"""
Phase 5C: Online Shallow CIFAR Vector Credit Pilot.

Minimal pilot: does vector field's frozen credit gain translate to online training?

Compare DFA, ScalarCB_eT, VectorField_eT_M4 on CIFAR-10, L=4, d=256.
Sweep warmup_ratio and term_weight.
"""
import os
import sys
import json
import argparse
import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
from torch.utils.data import DataLoader
import torchvision
import torchvision.transforms as transforms

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from models.residual_mlp import ResidualMLP
from models.value_net import ValueNet, SinusoidalTimeEmbed, create_ema_model, update_ema
from metrics.credit_metrics import (
    cosine_similarity_batch, perturbation_correlation, nudging_test
)


class VectorCreditNet(nn.Module):
    def __init__(self, d_hidden, s_dim, time_embed_dim=32, hidden_dim=256, num_layers=3):
        super().__init__()
        self.ln = nn.LayerNorm(d_hidden)
        self.time_embed = SinusoidalTimeEmbed(time_embed_dim)
        input_dim = d_hidden + time_embed_dim + s_dim
        layers = []
        for i in range(num_layers):
            in_d = input_dim if i == 0 else hidden_dim
            layers.append(nn.Linear(in_d, hidden_dim))
            layers.append(nn.GELU())
        layers.append(nn.Linear(hidden_dim, d_hidden))
        self.net = nn.Sequential(*layers)

    def forward(self, h, t, s):
        h_normed = self.ln(h)
        t_emb = self.time_embed(t)
        inp = torch.cat([h_normed, t_emb, s], dim=-1)
        return self.net(inp)


def get_cifar10(batch_size=128):
    transform_train = transforms.Compose([
        transforms.RandomCrop(32, padding=4),
        transforms.RandomHorizontalFlip(),
        transforms.ToTensor(),
        transforms.Normalize((0.4914, 0.4822, 0.4465), (0.2470, 0.2435, 0.2616)),
    ])
    transform_test = transforms.Compose([
        transforms.ToTensor(),
        transforms.Normalize((0.4914, 0.4822, 0.4465), (0.2470, 0.2435, 0.2616)),
    ])
    trainset = torchvision.datasets.CIFAR10(root='./data', train=True, download=True, transform=transform_train)
    testset = torchvision.datasets.CIFAR10(root='./data', train=False, download=True, transform=transform_test)
    train_loader = DataLoader(trainset, batch_size=batch_size, shuffle=True, num_workers=4, pin_memory=True)
    test_loader = DataLoader(testset, batch_size=batch_size, shuffle=False, num_workers=4, pin_memory=True)
    return train_loader, test_loader


def evaluate(model, test_loader, device):
    model.eval()
    correct, total = 0, 0
    with torch.no_grad():
        for x, y in test_loader:
            x = x.view(x.size(0), -1).to(device)
            y = y.to(device)
            logits = model(x)
            correct += (logits.argmax(1) == y).sum().item()
            total += x.size(0)
    return correct / total


def train_dfa(model, train_loader, test_loader, device, epochs, lr, wd):
    d = model.d_hidden
    L = model.num_blocks
    Bs = [torch.randn(d, 10, device=device) / np.sqrt(10) for _ in range(L)]
    block_opts = [optim.AdamW(b.parameters(), lr=lr, weight_decay=wd) for b in model.blocks]
    embed_opt = optim.AdamW(model.embed.parameters(), lr=lr, weight_decay=wd)
    head_opt = optim.AdamW(list(model.out_head.parameters()) + list(model.out_ln.parameters()), lr=lr, weight_decay=wd)
    scheds = [optim.lr_scheduler.CosineAnnealingLR(o, T_max=epochs) for o in block_opts] + \
             [optim.lr_scheduler.CosineAnnealingLR(embed_opt, T_max=epochs),
              optim.lr_scheduler.CosineAnnealingLR(head_opt, T_max=epochs)]
    log = {'train_loss': [], 'test_acc': []}
    for epoch in range(1, epochs + 1):
        model.train()
        total_loss, correct, total = 0, 0, 0
        for x, y in train_loader:
            x = x.view(x.size(0), -1).to(device)
            y = y.to(device)
            batch = x.size(0)
            with torch.no_grad():
                logits, hiddens = model(x, return_hidden=True)
                loss_val = F.cross_entropy(logits, y)
                e_T = logits.softmax(dim=-1)
                e_T[torch.arange(batch), y] -= 1
            hL = hiddens[-1].detach()
            loss_out = F.cross_entropy(model.out_head(model.out_ln(hL)), y)
            head_opt.zero_grad(); loss_out.backward(); head_opt.step()
            for l in range(L):
                a = (e_T @ Bs[l].T).detach()
                rms = (a**2).mean(-1, keepdim=True).sqrt() + 1e-6
                f = model.blocks[l](hiddens[l].detach())
                ll = (f * (a/rms)).sum(-1).mean()
                block_opts[l].zero_grad(); ll.backward()
                torch.nn.utils.clip_grad_norm_(model.blocks[l].parameters(), 1.0)
                block_opts[l].step()
            a0 = (e_T @ Bs[0].T).detach()
            rms0 = (a0**2).mean(-1, keepdim=True).sqrt() + 1e-6
            el = (model.embed(x) * (a0/rms0)).sum(-1).mean()
            embed_opt.zero_grad(); el.backward(); embed_opt.step()
            total_loss += loss_val.item() * batch; correct += (logits.argmax(1) == y).sum().item(); total += batch
        for s in scheds: s.step()
        test_acc = evaluate(model, test_loader, device)
        log['train_loss'].append(total_loss/total); log['test_acc'].append(test_acc)
        if epoch % 20 == 0 or epoch == 1:
            print(f"    [DFA] Ep {epoch}: loss={total_loss/total:.4f}, test={test_acc:.4f}")
    return log, Bs


def train_vector_online(model, train_loader, test_loader, device, epochs, lr, lr_fb, wd,
                         M=4, warmup_ratio=0.2, term_weight=1.0, eps=1e-3, beta=1.0):
    d = model.d_hidden
    L = model.num_blocks
    warmup_epochs = max(1, int(epochs * warmup_ratio))

    vector_net = VectorCreditNet(d_hidden=d, s_dim=10, time_embed_dim=32,
                                  hidden_dim=256, num_layers=3).to(device)
    Bs = [torch.randn(d, 10, device=device) / np.sqrt(10) for _ in range(L)]

    block_opts = [optim.AdamW(b.parameters(), lr=lr, weight_decay=wd) for b in model.blocks]
    embed_opt = optim.AdamW(model.embed.parameters(), lr=lr, weight_decay=wd)
    head_opt = optim.AdamW(list(model.out_head.parameters()) + list(model.out_ln.parameters()), lr=lr, weight_decay=wd)
    vec_opt = optim.Adam(vector_net.parameters(), lr=lr_fb)
    scheds = [optim.lr_scheduler.CosineAnnealingLR(o, T_max=epochs) for o in block_opts] + \
             [optim.lr_scheduler.CosineAnnealingLR(embed_opt, T_max=epochs),
              optim.lr_scheduler.CosineAnnealingLR(head_opt, T_max=epochs)]

    log = {'train_loss': [], 'test_acc': [], 'vloss': []}

    for epoch in range(1, epochs + 1):
        model.train(); vector_net.train()
        credit_blend = 0.0 if epoch <= warmup_epochs else min(1.0, (epoch - warmup_epochs) / max(1, warmup_epochs))
        total_loss, correct, total, total_vloss = 0, 0, 0, 0

        for x, y in train_loader:
            x = x.view(x.size(0), -1).to(device)
            y = y.to(device)
            batch = x.size(0)

            with torch.no_grad():
                logits, hiddens = model(x, return_hidden=True)
                loss_val = F.cross_entropy(logits, y)
                e_T = logits.softmax(dim=-1)
                e_T[torch.arange(batch), y] -= 1
                s = e_T.detach()

            hL = hiddens[-1].detach()

            # Train vector net: terminal matching
            loss_term = torch.tensor(0.0, device=device)
            if term_weight > 0:
                t_L = torch.ones(batch, device=device)
                a_term = vector_net(hL, t_L, s)
                hL_req = hL.clone().requires_grad_(True)
                logits_tgt = model.out_head(model.out_ln(hL_req))
                ce = F.cross_entropy(logits_tgt, y, reduction='sum')
                delta_L = torch.autograd.grad(ce, hL_req, create_graph=False)[0].detach()
                loss_term = ((a_term - delta_L) ** 2).sum(-1).mean()

            # Perturbation target: subsample 1 layer
            l_train = np.random.randint(0, L)
            h_l = hiddens[l_train].detach()
            t_l = torch.full((batch,), l_train / L, device=device)
            a_l = vector_net(h_l, t_l, s)

            loss_proj = torch.tensor(0.0, device=device)
            for _ in range(M):
                v = torch.randn_like(h_l)
                v = v / (v.norm(dim=-1, keepdim=True) + 1e-8)
                with torch.no_grad():
                    lp = F.cross_entropy(model.forward_from_layer(h_l + eps*v, l_train), y, reduction='none')
                    lm = F.cross_entropy(model.forward_from_layer(h_l - eps*v, l_train), y, reduction='none')
                    g_j = (lp - lm) / (2*eps)
                loss_proj = loss_proj + (((a_l * v).sum(-1) - g_j.detach())**2).mean()
            loss_proj = loss_proj / M

            vloss = term_weight * loss_term + beta * loss_proj
            vec_opt.zero_grad(); vloss.backward()
            torch.nn.utils.clip_grad_norm_(vector_net.parameters(), 1.0)
            vec_opt.step()
            total_vloss += vloss.item() * batch

            # Compute credits
            with torch.no_grad():
                vec_credits = [vector_net(hiddens[l].detach(),
                               torch.full((batch,), l/L, device=device), s).detach() for l in range(L)]
            dfa_credits = [(e_T @ Bs[l].T).detach() for l in range(L)]

            credits = []
            for l in range(L):
                if credit_blend >= 1.0:
                    credits.append(vec_credits[l])
                elif credit_blend <= 0.0:
                    credits.append(dfa_credits[l])
                else:
                    vr = (vec_credits[l]**2).mean(-1, keepdim=True).sqrt() + 1e-6
                    dr = (dfa_credits[l]**2).mean(-1, keepdim=True).sqrt() + 1e-6
                    credits.append(credit_blend * vec_credits[l]/vr + (1-credit_blend) * dfa_credits[l]/dr)

            # Update head
            loss_out = F.cross_entropy(model.out_head(model.out_ln(hL)), y)
            head_opt.zero_grad(); loss_out.backward(); head_opt.step()

            # Update blocks
            for l in range(L):
                a = credits[l]
                rms = (a**2).mean(-1, keepdim=True).sqrt() + 1e-6
                f = model.blocks[l](hiddens[l].detach())
                ll = (f * (a/rms)).sum(-1).mean()
                block_opts[l].zero_grad(); ll.backward()
                torch.nn.utils.clip_grad_norm_(model.blocks[l].parameters(), 1.0)
                block_opts[l].step()

            # Update embedding
            a0 = credits[0]
            rms0 = (a0**2).mean(-1, keepdim=True).sqrt() + 1e-6
            el = (model.embed(x) * (a0/rms0)).sum(-1).mean()
            embed_opt.zero_grad(); el.backward(); embed_opt.step()

            total_loss += loss_val.item()*batch; correct += (logits.argmax(1)==y).sum().item(); total += batch

        for s in scheds: s.step()
        test_acc = evaluate(model, test_loader, device)
        log['train_loss'].append(total_loss/total); log['test_acc'].append(test_acc)
        log['vloss'].append(total_vloss/total)
        if epoch % 20 == 0 or epoch == 1:
            phase = "warmup" if epoch <= warmup_epochs else f"blend={credit_blend:.2f}"
            print(f"    [vec_M{M}] Ep {epoch} ({phase}): loss={total_loss/total:.4f}, test={test_acc:.4f}")

    return log, vector_net


def compute_diagnostics(model, test_loader, device, method_name, value_net=None, vector_net=None, dfa_Bs=None):
    model.eval()
    if value_net: value_net.eval()
    if vector_net: vector_net.eval()
    L = model.num_blocks
    for x, y in test_loader:
        x = x.view(x.size(0), -1).to(device); y = y.to(device); break
    batch = x.size(0)

    logits_bp, hiddens_bp = model(x, return_hidden=True)
    for l in range(L+1): hiddens_bp[l].retain_grad()
    F.cross_entropy(logits_bp, y).backward()
    bp_grads = {l: hiddens_bp[l].grad.detach().clone() for l in range(L+1)}

    with torch.no_grad():
        logits, hiddens = model(x, return_hidden=True)
        e_T = logits.softmax(-1); e_T[torch.arange(batch), y] -= 1; s = e_T.detach()

    results = {'bp_cosine': [], 'perturbation_rho': [], 'nudging': {'0.001':[], '0.003':[], '0.01':[]}}
    for l in range(L):
        h_l = hiddens[l].detach(); t_l = torch.full((batch,), l/L, device=device)
        if method_name == 'dfa':
            a_l = (s @ dfa_Bs[l].T).detach()
        elif method_name.startswith('vec'):
            a_l = vector_net(h_l, t_l, s).detach()
        results['bp_cosine'].append(float(cosine_similarity_batch(a_l, bp_grads[l])))
        def make_fwd(sl):
            def f(h):
                with torch.no_grad():
                    c=h
                    for i in range(sl,L): c=c+model.blocks[i](c)
                    return F.cross_entropy(model.out_head(model.out_ln(c)),y,reduction='none')
            return f
        fwd = make_fwd(l)
        results['perturbation_rho'].append(float(perturbation_correlation(h_l, a_l, fwd, epsilon=1e-3, M=16)))
        for eta in [0.001, 0.003, 0.01]:
            results['nudging'][str(eta)].append(float(nudging_test(h_l, a_l, fwd, eta=eta)))
    return results


def run_config(L, d, method, seed, train_loader, test_loader, device,
               epochs=100, lr=1e-3, lr_fb=1e-3, wd=0.01,
               M=4, warmup_ratio=0.2, term_weight=1.0, eps=1e-3, beta=1.0):
    torch.manual_seed(seed); np.random.seed(seed); torch.cuda.manual_seed_all(seed)
    model = ResidualMLP(32*32*3, d, 10, L).to(device)
    config_str = f"L={L}, d={d}, {method}, s={seed}"
    if method.startswith('vec'): config_str += f", wr={warmup_ratio}, tw={term_weight}"
    print(f"\n  --- {config_str} ---")

    if method == 'dfa':
        log, Bs = train_dfa(model, train_loader, test_loader, device, epochs, lr, wd)
        diag = compute_diagnostics(model, test_loader, device, 'dfa', dfa_Bs=Bs)
    elif method.startswith('vec'):
        log, vnet = train_vector_online(model, train_loader, test_loader, device,
                                         epochs, lr, lr_fb, wd, M=M,
                                         warmup_ratio=warmup_ratio, term_weight=term_weight,
                                         eps=eps, beta=beta)
        diag = compute_diagnostics(model, test_loader, device, 'vec', vector_net=vnet)

    result = {
        'method': method, 'L': L, 'd': d, 'seed': seed,
        'warmup_ratio': warmup_ratio, 'term_weight': term_weight, 'M': M,
        'test_acc': log['test_acc'][-1],
        'mean_gamma': float(np.mean(diag['bp_cosine'])),
        'mean_rho': float(np.mean(diag['perturbation_rho'])),
        'mean_nudge': float(np.mean(diag['nudging']['0.003'])),
        'per_layer_gamma': diag['bp_cosine'],
        'per_layer_rho': diag['perturbation_rho'],
    }
    print(f"    Result: acc={result['test_acc']:.4f}, Gamma={result['mean_gamma']:.4f}, "
          f"rho={result['mean_rho']:.4f}, nudge={result['mean_nudge']:.6f}")
    return result


def main():
    parser = argparse.ArgumentParser(description='Phase 5C: Online CIFAR Vector Pilot')
    parser.add_argument('--L', type=int, default=4)
    parser.add_argument('--d', type=int, default=256)
    parser.add_argument('--epochs', type=int, default=100)
    parser.add_argument('--lr', type=float, default=1e-3)
    parser.add_argument('--lr_fb', type=float, default=1e-3)
    parser.add_argument('--wd', type=float, default=0.01)
    parser.add_argument('--M', type=int, default=4)
    parser.add_argument('--warmup_ratios', type=float, nargs='+', default=[0.0, 0.05, 0.2])
    parser.add_argument('--term_weights', type=float, nargs='+', default=[1.0, 4.0])
    parser.add_argument('--pert_eps', type=float, default=1e-3)
    parser.add_argument('--pert_beta', type=float, default=1.0)
    parser.add_argument('--seeds', type=int, nargs='+', default=[42])
    parser.add_argument('--batch_size', type=int, default=128)
    parser.add_argument('--gpu', type=int, default=2)
    parser.add_argument('--output_dir', type=str, default='results/online_vec_pilot')
    args = parser.parse_args()

    device = torch.device(f'cuda:{args.gpu}' if torch.cuda.is_available() else 'cpu')
    print(f"Using device: {device}")
    os.makedirs(args.output_dir, exist_ok=True)
    train_loader, test_loader = get_cifar10(args.batch_size)

    all_results = []

    for seed in args.seeds:
        # DFA baseline
        r = run_config(args.L, args.d, 'dfa', seed, train_loader, test_loader, device,
                       args.epochs, args.lr, args.lr_fb, args.wd)
        all_results.append(r)

        # Vector field sweep
        for wr in args.warmup_ratios:
            for tw in args.term_weights:
                r = run_config(args.L, args.d, 'vec_eT_M4', seed, train_loader, test_loader, device,
                               args.epochs, args.lr, args.lr_fb, args.wd,
                               M=args.M, warmup_ratio=wr, term_weight=tw,
                               eps=args.pert_eps, beta=args.pert_beta)
                all_results.append(r)

    # Summary
    dfa_baselines = {r['seed']: r for r in all_results if r['method'] == 'dfa'}
    print(f"\n{'='*90}")
    print("SUMMARY")
    print(f"{'='*90}")
    print(f"{'Method':<20} {'seed':>5} {'wr':>5} {'tw':>5} {'Acc':>6} {'Gamma':>7} {'rho':>7} {'nudge':>10} {'S1':>7} {'S2':>7}")
    print("-" * 90)

    positive = []
    for r in all_results:
        dfa = dfa_baselines.get(r['seed'], {})
        S1 = r['mean_gamma'] - dfa.get('mean_gamma', 0)
        S2 = r['mean_rho'] - dfa.get('mean_rho', 0)
        wr_s = f"{r.get('warmup_ratio', '-'):>5.2f}" if r['method'] != 'dfa' else "    -"
        tw_s = f"{r.get('term_weight', '-'):>5.1f}" if r['method'] != 'dfa' else "    -"
        print(f"{r['method']:<20} {r['seed']:>5} {wr_s} {tw_s} {r['test_acc']:>6.4f} "
              f"{r['mean_gamma']:>7.4f} {r['mean_rho']:>7.4f} {r['mean_nudge']:>10.6f} {S1:>7.4f} {S2:>7.4f}")
        if r['method'] != 'dfa' and S1 > 0 and S2 > 0:
            nb = r['mean_nudge'] < dfa.get('mean_nudge', 0)
            positive.append({**r, 'S1': S1, 'S2': S2, 'nudge_better': nb})

    if positive:
        print(f"\nPOSITIVE CONFIGS (S1>0 AND S2>0):")
        for p in positive:
            print(f"  {p['method']} wr={p['warmup_ratio']} tw={p['term_weight']}: "
                  f"S1={p['S1']:.4f} S2={p['S2']:.4f} nudge_better={p['nudge_better']}")
    else:
        print(f"\nNO POSITIVE CONFIGS.")

    out_path = os.path.join(args.output_dir, f'pilot_s{args.seeds[0]}.json')
    with open(out_path, 'w') as f:
        json.dump(all_results, f, indent=2)
    print(f"\nSaved to {out_path}")


if __name__ == '__main__':
    main()