import { useState, useMemo } from 'react'
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
import toast from 'react-hot-toast'
import { ChevronDown, Search } from 'lucide-react'
import client from '../api/client'

// ── Helpers ───────────────────────────────────────────────────────────────────

function fmt(n) {
  if (n == null) return '—'
  return n.toLocaleString('el-GR', { minimumFractionDigits: 2, maximumFractionDigits: 2 }) + ' €'
}

function fmtDateTime(iso) {
  if (!iso) return '—'
  return new Date(iso).toLocaleString('el-GR', { day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit' })
}

function daysSince(iso) {
  if (!iso) return null
  const days = Math.floor((Date.now() - new Date(iso).getTime()) / 86400000)
  if (days === 0) return 'Σήμερα'
  if (days === 1) return '1 μέρα'
  return `${days} μέρες`
}

const STATUS_CONFIG = {
  open:     { label: 'Ανοιχτή',    bg: '#fee2e2', color: '#dc2626' },
  closed:   { label: 'Κλειστή',   bg: '#dcfce7', color: '#16a34a' },
  forgiven: { label: 'Χαρίστηκε', bg: '#f3f4f6', color: '#6b7280' },
}

// ── Pay modal ─────────────────────────────────────────────────────────────────

function PayModal({ tab, onClose, onPay, isPending }) {
  const [amount, setAmount] = useState(String(Math.round(tab.balance * 100) / 100))
  const [method, setMethod] = useState('cash')
  const [notes, setNotes] = useState('')
  const parsed = parseFloat(amount)
  const canPay = parsed > 0 && parsed <= tab.balance + 0.005

  return (
    <div style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.45)', display: 'flex', alignItems: 'center', justifyContent: 'center', zIndex: 60, padding: 20 }}>
      <div style={{ background: 'white', borderRadius: 16, width: '100%', maxWidth: 400, boxShadow: '0 20px 60px rgba(0,0,0,0.18)' }}>
        <div style={{ padding: '18px 22px 14px', borderBottom: '1px solid #f0f0ef' }}>
          <div style={{ fontSize: 16, fontWeight: 700 }}>Πληρωμή Καρτέλας</div>
          <div style={{ fontSize: 13, color: '#6b7280', marginTop: 2 }}>{tab.customer_name}</div>
        </div>
        <div style={{ padding: '18px 22px', display: 'flex', flexDirection: 'column', gap: 14 }}>
          <div style={{ background: '#f9fafb', borderRadius: 10, padding: '12px 14px', display: 'flex', justifyContent: 'space-between' }}>
            <span style={{ fontSize: 13, color: '#6b7280' }}>Υπόλοιπο καρτέλας</span>
            <span style={{ fontSize: 15, fontWeight: 700, color: '#dc2626' }}>{fmt(tab.balance)}</span>
          </div>
          <div>
            <label style={{ fontSize: 12, fontWeight: 600, color: '#374151', display: 'block', marginBottom: 5 }}>Ποσό πληρωμής (€)</label>
            <input type="number" step="0.01" min="0.01"
              value={amount} onChange={e => setAmount(e.target.value)} autoFocus
              style={{ width: '100%', padding: '9px 12px', border: '1.5px solid #e5e7eb', borderRadius: 8, fontSize: 16, fontWeight: 600, outline: 'none', boxSizing: 'border-box' }} />
          </div>
          <div>
            <label style={{ fontSize: 12, fontWeight: 600, color: '#374151', display: 'block', marginBottom: 5 }}>Τρόπος πληρωμής</label>
            <div style={{ display: 'flex', gap: 6 }}>
              {[['cash', 'Μετρητά'], ['card', 'Κάρτα'], ['other', 'Άλλο']].map(([v, l]) => (
                <button key={v} onClick={() => setMethod(v)}
                  style={{
                    flex: 1, padding: '7px', borderRadius: 7, fontSize: 12.5, fontWeight: 600, cursor: 'pointer',
                    border: `1.5px solid ${method === v ? '#111827' : '#e5e7eb'}`,
                    background: method === v ? '#111827' : 'white',
                    color: method === v ? 'white' : '#6b7280',
                  }}>{l}</button>
              ))}
            </div>
          </div>
          <div>
            <label style={{ fontSize: 12, fontWeight: 600, color: '#374151', display: 'block', marginBottom: 5 }}>Σημείωση</label>
            <input value={notes} onChange={e => setNotes(e.target.value)} placeholder="προαιρετικό"
              style={{ width: '100%', padding: '8px 11px', border: '1px solid #e5e7eb', borderRadius: 8, fontSize: 13, outline: 'none', boxSizing: 'border-box' }} />
          </div>
        </div>
        <div style={{ padding: '14px 22px', borderTop: '1px solid #f0f0ef', display: 'flex', gap: 10, justifyContent: 'flex-end' }}>
          <button onClick={onClose} style={{ padding: '8px 18px', border: '1px solid #e5e7eb', background: 'white', borderRadius: 8, fontSize: 13, cursor: 'pointer' }}>Ακύρωση</button>
          <button onClick={() => onPay(parsed, method, notes || null)} disabled={!canPay || isPending}
            style={{ padding: '8px 20px', border: 'none', borderRadius: 8, fontSize: 13, fontWeight: 600, cursor: canPay ? 'pointer' : 'default', background: canPay ? '#16a34a' : '#e5e7eb', color: canPay ? 'white' : '#9ca3af' }}>
            {isPending ? 'Αποθήκευση…' : 'Καταγραφή Πληρωμής'}
          </button>
        </div>
      </div>
    </div>
  )
}

// ── Forgive confirm ───────────────────────────────────────────────────────────

function ForgiveModal({ tab, onClose, onForgive, isPending }) {
  const [reason, setReason] = useState('')
  return (
    <div style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.45)', display: 'flex', alignItems: 'center', justifyContent: 'center', zIndex: 60, padding: 20 }}>
      <div style={{ background: 'white', borderRadius: 16, width: '100%', maxWidth: 400, boxShadow: '0 20px 60px rgba(0,0,0,0.18)' }}>
        <div style={{ padding: '18px 22px 14px', borderBottom: '1px solid #f0f0ef' }}>
          <div style={{ fontSize: 16, fontWeight: 700, color: '#dc2626' }}>Χάρισμα Καρτέλας</div>
          <div style={{ fontSize: 13, color: '#6b7280', marginTop: 2 }}>{tab.customer_name} — υπόλοιπο {fmt(tab.balance)}</div>
        </div>
        <div style={{ padding: '18px 22px', display: 'flex', flexDirection: 'column', gap: 12 }}>
          <div style={{ padding: '12px 14px', background: '#fef2f2', borderRadius: 10, border: '1px solid #fecaca', fontSize: 13, color: '#7f1d1d', lineHeight: 1.5 }}>
            Το υπόλοιπο των {fmt(tab.balance)} θα διαγραφεί. Η ενέργεια δεν αναιρείται.
          </div>
          <div>
            <label style={{ fontSize: 12, fontWeight: 600, color: '#374151', display: 'block', marginBottom: 5 }}>Αιτιολογία</label>
            <input value={reason} onChange={e => setReason(e.target.value)} placeholder="π.χ. Καλή θέληση"
              style={{ width: '100%', padding: '8px 11px', border: '1px solid #e5e7eb', borderRadius: 8, fontSize: 13, outline: 'none', boxSizing: 'border-box' }} />
          </div>
        </div>
        <div style={{ padding: '14px 22px', borderTop: '1px solid #f0f0ef', display: 'flex', gap: 10, justifyContent: 'flex-end' }}>
          <button onClick={onClose} style={{ padding: '8px 18px', border: '1px solid #e5e7eb', background: 'white', borderRadius: 8, fontSize: 13, cursor: 'pointer' }}>Ακύρωση</button>
          <button onClick={() => onForgive(reason || null)} disabled={isPending}
            style={{ padding: '8px 20px', border: 'none', borderRadius: 8, fontSize: 13, fontWeight: 600, cursor: 'pointer', background: '#dc2626', color: 'white' }}>
            {isPending ? 'Αποθήκευση…' : 'Χάρισμα Υπολοίπου'}
          </button>
        </div>
      </div>
    </div>
  )
}

// ── Tab detail card (collapsible) ─────────────────────────────────────────────

function TabDetail({ tab, onPay, onClose, onForgive, defaultExpanded = false }) {
  const [expanded, setExpanded] = useState(defaultExpanded)
  const sc = STATUS_CONFIG[tab.status] || STATUS_CONFIG.open
  const canClose = tab.status === 'open' && tab.balance <= 0.005 && tab.entries.length > 0

  return (
    <div style={{ border: '1px solid #e5e7eb', borderRadius: 12, overflow: 'hidden', background: 'white' }}>
      {/* Clickable header — always visible */}
      <button
        onClick={() => setExpanded(e => !e)}
        style={{
          width: '100%', textAlign: 'left',
          padding: '14px 18px', background: '#f9fafb',
          borderBottom: expanded ? '1px solid #e5e7eb' : 'none',
          display: 'flex', alignItems: 'center', justifyContent: 'space-between',
          flexWrap: 'wrap', gap: 8, cursor: 'pointer',
        }}
      >
        <div style={{ display: 'flex', alignItems: 'center', gap: 10, minWidth: 0 }}>
          <ChevronDown
            size={16}
            style={{
              flexShrink: 0, color: '#9ca3af',
              transform: expanded ? 'rotate(180deg)' : 'rotate(0deg)',
              transition: 'transform 0.18s',
            }}
          />
          <div style={{ minWidth: 0 }}>
            <div style={{ fontSize: 15, fontWeight: 700, color: '#111315' }}>{tab.customer_name}</div>
            <div style={{ fontSize: 12, color: '#9ca3af', marginTop: 1 }}>
              Άνοιγμα: {fmtDateTime(tab.opened_at)} · {daysSince(tab.opened_at)} ανοιχτή
            </div>
          </div>
        </div>
        <div style={{ display: 'flex', alignItems: 'center', gap: 8, flexShrink: 0 }}>
          <span style={{ fontSize: 22, fontWeight: 800, color: tab.balance > 0 ? '#dc2626' : '#16a34a' }}>
            {fmt(tab.balance)}
          </span>
          <span style={{ fontSize: 11.5, fontWeight: 700, padding: '2px 8px', borderRadius: 99, background: sc.bg, color: sc.color }}>
            {sc.label}
          </span>
        </div>
      </button>

      {/* Expanded body */}
      {expanded && (
        <>
          {/* Stats */}
          <div style={{ display: 'grid', gridTemplateColumns: 'repeat(3,1fr)', gap: 1, background: '#f0f0ef' }}>
            {[
              { label: 'Συνολικές χρεώσεις', value: fmt(tab.total_charged) },
              { label: 'Πληρωμένο', value: fmt(tab.total_paid), color: '#16a34a' },
              { label: 'Υπόλοιπο', value: fmt(tab.balance), color: tab.balance > 0 ? '#dc2626' : '#16a34a' },
            ].map(s => (
              <div key={s.label} style={{ background: 'white', padding: '10px 14px', textAlign: 'center' }}>
                <div style={{ fontSize: 10, color: '#9ca3af', fontWeight: 700, textTransform: 'uppercase', letterSpacing: '0.04em' }}>{s.label}</div>
                <div style={{ fontSize: 15, fontWeight: 800, color: s.color || '#111315', marginTop: 2 }}>{s.value}</div>
              </div>
            ))}
          </div>

          {/* Entries */}
          {tab.entries.length > 0 && (
            <div style={{ padding: '12px 18px', borderBottom: '1px solid #f0f0ef' }}>
              <div style={{ fontSize: 11, fontWeight: 700, color: '#9ca3af', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: 8 }}>Χρεώσεις</div>
              <div style={{ display: 'flex', flexDirection: 'column', gap: 4 }}>
                {tab.entries.map(e => (
                  <div key={e.id} style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', fontSize: 13 }}>
                    <span style={{ color: '#374151' }}>{e.description || `Χρέωση #${e.id}`}</span>
                    <span style={{ fontWeight: 600, color: '#dc2626', whiteSpace: 'nowrap', marginLeft: 12 }}>{fmt(e.amount)}</span>
                  </div>
                ))}
              </div>
            </div>
          )}

          {/* Payments */}
          {tab.payments.length > 0 && (
            <div style={{ padding: '12px 18px', borderBottom: '1px solid #f0f0ef' }}>
              <div style={{ fontSize: 11, fontWeight: 700, color: '#9ca3af', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: 8 }}>Πληρωμές</div>
              <div style={{ display: 'flex', flexDirection: 'column', gap: 4 }}>
                {tab.payments.map(p => (
                  <div key={p.id} style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', fontSize: 13 }}>
                    <span style={{ color: '#374151' }}>
                      {p.received_by_name} · {fmtDateTime(p.created_at)}
                      {p.payment_method && <span style={{ color: '#9ca3af', marginLeft: 6 }}>({p.payment_method})</span>}
                      {p.notes && <span style={{ color: '#9ca3af', marginLeft: 6 }}>— {p.notes}</span>}
                    </span>
                    <span style={{ fontWeight: 600, color: '#16a34a', whiteSpace: 'nowrap', marginLeft: 12 }}>{fmt(p.amount)}</span>
                  </div>
                ))}
              </div>
            </div>
          )}

          {/* Actions */}
          {tab.status === 'open' && (
            <div style={{ padding: '12px 18px', display: 'flex', gap: 8, flexWrap: 'wrap' }}>
              {tab.balance > 0.005 && (
                <button onClick={() => onPay(tab)}
                  style={{ padding: '7px 16px', borderRadius: 8, border: 'none', background: '#16a34a', color: 'white', fontSize: 13, fontWeight: 600, cursor: 'pointer' }}>
                  Πληρωμή
                </button>
              )}
              {canClose && (
                <button onClick={() => onClose(tab)}
                  style={{ padding: '7px 16px', borderRadius: 8, border: '1px solid #d1d5db', background: 'white', color: '#374151', fontSize: 13, fontWeight: 600, cursor: 'pointer' }}>
                  Κλείσιμο Καρτέλας
                </button>
              )}
              <button onClick={() => onForgive(tab)}
                style={{ padding: '7px 16px', borderRadius: 8, border: '1px solid #fecaca', background: 'white', color: '#dc2626', fontSize: 13, fontWeight: 500, cursor: 'pointer', marginLeft: 'auto' }}>
                Χάρισμα Υπολοίπου
              </button>
            </div>
          )}
        </>
      )}
    </div>
  )
}

// ── Filter chip ───────────────────────────────────────────────────────────────

function FilterChip({ label, active, onClick }) {
  return (
    <button
      onClick={onClick}
      className={`px-3 py-1 rounded-full text-[12px] font-semibold border transition-colors ${
        active
          ? 'bg-slate-800 text-white border-slate-800'
          : 'bg-white text-slate-500 border-slate-200 hover:border-slate-400 hover:text-slate-700'
      }`}
    >
      {label}
    </button>
  )
}

// ── Main page ─────────────────────────────────────────────────────────────────

export default function TabsPage() {
  const qc = useQueryClient()
  const [statusFilter, setStatusFilter] = useState('open') // 'open' | 'closed' | 'all'
  const [search, setSearch] = useState('')
  const [modal, setModal] = useState(null)

  // Fetch open and closed separately — merge for client-side filtering
  const { data: openTabs = [], isLoading: loadingOpen } = useQuery({
    queryKey: ['tabs-open'],
    queryFn: () => client.get('/api/tabs/').then(r => r.data),
    staleTime: 15_000,
  })
  const { data: closedTabs = [], isLoading: loadingClosed } = useQuery({
    queryKey: ['tabs-closed'],
    queryFn: () => client.get('/api/tabs/', { params: { tab_status: 'closed' } }).then(r => r.data),
    staleTime: 15_000,
  })
  const tabs = [...openTabs, ...closedTabs]
  const isLoading = loadingOpen || loadingClosed

  const payTab = useMutation({
    mutationFn: ({ id, amount, payment_method, notes }) =>
      client.post(`/api/tabs/${id}/pay`, { amount, payment_method, notes }),
    onSuccess: () => {
      qc.invalidateQueries({ queryKey: ['tabs-open'] }); qc.invalidateQueries({ queryKey: ['tabs-closed'] })
      setModal(null)
      toast.success('Πληρωμή καταγράφηκε')
    },
    onError: (e) => toast.error(e?.response?.data?.detail || 'Σφάλμα'),
  })

  const closeTab = useMutation({
    mutationFn: (id) => client.post(`/api/tabs/${id}/close`, {}),
    onSuccess: () => {
      qc.invalidateQueries({ queryKey: ['tabs-open'] }); qc.invalidateQueries({ queryKey: ['tabs-closed'] })
      toast.success('Καρτέλα έκλεισε')
    },
    onError: (e) => toast.error(e?.response?.data?.detail || 'Σφάλμα'),
  })

  const forgiveTab = useMutation({
    mutationFn: ({ id, reason }) => client.post(`/api/tabs/${id}/forgive`, { reason }),
    onSuccess: () => {
      qc.invalidateQueries({ queryKey: ['tabs-open'] }); qc.invalidateQueries({ queryKey: ['tabs-closed'] })
      setModal(null)
      toast.success('Το υπόλοιπο χαρίστηκε')
    },
    onError: () => toast.error('Σφάλμα'),
  })

  // Live client-side filtering
  const filtered = useMemo(() => {
    let result = tabs
    if (statusFilter !== 'all') {
      result = result.filter(t => {
        if (statusFilter === 'open') return t.status === 'open'
        if (statusFilter === 'closed') return t.status === 'closed' || t.status === 'forgiven'
        return true
      })
    }
    if (search.trim()) {
      const q = search.trim().toLowerCase()
      result = result.filter(t => t.customer_name?.toLowerCase().includes(q))
    }
    return result
  }, [tabs, statusFilter, search])

  const openCount   = tabs.filter(t => t.status === 'open').length
  const closedCount = tabs.filter(t => t.status === 'closed' || t.status === 'forgiven').length
  const totalOutstanding = tabs.filter(t => t.status === 'open').reduce((s, t) => s + t.balance, 0)

  return (
    <div className="flex flex-col h-full overflow-hidden">
      {/* Toolbar */}
      <div className="px-6 py-3 border-b border-slate-200 bg-white shrink-0 flex items-center gap-3 flex-wrap">
        {/* Search */}
        <div className="relative flex items-center">
          <Search className="absolute left-2.5 h-3.5 w-3.5 text-slate-400 pointer-events-none" />
          <input
            type="text"
            value={search}
            onChange={e => setSearch(e.target.value)}
            placeholder="Αναζήτηση πελάτη…"
            className="pl-8 pr-3 py-1.5 text-[13px] bg-slate-50 border border-slate-200 rounded-lg w-48 focus:outline-none focus:ring-2 focus:ring-sky-500/30 focus:border-sky-400 transition placeholder:text-slate-400"
          />
        </div>

        {/* Status filter chips */}
        <div className="flex items-center gap-2">
          <FilterChip label={`Ανοιχτές (${openCount})`}   active={statusFilter === 'open'}   onClick={() => setStatusFilter('open')} />
          <FilterChip label={`Κλειστές (${closedCount})`} active={statusFilter === 'closed'} onClick={() => setStatusFilter('closed')} />
          <FilterChip label="Όλες"                         active={statusFilter === 'all'}    onClick={() => setStatusFilter('all')} />
        </div>

        {/* Summary */}
        <div className="ml-auto text-[12px] text-slate-400">
          {statusFilter === 'open' && totalOutstanding > 0 && (
            <span>Σύνολο: <strong className="text-red-600">{fmt(totalOutstanding)}</strong></span>
          )}
        </div>
      </div>

      {/* Tab list */}
      <div className="flex-1 overflow-y-auto px-6 py-4 flex flex-col gap-3">
        {isLoading && (
          <div className="text-center text-slate-400 text-[13px] py-12">Φόρτωση…</div>
        )}
        {!isLoading && filtered.length === 0 && (
          <div className="text-center text-slate-400 text-[14px] py-12">
            {search ? 'Δεν βρέθηκαν αποτελέσματα.' : 'Δεν υπάρχουν καρτέλες.'}
          </div>
        )}
        {filtered.map(tab => (
          <TabDetail
            key={tab.id}
            tab={tab}
            defaultExpanded={false}
            onPay={t => setModal({ type: 'pay', tab: t })}
            onClose={t => closeTab.mutate(t.id)}
            onForgive={t => setModal({ type: 'forgive', tab: t })}
          />
        ))}
      </div>

      {modal?.type === 'pay' && (
        <PayModal
          tab={modal.tab}
          onClose={() => setModal(null)}
          isPending={payTab.isPending}
          onPay={(amount, payment_method, notes) => payTab.mutate({ id: modal.tab.id, amount, payment_method, notes })}
        />
      )}

      {modal?.type === 'forgive' && (
        <ForgiveModal
          tab={modal.tab}
          onClose={() => setModal(null)}
          isPending={forgiveTab.isPending}
          onForgive={(reason) => forgiveTab.mutate({ id: modal.tab.id, reason })}
        />
      )}
    </div>
  )
}