import { useState } from 'react'
import { ArrowLeft, ArrowRight, Plus, ShieldCheck, UserX } from 'lucide-react'
import { Link, useParams } from 'react-router-dom'

import { ToolHeader } from '../../components/ToolHeader'
import { Modal, Panel } from '../../components/ui'
import { useCandidates } from '../../lib/queries'
import type { RApplication, RFunnelStage } from '../../lib/types'
import { recruitBrand } from './brand'
import { useDispositions, useMoveStage, usePipelineBoard, useSubmitCandidate } from './pipelineQueries'

const inputCls =
  'w-full rounded-lg border border-line/70 bg-navy-900 px-3 py-2 text-sm text-ink outline-none focus:border-recruit'

// The ladder, mirrored so the board can offer the next and previous rung. The server is the authority on
// whether a move is legal; this only decides what is offered.
const LADDER = ['sourced', 'screened', 'submitted', 'interviewing', 'offered', 'placed']

function stageColor(stage: string): string {
  if (stage === 'placed') return 'var(--color-ok)'
  if (stage === 'rejected' || stage === 'withdrawn') return 'var(--color-muted)'
  if (stage === 'offered') return 'var(--color-gold)'
  return 'var(--color-blue-soft)'
}

// The funnel bar. Width is the share of the widest rung, so the shape reads as a funnel; the label
// carries the actual count so the picture never has to be trusted on its own.
function FunnelBar({ stage, max }: { stage: RFunnelStage; max: number }) {
  const pct = max > 0 ? (stage.count / max) * 100 : 0
  return (
    <div className="flex items-center gap-3">
      <span className="w-24 shrink-0 text-[11px] font-semibold text-muted">{stage.label}</span>
      <div className="h-6 flex-1 overflow-hidden rounded-md bg-navy-950/60">
        <div
          className="flex h-full items-center justify-end rounded-md px-2 transition-all"
          style={{
            width: `${Math.max(pct, stage.count > 0 ? 6 : 0)}%`,
            background: `linear-gradient(90deg, color-mix(in srgb, ${stageColor(stage.stage)} 55%, transparent), ${stageColor(stage.stage)})`,
          }}
        >
          {stage.count > 0 && <span className="text-[10px] font-bold text-white">{stage.count}</span>}
        </div>
      </div>
      <span className="w-14 shrink-0 text-right text-[11px] text-faint">{stage.pct}%</span>
    </div>
  )
}

export function Pipeline() {
  const { reqId } = useParams()
  const q = usePipelineBoard(reqId ?? null)
  const disp = useDispositions()
  const submit = useSubmitCandidate(reqId ?? '')
  const move = useMoveStage(reqId ?? undefined)

  // The candidate list is reused rather than duplicated: submitting to a pipeline is choosing from the
  // bench the rest of the product already maintains. Through the shared hook, not a second inline query
  // on the same key, so any option added there (a select, a staleTime) actually reaches this screen.
  const candidates = useCandidates()

  const [addOpen, setAddOpen] = useState(false)
  const [candId, setCandId] = useState('')
  const [startStage, setStartStage] = useState('sourced')
  const [touch, setTouch] = useState('')

  const [disposing, setDisposing] = useState<{ app: RApplication; to: string } | null>(null)
  const [code, setCode] = useState('')
  const [reason, setReason] = useState('')

  if (q.isLoading) return <Panel className="grid place-items-center py-24 text-muted">Loading pipeline…</Panel>
  if (q.isError || !q.data) {
    return (
      <Panel className="grid place-items-center py-24 text-warn">
        Could not load this pipeline. {(q.error as Error)?.message}
      </Panel>
    )
  }
  const b = q.data
  const maxRung = b.funnel.length ? b.funnel[0].count : 0

  const doMove = (app: RApplication, to: string) => {
    if (to === 'rejected' || to === 'withdrawn') {
      setDisposing({ app, to })
      setCode('')
      setReason('')
      return
    }
    move.mutate({ id: app.id, expected_stage: app.stage, to_stage: to })
  }

  const confirmDisposition = () => {
    if (!disposing) return
    move.mutate(
      {
        id: disposing.app.id,
        expected_stage: disposing.app.stage,
        to_stage: disposing.to,
        disposition_code: code,
        reason,
      },
      { onSuccess: () => setDisposing(null) },
    )
  }

  const options = (disp.data?.dispositions ?? []).filter(
    (d) => !disposing || d.outcome === '' || d.outcome === disposing.to,
  )

  return (
    <div className="space-y-4">
      <ToolHeader name={recruitBrand.name} tagline="Pipeline" accent={recruitBrand.accent}>
        <Link
          to={`/recruit/requisitions/${reqId}`}
          className="flex items-center gap-2 rounded-lg border border-line/70 px-3 py-2 text-sm font-semibold text-muted hover:text-ink"
        >
          <ArrowLeft size={14} />
          Job order
        </Link>
        <button
          onClick={() => setAddOpen(true)}
          className="flex items-center gap-2 rounded-lg bg-gradient-to-r from-blue to-navy-700 px-4 py-2.5 text-sm font-bold text-white hover:brightness-110"
        >
          <Plus size={14} />
          Add candidate
        </button>
      </ToolHeader>

      <Panel>
        <div className="flex flex-wrap items-baseline justify-between gap-3">
          <h2 className="text-lg font-extrabold tracking-tight">{b.requisition_title}</h2>
          <p className="text-[11px] text-faint">
            {b.total} in pipeline · {b.active} active · {b.placed} of {b.openings} placed ·{' '}
            <strong style={{ color: b.seats_left === 0 ? 'var(--color-ok)' : 'var(--color-muted)' }}>
              {b.seats_left === 0 ? 'all seats filled' : `${b.seats_left} seat${b.seats_left === 1 ? '' : 's'} left`}
            </strong>
          </p>
        </div>
      </Panel>

      <div className="grid gap-4 lg:grid-cols-2">
        <Panel title="Funnel" hint="everyone who ever reached each stage">
          {/* Counted as high water marks, not current position. A candidate rejected at interview still
              counts as having reached interview, which is why this series can never widen. */}
          <div className="space-y-2">
            {b.funnel.map((s) => (
              <FunnelBar key={s.stage} stage={s} max={maxRung} />
            ))}
          </div>
          {b.total === 0 && (
            <p className="mt-3 text-center text-[11px] text-faint">
              No candidates yet. Add one to start the pipeline.
            </p>
          )}
        </Panel>

        <Panel title="Stage conversion" hint="share continuing to the next stage">
          {b.total === 0 ? (
            <p className="py-6 text-center text-[11px] text-faint">Conversion appears once candidates move.</p>
          ) : (
            <ul className="space-y-1.5">
              {b.conversion.map((c) => (
                <li key={`${c.from}-${c.to}`} className="flex items-center gap-2 text-[11px]">
                  <span className="w-40 shrink-0 text-muted">
                    {c.from_label} <ArrowRight size={9} className="inline" /> {c.to_label}
                  </span>
                  <div className="h-1.5 flex-1 overflow-hidden rounded-full bg-navy-950/60">
                    <div className="h-full rounded-full bg-recruit" style={{ width: `${c.rate}%` }} />
                  </div>
                  <span className="w-14 shrink-0 text-right font-semibold">{c.rate}%</span>
                </li>
              ))}
            </ul>
          )}
          {b.dispositions.length > 0 && (
            <div className="mt-4 border-t border-line/50 pt-3">
              <p className="mb-1.5 text-[10px] font-bold uppercase tracking-wider text-faint">
                Why candidates left
              </p>
              {/* Coded, not prose, because this is the grouping an adverse impact review needs. */}
              <ul className="space-y-1">
                {b.dispositions.map((d) => (
                  <li key={d.code} className="flex justify-between text-[11px]">
                    <span className="text-muted">
                      {disp.data?.dispositions.find((x) => x.code === d.code)?.label ?? d.code}
                    </span>
                    <span className="text-faint">
                      {d.count} · {d.pct}%
                    </span>
                  </li>
                ))}
              </ul>
            </div>
          )}
        </Panel>
      </div>

      <div className="grid gap-3 md:grid-cols-2 xl:grid-cols-4">
        {b.columns.map((col) => (
          <Panel key={col.stage} title={col.label} hint={String(col.count)}>
            {col.applications.length === 0 ? (
              <p className="py-4 text-center text-[11px] text-faint">Nobody here.</p>
            ) : (
              <ul className="space-y-2">
                {col.applications.map((a) => {
                  const i = LADDER.indexOf(a.stage)
                  const next = i >= 0 && i + 1 < LADDER.length ? LADDER[i + 1] : null
                  const prev = i > 0 ? LADDER[i - 1] : null
                  return (
                    <li key={a.id} className="rounded-lg border border-line/60 bg-navy-950/40 p-2.5">
                      <Link
                        to={`/recruit/applications/${a.id}`}
                        className="block truncate text-sm font-semibold hover:text-recruit"
                      >
                        {a.candidate_name}
                      </Link>
                      <p className="mt-0.5 flex flex-wrap items-center gap-x-2 text-[10px] text-faint">
                        {/* Clearance is a self reported indicator throughout this product, never a
                            verified status. The client FSO verifies through DISS at onboarding. */}
                        <span className="flex items-center gap-1" title="Self reported clearance indicator">
                          <ShieldCheck size={9} />
                          {a.clearance_level.replace(/_/g, ' ')}
                        </span>
                        <span>{a.days_in_stage.toFixed(1)}d here</span>
                        {a.furthest_stage !== a.stage && <span>reached {a.furthest_stage_label}</span>}
                      </p>
                      {a.disposition_code ? (
                        <p className="mt-1 text-[10px] text-muted">
                          {disp.data?.dispositions.find((x) => x.code === a.disposition_code)?.label ??
                            a.disposition_code}
                        </p>
                      ) : (
                        <div className="mt-1.5 flex flex-wrap gap-1">
                          {prev && (
                            <button
                              onClick={() => doMove(a, prev)}
                              disabled={move.isPending}
                              className="rounded border border-line/60 px-1.5 py-0.5 text-[10px] font-semibold text-faint hover:text-ink disabled:opacity-50"
                              title={`Back to ${prev}`}
                            >
                              <ArrowLeft size={9} />
                            </button>
                          )}
                          {next && (
                            <button
                              onClick={() => doMove(a, next)}
                              disabled={move.isPending}
                              className="rounded border border-recruit/50 px-1.5 py-0.5 text-[10px] font-semibold text-recruit hover:bg-recruit/10 disabled:opacity-50"
                            >
                              {next} <ArrowRight size={9} className="inline" />
                            </button>
                          )}
                          <button
                            onClick={() => doMove(a, 'rejected')}
                            disabled={move.isPending}
                            className="rounded border border-line/60 px-1.5 py-0.5 text-[10px] font-semibold text-faint hover:text-risk disabled:opacity-50"
                            title="Disposition"
                          >
                            <UserX size={9} />
                          </button>
                        </div>
                      )}
                    </li>
                  )
                })}
              </ul>
            )}
          </Panel>
        ))}
      </div>

      {move.isError && (
        <p className="rounded-lg border border-risk/40 bg-navy-950/40 p-3 text-xs text-risk">
          {(move.error as Error).message}
        </p>
      )}

      <Modal open={addOpen} onClose={() => setAddOpen(false)} title="Add a candidate to this pipeline">
        <div className="space-y-3">
          <label className="flex flex-col gap-1.5">
            <span className="text-[11px] font-bold uppercase tracking-wider text-muted">Candidate</span>
            <select value={candId} onChange={(e) => setCandId(e.target.value)} className={inputCls}>
              <option value="">Choose a candidate</option>
              {(candidates.data ?? []).map((c) => (
                <option key={c.id} value={c.id}>
                  {c.full_name}
                </option>
              ))}
            </select>
          </label>
          <label className="flex flex-col gap-1.5">
            <span className="text-[11px] font-bold uppercase tracking-wider text-muted">Start at</span>
            {/* A known candidate is often submitted straight to the client rather than walked up from
                sourced, so the starting rung is a choice. It cannot start at an outcome. */}
            <select value={startStage} onChange={(e) => setStartStage(e.target.value)} className={inputCls}>
              {LADDER.map((s) => (
                <option key={s} value={s}>
                  {s}
                </option>
              ))}
            </select>
          </label>
          <label className="flex flex-col gap-1.5">
            <span className="text-[11px] font-bold uppercase tracking-wider text-muted">Source</span>
            <input
              value={touch}
              onChange={(e) => setTouch(e.target.value)}
              placeholder="referral, job board, bench"
              className={inputCls}
            />
          </label>
          {submit.isError && <p className="text-xs text-risk">{(submit.error as Error).message}</p>}
          <div className="flex justify-end gap-2 pt-1">
            <button
              onClick={() => setAddOpen(false)}
              className="rounded-lg border border-line/70 px-3 py-2 text-sm font-semibold text-muted hover:text-ink"
            >
              Cancel
            </button>
            <button
              onClick={() =>
                submit.mutate(
                  { candidate_id: candId, stage: startStage, source_touch: touch },
                  {
                    onSuccess: () => {
                      setCandId('')
                      setTouch('')
                      setStartStage('sourced')
                      setAddOpen(false)
                    },
                  },
                )
              }
              disabled={!candId || submit.isPending}
              className="rounded-lg bg-gradient-to-r from-blue to-navy-700 px-4 py-2 text-sm font-bold text-white hover:brightness-110 disabled:opacity-50"
            >
              Add
            </button>
          </div>
        </div>
      </Modal>

      <Modal open={!!disposing} onClose={() => setDisposing(null)} title="Why is this candidate leaving?">
        <div className="space-y-3">
          <p className="text-sm text-muted">
            {disposing?.app.candidate_name} will be marked{' '}
            <strong>{disposing?.to === 'withdrawn' ? 'withdrawn' : 'rejected'}</strong>.
          </p>
          <div className="flex gap-2">
            {(['rejected', 'withdrawn'] as const).map((t) => (
              <button
                key={t}
                onClick={() => {
                  setDisposing(disposing ? { ...disposing, to: t } : null)
                  setCode('')
                }}
                className={`rounded-full px-3 py-1 text-xs font-semibold ${
                  disposing?.to === t
                    ? 'bg-recruit/25 text-recruit shadow-[inset_0_0_0_1px_var(--color-recruit)]'
                    : 'border border-line/60 bg-navy-900 text-faint hover:text-muted'
                }`}
              >
                {t === 'rejected' ? 'We passed' : 'They withdrew'}
              </button>
            ))}
          </div>
          <label className="flex flex-col gap-1.5">
            <span className="text-[11px] font-bold uppercase tracking-wider text-muted">Reason</span>
            {/* A closed vocabulary, served by the API. It is what makes an adverse impact report
                computable, and free text here would make it impossible. */}
            <select value={code} onChange={(e) => setCode(e.target.value)} className={inputCls}>
              <option value="">Choose a reason</option>
              {options.map((d) => (
                <option key={d.code} value={d.code}>
                  {d.label}
                </option>
              ))}
            </select>
          </label>
          <label className="flex flex-col gap-1.5">
            <span className="text-[11px] font-bold uppercase tracking-wider text-muted">Note (optional)</span>
            <textarea value={reason} onChange={(e) => setReason(e.target.value)} rows={2} className={inputCls} />
          </label>
          <p className="text-[10px] text-faint">
            The reason is recorded in a fixed vocabulary so selection rates can be reported by reason. It
            never records anything about the candidate as a person.
          </p>
          {move.isError && <p className="text-xs text-risk">{(move.error as Error).message}</p>}
          <div className="flex justify-end gap-2 pt-1">
            <button
              onClick={() => setDisposing(null)}
              className="rounded-lg border border-line/70 px-3 py-2 text-sm font-semibold text-muted hover:text-ink"
            >
              Cancel
            </button>
            <button
              onClick={confirmDisposition}
              disabled={!code || move.isPending}
              className="rounded-lg bg-gradient-to-r from-blue to-navy-700 px-4 py-2 text-sm font-bold text-white hover:brightness-110 disabled:opacity-50"
            >
              Confirm
            </button>
          </div>
        </div>
      </Modal>
    </div>
  )
}