"""
Example 3 — Unconditional VAE: Melt-Pool Side Profiles

Trains a minimal convolutional VAE on side-profile images and generates
new samples. No conditioning on process parameters.

Images are loaded from frames/side/ — already border-recolored by the
dataset pipeline. Only frames labeled Keyhole or Conduction are used
(Initial Emptiness and Forming Phase are excluded).

Architecture: 3×32×64 → latent z (dim=16) → 3×32×64

Set MAX_IMAGES to limit dataset size for a quick reviewer run.
Set MAX_IMAGES = None to use all available images.

Outputs saved to runs/generation_<timestamp>/:
  generation_epoch_NNN.png     — sample grid every SAMPLE_EVERY epochs
  generation_loss.png          — training loss curve
  generation_reconstructions.png
  generation_samples.png
  run.log

This is a proof-of-concept, not a benchmark.
"""

import csv
import logging
import sys
from datetime import datetime
from pathlib import Path

import numpy as np
import torch
import torch.nn as nn
from torch.utils.data import DataLoader, TensorDataset
from PIL import Image as PILImage
import matplotlib.pyplot as plt

# ------------------------------------------------------------------
# Config  ← edit DATA_DIRS to point at your data directories
# ------------------------------------------------------------------

DATA_DIRS = [
    Path(__file__).parent.parent / "rnl" / "final_data_processed",
    Path(__file__).parent.parent / "rnl" / "lrz_data_new_format",
]
OUT_ROOT = Path(__file__).parent.parent / "runs"

MAX_IMAGES  = 500    # reviewer-friendly cap (None = all images)
IMG_W       = 64
IMG_H       = 32
LATENT_DIM  = 16
BATCH_SIZE  = 64
EPOCHS      = 50
LR          = 1e-3
SAMPLE_EVERY = 10
RED_WEIGHT  = 50.0
RANDOM_SEED = 42
DEVICE      = "cuda" if torch.cuda.is_available() else "cpu"

VALID_LABELS = {"Keyhole", "Conduction"}

# ------------------------------------------------------------------
# Logger
# ------------------------------------------------------------------

class _ColorFormatter(logging.Formatter):
    _COLORS = {logging.INFO: "\033[32m", logging.WARNING: "\033[33m", logging.ERROR: "\033[31m"}
    _RESET = "\033[0m"; _BOLD = "\033[1m"

    def format(self, record):
        color = self._COLORS.get(record.levelno, self._RESET)
        t = self.formatTime(record, "%H:%M:%S")
        return f"{self._BOLD}{t}{self._RESET}  {color}{record.levelname:<8}{self._RESET}  {record.getMessage()}"


run_id  = datetime.now().strftime("%Y%m%d_%H%M%S")
out_dir = OUT_ROOT / f"generation_{run_id}"
out_dir.mkdir(parents=True, exist_ok=True)

log = logging.getLogger("vae")
log.setLevel(logging.DEBUG)
_ch = logging.StreamHandler(sys.stdout); _ch.setFormatter(_ColorFormatter()); log.addHandler(_ch)
_fh = logging.FileHandler(out_dir / "run.log")
_fh.setFormatter(logging.Formatter("%(asctime)s  %(levelname)-8s  %(message)s", datefmt="%H:%M:%S"))
log.addHandler(_fh)

log.info("=" * 60)
log.info(f"Run ID    : {run_id}")
log.info(f"Results   : {out_dir}")
log.info(f"Device    : {DEVICE}")
log.info(f"Resolution: {IMG_W}×{IMG_H}")
log.info("=" * 60)

# ------------------------------------------------------------------
# 1. Collect valid image paths from frames.csv
# ------------------------------------------------------------------

img_paths = []
for data_dir in DATA_DIRS:
    if not data_dir.is_dir():
        continue
    for sim_dir in sorted(data_dir.iterdir()):
        frames_csv = sim_dir / "frames.csv"
        if not frames_csv.exists():
            continue
        for row in csv.DictReader(frames_csv.open()):
            if row["label"] not in VALID_LABELS:
                continue
            path = sim_dir / row["side_filename"]
            if path.exists():
                img_paths.append(path)

import random
rng = random.Random(RANDOM_SEED)
rng.shuffle(img_paths)
if MAX_IMAGES is not None:
    img_paths = img_paths[:MAX_IMAGES]

log.info(f"Found {len(img_paths)} valid side-profile frames")

# ------------------------------------------------------------------
# 2. Load images (already border-recolored — just resize)
# ------------------------------------------------------------------

log.info("Loading images ...")
imgs = []
for path in img_paths:
    pil = PILImage.open(path).convert("RGB").resize((IMG_W, IMG_H), PILImage.Resampling.BILINEAR)
    imgs.append(np.array(pil))

data = torch.from_numpy(
    np.stack(imgs).astype(np.float32) / 255.0
).permute(0, 3, 1, 2)   # N×3×H×W

loader = DataLoader(TensorDataset(data), batch_size=BATCH_SIZE, shuffle=True, generator=torch.Generator().manual_seed(RANDOM_SEED))
log.info(f"Tensor shape: {tuple(data.shape)}")

# ------------------------------------------------------------------
# 3. Convolutional VAE  (3×32×64 input)
#
# Encoder spatial progression (H×W):
#   3×32×64 → 32×16×32 → 64×8×16 → 128×4×8 → 256×2×4
# Flatten → 2048 → mu / logvar (dim=16)
# ------------------------------------------------------------------

class Encoder(nn.Module):
    def __init__(self, latent_dim):
        super().__init__()
        self.conv = nn.Sequential(
            nn.Conv2d(3,   32,  4, 2, 1), nn.ReLU(),
            nn.Conv2d(32,  64,  4, 2, 1), nn.ReLU(),
            nn.Conv2d(64,  128, 4, 2, 1), nn.ReLU(),
            nn.Conv2d(128, 256, 4, 2, 1), nn.ReLU(),
        )
        self.fc_mu     = nn.Linear(256 * 2 * 4, latent_dim)
        self.fc_logvar = nn.Linear(256 * 2 * 4, latent_dim)

    def forward(self, x):
        h = self.conv(x).flatten(1)
        return self.fc_mu(h), self.fc_logvar(h)


class Decoder(nn.Module):
    def __init__(self, latent_dim):
        super().__init__()
        self.fc = nn.Linear(latent_dim, 256 * 2 * 4)
        self.deconv = nn.Sequential(
            nn.ConvTranspose2d(256, 128, 4, 2, 1), nn.ReLU(),
            nn.ConvTranspose2d(128, 64,  4, 2, 1), nn.ReLU(),
            nn.ConvTranspose2d(64,  32,  4, 2, 1), nn.ReLU(),
            nn.ConvTranspose2d(32,  3,   4, 2, 1), nn.Sigmoid(),
        )

    def forward(self, z):
        return self.deconv(self.fc(z).view(-1, 256, 2, 4))


class VAE(nn.Module):
    def __init__(self, latent_dim):
        super().__init__()
        self.encoder = Encoder(latent_dim)
        self.decoder = Decoder(latent_dim)

    def reparameterise(self, mu, logvar):
        return mu + (0.5 * logvar).exp() * torch.randn_like(mu)

    def forward(self, x):
        mu, logvar = self.encoder(x)
        return self.decoder(self.reparameterise(mu, logvar)), mu, logvar


def vae_loss(recon, x, mu, logvar):
    # Upweight melt-pool pixels (red channel dominant) so the VAE
    # doesn't ignore the small pool region against the background.
    mask    = ((x[:, 0] > 0.5) & (x[:, 1] < 0.25) & (x[:, 2] < 0.25)).unsqueeze(1).float()
    weights = 1.0 + (RED_WEIGHT - 1.0) * mask.expand_as(x)
    recon_loss = (weights * (recon - x).pow(2)).sum()
    kld        = -0.5 * torch.sum(1 + logvar - mu.pow(2) - logvar.exp())
    return recon_loss + kld

# ------------------------------------------------------------------
# 4. Train
# ------------------------------------------------------------------

torch.manual_seed(RANDOM_SEED)
model    = VAE(LATENT_DIM).to(DEVICE)
opt      = torch.optim.Adam(model.parameters(), lr=LR)
z_fixed  = torch.randn(16, LATENT_DIM, device=DEVICE)
loss_log = []

log.info(f"Training VAE for {EPOCHS} epochs  |  {len(data)} images  |  batch={BATCH_SIZE}")

for epoch in range(1, EPOCHS + 1):
    model.train()
    total = 0.0
    for (batch,) in loader:
        batch = batch.to(DEVICE)
        recon, mu, logvar = model(batch)
        loss = vae_loss(recon, batch, mu, logvar)
        opt.zero_grad(); loss.backward(); opt.step()
        total += loss.item()

    loss_per_img = total / len(data)
    loss_log.append(loss_per_img)
    log.info(f"  epoch {epoch:3d}/{EPOCHS}  loss/img: {loss_per_img:.4f}")

    if epoch % SAMPLE_EVERY == 0:
        model.eval()
        with torch.no_grad():
            samples = model.decoder(z_fixed).cpu().permute(0, 2, 3, 1).numpy()
        fig, axes = plt.subplots(2, 8, figsize=(14, 4))
        for i, ax in enumerate(axes.flat):
            ax.imshow(samples[i]); ax.axis("off")
        fig.suptitle(f"VAE samples — epoch {epoch}/{EPOCHS}  (loss/img={loss_per_img:.4f})", fontsize=10)
        plt.tight_layout()
        path = out_dir / f"generation_epoch_{epoch:03d}.png"
        plt.savefig(path, dpi=100); plt.close(fig)
        log.info(f"  → saved {path.name}")

# ------------------------------------------------------------------
# 5. Final plots
# ------------------------------------------------------------------

model.eval()
log.info("Generating final plots ...")

fig, ax = plt.subplots(figsize=(7, 3))
ax.plot(range(1, EPOCHS + 1), loss_log, lw=1.5)
ax.set_xlabel("Epoch"); ax.set_ylabel("Loss / image")
ax.set_title("VAE training loss")
plt.tight_layout()
plt.savefig(out_dir / "generation_loss.png", dpi=150); plt.close(fig)

N_SHOW = 8
with torch.no_grad():
    originals = data[:N_SHOW].to(DEVICE)
    recons, _, _ = model(originals)
    originals = originals.cpu().permute(0, 2, 3, 1).numpy()
    recons    = recons.cpu().permute(0, 2, 3, 1).numpy()
    samples   = model.decoder(torch.randn(16, LATENT_DIM, device=DEVICE)).cpu().permute(0, 2, 3, 1).numpy()

fig, axes = plt.subplots(2, N_SHOW, figsize=(14, 3))
for i in range(N_SHOW):
    axes[0, i].imshow(originals[i]); axes[0, i].axis("off")
    axes[1, i].imshow(recons[i]);    axes[1, i].axis("off")
axes[0, 0].set_ylabel("Real",  rotation=0, labelpad=30, va="center")
axes[1, 0].set_ylabel("Recon", rotation=0, labelpad=30, va="center")
fig.suptitle("VAE reconstructions — melt-pool side profiles", fontsize=11)
plt.tight_layout()
plt.savefig(out_dir / "generation_reconstructions.png", dpi=150); plt.close(fig)

fig, axes = plt.subplots(2, 8, figsize=(14, 4))
for i, ax in enumerate(axes.flat):
    ax.imshow(samples[i]); ax.axis("off")
fig.suptitle("Unconditional VAE samples — melt-pool side profiles", fontsize=11)
plt.tight_layout()
plt.savefig(out_dir / "generation_samples.png", dpi=150); plt.close(fig)

log.info(f"All outputs saved to {out_dir}")
log.info("Done.")