"""
Train a single expert adapter for smart contract vulnerability detection.

Usage:
    python train_expert.py --expert Reentrancy
    python train_expert.py --expert "Access Control"
    python train_expert.py --expert "Integer Overflow/Underflow"
    python train_expert.py --expert "Timestamp Dependence"
    python train_expert.py --expert "Unchecked Low-Level Calls"

Each expert is a LoRA adapter on Qwen2.5-Coder-3B-Instruct, trained to
answer: "Is this contract vulnerable with MY specific vulnerability type?"

Positives: contracts with the expert's vulnerability type
Negatives: safe contracts + contracts with OTHER vulnerability types
"""

import argparse
import os
import torch
from datasets import load_dataset
from peft import LoraConfig
from transformers import AutoModelForCausalLM, AutoTokenizer, BitsAndBytesConfig
from trl import SFTConfig, SFTTrainer
from huggingface_hub import HfApi
import trackio

BASE_MODEL = "Qwen/Qwen2.5-Coder-3B-Instruct"

# Expert → dataset mapping
EXPERT_DATASETS = {
    "Reentrancy": "jhsu12/solidity-vuln-expert-reentrancy",
    "Access Control": "jhsu12/solidity-vuln-expert-access-control",
    "Integer Overflow/Underflow": "jhsu12/solidity-vuln-expert-integer-overflow-underflow",
    "Timestamp Dependence": "jhsu12/solidity-vuln-expert-timestamp-dependence",
    "Unchecked Low-Level Calls": "jhsu12/solidity-vuln-expert-unchecked-low-level-calls",
}


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--expert", type=str, required=True,
                        choices=list(EXPERT_DATASETS.keys()),
                        help="Vulnerability type to train expert for")
    parser.add_argument("--output_dir", type=str, default=None)
    parser.add_argument("--lora_r", type=int, default=32)
    parser.add_argument("--epochs", type=int, default=5)
    parser.add_argument("--batch_size", type=int, default=2)
    parser.add_argument("--grad_accum", type=int, default=4)
    parser.add_argument("--lr", type=float, default=2e-4)
    parser.add_argument("--max_seq_len", type=int, default=1536)
    parser.add_argument("--push_to_hub", action="store_true", default=True)
    return parser.parse_args()


def main():
    args = parse_args()
    expert_name = args.expert
    dataset_id = EXPERT_DATASETS[expert_name]

    hub_model_id = f"jhsu12/solidity-vuln-expert-{expert_name.lower().replace(' ', '-').replace('/', '-')}-v1"
    output_dir = args.output_dir or f"./expert-{expert_name.lower().replace(' ', '-').replace('/', '-')}"

    print(f"=" * 60)
    print(f"  Training Expert: {expert_name}")
    print(f"  Base Model: {BASE_MODEL}")
    print(f"  Dataset: {dataset_id}")
    print(f"  Hub Model: {hub_model_id}")
    print(f"=" * 60)

    # GPU config
    HAS_BF16 = torch.cuda.is_bf16_supported() if torch.cuda.is_available() else False
    GPU_MEM = torch.cuda.get_device_properties(0).total_memory / 1e9 if torch.cuda.is_available() else 0
    print(f"\n🖥️  GPU: {torch.cuda.get_device_name(0) if torch.cuda.is_available() else 'CPU'}")
    print(f"💾 VRAM: {GPU_MEM:.1f} GB")
    print(f"🔢 BF16: {HAS_BF16}")

    compute_dtype = torch.bfloat16 if HAS_BF16 else torch.float16

    # Trackio monitoring
    trackio.init(
        project=f"solidity-expert-{expert_name.lower().replace(' ', '-').replace('/', '-')}",
        name=f"{expert_name.lower().replace(' ', '-').replace('/', '-')}-3b-v1",
    )

    # Load dataset
    print(f"\n📦 Loading dataset...")
    dataset = load_dataset(dataset_id)
    train_dataset = dataset["train"]
    eval_dataset = dataset["test"]
    print(f"   Train: {len(train_dataset)}  Eval: {len(eval_dataset)}")

    # Load model with 4-bit quantization
    bnb_config = BitsAndBytesConfig(
        load_in_4bit=True,
        bnb_4bit_quant_type="nf4",
        bnb_4bit_compute_dtype=compute_dtype,
        bnb_4bit_use_double_quant=True,
    )

    print(f"\n🤖 Loading {BASE_MODEL}...")
    model = AutoModelForCausalLM.from_pretrained(
        BASE_MODEL,
        quantization_config=bnb_config,
        device_map="auto",
        dtype=compute_dtype,
        trust_remote_code=True,
        attn_implementation="sdpa",
    )

    tokenizer = AutoTokenizer.from_pretrained(BASE_MODEL, trust_remote_code=True)
    if tokenizer.pad_token is None:
        tokenizer.pad_token = tokenizer.eos_token
    tokenizer.padding_side = "right"
    print("   ✅ Model loaded")

    # LoRA config
    peft_config = LoraConfig(
        r=args.lora_r,
        lora_alpha=16,
        lora_dropout=0.05,
        bias="none",
        task_type="CAUSAL_LM",
        target_modules="all-linear",
    )

    # Training config
    training_args = SFTConfig(
        output_dir=output_dir,
        num_train_epochs=args.epochs,
        per_device_train_batch_size=args.batch_size,
        per_device_eval_batch_size=1,
        gradient_accumulation_steps=args.grad_accum,
        eval_accumulation_steps=1,
        learning_rate=args.lr,
        bf16=HAS_BF16,
        fp16=not HAS_BF16,
        gradient_checkpointing=True,
        gradient_checkpointing_kwargs={"use_reentrant": False},
        max_length=args.max_seq_len,
        packing=False,
        optim="paged_adamw_8bit",
        warmup_steps=20,
        lr_scheduler_type="cosine",
        weight_decay=0.01,
        max_grad_norm=0.3,
        logging_steps=10,
        logging_first_step=True,
        logging_strategy="steps",
        disable_tqdm=True,
        report_to=["trackio"],
        save_strategy="epoch",
        eval_strategy="epoch",
        load_best_model_at_end=True,
        metric_for_best_model="eval_loss",
        push_to_hub=False,  # We push manually at the end
        seed=42,
    )

    # Train
    print(f"\n🏋️  Initializing trainer...")
    trainer = SFTTrainer(
        model=model,
        args=training_args,
        train_dataset=train_dataset,
        eval_dataset=eval_dataset,
        processing_class=tokenizer,
        peft_config=peft_config,
    )

    trainable = sum(p.numel() for p in model.parameters() if p.requires_grad)
    total = sum(p.numel() for p in model.parameters())
    print(f"   Trainable: {trainable:,} ({100*trainable/total:.2f}%)")

    print(f"\n🚀 Starting training for {expert_name} expert...")
    train_result = trainer.train()

    print(f"\n✅ Training complete!")
    print(f"   Train loss: {train_result.training_loss:.4f}")

    # Get best eval loss from training (eval already ran each epoch)
    best_eval_loss = trainer.state.best_metric
    print(f"\n📊 Best eval loss (from training): {best_eval_loss:.4f}")

    # Save
    save_dir = os.path.join(output_dir, "best_model")
    print(f"\n💾 Saving to {save_dir}...")
    trainer.save_model(save_dir)
    tokenizer.save_pretrained(save_dir)

    # Push to hub
    if args.push_to_hub:
        print(f"\n🚀 Pushing to {hub_model_id}...")
        api = HfApi()
        api.upload_folder(
            folder_path=save_dir,
            repo_id=hub_model_id,
            ignore_patterns=["optimizer*", "scheduler*", "training_args*", "trainer_state*", "rng_state*"],
            commit_message=f"Expert adapter for {expert_name} vulnerability detection (3B base)",
        )
        print(f"   ✅ Pushed to https://hf.co/{hub_model_id}")

    print(f"\n{'='*60}")
    print(f"  Expert {expert_name} Complete!")
    print(f"  Base Model: {BASE_MODEL}")
    print(f"  Train loss: {train_result.training_loss:.4f}")
    print(f"  Eval loss:  {best_eval_loss:.4f}")
    print(f"{'='*60}")


if __name__ == "__main__":
    main()