# Install Transformers
!pip install -q transformers

# --- Imports ---
import os
import torch
import torch.nn as nn
import pandas as pd
from sklearn.preprocessing import LabelEncoder
from sklearn.model_selection import train_test_split
from transformers import DebertaTokenizer, DebertaModel
from torch.optim import AdamW
from tqdm import tqdm

# --- Config ---
TEXT_COLUMN = 'Sanction_Context'
LABEL_COLUMNS = ['Red_Flag_Reason', 'Maker_Action', 'Escalation_Level',
                 'Risk_Category', 'Risk_Drivers', 'Investigation_Outcome']
DEVICE = torch.device("cuda" if torch.cuda.is_available() else "cpu")

# --- Load Data ---
df = pd.read_csv('/kaggle/input/deberta/synthetic_transactions_samples_5000.csv')
X = df[TEXT_COLUMN].tolist()
y = df[LABEL_COLUMNS]

# --- Label Encode ---
label_encoders = {}
y_encoded = pd.DataFrame()
for col in LABEL_COLUMNS:
    le = LabelEncoder()
    y_encoded[col] = le.fit_transform(y[col])
    label_encoders[col] = le

# --- Split Data ---
X_train, _, y_train, _ = train_test_split(X, y_encoded, test_size=0.2, random_state=42)

# --- Tokenize ---
tokenizer = DebertaTokenizer.from_pretrained("microsoft/deberta-base")
train_encodings = tokenizer(X_train, truncation=True, padding=True, max_length=128, return_tensors="pt")

# --- Model ---
class DebertaMultiOutput(nn.Module):
    def __init__(self, num_labels_per_output):
        super().__init__()
        self.deberta = DebertaModel.from_pretrained("microsoft/deberta-base")
        self.dropout = nn.Dropout(0.3)
        self.classifiers = nn.ModuleList([
            nn.Linear(self.deberta.config.hidden_size, n_labels) for n_labels in num_labels_per_output
        ])

    def forward(self, input_ids, attention_mask):
        outputs = self.deberta(input_ids=input_ids, attention_mask=attention_mask)
        pooled = self.dropout(outputs.last_hidden_state[:, 0])
        return [classifier(pooled) for classifier in self.classifiers]

# --- Prepare Labels ---
labels = [torch.tensor(y_train[col].values) for col in LABEL_COLUMNS]
num_labels = [len(le.classes_) for le in label_encoders.values()]

# --- Initialize Model ---
model = DebertaMultiOutput(num_labels).to(DEVICE)
optimizer = AdamW(model.parameters(), lr=2e-5)
loss_fn = nn.CrossEntropyLoss()

# --- Training Loop ---
model.train()
for epoch in range(3):
    total_loss = 0
    for i in tqdm(range(0, len(X_train), 16)):
        ids = train_encodings['input_ids'][i:i+16].to(DEVICE)
        mask = train_encodings['attention_mask'][i:i+16].to(DEVICE)
        y_batch = [label[i:i+16].to(DEVICE) for label in labels]

        optimizer.zero_grad()
        outputs = model(ids, mask)
        loss = sum(loss_fn(o, y) for o, y in zip(outputs, y_batch))
        loss.backward()
        optimizer.step()
        total_loss += loss.item()
    print(f"Epoch {epoch+1} Loss: {total_loss:.2f}")

# --- Save Model as .pth ---
save_dir = "output_models/deberta"
os.makedirs(save_dir, exist_ok=True)
save_path = os.path.join(save_dir, "deberta_model.pth")

torch.save({
    'model_state_dict': model.state_dict(),
    'tokenizer': tokenizer,
    'label_encoders': label_encoders,
    'num_labels': num_labels
}, save_path)

print(f"✅ DeBERTa model saved to '{save_path}'")