import { useState, Fragment } from 'react'
import { Link } from 'react-router-dom'
import { useQuery, useQueryClient } from '@tanstack/react-query'
import api from '../../utils/api'
import { formatDuration, formatDistance } from '../../utils/format'

const MEDALS = { 1: '🥇', 2: '🥈', 3: '🥉' }

// Compact +M:SS gap label (fastest effort shows nothing) — mirrors RouteLeaderboard.
function gapLabel(gapS) {
  if (gapS == null || gapS <= 0.5) return null
  return `+${formatDuration(gapS)}`
}

// Top-10 leaderboard for a single segment, styled to match RouteLeaderboard.
function Leaderboard({ segmentId, activityId }) {
  const { data } = useQuery({
    queryKey: ['segment', segmentId],
    queryFn: () => api.get(`/segments/${segmentId}`).then(r => r.data),
  })
  if (!data) return <p className="text-xs text-gray-600 py-2">Loading…</p>
  if (!data.leaderboard?.length) return <p className="text-xs text-gray-600 py-2">No efforts yet — still matching.</p>

  const top = data.leaderboard.slice(0, 10)
  const fastest = top[0].duration_s
  return (
    <table className="w-full text-sm mt-1 mb-2">
      <thead>
        <tr className="text-xs text-gray-500 border-b border-gray-800">
          <th className="text-left pb-2 font-medium">#</th>
          <th className="text-left pb-2 font-medium">Activity</th>
          <th className="text-right pb-2 font-medium">Time</th>
          <th className="text-right pb-2 font-medium">Δ</th>
        </tr>
      </thead>
      <tbody>
        {top.map((e) => {
          const isCurrent = e.activity_id === activityId
          const gap = gapLabel(e.duration_s - fastest)
          return (
            <tr
              key={e.activity_id}
              className={`border-b border-gray-800/50 transition-colors ${
                isCurrent ? 'bg-emerald-500/15 hover:bg-emerald-500/20' : 'hover:bg-gray-800/30'
              }`}
            >
              <td className={`py-2 ${e.rank === 1 ? 'text-yellow-400' : 'text-gray-400'}`}>
                {e.rank === 1 ? '🏆' : e.rank}
              </td>
              <td className="py-2">
                <Link
                  to={`/activities/${e.activity_id}`}
                  className={`hover:underline ${isCurrent ? 'text-emerald-300 font-medium' : 'text-gray-300'}`}
                >
                  {e.activity_name}
                </Link>
              </td>
              <td className={`py-2 text-right font-mono ${isCurrent ? 'text-emerald-300 font-semibold' : 'text-gray-200'}`}>
                {formatDuration(e.duration_s)}
              </td>
              <td className="py-2 text-right font-mono text-gray-500">
                {gap == null ? '--' : gap}
              </td>
            </tr>
          )
        })}
      </tbody>
    </table>
  )
}

export default function SegmentsPanel({ segments, activityId }) {
  const qc = useQueryClient()
  const [open, setOpen] = useState(null)

  const remove = async (id) => {
    if (!confirm('Delete this segment?')) return
    await api.delete(`/segments/${id}`)
    qc.invalidateQueries()
  }

  return (
    <div className="overflow-x-auto">
      <table className="w-full text-sm">
        <thead>
          <tr className="text-xs text-gray-500 border-b border-gray-800">
            <th className="text-left pb-2 font-medium">Segment</th>
            <th className="text-right pb-2 font-medium">This run</th>
            <th className="text-right pb-2 font-medium">Best</th>
            <th className="text-right pb-2 font-medium">Place</th>
            <th className="pb-2" />
          </tr>
        </thead>
        <tbody>
          {segments.map(seg => {
            const isPodium = seg.rank && seg.rank <= 3
            const delta = seg.best_s != null ? seg.duration_s - seg.best_s : null
            const isOpen = open === seg.segment_id
            return (
              <Fragment key={seg.segment_id}>
                <tr
                  className="border-b border-gray-800/50 transition-colors hover:bg-gray-800/30"
                >
                  <td className="py-2">
                    <button
                      onClick={() => setOpen(isOpen ? null : seg.segment_id)}
                      className="text-left text-gray-300 hover:text-white"
                    >
                      <span className="text-gray-500 mr-1">{isOpen ? '▾' : '▸'}</span>
                      {seg.name}
                      <span className="text-gray-600 ml-2 text-xs">{formatDistance(seg.distance_m)}</span>
                    </button>
                  </td>
                  <td className={`py-2 text-right font-mono ${isPodium ? 'text-yellow-400 font-semibold' : 'text-gray-200'}`}>
                    {formatDuration(seg.duration_s)}
                  </td>
                  <td className="py-2 text-right font-mono text-gray-500">
                    {seg.best_s != null ? formatDuration(seg.best_s) : '--'}
                  </td>
                  <td className="py-2 text-right font-mono">
                    {isPodium
                      ? <span title="Podium time on this activity" className="text-yellow-400">{MEDALS[seg.rank]}</span>
                      : delta != null
                        ? <span className="text-gray-500">+{formatDuration(delta)}</span>
                        : <span className="text-gray-700">--</span>}
                  </td>
                  <td className="py-2 text-right">
                    <button onClick={() => remove(seg.segment_id)} className="text-gray-700 hover:text-red-400 text-xs" title="Delete segment">✕</button>
                  </td>
                </tr>
                {isOpen && (
                  <tr>
                    <td colSpan={5} className="bg-gray-950/40">
                      <Leaderboard segmentId={seg.segment_id} activityId={activityId} />
                    </td>
                  </tr>
                )}
              </Fragment>
            )
          })}
        </tbody>
      </table>
    </div>
  )
}