"""Full CTA TRAINING-step trace — covers everything that's MISSING from
trace_cta_forward.py:

  1. Constructs a mini-batch: 1 real + 1 fake from HDTF-paired (so they share
     the same driving audio — the structural premise of CTA).
  2. Walks through `predict_pairs()` exposing the cross-attention internals
     (Q/K/V shapes, attention map shape) of f_{A→V} and f_{V→A}.
  3. Computes ALL FIVE losses exactly as `CTALitModule.training_step` does:
        loss_av    (REAL-only, drives predictors + backbones)
        loss_va    (REAL-only, drives predictors + backbones)
        loss_asym  (BOTH, margin loss on the asymmetry score)
        loss_cls   (BOTH, BCE on classifier;  L_AV/L_VA are detach()ed)
        loss_aux   (FAKE-paired, cross-generator asym consistency)
     Each loss's value, sample-mask, gradient destination is logged.
  4. Performs ONE backward step and reports which parameters received non-zero
     gradients per loss — proving "predictor is trained on real ONLY",
     "detach() blocks BCE → predictor", etc.

This is a debug / paper-figure-aid script; not used during training.

Usage:
    /opt/conda/envs/pytorch/bin/python3 scripts/analysis/trace_cta_training.py \\
        --ckpt outputs/cta_diffusion_combined_20260604_205145/checkpoints/epoch16-valauc1.0000.ckpt
"""
from __future__ import annotations

import argparse
import os
import sys
import textwrap
from pathlib import Path

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F

# silence weights_only restriction
import lightning_fabric.utilities.cloud_io as _lf_cloud_io
_orig_torch_load = torch.load
def _unsafe_torch_load(*args, **kwargs):
    kwargs["weights_only"] = False
    return _orig_torch_load(*args, **kwargs)
_lf_cloud_io.torch.load = _unsafe_torch_load
torch.load = _unsafe_torch_load

sys.path.insert(0, str(Path(__file__).resolve().parents[2]))

from omegaconf import OmegaConf

from src.data.fairtalking_dataset import load_video_clip, load_audio_clip
from src.data.transforms import build_video_transform
from src.methods import build_method


# ============================================================================
# Pretty-print helpers
# ============================================================================
HRULE  = "─" * 92
DHRULE = "═" * 92
def banner(title: str, level: int = 0):
    print()
    print(DHRULE if level == 0 else HRULE)
    print(f"  {title}")
    print(DHRULE if level == 0 else HRULE)


def step(n, title):
    print(f"\n  ── Step {n}: {title} ".ljust(94, "─"))


def tprint(name, x, indent=2, more=""):
    sp = " " * indent
    if isinstance(x, torch.Tensor):
        info = (f"shape={tuple(x.shape)}  dtype={str(x.dtype).replace('torch.', '')}  "
                f"range=[{x.min().item():+.4f}, {x.max().item():+.4f}]")
        if x.is_floating_point() or x.is_complex():
            info += f"  mean={x.float().mean().item():+.4f}"
        else:
            info += f"  values={x.detach().cpu().tolist()[:8]}"
        if x.requires_grad or x.grad_fn is not None:
            info += "  grad_fn=" + (type(x.grad_fn).__name__ if x.grad_fn else "(leaf,req)")
    else:
        info = f"{type(x).__name__} = {x}"
    print(f"{sp}{name:30s} {info}")
    if more:
        print(f"{sp}{'':30s} ↳ {more}")


def explain(text, indent=4):
    sp = " " * indent
    wrapped = textwrap.fill(text, width=92 - indent,
                            initial_indent=sp, subsequent_indent=sp)
    print(f"\033[2m{wrapped}\033[0m")


# ============================================================================
# Cross-attention introspection
# ============================================================================
def expose_cross_attention(predictor, src_tokens, tgt_tokens, name="f_AV"):
    """Run the predictor with a forward hook that captures the FIRST
    decoder layer's cross-attention input/output. Prints Q/K/V shapes
    and attention shape so the figure can show 'cross-attention' explicitly.
    """
    captured = {}
    layer0 = predictor.decoder.layers[0]

    def hook(module, args, kwargs, output):
        # nn.TransformerDecoderLayer's multihead_attn is the cross-attention.
        # Its forward signature is (query, key, value, ...).
        # We don't directly intercept multihead_attn here; instead, we
        # capture the layer-level inputs.
        captured["tgt"] = args[0]      # query input to the cross-attn
        captured["memory"] = args[1]   # key/value memory (audio for f_AV)
        if isinstance(output, tuple):
            captured["out"] = output[0]
        else:
            captured["out"] = output
    handle = layer0.register_forward_hook(hook, with_kwargs=True)

    out = predictor(src_tokens=src_tokens, tgt_query=tgt_tokens)
    handle.remove()

    print(f"     {name} cross-attention (first decoder layer):")
    if "tgt" in captured:
        tprint(f"   query  (= tgt projection)", captured["tgt"], indent=4)
        tprint(f"   key/value memory (= src)", captured["memory"], indent=4)
        tprint(f"   layer-0 output", captured["out"], indent=4)

    n_heads = layer0.multihead_attn.num_heads
    head_dim = layer0.multihead_attn.embed_dim // n_heads
    print(f"     n_heads={n_heads}, head_dim={head_dim}, depth={len(predictor.decoder.layers)} layers")
    return out


# ============================================================================
# Sample loader (HDTF-paired, real & fake share audio)
# ============================================================================
def load_paired_inputs(hdtf_root, num, fake_gen,
                       num_frames=16, frame_stride=2, frame_size=224,
                       audio_seconds=2.56, audio_sample_rate=16000):
    root = Path(hdtf_root)
    rv = root / "Real" / f"{num}_Fake_HDTF.mp4"
    fv = root / fake_gen / f"{num}_Fake_HDTF_{fake_gen}.mp4"
    aw = root / "_audio" / "Real" / f"{num}_Fake_HDTF.wav"
    for p in (rv, fv, aw):
        if not p.exists():
            raise SystemExit(f"missing: {p}")

    real_video = load_video_clip(str(rv), num_frames, frame_stride, frame_size)
    fake_video = load_video_clip(str(fv), num_frames, frame_stride, frame_size)
    audio = load_audio_clip(str(aw), audio_seconds, audio_sample_rate)
    return rv, fv, aw, real_video, fake_video, audio


# ============================================================================
# Helpers for backward-trace
# ============================================================================
def grad_summary(module, label, indent=4):
    """Walk all parameters, count how many have non-zero gradient (after
    backward of one specific loss). Returns nothing; prints a compact line.
    """
    nz, total, l2 = 0, 0, 0.0
    for p in module.parameters():
        total += 1
        if p.grad is not None and p.requires_grad:
            g = p.grad
            if torch.any(g != 0):
                nz += 1
                l2 += g.detach().pow(2).sum().item()
    sp = " " * indent
    rms = (l2 ** 0.5)
    print(f"{sp}{label:35s} {nz}/{total} params with non-zero grad   "
          f"||grad||₂ = {rms:8.4e}")


def zero_all_grads(model):
    for p in model.parameters():
        if p.grad is not None:
            p.grad.zero_()


# ============================================================================
def parse_args():
    p = argparse.ArgumentParser()
    p.add_argument("--ckpt",
        default="outputs/cta_diffusion_combined_20260604_205145/checkpoints/epoch16-valauc1.0000.ckpt")
    p.add_argument("--hdtf_root", default="/apdcephfs_gy5/share_303628665/joyewu/HDTF-paird")
    p.add_argument("--num", default="033")
    p.add_argument("--fake_generator", default="AniPortrait")
    return p.parse_args()


def main():
    args = parse_args()
    device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

    banner("CTA  TRAINING-STEP  TRACE  (forward + 5 losses + backward gradient routing)", 0)
    print(f"  ckpt:   {args.ckpt}")
    print(f"  device: {device}")

    # ---- model -----------------------------------------------------------
    state = torch.load(args.ckpt, map_location="cpu")
    hp = state.get("hyper_parameters", {})
    if not hp:
        raise SystemExit("ckpt missing hyper_parameters")
    method_cfg = OmegaConf.create(hp["method_cfg"])
    backbone_cfg = OmegaConf.create(hp["backbone_cfg"])
    data_cfg = OmegaConf.create(hp["data_cfg"])

    print()
    print(f"  loss weights:  av={method_cfg.loss.av_weight}  va={method_cfg.loss.va_weight}  "
          f"asym={method_cfg.loss.asym_weight}  cls={method_cfg.loss.cls_weight}  "
          f"aux={method_cfg.aux_crossgen.weight}  (aux enabled={method_cfg.aux_crossgen.enabled})")

    model = build_method(
        method_name=method_cfg.name,
        method_cfg=method_cfg,
        backbone_cfg=backbone_cfg,
        data_cfg=data_cfg,
    )
    sd = state.get("state_dict", state)
    model.load_state_dict(sd, strict=False)
    model.to(device)
    # IMPORTANT: use eval() so dropout is OFF (gives real numerical values
    # rather than NaNs). Gradients still flow normally — eval() only changes
    # the behavior of dropout/BatchNorm, not autograd.
    model.eval()

    # Convenient handles to sub-modules for grad inspection
    sub = {
        "video_backbone":     model.model.video,
        "audio_backbone":     model.model.audio,
        "f_A→V predictor":    model.model.av_pred,
        "f_V→A predictor":    model.model.va_pred,
        "classifier head":    model.model.cls,
    }

    # ---- inputs ----------------------------------------------------------
    rv_path, fv_path, aw_path, real_video, fake_video, audio = load_paired_inputs(
        args.hdtf_root, args.num, args.fake_generator,
        num_frames=data_cfg.num_frames,
        frame_stride=data_cfg.frame_stride,
        frame_size=data_cfg.frame_size,
        audio_seconds=data_cfg.audio_seconds,
        audio_sample_rate=data_cfg.audio_sample_rate,
    )
    train_transform = build_video_transform(data_cfg.aug, training=True)
    real_norm = train_transform(real_video)
    fake_norm = train_transform(fake_video)

    banner("INPUT BATCH (1 real + 1 fake)", 1)
    print(f"    real video:  {rv_path}")
    print(f"    fake video:  {fv_path}")
    print(f"    audio (real, shared by both samples):  {aw_path}")

    # batch the two samples together — order [real, fake], labels [0, 1]
    video_batch = torch.stack([real_norm, fake_norm], dim=0).to(device)
    audio_batch = torch.stack([audio,     audio    ], dim=0).to(device)
    labels      = torch.tensor([0, 1], dtype=torch.long, device=device)
    tprint("video batch (B,T,3,H,W)", video_batch)
    tprint("audio batch (B,S)",       audio_batch)
    tprint("labels       (B,)",       labels)

    # =====================================================================
    # FORWARD
    # =====================================================================
    banner("FORWARD  (predict_pairs + cross-attention introspection)", 0)

    step(1, "video backbone (VideoMAE)")
    v = model.model.video(video_batch)
    tprint("v.tokens (B,N,768)", v["tokens"])
    tprint("v.pooled (B,768)",   v["pooled"])
    explain("Token grid: (16/2)·(224/16)² = 8 × 14 × 14 = 1568 spatiotemporal tokens.")

    step(2, "audio backbone (Wav2Vec2)")
    a = model.model.audio(audio_batch)
    tprint("a.tokens (B,T_a,768)", a["tokens"])
    tprint("a.pooled (B,768)",     a["pooled"])

    step(3, "cross-modal predictor f_{A→V}  (audio → video manifold)")
    explain("Cross-attention: query=projected v.tokens (target side), "
            "key/value=projected a.tokens (source memory). Each video token "
            "attends to ALL audio tokens to refine its prediction.")
    v_pred = expose_cross_attention(model.model.av_pred, a["tokens"], v["tokens"], name="f_AV")
    tprint("v_pred (B,N,768)", v_pred)

    step(4, "cross-modal predictor f_{V→A}  (video → audio manifold)")
    a_pred = expose_cross_attention(model.model.va_pred, v["tokens"], a["tokens"], name="f_VA")
    tprint("a_pred (B,T_a,768)", a_pred)

    step(5, "per-sample MSE residuals  L_AV  and  L_VA")
    explain("Computed with reduction='none' then averaged over (token, channel), "
            "so each sample gets its own scalar.")
    l_av = F.mse_loss(v_pred, v["tokens"], reduction="none").mean(dim=[1, 2])
    l_va = F.mse_loss(a_pred, a["tokens"], reduction="none").mean(dim=[1, 2])
    asym = l_va - l_av
    print(f"     L_AV  per sample: {l_av.detach().tolist()}")
    print(f"     L_VA  per sample: {l_va.detach().tolist()}")
    print(f"     asym  per sample: {asym.detach().tolist()}")
    print(f"        ↳ index 0 = real,  index 1 = fake")

    # =====================================================================
    # FIVE LOSSES
    # =====================================================================
    banner("FIVE LOSSES  (mirror of CTALitModule.training_step)", 0)

    is_real  = (labels == 0).float()                       # [1, 0]
    denom_r  = is_real.sum().clamp(min=1.0)
    print(f"   is_real mask  = {is_real.detach().tolist()}    "
          f"(1 means 'count this sample',  0 means 'mask out')")

    # ---- loss_av / loss_va: REAL only, drives predictor + backbones ------
    step(1, "loss_av = mean(L_AV  |  label==0)        — REAL only")
    explain("fake's contribution is multiplied by 0 ⇒ no gradient through "
            "the A→V predictor for fake samples.")
    loss_av = (l_av * is_real).sum() / denom_r
    tprint("loss_av  (scalar)", loss_av)

    step(2, "loss_va = mean(L_VA  |  label==0)        — REAL only")
    loss_va = (l_va * is_real).sum() / denom_r
    tprint("loss_va  (scalar)", loss_va)

    # ---- loss_asym: BOTH, margin pushes fake's asym below real's --------
    step(3, "loss_asym = ReLU(asym_fake_mean − asym_real_mean)   — BOTH (margin)")
    explain("If fake's asym is already lower than real's (the desired ranking), "
            "ReLU(·) = 0 ⇒ no gradient. Else it pushes them apart. "
            "Weak signal (weight 0.5) so predictors don't collapse.")
    asym_r = asym[labels == 0]
    asym_f = asym[labels == 1]
    loss_asym = F.relu(asym_f.mean() - asym_r.mean())
    tprint("loss_asym  (scalar)", loss_asym,
           more=f"asym_r mean={asym_r.mean().item():+.4f},  asym_f mean={asym_f.mean().item():+.4f}")

    # ---- loss_cls: BOTH, drives classifier + backbones (predictor detached) -----
    step(4, "loss_cls  = BCE(score, label)            — BOTH;  L_AV/L_VA detach()ed")
    explain("`l_av.detach()` and `l_va.detach()` cut the gradient path "
            "from BCE back into the predictors. The classifier head can use "
            "the asym scalars as features but cannot rewrite them.")
    logits = model.model.classify(
        v["pooled"], a["pooled"],
        l_av.detach(),       # ← detach()
        l_va.detach(),       # ← detach()
    )
    print(f"     logits  per sample: {logits.detach().squeeze(-1).tolist()}")
    print(f"     scores  per sample: {torch.sigmoid(logits.squeeze(-1)).detach().tolist()}")
    loss_cls = F.binary_cross_entropy_with_logits(logits.squeeze(-1), labels.float())
    tprint("loss_cls  (scalar)", loss_cls)

    # ---- loss_aux: only computable if alt_video exists in batch ----------
    step(5, "loss_aux  = MSE(asym, asym_alt_generator)  — paired FAKEs only")
    explain("This batch has no alt_video / alt_audio (HDTF-paired isn't dual-generator "
            "paired). In real training a fake clip can be paired with the SAME identity's "
            "fake from a different generator; loss_aux pushes their s_asym to be close, "
            "yielding a generator-invariant signal. Here loss_aux = 0.")
    loss_aux = asym.new_zeros([])
    tprint("loss_aux  (scalar; 0 because no alt batch)", loss_aux)

    # ---- total ----------------------------------------------------------
    step(6, "total = Σ wᵢ · lossᵢ")
    total = (
        method_cfg.loss.av_weight   * loss_av   +
        method_cfg.loss.va_weight   * loss_va   +
        method_cfg.loss.asym_weight * loss_asym +
        method_cfg.loss.cls_weight  * loss_cls  +
        method_cfg.aux_crossgen.weight * loss_aux
    )
    tprint("total loss  (scalar)", total,
           more=f"= {method_cfg.loss.av_weight}·loss_av + {method_cfg.loss.va_weight}·loss_va "
                f"+ {method_cfg.loss.asym_weight}·loss_asym + {method_cfg.loss.cls_weight}·loss_cls "
                f"+ {method_cfg.aux_crossgen.weight}·loss_aux")

    # =====================================================================
    # BACKWARD — one loss at a time, see who actually receives gradients
    # =====================================================================
    banner("BACKWARD GRADIENT ROUTING  (one loss at a time, count non-zero gradients per submodule)", 0)
    explain("For each individual loss, we zero all gradients, call .backward(retain_graph=True), "
            "and report how many parameters in each submodule have non-zero grads. "
            "This makes 'who is trained by what' explicit.")

    individual_losses = [
        ("loss_av",   loss_av,   "real-only mse on A→V"),
        ("loss_va",   loss_va,   "real-only mse on V→A"),
        ("loss_asym", loss_asym, "margin between asym_fake and asym_real"),
        ("loss_cls",  loss_cls,  "BCE on classifier (detach() on l_av/l_va)"),
    ]

    for nm, l, desc in individual_losses:
        zero_all_grads(model)
        if l.requires_grad and l.grad_fn is not None:
            try:
                l.backward(retain_graph=True)
            except RuntimeError as e:
                print(f"\n  [{nm}]  backward FAILED: {e}")
                continue
        print(f"\n  [{nm:9s}]  {desc}")
        for label, m in sub.items():
            grad_summary(m, label)

    # =====================================================================
    # FINAL SUMMARY TABLE
    # =====================================================================
    banner("F I N A L   T A B L E  (this is what you'd label on the framework figure)", 0)
    print()
    print(f"   {'sample':<6s}  {'L_AV':>10s}  {'L_VA':>10s}  {'asym':>10s}  {'logit':>10s}  {'score':>8s}  {'label':>6s}")
    print(f"   {'──────':<6s}  {'──────────':>10s}  {'──────────':>10s}  {'──────────':>10s}  {'──────────':>10s}  {'──────':>8s}  {'──────':>6s}")
    for i, name in enumerate(["real", "fake"]):
        gt = "0 (real)" if i == 0 else "1 (fake)"
        sc = torch.sigmoid(logits[i].squeeze()).item()
        print(f"   {name:<6s}  {l_av[i].item():>10.5f}  {l_va[i].item():>10.5f}  "
              f"{asym[i].item():>+10.5f}  {logits[i].squeeze().item():>+10.4f}  {sc:>8.4f}  {gt:>6s}")

    print()
    print(f"   loss decomposition this batch:")
    print(f"      loss_av   = {loss_av.item():.6f}")
    print(f"      loss_va   = {loss_va.item():.6f}")
    print(f"      loss_asym = {loss_asym.item():.6f}")
    print(f"      loss_cls  = {loss_cls.item():.6f}")
    print(f"      loss_aux  = {loss_aux.item():.6f}")
    print(f"      ─────────────────────")
    print(f"      total     = {total.item():.6f}")
    print()


if __name__ == "__main__":
    main()