import { useState, useEffect, useCallback } from 'react'
import { FaFilePdf, FaPlus, FaLink, FaSpinner, FaRotate } from 'react-icons/fa6'
import { databases, DATABASE_ID, COLLECTIONS } from '../lib/appwrite'
import { integrationsApi, formatMoney, INVOICE_STATUS } from '../lib/integrationsApi'
import { useInvoices } from '../hooks/useInvoices'
import { customerStage, isInvoiceReady } from '../lib/leads'

const card = {
  background: 'rgba(45, 55, 72, 0.5)',
  borderRadius: '12px',
  padding: '16px',
  border: '1px solid rgba(16, 185, 129, 0.2)',
}

export default function InvoicePanel({ ticket }) {
  const [customer, setCustomer] = useState(null)
  const [customerLoading, setCustomerLoading] = useState(true)
  const [customerError, setCustomerError] = useState(null)

  const loadCustomer = useCallback(async () => {
    if (!ticket.customerId) {
      setCustomer(null)
      setCustomerLoading(false)
      return
    }
    setCustomerLoading(true)
    try {
      const doc = await databases.getDocument(DATABASE_ID, COLLECTIONS.CUSTOMERS, ticket.customerId)
      setCustomer(doc)
      setCustomerError(null)
    } catch (err) {
      setCustomerError(err.message)
      setCustomer(null)
    } finally {
      setCustomerLoading(false)
    }
  }, [ticket.customerId])

  useEffect(() => {
    loadCustomer()
  }, [loadCustomer])

  const clientId = customer?.invoiceNinjaClientId || null
  const { invoices, loading, error, refresh } = useInvoices(clientId)

  if (customerLoading) {
    return (
      <div style={card}>
        <FaSpinner className="spinner" /> Kunde wird geladen...
      </div>
    )
  }

  if (!ticket.customerId) {
    return (
      <div style={card}>
        <p style={{ color: '#a0aec0', margin: 0 }}>Kein Kunde am Ticket verknüpft, keine Rechnungen verfügbar.</p>
      </div>
    )
  }

  return (
    <div style={card}>
      <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: '12px' }}>
        <h5 style={{ color: 'var(--dark-text)', fontWeight: 'bold', margin: 0, fontSize: '16px' }}>
          Rechnungen {customer?.name ? `- ${customer.name}` : ''}
        </h5>
        {clientId && (
          <button className="btn" onClick={refresh} title="Aktualisieren"
            style={{ background: '#374151', color: 'white', border: 'none', padding: '6px 10px', borderRadius: '6px', cursor: 'pointer' }}>
            <FaRotate />
          </button>
        )}
      </div>

      {customerError && <div className="text-red" style={{ marginBottom: 8 }}>{customerError}</div>}

      {customer && customerStage(customer) === 'lead' ? (
        <p style={{ color: '#a0aec0', margin: 0 }}>
          Dieser Kunde ist noch ein Lead. Erst zum festen Kunden machen (im Kunden-Bereich, vollständige Daten nötig), dann sind Rechnungen möglich.
        </p>
      ) : !clientId && !isInvoiceReady(customer) ? (
        <p style={{ color: '#a0aec0', margin: 0 }}>
          Rechnungsdaten unvollständig. Bitte im Kunden-Bereich Unternehmen, E-Mail, Straße, PLZ und Stadt ergänzen.
        </p>
      ) : !clientId ? (
        <LinkClient customer={customer} onLinked={loadCustomer} />
      ) : (
        <InvoiceList invoices={invoices} loading={loading} error={error} />
      )}
    </div>
  )
}

// ---------------------------------------------------- Verknuepfung -----------
function LinkClient({ customer, onLinked }) {
  const [search, setSearch] = useState(customer?.name || '')
  const [results, setResults] = useState([])
  const [busy, setBusy] = useState(false)
  const [error, setError] = useState(null)
  const [saving, setSaving] = useState(false)

  const doSearch = async () => {
    setBusy(true)
    setError(null)
    try {
      const data = await integrationsApi.listClients(search)
      setResults(data.clients || [])
    } catch (err) {
      setError(err.message)
    } finally {
      setBusy(false)
    }
  }

  useEffect(() => {
    doSearch()
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [])

  const saveMapping = async (clientId) => {
    setSaving(true)
    setError(null)
    try {
      await databases.updateDocument(DATABASE_ID, COLLECTIONS.CUSTOMERS, customer.$id, {
        invoiceNinjaClientId: clientId,
      })
      onLinked()
    } catch (err) {
      setError(err.message)
      setSaving(false)
    }
  }

  const createAndLink = async () => {
    setSaving(true)
    setError(null)
    try {
      const data = await integrationsApi.createClient({
        name: customer.name || customer.companyName || 'Neuer Kunde',
        email: customer.email || '',
        phone: customer.phone || '',
        address: customer.location || '',
      })
      if (data.client?.id) {
        await saveMapping(data.client.id)
      } else {
        throw new Error('Client konnte nicht angelegt werden')
      }
    } catch (err) {
      setError(err.message)
      setSaving(false)
    }
  }

  return (
    <div>
      <p style={{ color: '#a0aec0', fontSize: '13px', marginTop: 0 }}>
        Dieser Kunde ist noch nicht mit InvoiceNinja verknüpft.
      </p>
      <div style={{ display: 'flex', gap: '8px', marginBottom: '10px' }}>
        <input
          className="form-control"
          style={{ margin: 0 }}
          placeholder="InvoiceNinja-Kunde suchen …"
          value={search}
          onChange={(e) => setSearch(e.target.value)}
          onKeyDown={(e) => e.key === 'Enter' && doSearch()}
        />
        <button className="btn btn-green" style={{ margin: 0 }} onClick={doSearch} disabled={busy}>
          {busy ? <FaSpinner className="spinner" /> : 'Suchen'}
        </button>
      </div>

      {error && <div className="text-red" style={{ marginBottom: 8 }}>{error}</div>}

      <div style={{ maxHeight: '180px', overflowY: 'auto', marginBottom: '10px' }}>
        {results.map((c) => (
          <div key={c.id} style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', padding: '8px', borderBottom: '1px solid rgba(255,255,255,0.06)' }}>
            <div>
              <strong style={{ color: 'var(--dark-text)' }}>{c.name}</strong>
              {c.number ? <span style={{ color: '#a0aec0' }}> · {c.number}</span> : null}
              {c.email ? <div style={{ color: '#a0aec0', fontSize: '12px' }}>{c.email}</div> : null}
            </div>
            <button className="btn btn-green" style={{ margin: 0 }} disabled={saving} onClick={() => saveMapping(c.id)}>
              <FaLink /> Verknüpfen
            </button>
          </div>
        ))}
        {!busy && results.length === 0 && (
          <p style={{ color: '#a0aec0', fontSize: '13px' }}>Keine Treffer.</p>
        )}
      </div>

      <button className="btn" style={{ background: '#3b82f6', color: 'white', border: 'none', padding: '10px 16px', borderRadius: '8px', cursor: 'pointer' }} disabled={saving} onClick={createAndLink}>
        {saving ? <FaSpinner className="spinner" /> : <><FaPlus /> Neuen InvoiceNinja-Kunden anlegen &amp; verknüpfen</>}
      </button>
    </div>
  )
}

// ---------------------------------------------------- Rechnungsliste ---------
// Nur anzeigen: neue Rechnungen entstehen direkt in InvoiceNinja
function InvoiceList({ invoices, loading, error }) {
  const [openingId, setOpeningId] = useState(null)

  const openPdf = async (id) => {
    setOpeningId(id)
    try {
      await integrationsApi.openInvoicePdf(id)
    } catch (err) {
      alert('PDF konnte nicht geöffnet werden: ' + err.message)
    } finally {
      setOpeningId(null)
    }
  }

  return (
    <div>
      {error && <div className="text-red" style={{ marginBottom: 8 }}>{error}</div>}

      {loading ? (
        <p style={{ color: '#a0aec0' }}><FaSpinner className="spinner" /> Rechnungen werden geladen...</p>
      ) : invoices.length === 0 ? (
        <p style={{ color: '#a0aec0', fontSize: '13px' }}>Noch keine Rechnungen für diesen Kunden.</p>
      ) : (
        <div style={{ overflowX: 'auto' }}>
          <table className="table" style={{ width: '100%', fontSize: '13px' }}>
            <thead>
              <tr style={{ color: '#a0aec0', textAlign: 'left' }}>
                <th>Nr.</th><th>Datum</th><th>Fällig</th><th>Betrag</th><th>Offen</th><th>Status</th><th></th>
              </tr>
            </thead>
            <tbody>
              {invoices.map((inv) => {
                const st = INVOICE_STATUS[inv.status_id] || { label: '–', color: '#a0aec0' }
                const overdue = Number(inv.balance) > 0 && inv.due_date && new Date(inv.due_date) < new Date()
                return (
                  <tr key={inv.id}>
                    <td style={{ color: 'var(--dark-text)' }}>{inv.number || inv.id?.slice(-6)}</td>
                    <td style={{ color: '#cbd5e0' }}>{inv.date || '-'}</td>
                    <td style={{ color: overdue ? '#ef4444' : '#cbd5e0' }}>{inv.due_date || '-'}</td>
                    <td style={{ color: 'var(--dark-text)' }}>{formatMoney(inv.amount)}</td>
                    <td style={{ color: Number(inv.balance) > 0 ? '#f59e0b' : '#10b981' }}>{formatMoney(inv.balance)}</td>
                    <td><span style={{ color: st.color, fontWeight: 'bold' }}>{st.label}{overdue ? ' (überfällig)' : ''}</span></td>
                    <td>
                      <button className="btn" title="PDF öffnen" disabled={openingId === inv.id}
                        style={{ background: '#ef4444', color: 'white', border: 'none', padding: '6px 10px', borderRadius: '6px', cursor: 'pointer' }}
                        onClick={() => openPdf(inv.id)}>
                        {openingId === inv.id ? <FaSpinner className="spinner" /> : <FaFilePdf />}
                      </button>
                    </td>
                  </tr>
                )
              })}
            </tbody>
          </table>
        </div>
      )}
    </div>
  )
}