(), lr=args.lr, weight_decay=args.weight_decay, betas=(0.9, 0.999))
    scheduler = CosineWarmupScheduler(optimizer, args.warmup_steps, args.num_steps)
    scaler = torch.amp.GradScaler(enabled=(use_amp and amp_dtype == torch.float16))

    start_step = 0
    loss_history = []
    if args.resume:
        ckpt = torch.load(args.resume, map_location=device, weights_only=False)
        model.load_state_dict(ckpt["model_state_dict"])
        optimizer.load_state_dict(ckpt["optimizer_state_dict"])
        start_step = ckpt["step"]
        loss_history = ckpt.get("loss_history", [])
        for _ in range(start_step): scheduler.step()

    os.makedirs(args.output_dir, exist_ok=True)
    with open(os.path.join(args.output_dir, "config.json"), "w") as f:
        json.dump({"model_config": args.config, "model_params": model_cfg, "training": vars(args)}, f, indent=2)

    model.train()
    step, epoch, running_loss, best_loss = start_step, 0, 0.0, float("inf")
    start_time = time.time()

    while step < args.num_steps:
        epoch += 1
        for batch in loader:
            if step >= args.num_steps: break
            latent = batch["latent"].to(device, non_blocking=True)
            text_embed = batch["text_embed"].to(device, non_blocking=True)

            with torch.amp.autocast(device_type=device.type, dtype=amp_dtype, enabled=use_amp):
                losses = flow_matching_loss(model, latent, text_embed, num_iterations=args.num_iterations, timestep_sampling="logit_normal")
                loss = losses["loss"]

            optimizer.zero_grad(set_to_none=True)
            if scaler.is_enabled():
                scaler.scale(loss).backward()
                scaler.unscale_(optimizer)
                grad_norm = torch.nn.utils.clip_grad_norm_(model.parameters(), args.grad_clip)
                scaler.step(optimizer)
                scaler.update()
            else:
                loss.backward()
                grad_norm = torch.nn.utils.clip_grad_norm_(model.parameters(), args.grad_clip)
                optimizer.step()

            scheduler.step()
            step += 1
            running_loss += loss.item()
            loss_history.append(loss.item())

            if step % args.log_every == 0:
                avg = running_loss / args.log_every
                gn = grad_norm.item() if isinstance(grad_norm, torch.Tensor) else grad_norm
                print(f"step={step:>6d} | loss={avg:.4f} | grad={gn:.3f} | lr={scheduler.get_lr()[0]:.2e} | {time.time()-start_time:.0f}s")
                if avg < best_loss: best_loss = avg
                running_loss = 0.0

            if step % args.save_every == 0:
                p = os.path.join(args.output_dir, f"iris_{args.config}_step{step}.pt")
                torch.save({"step": step, "model_state_dict": model.state_dict(), "optimizer_state_dict": optimizer.state_dict(), "loss_history": loss_history, "config": model_cfg}, p)
                print(f"  Saved: {p}")

    final = os.path.join(args.output_dir, f"iris_{args.config}_final.pt")
    torch.save({"step": step, "model_state_dict": model.state_dict(), "optimizer_state_dict": optimizer.state_dict(), "loss_history": loss_history, "config": model_cfg, "config_name": args.config}, final)
    f10 = sum(loss_history[:100]) / min(100, len(loss_history))
    l10 = sum(loss_history[-100:]) / min(100, len(loss_history))
    print(f"Done: {step} steps, loss {f10:.4f} -> {l10:.4f} ({(1-l10/f10)*100:.1f}% reduction). Saved: {final}")

if __name__ == "__main__":
    main()