"""邀请归因服务：邀请码生成、分享/扫码归因、小程序码生成、邀请统计。"""
from __future__ import annotations

import secrets
import string
import time
from datetime import datetime

from .. import config
from ..infrastructure.repositories import Database


def _now() -> str:
    return datetime.now().strftime("%Y-%m-%d %H:%M:%S")


def gen_invite_code(length: int = 8) -> str:
    """生成易读邀请码（排除易混淆字符）。"""
    alphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
    return "".join(secrets.choice(alphabet) for _ in range(length))


async def ensure_invite_code(db: Database, user_id: str) -> str:
    """确保用户有邀请码，没有则生成。返回邀请码。"""
    user = await db.users.get(user_id)
    if not user:
        return ""
    code = user.get("invite_code", "")
    if code:
        return code
    # 生成唯一邀请码
    for _ in range(10):
        code = gen_invite_code()
        existing = await db.users.get_by_invite_code(code)
        if not existing:
            break
    else:
        code = gen_invite_code(10)
    await db.users.update(user_id, invite_code=code)
    return code


async def resolve_inviter(db: Database, inviter: str) -> dict | None:
    """解析邀请人：inviter 可以是用户ID或邀请码。"""
    if not inviter:
        return None
    # 先按邀请码查
    user = await db.users.get_by_invite_code(inviter)
    if user:
        return user
    # 再按用户ID查
    user = await db.users.get(inviter)
    if user:
        return user
    return None


async def bind_invitee(db: Database, invitee_id: str, inviter: str, openid: str = "",
                       channel: str = "", scene: str = "", env: str = "trial", ip: str = "") -> bool:
    """新用户绑定邀请人（仅当用户尚未有邀请人时）。返回是否成功绑定。"""
    if not inviter or not invitee_id:
        return False
    invitee = await db.users.get(invitee_id)
    if not invitee:
        return False
    # 已有邀请人则不覆盖
    if invitee.get("inviter_id"):
        return False
    inviter_user = await resolve_inviter(db, inviter)
    if not inviter_user:
        return False
    # 不能邀请自己
    if inviter_user["id"] == invitee_id:
        return False
    await db.users.update(invitee_id, inviter_id=inviter_user["id"], invited_at=_now())
    # 记录归因
    await db.invite_records.add(
        inviter_id=inviter_user["id"],
        invite_code=inviter_user.get("invite_code", ""),
        invitee_id=invitee_id,
        invitee_openid=openid,
        action="register",
        channel=channel,
        scene=scene,
        env=env,
        ip=ip,
    )
    return True


async def record_share(db: Database, user_id: str, channel: str = "share_app",
                       scene: str = "", env: str = "trial", ip: str = "") -> None:
    """记录分享行为。"""
    if not user_id:
        return
    code = await ensure_invite_code(db, user_id)
    await db.invite_records.add(
        inviter_id=user_id,
        invite_code=code,
        action="share",
        channel=channel,
        scene=scene,
        env=env,
        ip=ip,
    )
    # 递增分享次数
    user = await db.users.get(user_id)
    if user:
        await db.users.update(user_id, invite_share_count=int(user.get("invite_share_count", 0)) + 1)


async def record_scan(db: Database, inviter: str, openid: str = "",
                      channel: str = "qrcode", scene: str = "", env: str = "trial", ip: str = "") -> None:
    """记录扫码行为（被邀请人扫码时）。"""
    inviter_user = await resolve_inviter(db, inviter)
    if not inviter_user:
        return
    await db.invite_records.add(
        inviter_id=inviter_user["id"],
        invite_code=inviter_user.get("invite_code", ""),
        invitee_openid=openid,
        action="scan",
        channel=channel,
        scene=scene,
        env=env,
        ip=ip,
    )


async def get_invite_stats(db: Database, user_id: str) -> dict:
    """获取用户邀请统计。"""
    code = await ensure_invite_code(db, user_id)
    # 邀请的用户列表
    invitees = await db.users.get_invitees(user_id)
    # 分享次数
    user = await db.users.get(user_id)
    share_count = int(user.get("invite_share_count", 0)) if user else 0
    # 扫码次数
    scan_count = await db.invite_records.count_by(inviter_id=user_id, action="scan")
    # 注册成功数
    register_count = len(invitees)
    from ..infrastructure.oss import resolve_url
    return {
        "invite_code": code,
        "share_count": share_count,
        "scan_count": scan_count,
        "register_count": register_count,
        "invitees": [
            {
                "id": u["id"],
                "nickname": u.get("nickname", ""),
                "avatar": resolve_url(u.get("avatar", "")),
                "invited_at": u.get("invited_at", ""),
            }
            for u in invitees
        ],
    }


async def get_wxacode(db: Database, user_id: str, scene: str = "home",
                      page: str = "pages/index/index", env: str = "trial",
                      width: int = 430) -> dict:
    """生成带邀请参数的小程序码。

    scene 格式：inviter=<user_id>&scene=<场景>
    体验版和正式版使用不同的 access_token（由 wechat 模块处理）。
    """
    code = await ensure_invite_code(db, user_id)
    # scene 最长32字符，用邀请码代替用户ID
    scene_str = f"i={code[:8]}&s={scene[:10]}"
    try:
        from ..services import wechat
        img_buffer = await wechat.get_wxacode(
            scene=scene_str,
            page=page,
            env_version=env,
        )
        return {"success": True, "image": img_buffer, "scene": scene_str, "invite_code": code}
    except Exception as exc:
        return {"success": False, "error": str(exc), "invite_code": code}