# ==============================================
# Stephen Model Fine-Tuning Script (LoRA + PEFT)
# Clean + Debug-Enhanced for Grad & Deprecation Warnings
# ==============================================

!pip install -q "transformers>=4.44.0" "datasets" "peft>=0.12.0" accelerate bitsandbytes sentencepiece huggingface_hub

import os
from datetime import datetime
from huggingface_hub import login, whoami
from datasets import load_dataset
from transformers import (
    AutoTokenizer, AutoModelForCausalLM, TrainingArguments,
    Trainer, DataCollatorForLanguageModeling, BitsAndBytesConfig
)
from peft import LoraConfig, get_peft_model
from peft import prepare_model_for_kbit_training
import torch

# ==============================================
# Logging helper
# ==============================================
def log(msg):
    print(f"[{datetime.now().strftime('%H:%M:%S')}] {msg}")

# ==============================================
# 1. Hugging Face Login
# ==============================================
HF_TOKEN = os.getenv("HF_TOKEN")
if not HF_TOKEN:
    raise ValueError("❌ HF_TOKEN environment variable not set.")

log("Logging into Hugging Face...")
login(token=HF_TOKEN, add_to_git_credential=True)
log(f"Logged in as: {whoami()['name']} ✅")

# ==============================================
# 2. Load Dataset
# ==============================================
dataset_name = "dgtalbug/stephen-dataset"  # CHANGE THIS
data_file = "stephen.jsonl"                # CHANGE THIS

log(f"Loading dataset: {dataset_name}/{data_file} ...")
dataset = load_dataset(dataset_name, data_files=data_file, split="train")
log(f"Dataset loaded — {len(dataset)} rows")
log(f"First example: {dataset[0]}")

# ==============================================
# 3. Load Base Model & Tokenizer
# ==============================================
base_model = "dgtalbug/stable-code-instruct-3b"  # CHANGE THIS
log(f"Loading base model: {base_model}...")

tokenizer = AutoTokenizer.from_pretrained(
    base_model,
    token=HF_TOKEN,
    use_fast=True
)
if tokenizer.pad_token is None:
    tokenizer.pad_token = tokenizer.eos_token

# ✅ Quantization config
bnb_config = BitsAndBytesConfig(
    load_in_8bit=True,
    llm_int8_threshold=6.0
)

try:
    model = AutoModelForCausalLM.from_pretrained(
        base_model,
        token=HF_TOKEN,
        device_map="auto",
        torch_dtype=torch.float16,
        trust_remote_code=True,
        return_dict=True,
        quantization_config=bnb_config
    )
except Exception as e:
    log(f"⚠️ Quantized load failed: {e} — falling back to fp16.")
    model = AutoModelForCausalLM.from_pretrained(
        base_model,
        token=HF_TOKEN,
        device_map="auto",
        torch_dtype=torch.float16,
        trust_remote_code=True,
        return_dict=True
    )

log("Base model loaded ✅")

# ==============================================
# 4. LoRA Config
# ==============================================
# log("Configuring LoRA...")
# lora_config = LoraConfig(
#     r=16,
#     lora_alpha=32,
#     target_modules=["q_proj", "v_proj", "k_proj", "o_proj"],
#     lora_dropout=0.05,
#     bias="none",
#     task_type="CAUSAL_LM"
# )
# model = get_peft_model(model, lora_config)

# # ✅ Ensure LoRA params require grad
# for name, param in model.named_parameters():
#     if "lora" in name:
#         param.requires_grad = True
#     else:
#         param.requires_grad = False

# # ✅ Sanity check: see how many params are trainable
# model.print_trainable_parameters()

# log("LoRA config applied ✅")
log("Configuring LoRA...")

# First, prepare for 8-bit training (important for bitsandbytes)
model = prepare_model_for_kbit_training(model)

# LoRA config
lora_config = LoraConfig(
    r=16,
    lora_alpha=32,
    target_modules=["q_proj", "v_proj", "k_proj", "o_proj"],  # adjust if needed
    lora_dropout=0.05,
    bias="none",
    task_type="CAUSAL_LM"
)

# Apply LoRA
model = get_peft_model(model, lora_config)

# Double-check trainable params
trainable_params = []
for name, param in model.named_parameters():
    if param.requires_grad:
        trainable_params.append(name)

if not trainable_params:
    raise RuntimeError("❌ No parameters set to require gradients! LoRA not applied correctly.")

log(f"✅ Found {len(trainable_params)} trainable parameters.")
log(f"First 20 trainable params: {trainable_params[:20]}")

# Print PEFT/LoRA summary
model.print_trainable_parameters()
# ==============================================
# 5. Tokenize Dataset
# ==============================================
log("Tokenizing dataset...")

first_row = dataset[0]
if "text" in first_row:
    text_key = "text"
elif "prompt" in first_row:
    text_key = "prompt"
else:
    text_key = list(first_row.keys())[0]

log(f"Using text key: '{text_key}'")

def tokenize_fn(example):
    tokenized = tokenizer(example[text_key], truncation=True, padding="max_length", max_length=512)
    tokenized["labels"] = tokenized["input_ids"].copy()  # ✅ Ensure labels exist for grad
    return tokenized

tokenized_dataset = dataset.map(tokenize_fn, batched=True, remove_columns=dataset.column_names)
log("Tokenization complete ✅")
log(f"Tokenized sample: {tokenized_dataset[0]}")

# ==============================================
# 6. Data Collator
# ==============================================
data_collator = DataCollatorForLanguageModeling(tokenizer, mlm=False)

# ==============================================
# 7. Training Arguments
# ==============================================
output_dir = "./stephen-lora"
log("Preparing training arguments...")

training_args = TrainingArguments(
    output_dir=output_dir,
    overwrite_output_dir=True,
    per_device_train_batch_size=8,
    gradient_accumulation_steps=2,
    gradient_checkpointing=True,
    warmup_steps=50,
    num_train_epochs=3,
    max_steps=-1,
    learning_rate=1e-4,
    lr_scheduler_type="cosine",
    fp16=True,
    optim="adamw_torch",
    logging_dir="./logs",
    logging_steps=20,
    save_strategy="epoch",
    save_total_limit=2,
    push_to_hub=True,
    hub_strategy="end",
    ddp_find_unused_parameters=False,
    label_names=["labels"]
)
log("Training arguments ready ✅")

# ==============================================
# 8. Debugging Helper Hooks
# ==============================================
def debug_batch(batch):
    log(f"🔍 Debug batch keys: {list(batch.keys())}")
    log(f"🔍 First input_ids: {batch['input_ids'][0][:10]}")
    log(f"🔍 First labels: {batch['labels'][0][:10]}")
    log(f"🔍 labels.requires_grad? {torch.tensor(batch['labels']).requires_grad}")

# ==============================================
# 9. Custom Trainer (safe + debug)
# ==============================================
class SafeTrainer(Trainer):
    def compute_loss(self, model, inputs, return_outputs=False, **kwargs):
        # Debug batch content once
        if self.state.global_step == 0:
            debug_batch(inputs)
        if "labels" not in inputs:
            inputs["labels"] = inputs["input_ids"].clone()
        outputs = model(**inputs)
        loss = outputs.get("loss") if isinstance(outputs, dict) else outputs[0]
        return (loss, outputs) if return_outputs else loss

log("Initializing Trainer...")
trainer = SafeTrainer(
    model=model,
    args=training_args,
    train_dataset=tokenized_dataset,
    data_collator=data_collator
)
log("Trainer initialized ✅")

# ==============================================
# 10. Train & Push
# ==============================================
trainable_params = [n for n, p in model.named_parameters() if p.requires_grad]
log(f"Trainable params count: {len(trainable_params)}")
log(f"First 20 trainable params: {trainable_params[:20]}")

last_ckpt = None
if os.path.isdir(output_dir):
    checkpoints = [d for d in os.listdir(output_dir) if d.startswith("checkpoint-")]
    if checkpoints:
        last_ckpt = os.path.join(output_dir, sorted(checkpoints)[-1])

if last_ckpt and os.path.isdir(last_ckpt):
    log(f"Resuming from checkpoint: {last_ckpt}")
    trainer.train(resume_from_checkpoint=last_ckpt)
else:
    log("No checkpoint found — starting fresh training.")
    trainer.train()

log("Training completed ✅")

try:
    log("Pushing fine-tuned model to Hugging Face Hub...")
    trainer.push_to_hub(repo_id="dgtalbug/stephen", token=HF_TOKEN)
    log(f"Model pushed to: https://huggingface.co/dgtalbug/stephen ✅")
except Exception as e:
    log(f"⚠️ Push to hub failed: {e}")