import { useEffect, useState, type FormEvent } from 'react'
import { Eye, EyeOff } from 'lucide-react'
import { Breadcrumbs } from '../components/Breadcrumbs'
import { PageTitle } from '../components/PageTitle'
import { Switch } from '../components/Switch'
import { Tooltip } from '../components/Tooltip'
import { useToast } from '../context/ToastContext'
import { useT } from '../i18n/useT'
import type { BusinessMessageKey } from '../i18n/messages'
import { ApiError } from '../lib/api'
import {
  DEFAULT_EPAYMENT_SETTINGS,
  getSettings,
  updateStoreSettings,
  type EPaymentSettings,
  type PaymentGatewayId,
} from '../services/settingsService'
import pageStyles from '../components/PageContent.module.css'
import sharedStyles from './ProductSettingsPage.module.css'
import fieldStyles from './AddNewProductPage.module.css'
import styles from './SettingsPage.module.css'

const COMING_SOON_GATEWAYS: {
  id: Exclude<PaymentGatewayId, 'mellat' | 'zarinpal'>
  nameKey: BusinessMessageKey
  descKey: BusinessMessageKey
}[] = [
  {
    id: 'sep',
    nameKey: 'website.ePayment.gateway.sep',
    descKey: 'website.ePayment.gateway.sepDesc',
  },
  {
    id: 'snappay',
    nameKey: 'website.ePayment.gateway.snappay',
    descKey: 'website.ePayment.gateway.snappayDesc',
  },
  {
    id: 'digipay',
    nameKey: 'website.ePayment.gateway.digipay',
    descKey: 'website.ePayment.gateway.digipayDesc',
  },
]

function nextDefaultGateway(
  current: EPaymentSettings,
  gatewayId: PaymentGatewayId,
  enabled: boolean,
): PaymentGatewayId | null {
  if (enabled && !current.defaultGateway) return gatewayId
  if (!enabled && current.defaultGateway === gatewayId) {
    if (gatewayId !== 'mellat' && current.gateways.mellat.enabled) return 'mellat'
    if (gatewayId !== 'zarinpal' && current.gateways.zarinpal.enabled) {
      return 'zarinpal'
    }
    return null
  }
  return current.defaultGateway
}

export function SettingsPage() {
  const t = useT()
  const { showToast } = useToast()
  const [ePayment, setEPayment] = useState<EPaymentSettings>(DEFAULT_EPAYMENT_SETTINGS)
  const [passwordDraft, setPasswordDraft] = useState('')
  const [showPassword, setShowPassword] = useState(false)
  const [isLoading, setIsLoading] = useState(true)
  const [savingKey, setSavingKey] = useState<string | null>(null)
  const [error, setError] = useState('')

  useEffect(() => {
    const controller = new AbortController()
    void loadSettings(controller.signal)
    return () => controller.abort()
  }, [])

  async function loadSettings(signal?: AbortSignal) {
    setIsLoading(true)
    setError('')

    try {
      const data = await getSettings(signal)
      setEPayment(data.settings.store.ePayment ?? DEFAULT_EPAYMENT_SETTINGS)
      setPasswordDraft('')
    } catch (err) {
      if (err instanceof DOMException && err.name === 'AbortError') return
      if (err instanceof ApiError) {
        setError(err.message)
      } else {
        setError(t('productSettings.errorLoad'))
      }
    } finally {
      setIsLoading(false)
    }
  }

  async function patchEPayment(
    saving: string,
    next: EPaymentSettings,
    password?: string,
  ) {
    setSavingKey(saving)
    setError('')

    try {
      const payload: EPaymentSettings = {
        ...next,
        gateways: {
          ...next.gateways,
          mellat: {
            ...next.gateways.mellat,
            password: password ?? '',
          },
          zarinpal: {
            ...next.gateways.zarinpal,
            merchantId: next.gateways.zarinpal.merchantId.trim(),
          },
        },
      }

      const data = await updateStoreSettings({ ePayment: payload })
      setEPayment(data.settings.store.ePayment ?? DEFAULT_EPAYMENT_SETTINGS)
      if (password) setPasswordDraft('')
      showToast(t('productSettings.saved'), 'success')
    } catch (err) {
      if (err instanceof ApiError) {
        setError(err.message)
      } else {
        setError(t('productSettings.errorSave'))
      }
    } finally {
      setSavingKey(null)
    }
  }

  async function handleMasterToggle(checked: boolean) {
    await patchEPayment('master', {
      ...ePayment,
      enabled: checked,
      defaultGateway: checked
        ? ePayment.defaultGateway ??
          (ePayment.gateways.mellat.enabled
            ? 'mellat'
            : ePayment.gateways.zarinpal.enabled
              ? 'zarinpal'
              : 'mellat')
        : ePayment.defaultGateway,
    })
  }

  async function handleMellatToggle(checked: boolean) {
    await patchEPayment('mellat-enabled', {
      ...ePayment,
      gateways: {
        ...ePayment.gateways,
        mellat: { ...ePayment.gateways.mellat, enabled: checked },
      },
      defaultGateway: nextDefaultGateway(ePayment, 'mellat', checked),
    })
  }

  async function handleZarinpalToggle(checked: boolean) {
    await patchEPayment('zarinpal-enabled', {
      ...ePayment,
      gateways: {
        ...ePayment.gateways,
        zarinpal: { ...ePayment.gateways.zarinpal, enabled: checked },
      },
      defaultGateway: nextDefaultGateway(ePayment, 'zarinpal', checked),
    })
  }

  async function handleSaveMellatCredentials(event: FormEvent) {
    event.preventDefault()
    const terminalId = ePayment.gateways.mellat.terminalId.trim()
    const username = ePayment.gateways.mellat.username.trim()

    if (ePayment.gateways.mellat.enabled && (!terminalId || !username)) {
      setError(t('website.ePayment.error.credentials'))
      return
    }

    if (
      ePayment.gateways.mellat.enabled &&
      !ePayment.gateways.mellat.passwordSet &&
      !passwordDraft.trim()
    ) {
      setError(t('website.ePayment.error.passwordRequired'))
      return
    }

    await patchEPayment(
      'mellat-credentials',
      {
        ...ePayment,
        gateways: {
          ...ePayment.gateways,
          mellat: {
            ...ePayment.gateways.mellat,
            terminalId,
            username,
          },
        },
      },
      passwordDraft.trim() || undefined,
    )
  }

  async function handleSaveZarinpalCredentials(event: FormEvent) {
    event.preventDefault()
    const merchantId = ePayment.gateways.zarinpal.merchantId.trim()

    if (ePayment.gateways.zarinpal.enabled && !merchantId) {
      setError(t('website.ePayment.error.zarinpalMerchant'))
      return
    }

    await patchEPayment('zarinpal-credentials', {
      ...ePayment,
      gateways: {
        ...ePayment.gateways,
        zarinpal: {
          ...ePayment.gateways.zarinpal,
          merchantId,
        },
      },
    })
  }

  return (
    <main className={pageStyles.content}>
      <Breadcrumbs
        items={[
          { label: 'Dashboard', href: '/' },
          { label: 'Settings' },
        ]}
      />

      <div className={pageStyles.pageHeader}>
        <div>
          <PageTitle en="SETTINGS">{t('title.settings')}</PageTitle>
          <p className={pageStyles.pageSubtitle}>{t('settings.subtitle')}</p>
        </div>
      </div>

      {error ? <div className={sharedStyles.alertError}>{error}</div> : null}

      {isLoading ? (
        <p className={sharedStyles.status}>{t('productSettings.loading')}</p>
      ) : (
        <div className={styles.stack}>
          <section className={sharedStyles.panel}>
            <h3 className={sharedStyles.sectionTitle}>{t('title.ePayment')}</h3>
            <div className={sharedStyles.list}>
              <div className={sharedStyles.row}>
                <div className={sharedStyles.rowText}>
                  <label className={sharedStyles.rowLabel} htmlFor="epayment-master">
                    {t('website.ePayment.master')}
                  </label>
                  <p className={sharedStyles.rowDescription}>
                    {t('website.ePayment.masterDesc')}
                  </p>
                </div>
                <Switch
                  id="epayment-master"
                  checked={ePayment.enabled}
                  disabled={savingKey !== null}
                  onChange={(checked) => void handleMasterToggle(checked)}
                />
              </div>
            </div>
          </section>

          <section className={styles.gatewayCard} data-card-hover>
            <div className={styles.gatewayHeader}>
              <div>
                <h3 className={styles.gatewayTitle}>
                  {t('website.ePayment.gateway.mellat')}
                </h3>
                <p className={styles.gatewayDesc}>
                  {t('website.ePayment.gateway.mellatDesc')}
                </p>
              </div>
              <Switch
                id="epayment-mellat"
                checked={ePayment.gateways.mellat.enabled}
                disabled={savingKey !== null || !ePayment.enabled}
                onChange={(checked) => void handleMellatToggle(checked)}
              />
            </div>

            <form className={styles.credentials} onSubmit={handleSaveMellatCredentials}>
              <div className={`${fieldStyles.field} ${styles.field}`}>
                <label htmlFor="mellat-terminal">
                  {t('website.ePayment.terminalId')}
                </label>
                <input
                  id="mellat-terminal"
                  type="text"
                  inputMode="numeric"
                  autoComplete="off"
                  dir="ltr"
                  value={ePayment.gateways.mellat.terminalId}
                  disabled={savingKey !== null}
                  onChange={(e) =>
                    setEPayment((current) => ({
                      ...current,
                      gateways: {
                        ...current.gateways,
                        mellat: {
                          ...current.gateways.mellat,
                          terminalId: e.target.value,
                        },
                      },
                    }))
                  }
                />
              </div>

              <div className={`${fieldStyles.field} ${styles.field}`}>
                <label htmlFor="mellat-username">
                  {t('website.ePayment.username')}
                </label>
                <input
                  id="mellat-username"
                  type="text"
                  autoComplete="off"
                  dir="ltr"
                  value={ePayment.gateways.mellat.username}
                  disabled={savingKey !== null}
                  onChange={(e) =>
                    setEPayment((current) => ({
                      ...current,
                      gateways: {
                        ...current.gateways,
                        mellat: {
                          ...current.gateways.mellat,
                          username: e.target.value,
                        },
                      },
                    }))
                  }
                />
              </div>

              <div className={`${fieldStyles.field} ${styles.field}`}>
                <label htmlFor="mellat-password">
                  {t('website.ePayment.password')}
                  {ePayment.gateways.mellat.passwordSet ? (
                    <span className={styles.hint}>
                      {' '}
                      ({t('website.ePayment.passwordSet')})
                    </span>
                  ) : null}
                </label>
                <div className={styles.passwordWrap}>
                  <input
                    id="mellat-password"
                    type={showPassword ? 'text' : 'password'}
                    autoComplete="new-password"
                    dir="ltr"
                    placeholder={
                      ePayment.gateways.mellat.passwordSet
                        ? t('website.ePayment.passwordPlaceholderSet')
                        : t('website.ePayment.passwordPlaceholder')
                    }
                    value={passwordDraft}
                    disabled={savingKey !== null}
                    onChange={(e) => setPasswordDraft(e.target.value)}
                  />
                  <Tooltip
                    label={
                      showPassword
                        ? t('website.ePayment.hidePassword')
                        : t('website.ePayment.showPassword')
                    }
                  >
                    <button
                      type="button"
                      className={styles.passwordToggle}
                      onClick={() => setShowPassword((v) => !v)}
                      aria-label={
                        showPassword
                          ? t('website.ePayment.hidePassword')
                          : t('website.ePayment.showPassword')
                      }
                    >
                      {showPassword ? <EyeOff size={16} /> : <Eye size={16} />}
                    </button>
                  </Tooltip>
                </div>
              </div>

              <div className={styles.actions}>
                <button
                  type="submit"
                  className={styles.saveBtn}
                  disabled={savingKey !== null}
                >
                  {savingKey === 'mellat-credentials'
                    ? t('storeSettings.saving')
                    : t('website.ePayment.saveCredentials')}
                </button>
              </div>
            </form>
          </section>

          <section className={styles.gatewayCard} data-card-hover>
            <div className={styles.gatewayHeader}>
              <div>
                <h3 className={styles.gatewayTitle}>
                  {t('website.ePayment.gateway.zarinpal')}
                </h3>
                <p className={styles.gatewayDesc}>
                  {t('website.ePayment.gateway.zarinpalDesc')}
                </p>
              </div>
              <Switch
                id="epayment-zarinpal"
                checked={ePayment.gateways.zarinpal.enabled}
                disabled={savingKey !== null || !ePayment.enabled}
                onChange={(checked) => void handleZarinpalToggle(checked)}
              />
            </div>

            <form className={styles.credentials} onSubmit={handleSaveZarinpalCredentials}>
              <div className={`${fieldStyles.field} ${styles.field}`}>
                <label htmlFor="zarinpal-merchant">
                  {t('website.ePayment.merchantId')}
                </label>
                <input
                  id="zarinpal-merchant"
                  type="text"
                  autoComplete="off"
                  dir="ltr"
                  spellCheck={false}
                  placeholder={t('website.ePayment.merchantIdPlaceholder')}
                  value={ePayment.gateways.zarinpal.merchantId}
                  disabled={savingKey !== null}
                  onChange={(e) =>
                    setEPayment((current) => ({
                      ...current,
                      gateways: {
                        ...current.gateways,
                        zarinpal: {
                          ...current.gateways.zarinpal,
                          merchantId: e.target.value,
                        },
                      },
                    }))
                  }
                />
              </div>

              <div className={`${sharedStyles.row} ${styles.fullRow}`}>
                <div className={sharedStyles.rowText}>
                  <label className={sharedStyles.rowLabel} htmlFor="zarinpal-sandbox">
                    {t('website.ePayment.sandbox')}
                  </label>
                  <p className={sharedStyles.rowDescription}>
                    {t('website.ePayment.sandboxDesc')}
                  </p>
                </div>
                <Switch
                  id="zarinpal-sandbox"
                  checked={ePayment.gateways.zarinpal.sandbox}
                  disabled={savingKey !== null}
                  onChange={(checked) =>
                    setEPayment((current) => ({
                      ...current,
                      gateways: {
                        ...current.gateways,
                        zarinpal: {
                          ...current.gateways.zarinpal,
                          sandbox: checked,
                        },
                      },
                    }))
                  }
                />
              </div>

              <div className={styles.actions}>
                <button
                  type="submit"
                  className={styles.saveBtn}
                  disabled={savingKey !== null}
                >
                  {savingKey === 'zarinpal-credentials'
                    ? t('storeSettings.saving')
                    : t('website.ePayment.saveCredentials')}
                </button>
              </div>
            </form>
          </section>

          <div className={styles.comingSoonGrid}>
            {COMING_SOON_GATEWAYS.map((gateway) => (
              <section key={gateway.id} className={styles.comingSoonCard}>
                <div className={styles.gatewayHeader}>
                  <div>
                    <h3 className={styles.gatewayTitle}>{t(gateway.nameKey)}</h3>
                    <p className={styles.gatewayDesc}>{t(gateway.descKey)}</p>
                  </div>
                  <span className={styles.badge}>{t('website.ePayment.comingSoon')}</span>
                </div>
              </section>
            ))}
          </div>
        </div>
      )}
    </main>
  )
}