import { useEffect, useRef, useState } from 'react'
import { useNavigate, useSearchParams } from 'react-router-dom'
import { Badge, Button, DataTable, EmptyState, ErrorState, FilterChips, PageHeader, Skeleton, Toolbar } from '@sims/ui'
import { getClients, CLIENT_STATUSES, type ClientStatus, type DocStatus } from '../api'
import { ClientFormDialog } from '../components/ClientFormDialog'

/**
 * Tiny fetch-render hook shared by the HQ pages (same shape as backoffice live.tsx).
 *
 * When `deps` change we clear the previous `data` first, so a new subject (e.g. a
 * different client id) shows a loading state instead of flashing the old record
 * underneath the new one. A manual `reload()` is a refresh, not a new subject, so it
 * keeps the current data on screen while it refetches. `isLoading` is additive —
 * existing callers that only read `{ data, error, reload }` are unaffected.
 */
export function useData<T>(loader: () => Promise<T>, deps: unknown[] = []): {
  data?: T; error?: string; reload: () => void; isLoading: boolean
} {
  const [data, setData] = useState<T | undefined>()
  const [error, setError] = useState<string | undefined>()
  const [isLoading, setIsLoading] = useState(true)
  const seqRef = useRef(0)
  // Latest loader without making it a dep of the fetch effect (deps drive refetch).
  const loaderRef = useRef(loader)
  loaderRef.current = loader

  const run = (reset: boolean) => {
    setError(undefined)
    if (reset) setData(undefined)
    setIsLoading(true)
    const mySeq = ++seqRef.current
    loaderRef.current()
      .then((d) => { if (seqRef.current === mySeq) { setData(d); setIsLoading(false) } })
      .catch((e: Error) => { if (seqRef.current === mySeq) { setError(e.message); setIsLoading(false) } })
  }
  const reload = () => run(false)

  // Deps changed → new subject: reset so the previous record can't flash through.
  // eslint-disable-next-line react-hooks/exhaustive-deps
  useEffect(() => run(true), deps)

  return { data, error, reload, isLoading }
}

/** Debounce a fast-changing value (e.g. a search box) so a dep fires ~300ms after typing stops. */
export function useDebounced<T>(value: T, ms = 300): T {
  const [debounced, setDebounced] = useState(value)
  useEffect(() => {
    const t = setTimeout(() => setDebounced(value), ms)
    return () => clearTimeout(t)
  }, [value, ms])
  return debounced
}

type Tone = 'ok' | 'warn' | 'err' | 'accent'

export const CLIENT_TONE: Record<ClientStatus, Tone> = {
  lead: 'accent', active: 'ok', dormant: 'warn', lost: 'err',
}

export const DOC_TONE: Record<DocStatus, Tone> = {
  draft: 'warn', sent: 'accent', accepted: 'ok', invoiced: 'accent',
  part_paid: 'warn', paid: 'ok', lost: 'err', cancelled: 'err',
}

/** Client registry — search, list, inline create; row click opens the Client 360°. */
export function Clients() {
  const nav = useNavigate()
  const [q, setQ] = useState('')
  // D18 WS-F: the old book's two working filters, applied server-side.
  const [district, setDistrict] = useState('')
  const [sector, setSector] = useState('')
  // Debounced so typing in the search box doesn't fire a server request per keystroke.
  const qDebounced = useDebounced(q)
  const { data, error, reload } = useData(
    () => getClients(qDebounced, { district, sector }), [qDebounced, district, sector],
  )
  const [sp, setSp] = useSearchParams()
  const [creating, setCreating] = useState(sp.get('new') === '1')
  const [statusFilter, setStatusFilter] = useState('all')
  useEffect(() => {
    if (sp.get('new') === '1') { setCreating(true); setSp({}, { replace: true }) }
  }, [sp, setSp])
  const counts = new Map<string, number>()
  for (const c of data ?? []) counts.set(c.status, (counts.get(c.status) ?? 0) + 1)
  const shown = (data ?? []).filter((c) => statusFilter === 'all' || c.status === statusFilter)
  const why = [
    q !== '' ? ` matching “${q}”` : '',
    statusFilter !== 'all' ? ` with status ${statusFilter}` : '',
  ].filter((x) => x !== '').join('')

  return (
    <div className="wf-page">
      <PageHeader
        title="Clients"
        desc="Every shop we serve — leads through lost. Click a row for the client 360°."
        actions={<Button tone="primary" onClick={() => setCreating((v) => !v)}>New client</Button>}
      />
      <Toolbar>
        <input
          className="wf" style={{ maxWidth: 280 }} placeholder="Search name / code / GSTIN…"
          aria-label="Search clients"
          value={q} onChange={(e) => setQ(e.target.value)}
        />
        <input
          className="wf" style={{ maxWidth: 140 }} placeholder="District" aria-label="District"
          value={district} onChange={(e) => setDistrict(e.target.value)}
        />
        <input
          className="wf" style={{ maxWidth: 120 }} placeholder="Sector" aria-label="Sector"
          value={sector} onChange={(e) => setSector(e.target.value)}
        />
        <FilterChips
          active={statusFilter}
          onChange={setStatusFilter}
          chips={[
            { key: 'all', label: 'All', count: data?.length ?? 0 },
            ...CLIENT_STATUSES.map((s) => ({ key: s, label: s, count: counts.get(s) ?? 0 })),
          ]}
        />
        <span className="spacer" />
        <Badge>{shown.length} shown</Badge>
      </Toolbar>
      <ClientFormDialog
        open={creating}
        onClose={() => setCreating(false)}
        onSaved={(c) => { reload(); nav(`/clients/${c.id}`) }}
      />
      {error !== undefined && <ErrorState message={error} onRetry={reload} />}
      {data === undefined && error === undefined ? <Skeleton rows={6} />
        : shown.length === 0 ? <EmptyState>No clients{why !== '' ? why : ' yet — add the first one'}.</EmptyState> : (
        <DataTable
          columns={[
            { key: 'code', label: 'Code', mono: true }, { key: 'name', label: 'Name' },
            { key: 'status', label: 'Status' }, { key: 'state', label: 'State' },
            { key: 'contact', label: 'Contact' },
          ]}
          onRowClick={(_row, i) => nav(`/clients/${shown[i]!.id}`)}
          rows={shown.map((c) => ({
            code: c.code, name: c.name,
            status: <Badge tone={CLIENT_TONE[c.status]}>{c.status}</Badge>,
            state: c.stateCode,
            contact: c.contacts[0]?.email ?? c.contacts[0]?.phone ?? '—',
          }))}
        />
      )}
    </div>
  )
}