"""
translator.py
腾讯云 (批量接口+动态分包+多账号轮询) + 百度翻译 API 封装
⚠️ 需在 HF 空间的 “Variables” 页设置以下环境变量
------------------------------------------------------------------
TENCENT_CREDENTIALS_JSON  形如:
[
  {"secret_id": "AKIDxxxx", "secret_key": "yyyy"},
  {"secret_id": "AKIDaaaa", "secret_key": "bbbb"}
]
TENCENT_SECRET_ID         (兼容旧配置) 单个 SecretId
TENCENT_SECRET_KEY        (兼容旧配置) 单个 SecretKey
------------------------------------------------------------------
BAIDU_CREDENTIALS_JSON    形如:
[
  {"app_id": "xxxx", "secret_key": "yyyy"}
]
------------------------------------------------------------------
"""
import hashlib, hmac, json, os, random, time
from datetime import datetime
from typing import List, Sequence, Optional, Dict, Any

import requests

_tencent_creds_list = json.loads(os.environ.get("TENCENT_CREDENTIALS_JSON", "[]"))

# 兼容旧的单账号配置
_legacy_id = os.environ.get("TENCENT_SECRET_ID")
_legacy_key = os.environ.get("TENCENT_SECRET_KEY")
if _legacy_id and _legacy_key:
    if not any(c.get("secret_id") == _legacy_id for c in _tencent_creds_list):
        _tencent_creds_list.append({"secret_id": _legacy_id, "secret_key": _legacy_key})

TENCENT_TRANSLATE_URL = os.environ.get("TENCENT_TRANSLATE_URL", "https://tmt.tencentcloudapi.com")

_tencent_idx: int = 0


BAIDU_TRANSLATE_URL = os.environ.get("BAIDU_TRANSLATE_URL", "https://fanyi-api.baidu.com/api/trans/vip/translate")
_baidu_creds_list = json.loads(os.environ.get("BAIDU_CREDENTIALS_JSON", "[]"))

# 全局索引，用于轮询
_baidu_idx: int = 0


# 腾讯云翻译逻辑 (批量接口 TextTranslateBatch)
def _sign(key: bytes, msg: str) -> bytes:
    return hmac.new(key, msg.encode("utf-8"), hashlib.sha256).digest()

def _tc3_signature(secret_key: str, date: str, service: str, string_to_sign: str) -> str:
    secret_date     = _sign(("TC3" + secret_key).encode(), date)
    secret_service  = _sign(secret_date, service)
    secret_signing  = _sign(secret_service, "tc3_request")
    return hmac.new(secret_signing, string_to_sign.encode("utf-8"), hashlib.sha256).hexdigest()

def _call_tencent_batch_once(cred: Dict[str, str], text_list: List[str], src: str, tgt: str) -> List[str]:
    """
    调用腾讯云 TextTranslateBatch 接口
    """
    secret_id = cred["secret_id"]
    secret_key = cred["secret_key"]
    
    service  = "tmt"
    host     = "tmt.tencentcloudapi.com"
    action   = "TextTranslateBatch" 
    version  = "2018-03-21"
    region   = "ap-beijing"
    ts       = int(time.time())
    date     = datetime.utcfromtimestamp(ts).strftime("%Y-%m-%d")
    algorithm = "TC3-HMAC-SHA256"

    payload = {
        "SourceTextList": text_list, 
        "Source":     src,
        "Target":     tgt,
        "ProjectId":  0,
    }
    
    payload_str = json.dumps(payload, ensure_ascii=False)

    canonical_request = "\n".join([
        "POST",
        "/",
        "",
        f"content-type:application/json; charset=utf-8\nhost:{host}\nx-tc-action:{action.lower()}\n",
        "content-type;host;x-tc-action",
        hashlib.sha256(payload_str.encode()).hexdigest(),
    ])

    credential_scope    = f"{date}/{service}/tc3_request"
    string_to_sign      = "\n".join([
        algorithm, str(ts), credential_scope,
        hashlib.sha256(canonical_request.encode()).hexdigest(),
    ])

    signature = _tc3_signature(secret_key, date, service, string_to_sign)

    authorization = (
        f"{algorithm} Credential={secret_id}/{credential_scope}, "
        f"SignedHeaders=content-type;host;x-tc-action, Signature={signature}"
    )
    headers = {
        "Authorization":  authorization,
        "Content-Type":   "application/json; charset=utf-8",
        "Host":           host,
        "X-TC-Action":    action,
        "X-TC-Timestamp": str(ts),
        "X-TC-Version":   version,
        "X-TC-Region":    region,
    }

    resp = requests.post(TENCENT_TRANSLATE_URL, headers=headers, data=payload_str, timeout=8)
    resp.raise_for_status()
    data = resp.json()
    
    if "Response" in data and "Error" in data["Response"]:
        err_code = data["Response"]["Error"].get("Code", "")
        err_msg = data["Response"]["Error"].get("Message", "")
        raise Exception(f"Tencent Biz Error: {err_code} - {err_msg}")

    return data["Response"]["TargetTextList"]


def _translate_with_tencent_pool(texts: Sequence[str], src="auto", tgt="zh") -> Optional[List[str]]:
    """
    腾讯云入口：
    1. 动态分包：同时考虑字符数限制 (<6000) 和 条数限制。
       - 累计字符数 < 5000 (安全阈值)
       - 单批次条数 < 50 (安全阈值)
    2. 账号轮询 (Polling)：每组请求如果失败，会自动换号重试。
    """
    global _tencent_idx, _tencent_creds_list
    
    if not _tencent_creds_list:
        return None

    # 配置安全阈值
    MAX_CHARS_PER_BATCH = 5000  # 官方限制 6000，留 1000 buffer
    MAX_ITEMS_PER_BATCH = 50    # 避免单次数组过大

    chunks = []
    current_chunk = []
    current_char_count = 0
    
    for text in texts:
        text_len = len(text)
        
        # 检查加入当前文本是否会超限
        if current_chunk and (
            (current_char_count + text_len > MAX_CHARS_PER_BATCH) or 
            (len(current_chunk) >= MAX_ITEMS_PER_BATCH)
        ):
            # 结算当前块
            chunks.append(current_chunk)
            current_chunk = []
            current_char_count = 0
            
        current_chunk.append(text)
        current_char_count += text_len
        
    # 处理剩余的最后一块
    if current_chunk:
        chunks.append(current_chunk)

    all_results = []
    
    for chunk in chunks:
        chunk_success = False
        
        attempts = len(_tencent_creds_list)
        for _ in range(attempts):
            cred = _tencent_creds_list[_tencent_idx]
            _tencent_idx = (_tencent_idx + 1) % len(_tencent_creds_list)
            
            try:
                res = _call_tencent_batch_once(cred, list(chunk), src, tgt)
                all_results.extend(res)
                chunk_success = True
                break # 成功则跳出重试
            except Exception as e:
                safe_id = cred['secret_id'][:4] + "****"
                print(f"[translator] Tencent ID {safe_id} failed on batch: {e}. Switching...")
                continue
        
        if not chunk_success:
            print("[translator] All Tencent credentials failed for a batch. Falling back to Baidu.")
            return None # 只要有一个分片失败，整体降级，保证一致性

    return all_results


# 百度翻译逻辑
def _translate_with_baidu_pool(texts: Sequence[str], src="auto", tgt="zh") -> Optional[List[str]]:
    global _baidu_idx, _baidu_creds_list
    
    if not _baidu_creds_list:
        return None
        
    cred = _baidu_creds_list[_baidu_idx]
    _baidu_idx = (_baidu_idx + 1) % len(_baidu_creds_list)
    
    app_id, secret_key = cred["app_id"], cred["secret_key"]
    salt  = random.randint(32768, 65536)
    
    query = "\n".join(texts)
    
    sign  = hashlib.md5((app_id + query + str(salt) + secret_key).encode()).hexdigest()
    
    params = {
        "q": query, "from": src, "to": tgt,
        "appid": app_id, "salt": salt, "sign": sign,
    }
    try:
        resp = requests.get(BAIDU_TRANSLATE_URL, params=params, timeout=8)
        resp.raise_for_status()
        data = resp.json()
        if "error_code" in data:
             raise Exception(f"Baidu Biz Error: {data['error_code']} - {data.get('error_msg')}")
        return [item["dst"] for item in data["trans_result"]]
    except Exception as e:
        print(f"[translator] Baidu API error → {e}")
        return None


# 对外统一入口
def translate_texts(texts: Sequence[str],
                    src_lang: str = "auto",
                    tgt_lang: str = "zh") -> List[str]:
    """
    逻辑：
    1. 尝试腾讯云 (批量接口 + 多账号轮询)
    2. 失败降级到百度云
    3. 还失败返回原文
    """
    if not texts:
        return []

    # 1. 优先尝试腾讯云
    out = _translate_with_tencent_pool(texts, src_lang, tgt_lang)
    
    # 2. 失败降级到百度
    if out is None:
        out = _translate_with_baidu_pool(texts, src_lang, tgt_lang)
        
    return out or list(texts)