"""
Training script for 2-stage fMRI encoding with Flow Matching.
Stage 1: Train MultiSubjectConvLinearEncoder (Mean Anchor)
Stage 2: Train Conditional Flow Matching (Neural Vector Field) per subject.
"""

import argparse
import json
import math
import sys
import time
from pathlib import Path
from typing import Dict, Any, Optional

import numpy as np
import torch
import torch.nn as nn
from omegaconf import DictConfig, OmegaConf
from torch.utils.data import DataLoader
from timm.utils import AverageMeter, random_seed

from .visualize import plot_loss_curve
from .data import (
    Algonauts2025Dataset,
    load_algonauts2025_friends_fmri,
    load_algonauts2025_movie10_fmri,
    load_sharded_features,
    episode_filter,
)
from .stage1.medarc_architecture import MultiSubjectConvLinearEncoder
from .stage2.CFM import CFM
from .metric import pearsonr_score

# DEFAULT_DATA_DIR = ROOT.parent / "algonauts2025/datasets" # Adjust based on workspace
DEFAULT_DATA_DIR = Path("/raid/lttung05/fmri_encoder/data")
SUBJECTS = (1, 2, 3, 5)


def load_features(cfg: DictConfig, model: str, layer: str) -> dict[str, np.ndarray]:
    data_dir = Path(cfg.datasets_root or DEFAULT_DATA_DIR)
    friends_features = load_sharded_features(
        data_dir / "features", model=model, layer=layer, series="friends"
    )
    movie10_features = load_sharded_features(
        data_dir / "features", model=model, layer=layer, series="movie10"
    )
    features = {**friends_features, **movie10_features}
    return features


def pool_features(features: dict[str, np.ndarray]) -> dict[str, np.ndarray]:
    pooled = {}
    for key, feat in features.items():
        assert feat.ndim in {2, 3}
        if feat.ndim == 3:
            feat = feat.mean(axis=1)
        pooled[key] = feat
    return pooled


def make_data_loaders(cfg: DictConfig) -> dict[str, DataLoader]:
    print("loading fmri data")

    data_dir = Path(cfg.datasets_root or DEFAULT_DATA_DIR)
    subjects = cfg.get("subjects", SUBJECTS)

    friends_fmri = load_algonauts2025_friends_fmri(
        data_dir / "algonauts_2025.competitors", subjects=subjects
    )
    movie10_fmri = load_algonauts2025_movie10_fmri(
        data_dir / "algonauts_2025.competitors", subjects=subjects
    )
    all_fmri = {**friends_fmri, **movie10_fmri}
    all_episodes = list(all_fmri)

    all_features = []
    for feat_name in cfg.include_features:
        model, layer = feat_name.split("/")
        feat_cfg = cfg.features[model]
        model_name = feat_cfg.model
        layer_name = feat_cfg.layers[layer]
        print(f"loading features {feat_name} ({model_name}/{layer_name})")
        features = load_features(cfg, model_name, layer_name)

        if cfg.stage1.model.global_pool == "avg":
            features = pool_features(features)

        all_features.append(features)

    data_loaders = {}

    for ds_name, ds_cfg in cfg.datasets.items():
        print(f"loading dataset: {ds_name}\n\n{OmegaConf.to_yaml(ds_cfg)}")

        ds_cfg = ds_cfg.copy()
        filter_cfg = ds_cfg.pop("filter")
        filter_fn = episode_filter(**filter_cfg)
        ds_episodes = list(filter(filter_fn, all_episodes))
        # print(f"episodes: {ds_name}:\n\n{ds_episodes}")

        dataset = Algonauts2025Dataset(
            episode_list=ds_episodes,
            fmri_data=all_fmri,
            feat_data=all_features,
            **ds_cfg,
        )

        batch_size = cfg.batch_size if ds_name == "train" else 1
        loader = DataLoader(dataset, batch_size=batch_size)

        data_loaders[ds_name] = loader

    return data_loaders


def train_one_epoch_condition(
    *,
    epoch: int,
    model: torch.nn.Module,
    train_loader: DataLoader,
    optimizer: torch.optim.Optimizer,
    device: torch.device,
):
    model.train()

    use_cuda = device.type == "cuda"
    if use_cuda:
        torch.cuda.empty_cache()
        torch.cuda.reset_peak_memory_stats()

    loss_m = AverageMeter()
    data_time_m = AverageMeter()
    step_time_m = AverageMeter()

    end = time.monotonic()

    for batch_idx, batch in enumerate(train_loader):
        feats = [f.to(device) for f in batch["features"]]
        fmri = batch["fmri"].to(device)  # (B, S, T, V) = [16, 4, 64, 1000]
        # print(fmri.shape)
        batch_size = fmri.size(0)
        data_time = time.monotonic() - end

        pred = model(feats)  # (B, S, T, V)

        loss = nn.MSELoss()(pred, fmri)
        loss_item = loss.item()

        if math.isnan(loss_item) or math.isinf(loss_item):
            raise RuntimeError(
                f"NaN/Inf loss encountered on step {batch_idx + 1}; exiting"
            )

        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        if use_cuda:
            torch.cuda.synchronize()
        step_time = time.monotonic() - end

        loss_m.update(loss_item, batch_size)
        data_time_m.update(data_time, batch_size)
        step_time_m.update(step_time, batch_size)

        if (batch_idx + 1) % 20 == 0:
            tput = batch_size / step_time_m.avg
            if use_cuda:
                alloc_mem_gb = torch.cuda.max_memory_allocated() / 1e9
                res_mem_gb = torch.cuda.max_memory_reserved() / 1e9
            else:
                alloc_mem_gb = res_mem_gb = 0.0

            print(
                f"Stage 1 Train: {epoch:>3d} [{batch_idx:>3d}]"
                f"  Loss: {loss_m.val:#.3g} ({loss_m.avg:#.3g})"
                f"  Time: {data_time_m.avg:.3f},{step_time_m.avg:.3f} {tput:.0f}/s"
                f"  Mem: {alloc_mem_gb:.2f},{res_mem_gb:.2f} GB"
            )

        end = time.monotonic()

    return loss_m.avg


def train_one_epoch_flow_matching(
    *,
    epoch: int,
    stage1_model: torch.nn.Module,
    stage2_models: nn.ModuleDict,  # subject_id -> CFM
    train_loader: DataLoader,
    optimizers: Dict[str, torch.optim.Optimizer],
    device: torch.device,
    subjects: list,
):
    stage1_model.eval()
    for model in stage2_models.values():
        model.train()

    use_cuda = device.type == "cuda"
    if use_cuda:
        torch.cuda.empty_cache()
        torch.cuda.reset_peak_memory_stats()

    loss_m = AverageMeter()
    data_time_m = AverageMeter()
    step_time_m = AverageMeter()

    end = time.monotonic()

    for batch_idx, batch in enumerate(train_loader):
        feats = [f.to(device) for f in batch["features"]]
        fmri = batch["fmri"].to(device)  # (B, S, T, V)
        batch_size = fmri.size(0)
        data_time = time.monotonic() - end

        # Get Mean Anchor from Stage 1 (Frozen)
        with torch.no_grad():
            mu_anchor = stage1_model(feats)  # (B, S, T, V)

        batch_loss = 0

        # Train per-subject vector field
        for i, sub in enumerate(subjects):
            sub_key = str(sub)
            cfm = stage2_models[sub_key]
            optimizer = optimizers[sub_key]

            # Prepare data for CFM: Expects (B, C, T)
            # Input data: (B, T, V) -> Transpose to (B, V, T)
            x1 = fmri[:, i].transpose(1, 2)
            mu = mu_anchor[:, i].transpose(1, 2)

            # CFM Compute Loss: x1=Target, mu=Condition
            loss, _ = cfm.compute_loss(x1, mu)

            optimizer.zero_grad()
            loss.backward()
            optimizer.step()

            batch_loss += loss.item()

        loss_item = batch_loss / len(subjects)

        if math.isnan(loss_item) or math.isinf(loss_item):
            raise RuntimeError(
                f"NaN/Inf loss encountered on step {batch_idx + 1}; exiting"
            )

        if use_cuda:
            torch.cuda.synchronize()
        step_time = time.monotonic() - end

        loss_m.update(loss_item, fmri.size(0))
        data_time_m.update(data_time, batch_size)
        step_time_m.update(step_time, batch_size)

        if (batch_idx + 1) % 20 == 0:
            tput = batch_size / step_time_m.avg
            if use_cuda:
                alloc_mem_gb = torch.cuda.max_memory_allocated() / 1e9
                res_mem_gb = torch.cuda.max_memory_reserved() / 1e9
            else:
                alloc_mem_gb = res_mem_gb = 0.0

            print(
                f"Stage 2 Train: {epoch:>3d} [{batch_idx:>3d}]"
                f"  Loss: {loss_m.val:#.3g} ({loss_m.avg:#.3g})"
                f"  Time: {data_time_m.avg:.3f},{step_time_m.avg:.3f} {tput:.0f}/s"
                f"  Mem: {alloc_mem_gb:.2f},{res_mem_gb:.2f} GB"
            )

        end = time.monotonic()

    return loss_m.avg


@torch.no_grad()
def evaluate_stage1(
    *,
    epoch: int,
    model: torch.nn.Module,
    val_loader: DataLoader,
    device: torch.device,
    subjects: list,
    ds_name: str = "val",
):
    model.eval()

    loss_m = AverageMeter()
    samples = []
    outputs = []

    for batch_idx, batch in enumerate(val_loader):
        feats = [f.to(device) for f in batch["features"]]
        fmri = batch["fmri"].to(device)
        batch_size = fmri.size(0)

        pred = model(feats)
        loss = nn.MSELoss()(pred, fmri)
        loss_m.update(loss.item(), batch_size)

        N, S, L, C = fmri.shape
        assert N, S == (1, 4)

        outputs.append(pred.cpu().numpy().swapaxes(0, 1).reshape((S, N * L, C)))
        samples.append(fmri.cpu().numpy().swapaxes(0, 1).reshape((S, N * L, C)))

    outputs = np.concatenate(outputs, axis=1)
    samples = np.concatenate(samples, axis=1)

    metrics = {}

    # Encoding accuracy metrics
    dim = samples.shape[-1]
    acc = 0.0
    acc_map = np.zeros(dim)
    for ii, sub in enumerate(subjects):
        y_true = samples[ii].reshape(-1, dim)
        y_pred = outputs[ii].reshape(-1, dim)
        metrics[f"accmap_sub-{sub}"] = acc_map_i = pearsonr_score(y_true, y_pred)
        metrics[f"acc_sub-{sub}"] = acc_i = np.mean(acc_map_i)
        acc_map += acc_map_i / len(subjects)
        acc += acc_i / len(subjects)

    metrics["accmap_avg"] = acc_map
    metrics["acc_avg"] = acc
    accs_fmt = ",".join(
        f"{val:.3f}" for key, val in metrics.items() if key.startswith("acc_sub-")
    )

    print(
        f"Evaluate Stage 1 ({ds_name}): {epoch:>3d}"
        f"  Loss: {loss_m.avg:#.3g}"
        f"  Acc: {accs_fmt} ({acc:.3f})"
    )

    return acc, metrics


@torch.no_grad()
def evaluate_stage2(
    *,
    epoch: int,
    stage1_model: torch.nn.Module,
    stage2_models: nn.ModuleDict,
    val_loader: DataLoader,
    device: torch.device,
    subjects: list,
    ds_name: str = "val",
    n_timesteps: int = 10,
):
    stage1_model.eval()
    for model in stage2_models.values():
        model.eval()

    samples = []
    outputs = []

    for batch in val_loader:
        feats = [f.to(device) for f in batch["features"]]
        fmri = batch["fmri"].to(device)

        mu_anchor = stage1_model(feats)

        batch_preds = []
        for i, sub in enumerate(subjects):
            sub_key = str(sub)
            cfm = stage2_models[sub_key]

            mu = mu_anchor[:, i].transpose(1, 2)

            # Predict
            pred = cfm(mu, n_timesteps=n_timesteps)  # (B, V, T)
            pred = pred.transpose(1, 2).unsqueeze(1)  # (B, 1, T, V)
            batch_preds.append(pred)

        pred_combined = torch.cat(batch_preds, dim=1)  # (B, S, T, V)

        N, S, L, C = fmri.shape
        assert N, S == (1, 4)

        outputs.append(
            pred_combined.cpu().numpy().swapaxes(0, 1).reshape((S, N * L, C))
        )
        samples.append(fmri.cpu().numpy().swapaxes(0, 1).reshape((S, N * L, C)))

    outputs = np.concatenate(outputs, axis=1)
    samples = np.concatenate(samples, axis=1)

    metrics = {}

    dim = samples.shape[-1]
    acc = 0.0
    acc_map = np.zeros(dim)
    for ii, sub in enumerate(subjects):
        y_true = samples[ii].reshape(-1, dim)
        y_pred = outputs[ii].reshape(-1, dim)
        metrics[f"accmap_sub-{sub}"] = acc_map_i = pearsonr_score(y_true, y_pred)
        metrics[f"acc_sub-{sub}"] = acc_i = np.mean(acc_map_i)
        acc_map += acc_map_i / len(subjects)
        acc += acc_i / len(subjects)

    metrics["accmap_avg"] = acc_map
    metrics["acc_avg"] = acc
    accs_fmt = ",".join(
        f"{val:.3f}" for key, val in metrics.items() if key.startswith("acc_sub-")
    )

    print(f"Evaluate Stage 2 ({ds_name}): {epoch:>3d}" f"  Acc: {accs_fmt} ({acc:.3f})")

    return acc, metrics


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--cfg-path", type=str, default="config.yml")
    args = parser.parse_args()

    cfg = OmegaConf.load(args.cfg_path)
    print("Config loaded:\n", OmegaConf.to_yaml(cfg))

    out_dir = Path(cfg.out_dir)
    out_dir.mkdir(parents=True, exist_ok=True)
    OmegaConf.save(cfg, out_dir / "config.yaml")

    random_seed(cfg.seed)
    device = torch.device(cfg.device)

    # --- Data Loading ---
    data_loaders = make_data_loaders(cfg)
    train_loader = data_loaders["train"]
    val_loaders = data_loaders.copy()
    val_loaders.pop("train")

    # --- Model Setup: Stage 1 ---
    print("Creating Stage 1 Model (Encoder)...")

    # Get feat dims from first batch
    sample_batch = next(iter(train_loader))
    feat_dims = [f.shape[-1] for f in sample_batch["features"]]

    subjects_list = cfg.get("subjects", SUBJECTS)

    stage1_model = MultiSubjectConvLinearEncoder(
        num_subjects=len(subjects_list),
        feat_dims=feat_dims,
        # hidden_model=hidden_model,
        **cfg.stage1.model,
    ).to(device)

    optimizer1 = torch.optim.AdamW(
        stage1_model.parameters(),
        lr=cfg.stage1.lr,
        weight_decay=cfg.stage1.weight_decay,
    )

    # --- Training Loop: Stage 1 ---
    print("--- Starting Stage 1 Training (Mean Anchor) ---")
    best_score_s1 = -1.0
    stage1_train_losses = []
    stage1_val_accs = []

    for epoch in range(cfg.stage1.epochs):
        train_loss = train_one_epoch_condition(
            epoch=epoch,
            model=stage1_model,
            train_loader=train_loader,
            optimizer=optimizer1,
            device=device,
        )
        stage1_train_losses.append(train_loss)

        # Validation
        val_acc = None
        for name, loader in val_loaders.items():
            acc, _ = evaluate_stage1(
                epoch=epoch,
                model=stage1_model,
                val_loader=loader,
                device=device,
                subjects=subjects_list,
                ds_name=name,
            )
            if name == cfg.val_set_name:
                val_acc = acc

        stage1_val_accs.append(val_acc if val_acc is not None else 0.0)

        if val_acc is not None and val_acc > best_score_s1:
            best_score_s1 = val_acc
            torch.save(stage1_model.state_dict(), out_dir / "stage1_best.pt")
            print("Saved best Stage 1 model.")

    plot_loss_curve(
        stage1_train_losses,
        stage1_val_accs,
        out_dir,
        filename="stage1_loss_curve.png",
        prefix="Stage 1",
    )

    print(f"Stage 1 Training Complete. Best model at Pearson's r {best_score_s1}")

    # Reload best stage 1 model
    stage1_model.load_state_dict(torch.load(out_dir / "stage1_best.pt"))
    stage1_model.eval()

    # --- Model Setup: Stage 2 ---
    print("Creating Stage 2 Models (Flow Matching)...")
    stage2_models = nn.ModuleDict()
    optimizers2 = {}

    # Determine target dim from data (V parameter)
    target_dim = sample_batch["fmri"].shape[-1]

    cfm_params = cfg.stage2.cfm
    velocity_net_params = cfg.stage2.velocity_net
    source_ve_params = cfg.stage2.source_ve
    transport_params = cfg.stage2.transport

    for sub in subjects_list:
        sub_key = str(sub)
        # Create one CFM per subject for "neural vector field per subject"
        cfm_model = CFM(
            feat_dim=target_dim,
            cfm_params=cfm_params,
            velocity_net_params=velocity_net_params,
            source_ve_params=source_ve_params,
            transport_params=transport_params,
        ).to(device)

        stage2_models[sub_key] = cfm_model
        optimizers2[sub_key] = torch.optim.AdamW(
            cfm_model.parameters(),
            lr=cfg.stage2.lr,
            weight_decay=cfg.stage2.weight_decay,
        )

    # --- Training Loop: Stage 2 ---
    print("--- Starting Stage 2 Training (Vector Fields) ---")

    stage2_train_losses = []

    for epoch in range(cfg.stage2.epochs):
        train_loss = train_one_epoch_flow_matching(
            epoch=epoch,
            stage1_model=stage1_model,
            stage2_models=stage2_models,
            train_loader=train_loader,
            optimizers=optimizers2,
            device=device,
            subjects=subjects_list,
        )
        stage2_train_losses.append(train_loss)

        # Checkpointing
        if epoch % 5 == 0 or epoch == cfg.stage2.epochs - 1:
            ckpt_path = out_dir / f"stage2_epoch_{epoch}.pt"
            torch.save(stage2_models.state_dict(), ckpt_path)
            print(f"Saved Stage 2 checkpoint to {ckpt_path}")

    # --- Add Evaluation
    print("Evaluating final Stage 2 model...")
    for name, loader in val_loaders.items():
        evaluate_stage2(
            epoch=cfg.stage2.epochs,
            stage1_model=stage1_model,
            stage2_models=stage2_models,
            val_loader=loader,
            device=device,
            subjects=subjects_list,
            ds_name=name,
            n_timesteps=cfg.stage2.get("n_timesteps", 25),
        )

    plot_loss_curve(
        stage2_train_losses,
        out_path=out_dir,
        filename="stage2_loss_curve.png",
        prefix="Stage 2",
    )

    print("Done! All training complete.")


if __name__ == "__main__":
    main()