import * as Localization from 'expo-localization';
import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';

import { getItemSync, setItem } from '@/utils/kvStore';

export const LANGUAGE_PREFERENCE_KEY = 'app_language_preference';
export const SUPPORTED_LANGUAGES = ['zh', 'en'] as const;
export type AppLanguage = typeof SUPPORTED_LANGUAGES[number];

const fallbackLanguage: AppLanguage = 'zh';

const personalScreenResources = {
  edit: '编辑',
  login: '登录',
  memberNumber: '会员编号: {{number}}',
  aiUsage: '免费AI次数: {{value}}',
  aiUsageUnlimited: '无限',
  fishRecord: '能量记录',
  stats: {
    height: '身高',
    weight: '体重',
    age: '年龄',
    ageSuffix: '岁',
  },
  membership: {
    badge: '尊享会员',
    planFallback: 'VIP 会员',
    expiryLabel: '会员有效期',
    changeButton: '更改会员套餐',
    validForever: '长期有效',
    dateFormat: 'YYYY年MM月DD日',
  },
  sections: {
    notifications: '通知',
    developer: '开发者',
    other: '其他',
    account: '账号与安全',
    language: '语言',
    healthData: '健康数据授权',
  },
  menu: {
    notificationSettings: '通知设置',
    developerOptions: '开发者选项',
    pushSettings: '推送通知设置',
    privacyPolicy: '隐私政策',
    feedback: '意见反馈',
    userAgreement: '用户协议',
    logout: '退出登录',
    deleteAccount: '注销帐号',
    healthDataPermissions: '健康数据授权说明',
  },
  language: {
    title: '语言',
    menuTitle: '界面语言',
    modalTitle: '选择语言',
    modalSubtitle: '选择后界面会立即更新',
    cancel: '取消',
    options: {
      zh: {
        label: '中文',
        description: '推荐中文用户使用',
      },
      en: {
        label: '英文',
        description: '使用英文界面',
      },
    },
  },
};

const healthPermissionsResources = {
  title: '健康数据授权说明',
  subtitle: '我们通过 Apple Health 的 HealthKit/CareKit 接口同步必要的数据，让训练、恢复和提醒更贴合你的身体状态。',
  cards: {
    usage: {
      title: '我们会读取 / 写入的数据',
      items: [
        '运动与活动：步数、活动能量、锻炼记录用于生成训练表现和热力图。',
        '身体指标：身高、体重、体脂率帮助制定个性化训练与营养建议。',
        '睡眠与恢复：睡眠时长与阶段用于智能提醒与恢复建议。',
        '水分摄入：读取与写入饮水记录，保持与「健康」App 一致。',
      ],
    },
    purpose: {
      title: '使用这些数据的目的',
      items: [
        '提供个性化训练计划、挑战与恢复建议。',
        '在统计页展示长期趋势，帮助你理解身体变化。',
        '减少重复输入，在提醒与挑战中自动同步进度。',
      ],
    },
    control: {
      title: '你的控制权',
      items: [
        '授权流程完全由 Apple Health 控制，你可随时在 iOS 设置 > 健康 > 数据访问与设备 中更改权限。',
        '未授权的数据不会被访问，撤销授权后我们会清理相关缓存。',
        '核心功能依旧可用，并提供手动输入等替代方案。',
      ],
    },
    privacy: {
      title: '数据存储与隐私',
      items: [
        '健康数据仅存储在你的设备上，我们不会上传服务器或共享给第三方。',
        '只有在需要同步的功能中才会保存聚合后的匿名统计值。',
        '我们遵循 Apple 的审核要求，任何变更都会提前告知。',
      ],
    },
  },
  callout: {
    title: '未授权会怎样？',
    items: [
      '相关模块会提示你授权，并提供手动记录入口。',
      '拒绝授权不会影响其它与健康数据无关的功能。',
    ],
  },
  contact: {
    title: '需要更多帮助？',
    description: '如果你对 HealthKit / CareKit 的使用方式有疑问，可通过以下邮箱或在个人中心提交反馈：',
    email: 'richardwei1995@gmail.com',
  },
};

const resources = {
  zh: {
    translation: {
      personal: personalScreenResources,
      healthPermissions: healthPermissionsResources,
    },
  },
  en: {
    translation: {
      personal: {
        edit: 'Edit',
        login: 'Log in',
        memberNumber: 'Member ID: {{number}}',
        aiUsage: 'Free AI credits: {{value}}',
        aiUsageUnlimited: 'Unlimited',
        fishRecord: 'Energy log',
        stats: {
          height: 'Height',
          weight: 'Weight',
          age: 'Age',
          ageSuffix: ' yrs',
        },
        membership: {
          badge: 'Premium member',
          planFallback: 'VIP Membership',
          expiryLabel: 'Valid until',
          changeButton: 'Change plan',
          validForever: 'No expiry',
          dateFormat: 'YYYY-MM-DD',
        },
        sections: {
          notifications: 'Notifications',
          developer: 'Developer',
          other: 'Other',
          account: 'Account & Security',
          language: 'Language',
          healthData: 'Health data permissions',
        },
        menu: {
          notificationSettings: 'Notification settings',
          developerOptions: 'Developer options',
          pushSettings: 'Push notification settings',
          privacyPolicy: 'Privacy policy',
          feedback: 'Feedback',
          userAgreement: 'User agreement',
          logout: 'Log out',
          deleteAccount: 'Delete account',
          healthDataPermissions: 'Health data disclosure',
        },
        language: {
          title: 'Language',
          menuTitle: 'Display language',
          modalTitle: 'Choose language',
          modalSubtitle: 'Your selection applies immediately',
          cancel: 'Cancel',
          options: {
            zh: {
              label: 'Chinese',
              description: 'Use the Chinese interface',
            },
            en: {
              label: 'English',
              description: 'Use the app in English',
            },
          },
        },
      },
      healthPermissions: {
        title: 'Health data disclosure',
        subtitle: 'We integrate with Apple Health through HealthKit and CareKit to deliver precise training, recovery, and reminder experiences.',
        cards: {
          usage: {
            title: 'Data we read or write',
            items: [
              'Activity: steps, active energy, and workouts fuel performance charts and rings.',
              'Body metrics: height, weight, and body fat keep plans and nutrition tips personalized.',
              'Sleep & recovery: duration and stages unlock recovery advice and reminders.',
              'Hydration: we read and write water intake so Health and the app stay in sync.',
            ],
          },
          purpose: {
            title: 'Why we need it',
            items: [
              'Generate adaptive training plans, challenges, and recovery nudges.',
              'Display long-term trends so you can understand progress at a glance.',
              'Reduce manual input by syncing reminders and challenge progress automatically.',
            ],
          },
          control: {
            title: 'Your control',
            items: [
              'Permissions are granted inside Apple Health; change them anytime under iOS Settings > Health > Data Access & Devices.',
              'We never access data you do not authorize, and cached values are removed if you revoke access.',
              'Core functionality keeps working and offers manual input alternatives.',
            ],
          },
          privacy: {
            title: 'Storage & privacy',
            items: [
              'Health data stays on your device — we do not upload it or share it with third parties.',
              'Only aggregated, anonymized stats are synced when absolutely necessary.',
              'We follow Apple’s review requirements and will notify you before any changes.',
            ],
          },
        },
        callout: {
          title: 'What if I skip authorization?',
          items: [
            'The related modules will ask for permission and provide manual logging options.',
            'Declining does not break other areas of the app that do not rely on Health data.',
          ],
        },
        contact: {
          title: 'Need help?',
          description: 'Questions about HealthKit or CareKit? Reach out via email or the in-app feedback form:',
          email: 'richardwei1995@gmail.com',
        },
      },
    },
  },
};

export const isSupportedLanguage = (language?: string | null): language is AppLanguage => {
  if (!language) return false;
  return SUPPORTED_LANGUAGES.some((code) => language === code || language.startsWith(`${code}-`));
};

export const getNormalizedLanguage = (language?: string | null): AppLanguage => {
  if (!language) return fallbackLanguage;
  const normalized = SUPPORTED_LANGUAGES.find((code) => language === code || language.startsWith(`${code}-`));
  return normalized ?? fallbackLanguage;
};

const getStoredLanguage = (): AppLanguage | null => {
  try {
    const stored = getItemSync?.(LANGUAGE_PREFERENCE_KEY) as AppLanguage | null | undefined;
    if (stored && isSupportedLanguage(stored)) {
      return stored;
    }
  } catch (error) {
    // ignore storage errors and fall back to device preference
  }
  return null;
};

const getDeviceLanguage = (): AppLanguage | null => {
  try {
    const locales = Localization.getLocales();
    const preferred = locales.find((locale) => locale.languageCode && isSupportedLanguage(locale.languageCode));
    return preferred?.languageCode as AppLanguage | undefined || null;
  } catch (error) {
    return null;
  }
};

const initialLanguage = getStoredLanguage() ?? getDeviceLanguage() ?? fallbackLanguage;

void i18n.use(initReactI18next).init({
  compatibilityJSON: 'v4',
  resources,
  lng: initialLanguage,
  fallbackLng: fallbackLanguage,
  interpolation: {
    escapeValue: false,
  },
  returnNull: false,
});

export const changeAppLanguage = async (language: AppLanguage) => {
  const nextLanguage = isSupportedLanguage(language) ? language : fallbackLanguage;
  await i18n.changeLanguage(nextLanguage);
  await setItem(LANGUAGE_PREFERENCE_KEY, nextLanguage);
};

export default i18n;