import json
import os
from transformers import AutoTokenizer

# 1. 配置
MODEL_PATH = "/home/at0842/ycl466704.ai13/.cache/huggingface/hub/models--openai--gpt-oss-20b/snapshots/6cee5e81ee83917806bbde320786a8fb61efebee"
INPUT_JSONL = "all_dupcleaned_data_turn.jsonl"
OUTPUT_JSONL = "all_dupcleaned_data_turn_gpt_oss_20b_pretokenized.jsonl"
MAX_LENGTH = 14436 

if not os.path.exists(MODEL_PATH):
    print(f"❌ 錯誤：找不到模型路徑 {MODEL_PATH}")
    exit()

print(f"⏳ 正在初始化 GPT-OSS 20B Tokenizer...")
tokenizer = AutoTokenizer.from_pretrained(MODEL_PATH, trust_remote_code=True)

# 事先取得 <|return|> 的 ID
RETURN_TOKEN_ID = tokenizer.convert_tokens_to_ids("<|return|>")

def process_entry(entry, index):
    try:
        messages = entry.get("messages", [])
        raw_tools = entry.get("tools", None) 
        
        # --- 工具格式化 ---
        formatted_tools = None
        if raw_tools and isinstance(raw_tools, list):
            formatted_tools = []
            for t in raw_tools:
                if isinstance(t, dict) and "function" in t:
                    formatted_tools.append(t)
                else:
                    formatted_tools.append({
                        "type": "function",
                        "function": t
                    })

        if not isinstance(messages, list) or len(messages) < 2:
            return None, "對話輪次不足"
        
        if messages[-1].get("role") != "assistant":
            return None, f"最後一則不是 assistant (抓到的是: {messages[-1].get('role')})"

        # 1. 取得原始完整序列 (關閉自動剪裁)
        full_ids = tokenizer.apply_chat_template(
            messages, 
            tools=formatted_tools,
            tokenize=True, 
            add_generation_prompt=False,
            truncation=False 
        )
        
        # --- 核心邏輯：手動補強結束符號 ---
        # 如果最後一個 ID 不是 <|return|>，手動補上
        if full_ids[-1] != RETURN_TOKEN_ID:
            full_ids.append(RETURN_TOKEN_ID)
            
        # 2. 補完結束符後，再進行長度檢查
        actual_length = len(full_ids)
        if actual_length > MAX_LENGTH:
            return None, f"加上結束符後過長 ({actual_length} > {MAX_LENGTH})"

        # 3. 計算 Context 長度 (提示部分)
        context_ids = tokenizer.apply_chat_template(
            messages[:-1], 
            tools=formatted_tools,
            tokenize=True, 
            add_generation_prompt=True,
            truncation=False
        )   
        
        start_idx = len(context_ids)
        
        # 安全檢查
        if start_idx >= actual_length:
            return None, "計算錯誤：Context 長度大於等於總長度"

        # 4. 製作 Labels (包含剛才補上的結束符號)
        labels = [-100] * actual_length
        for i in range(start_idx, actual_length):
            labels[i] = full_ids[i]
            
        return {
            "input_ids": full_ids,
            "attention_mask": [1] * actual_length,
            "labels": labels
        }, None

    except Exception as e:
        return None, str(e)

# --- 執行主程式 ---
success_count = 0
drop_count = 0

print(f" 🚀 開始處理資料...")

with open(INPUT_JSONL, "r", encoding="utf-8") as f_in, \
     open(OUTPUT_JSONL, "w", encoding="utf-8") as f_out:
    
    for i, line in enumerate(f_in):
        line = line.strip()
        if not line: continue
        
        try:
            entry = json.loads(line)
            result, error_msg = process_entry(entry, i)
            
            if result:
                f_out.write(json.dumps(result, ensure_ascii=False) + "\n")
                success_count += 1
                
                if success_count == 1:
                    print("\n" + "="*60)
                    print("【首筆資料切分預覽 - 修正結尾版】")
                    loss_indices = [idx for idx, val in enumerate(result['labels']) if val != -100]
                    loss_tokens = [result['input_ids'][idx] for idx in loss_indices]
                    target_text = tokenizer.decode(loss_tokens)
                    print(f" Target (計算 Loss 部分): \n{target_text}")
                    print(f" 總長度: {len(result['input_ids'])}")
                    
                    last_tokens = tokenizer.convert_ids_to_tokens(result['input_ids'][-3:])
                    print(f" 序列末端三個 Token: {last_tokens}")
                    print("="*60 + "\n")
            else:
                drop_count += 1
                
        except Exception as e:
            drop_count += 1

print(f" ✅ 處理完成！")
print(f" 成功筆數: {success_count}")
print(f" 丟棄筆數: {drop_count}")
print(f" 結果檔案: {OUTPUT_JSONL}")