from __future__ import annotations

import hashlib
import hmac
import secrets

from django.conf import settings
from django.contrib.auth.models import AbstractUser
from django.db import models
from django.db.models import Q


class User(AbstractUser):
    class Status(models.TextChoices):
        ACTIVE = "active", "正常"
        DISABLED = "disabled", "禁用"

    email = models.EmailField("邮箱", unique=True)
    payment_user_id = models.CharField(
        "支付系统用户 ID",
        max_length=128,
        blank=True,
        help_text="外部支付系统用户标识，可为空。",
    )
    status = models.CharField(
        "状态",
        max_length=20,
        choices=Status.choices,
        default=Status.ACTIVE,
    )
    created_at = models.DateTimeField("创建时间", auto_now_add=True)

    @property
    def is_business_active(self) -> bool:
        return self.status == self.Status.ACTIVE and self.is_active

    class Meta:
        db_table = "user"
        verbose_name = "用户"
        verbose_name_plural = "用户"


class UserWallet(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        verbose_name="用户",
        on_delete=models.PROTECT,
        related_name="wallet",
    )
    points_balance = models.BigIntegerField("点数余额", default=0)
    created_at = models.DateTimeField("创建时间", auto_now_add=True)
    updated_at = models.DateTimeField("更新时间", auto_now=True)

    class Meta:
        db_table = "user_wallet"
        verbose_name = "用户钱包"
        verbose_name_plural = "用户钱包"
        ordering = ("user_id",)
        constraints = [
            models.CheckConstraint(
                condition=Q(points_balance__gte=0),
                name="user_wallet_points_balance_non_negative",
            ),
        ]

    def __str__(self) -> str:
        return f"{self.user} wallet: {self.points_balance}"


class ApiKey(models.Model):
    KEY_PREFIX_LENGTH = 16

    class Status(models.TextChoices):
        ACTIVE = "active", "有效"
        REVOKED = "revoked", "已吊销"

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        verbose_name="用户",
        on_delete=models.PROTECT,
        related_name="api_keys",
    )
    name = models.CharField("名称", max_length=80, blank=True)
    key_hash = models.CharField("API Key 哈希", max_length=64, unique=True, editable=False)
    key_prefix = models.CharField("Key 前缀", max_length=32, editable=False)
    status = models.CharField(
        "状态",
        max_length=20,
        choices=Status.choices,
        default=Status.ACTIVE,
    )
    last_used_at = models.DateTimeField("最后使用时间", null=True, blank=True)
    created_at = models.DateTimeField("创建时间", auto_now_add=True)
    updated_at = models.DateTimeField("更新时间", auto_now=True)

    class Meta:
        db_table = "api_key"
        verbose_name = "API 密钥"
        verbose_name_plural = "API 密钥"
        ordering = ("-created_at", "-id")
        indexes = [
            models.Index(fields=("user", "status")),
            models.Index(fields=("key_prefix",)),
        ]

    def __str__(self) -> str:
        return f"{self.user} {self.key_prefix}"

    @classmethod
    def generate_plaintext_key(cls) -> str:
        return f"sk_cmhub_{secrets.token_urlsafe(32)}"

    @classmethod
    def hash_key(cls, raw_key: str) -> str:
        return hashlib.sha256(raw_key.encode("utf-8")).hexdigest()

    @classmethod
    def build_prefix(cls, raw_key: str) -> str:
        return raw_key[: cls.KEY_PREFIX_LENGTH]

    @classmethod
    def create_for_user(cls, user, *, name: str = "") -> tuple["ApiKey", str]:
        raw_key = cls.generate_plaintext_key()
        api_key = cls(user=user, name=name)
        api_key.set_key(raw_key)
        api_key.save()
        return api_key, raw_key

    def set_key(self, raw_key: str) -> None:
        self.key_hash = self.hash_key(raw_key)
        self.key_prefix = self.build_prefix(raw_key)

    def matches_key(self, raw_key: str) -> bool:
        return hmac.compare_digest(self.key_hash, self.hash_key(raw_key))

    @property
    def is_active_key(self) -> bool:
        return self.status == self.Status.ACTIVE