"""chat.z.ai reverse-engineered Python client."""

from __future__ import annotations

import asyncio
import base64
import hashlib
import hmac
import json
import os
import time
import uuid
from datetime import datetime, timezone, timedelta
from urllib.parse import urlencode

import httpx

BASE_URL = "https://chat.z.ai"
HMAC_SECRET = "key-@@@@)))()((9))-xxxx&&&%%%%%"
FE_VERSION = "prod-fe-1.0.231"
CLIENT_VERSION = "0.0.1"
DEFAULT_MODEL = "glm-5"
USER_AGENT = (
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
    "AppleWebKit/537.36 (KHTML, like Gecko) "
    "Chrome/144.0.0.0 Safari/537.36"
)


def _env_float(name: str, default: float) -> float:
    raw = os.getenv(name)
    if raw is None:
        return default
    try:
        return float(raw)
    except ValueError:
        return default


def _env_int(name: str, default: int) -> int:
    raw = os.getenv(name)
    if raw is None:
        return default
    try:
        return int(raw)
    except ValueError:
        return default


def _env_bool(name: str, default: bool = False) -> bool:
    raw = os.getenv(name)
    if raw is None:
        return default
    return raw.strip().lower() in {"1", "true", "yes", "on"}


HTTP_TIMEOUT_SECONDS = max(1.0, _env_float("ZAI_HTTP_TIMEOUT_SECONDS", 60.0))
HTTP_CONNECT_TIMEOUT_SECONDS = max(
    1.0, _env_float("ZAI_HTTP_CONNECT_TIMEOUT_SECONDS", 10.0)
)
HTTP_MAX_CONNECTIONS = max(1, _env_int("ZAI_HTTP_MAX_CONNECTIONS", 512))
HTTP_MAX_KEEPALIVE_CONNECTIONS = max(
    1,
    min(
        HTTP_MAX_CONNECTIONS,
        _env_int("ZAI_HTTP_MAX_KEEPALIVE_CONNECTIONS", 256),
    ),
)
HTTP_KEEPALIVE_EXPIRY_SECONDS = max(
    1.0, _env_float("ZAI_HTTP_KEEPALIVE_EXPIRY_SECONDS", 30.0)
)
HTTP2_ENABLED = _env_bool("ZAI_HTTP2_ENABLED", False)


class ZaiClient:
    def __init__(self) -> None:
        timeout = httpx.Timeout(
            timeout=HTTP_TIMEOUT_SECONDS,
            connect=HTTP_CONNECT_TIMEOUT_SECONDS,
        )
        limits = httpx.Limits(
            max_connections=HTTP_MAX_CONNECTIONS,
            max_keepalive_connections=HTTP_MAX_KEEPALIVE_CONNECTIONS,
            keepalive_expiry=HTTP_KEEPALIVE_EXPIRY_SECONDS,
        )
        self.client = httpx.AsyncClient(
            base_url=BASE_URL,
            timeout=timeout,
            limits=limits,
            http2=HTTP2_ENABLED,
            headers={
                "User-Agent": USER_AGENT,
                "Accept-Language": "zh-CN",
                "Referer": f"{BASE_URL}/",
                "Origin": BASE_URL,
            },
        )
        self.token: str | None = None
        self.user_id: str | None = None
        self.username: str | None = None

    async def close(self) -> None:
        await self.client.aclose()

    # ── auth ────────────────────────────────────────────────────────

    async def auth_as_guest(self) -> dict:
        """GET /api/v1/auths/ — creates a guest session and returns user info."""
        resp = await self.client.get(
            "/api/v1/auths/",
            headers={"Content-Type": "application/json"},
        )
        resp.raise_for_status()
        data = resp.json()
        self.token = data["token"]
        self.user_id = data["id"]
        self.username = data.get("name") or data.get("email", "").split("@")[0]
        return data

    # ── models ──────────────────────────────────────────────────────

    async def get_models(self) -> list:
        """GET /api/models — returns available model list."""
        resp = await self.client.get(
            "/api/models",
            headers={
                "Content-Type": "application/json",
                "Accept": "application/json",
                **({"Authorization": f"Bearer {self.token}"} if self.token else {}),
            },
        )
        resp.raise_for_status()
        return resp.json()

    # ── chat CRUD ───────────────────────────────────────────────────

    async def create_chat(
        self,
        user_message: str,
        model: str = DEFAULT_MODEL,
    ) -> dict:
        """POST /api/v1/chats/new — creates a new chat session."""
        msg_id = str(uuid.uuid4())
        ts = int(time.time())
        body = {
            "chat": {
                "id": "",
                "title": "新聊天",
                "models": [model],
                "params": {},
                "history": {
                    "messages": {
                        msg_id: {
                            "id": msg_id,
                            "parentId": None,
                            "childrenIds": [],
                            "role": "user",
                            "content": user_message,
                            "timestamp": ts,
                            "models": [model],
                        }
                    },
                    "currentId": msg_id,
                },
                "tags": [],
                "flags": [],
                "features": [
                    {
                        "type": "tool_selector",
                        "server": "tool_selector_h",
                        "status": "hidden",
                    }
                ],
                "mcp_servers": [],
                "enable_thinking": True,
                "auto_web_search": False,
                "message_version": 1,
                "extra": {},
                "timestamp": int(time.time() * 1000),
            }
        }
        resp = await self.client.post(
            "/api/v1/chats/new",
            headers={
                "Content-Type": "application/json",
                "Accept": "application/json",
                **({"Authorization": f"Bearer {self.token}"} if self.token else {}),
            },
            json=body,
        )
        resp.raise_for_status()
        return resp.json()

    # ── signature ───────────────────────────────────────────────────

    @staticmethod
    def _generate_signature(
        sorted_payload: str, prompt: str, timestamp: str
    ) -> str:
        """
        Two-layer HMAC-SHA256 matching DLHfQWwv.js.

        1. b64_prompt  = base64(utf8(prompt))
        2. message     = "{sorted_payload}|{b64_prompt}|{timestamp}"
        3. time_bucket = floor(int(timestamp) / 300_000)
        4. derived_key = HMAC-SHA256(HMAC_SECRET, str(time_bucket)) → hex string
        5. signature   = HMAC-SHA256(derived_key_hex_bytes, message) → hex
        """
        b64_prompt = base64.b64encode(prompt.encode("utf-8")).decode("ascii")
        message = f"{sorted_payload}|{b64_prompt}|{timestamp}"
        time_bucket = int(timestamp) // (5 * 60 * 1000)

        derived_key_hex = hmac.new(
            HMAC_SECRET.encode("utf-8"),
            str(time_bucket).encode("utf-8"),
            hashlib.sha256,
        ).hexdigest()

        signature = hmac.new(
            derived_key_hex.encode("utf-8"),
            message.encode("utf-8"),
            hashlib.sha256,
        ).hexdigest()
        return signature

    def _build_query_and_signature(
        self, prompt: str, chat_id: str
    ) -> tuple[str, str]:
        """Build the full URL query string and X-Signature header.

        Returns (full_query_string, signature).
        """
        timestamp_ms = str(int(time.time() * 1000))
        request_id = str(uuid.uuid4())

        now = datetime.now(timezone.utc)

        # Core params (used for sortedPayload)
        core = {
            "timestamp": timestamp_ms,
            "requestId": request_id,
            "user_id": self.user_id,
        }

        # sortedPayload: Object.entries(core).sort(by key).join(",")
        sorted_payload = ",".join(
            f"{k},{v}" for k, v in sorted(core.items(), key=lambda x: x[0])
        )

        # Compute signature over the prompt
        signature = self._generate_signature(sorted_payload, prompt, timestamp_ms)

        # Browser/device fingerprint params
        extra = {
            "version": CLIENT_VERSION,
            "platform": "web",
            "token": self.token or "",
            "user_agent": USER_AGENT,
            "language": "zh-CN",
            "languages": "zh-CN",
            "timezone": "Asia/Shanghai",
            "cookie_enabled": "true",
            "screen_width": "1920",
            "screen_height": "1080",
            "screen_resolution": "1920x1080",
            "viewport_height": "919",
            "viewport_width": "944",
            "viewport_size": "944x919",
            "color_depth": "24",
            "pixel_ratio": "1.25",
            "current_url": f"{BASE_URL}/c/{chat_id}",
            "pathname": f"/c/{chat_id}",
            "search": "",
            "hash": "",
            "host": "chat.z.ai",
            "hostname": "chat.z.ai",
            "protocol": "https:",
            "referrer": "",
            "title": "Z.ai - Free AI Chatbot & Agent powered by GLM-5 & GLM-4.7",
            "timezone_offset": "-480",
            "local_time": now.strftime("%Y-%m-%dT%H:%M:%S.")
            + f"{now.microsecond // 1000:03d}Z",
            "utc_time": now.strftime("%a, %d %b %Y %H:%M:%S GMT"),
            "is_mobile": "false",
            "is_touch": "false",
            "max_touch_points": "10",
            "browser_name": "Chrome",
            "os_name": "Windows",
            "signature_timestamp": timestamp_ms,
        }

        all_params = {**core, **extra}
        query_string = urlencode(all_params)

        return query_string, signature

    # ── chat completions (SSE) ──────────────────────────────────────

    async def chat_completions(
        self,
        chat_id: str,
        messages: list[dict],
        prompt: str,
        *,
        model: str = DEFAULT_MODEL,
        parent_message_id: str | None = None,
        tools: list[dict] | None = None,
    ):
        """POST /api/v2/chat/completions — streams SSE response.

        Yields the full event ``data`` dict for each SSE frame.
        """
        query_string, signature = self._build_query_and_signature(prompt, chat_id)

        msg_id = str(uuid.uuid4())
        user_msg_id = str(uuid.uuid4())

        now = datetime.now(timezone(timedelta(hours=8)))
        variables = {
            "{{USER_NAME}}": self.username or "Guest",
            "{{USER_LOCATION}}": "Unknown",
            "{{CURRENT_DATETIME}}": now.strftime("%Y-%m-%d %H:%M:%S"),
            "{{CURRENT_DATE}}": now.strftime("%Y-%m-%d"),
            "{{CURRENT_TIME}}": now.strftime("%H:%M:%S"),
            "{{CURRENT_WEEKDAY}}": now.strftime("%A"),
            "{{CURRENT_TIMEZONE}}": "Asia/Shanghai",
            "{{USER_LANGUAGE}}": "zh-CN",
        }

        body = {
            "stream": True,
            "model": model,
            "messages": messages,
            "signature_prompt": prompt,
            "params": {},
            "extra": {},
            "features": {
                "image_generation": False,
                "web_search": False,
                "auto_web_search": False,
                "preview_mode": True,
                "flags": [],
                "enable_thinking": True,
            },
            "variables": variables,
            "chat_id": chat_id,
            "id": msg_id,
            "current_user_message_id": user_msg_id,
            "current_user_message_parent_id": parent_message_id,
            "background_tasks": {
                "title_generation": True,
                "tags_generation": True,
            },
        }
        if tools:
            body["tools"] = tools

        headers = {
            "Content-Type": "application/json",
            "Accept": "*/*",
            "Accept-Language": "zh-CN",
            "X-FE-Version": FE_VERSION,
            "X-Signature": signature,
            **({"Authorization": f"Bearer {self.token}"} if self.token else {}),
        }

        url = f"{BASE_URL}/api/v2/chat/completions?{query_string}"

        async with self.client.stream(
            "POST", url, headers=headers, json=body,
        ) as resp:
            if resp.status_code != 200:
                error_body = await resp.aread()
                raise RuntimeError(
                    f"chat/completions {resp.status_code}: {error_body.decode()}"
                )
            async for line in resp.aiter_lines():
                if not line.startswith("data: "):
                    continue
                raw = line[6:]
                if raw.strip() == "[DONE]":
                    return
                try:
                    event = json.loads(raw)
                except json.JSONDecodeError:
                    continue
                data = event.get("data", {})
                yield data
                if data.get("done"):
                    return


async def main() -> None:
    client = ZaiClient()
    try:
        # 1. Authenticate as guest
        print("[1] Authenticating as guest...")
        auth = await client.auth_as_guest()
        print(f"    user_id : {auth['id']}")
        print(f"    email   : {auth.get('email', 'N/A')}")
        print(f"    token   : {auth['token'][:40]}...")

        # 2. Fetch models
        print("\n[2] Fetching models...")
        models_resp = await client.get_models()
        if isinstance(models_resp, dict) and "data" in models_resp:
            names = [m.get("id", m.get("name", "?")) for m in models_resp["data"]]
        elif isinstance(models_resp, list):
            names = [m.get("id", m.get("name", "?")) for m in models_resp]
        else:
            names = [str(models_resp)[:80]]
        print(f"    models  : {', '.join(names[:10])}")

        # 3. Create chat
        user_message = "Hello"
        print(f"\n[3] Creating chat with first message: {user_message!r}")
        messages = [{"role": "user", "content": user_message}]
        chat = await client.create_chat(user_message)
        chat_id = chat["id"]
        print(f"    chat_id : {chat_id}")

        # 4. Stream chat completions
        print(f"\n[4] Streaming chat completions (model={DEFAULT_MODEL})...\n")
        messages = [{"role": "user", "content": user_message}]

        thinking_started = False
        answer_started = False
        async for data in client.chat_completions(
            chat_id=chat_id,
            messages=messages,
            prompt=user_message,
        ):
            phase = data.get("phase", "")
            delta = data.get("delta_content", "")
            if phase == "thinking":
                if not thinking_started:
                    print("[thinking] ", end="", flush=True)
                    thinking_started = True
                print(delta, end="", flush=True)
            elif phase == "answer":
                if not answer_started:
                    if thinking_started:
                        print("\n")
                    print("[answer]   ", end="", flush=True)
                    answer_started = True
                print(delta, end="", flush=True)
            elif phase == "done":
                break
        print("\n\n[done]")

    finally:
        await client.close()


if __name__ == "__main__":
    asyncio.run(main())