"""
translator.py
腾讯云 + 百度翻译 API 轮询封装
⚠️ 需在 HF 空间的 “Variables” 页设置以下环境变量
------------------------------------------------------------------
TENCENT_SECRET_ID        腾讯云 SecretId
TENCENT_SECRET_KEY       腾讯云 SecretKey
TENCENT_TRANSLATE_URL    (可选) 默认 https://tmt.tencentcloudapi.com
BAIDU_TRANSLATE_URL      (可选) 默认 https://fanyi-api.baidu.com/api/trans/vip/translate
BAIDU_CREDENTIALS_JSON   形如:
[
  {"app_id": "xxxx", "secret_key": "yyyy"},
  {"app_id": "aaaa", "secret_key": "bbbb"}
]
------------------------------------------------------------------
"""
import hashlib, hmac, json, os, random, time
from datetime import datetime
from typing import List, Sequence, Optional

import requests

# ------------------------------------------------------------------
# 读取环境变量
# ------------------------------------------------------------------
TENCENT_SECRET_ID  = os.environ.get("TENCENT_SECRET_ID")
TENCENT_SECRET_KEY = os.environ.get("TENCENT_SECRET_KEY")
TENCENT_TRANSLATE_URL = os.environ.get("TENCENT_TRANSLATE_URL", "https://tmt.tencentcloudapi.com")

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

# 内部轮询索引
_baidu_idx: int = 0
def _next_baidu_cred():
    global _baidu_idx
    if not BAIDU_CREDENTIALS:
        return None
    cred = BAIDU_CREDENTIALS[_baidu_idx]
    _baidu_idx = (_baidu_idx + 1) % len(BAIDU_CREDENTIALS)
    return cred

# ------------------------------------------------------------------
# 腾讯翻译
# ------------------------------------------------------------------
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 _translate_with_tencent(texts: Sequence[str], src="auto", tgt="zh") -> Optional[List[str]]:
    """优先使用腾讯云翻译。失败返回 None"""
    if not (TENCENT_SECRET_ID and TENCENT_SECRET_KEY):
        return None                                           # 未配置凭证
    service  = "tmt"
    host     = "tmt.tencentcloudapi.com"
    action   = "TextTranslate"
    version  = "2018-03-21"
    region   = "ap-beijing"
    ts       = int(time.time())
    date     = datetime.utcfromtimestamp(ts).strftime("%Y-%m-%d")
    algorithm = "TC3-HMAC-SHA256"

    payload = {
        "SourceText": "\n".join(texts),
        "Source":     src,
        "Target":     tgt,
        "ProjectId":  0,
    }
    payload_str = json.dumps(payload, ensure_ascii=False)

    # ---------- step‑1 canonical request ----------
    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(),
    ])

    # ---------- step‑2 string to sign ----------
    credential_scope   = f"{date}/{service}/tc3_request"
    string_to_sign     = "\n".join([
        algorithm, str(ts), credential_scope,
        hashlib.sha256(canonical_request.encode()).hexdigest(),
    ])

    # ---------- step‑3 signature ----------
    signature = _tc3_signature(TENCENT_SECRET_KEY, date, service, string_to_sign)

    # ---------- step‑4 headers ----------
    authorization = (
        f"{algorithm} Credential={TENCENT_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,
    }

    # ---------- request ----------
    try:
        resp = requests.post(TENCENT_TRANSLATE_URL, headers=headers, data=payload_str, timeout=8)
        resp.raise_for_status()
        data = resp.json()
        return data["Response"]["TargetText"].split("\n")
    except Exception as e:
        print(f"[translator] Tencent API error → {e}")
        return None

# ------------------------------------------------------------------
# 百度翻译
# ------------------------------------------------------------------
def _translate_with_baidu(texts: Sequence[str], src="auto", tgt="zh") -> Optional[List[str]]:
    creds = _next_baidu_cred()
    if creds is None:
        return None                                           # 未配置凭证
    app_id, secret_key = creds["app_id"], creds["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()
        return [item["dst"] for item in data["trans_result"]]
    except Exception as e:
        print(f"[translator] Baidu API error → {e}")
        return None

# ------------------------------------------------------------------
# 对外统一函数
# ------------------------------------------------------------------
def translate_texts(texts: Sequence[str],
                    src_lang: str = "auto",
                    tgt_lang: str = "zh") -> List[str]:
    """
    优先 Tencent → 失败再 Baidu → 如果都失败，返回原文。
    """
    if not texts:
        return []

    out = _translate_with_tencent(texts, src_lang, tgt_lang)
    if out is None:
        out = _translate_with_baidu(texts, src_lang, tgt_lang)
    return out or list(texts)