import { useState, useEffect } from 'react'
import { searchDistricts } from '../hooks/useApi.js'

const TOP_DISTRICTS_URL = `${import.meta.env.BASE_URL}data/top_districts.json`
const SUGGESTION_COUNT = 8

// Module-level cache: the fixture covers every state, so it is fetched at most
// once per page load no matter how many states the visitor browses through.
let topDistrictsPromise = null

function loadTopDistricts() {
  if (!topDistrictsPromise) {
    topDistrictsPromise = fetch(TOP_DISTRICTS_URL)
      .then((res) => {
        if (!res.ok) throw new Error(`HTTP ${res.status} loading ${TOP_DISTRICTS_URL}`)
        return res.json()
      })
      .catch((err) => {
        // Don't poison the cache with a rejected promise — let a later visit retry.
        topDistrictsPromise = null
        throw err
      })
  }
  return topDistrictsPromise
}

/**
 * District search screen with:
 * 1. "Interesting" suggestions — the districts with the most arrests in the
 *    selected state, read from the committed `public/data/top_districts.json`
 *    fixture (built by `scripts/build-top-districts.mjs`).
 * 2. Live-search as you type → /api/v1/districts?q=...&state=XX
 *
 * The suggestions used to be computed at runtime from
 * `/estimates?state=XX&year=21-22&limit=500`. That endpoint returns rows
 * `ORDER BY LEAID, RACE, SEX` at eight rows per district, so the cap selected
 * the ~62 lowest-LEAID districts in the state rather than the busiest ones —
 * California has 11,488 rows. The fixture is ranked over the complete result
 * set, and it also removes a multi-second fetch from this screen.
 */
export default function DistrictSearch({ state, onSelect, onBack }) {
  const [query, setQuery] = useState('')
  const [searchResults, setSearchResults] = useState([])
  const [suggestions, setSuggestions] = useState([])   // "interesting" districts sorted by arrests desc
  const [loadingSugg, setLoadingSugg] = useState(true)
  const [loadingSearch, setLoadingSearch] = useState(false)

  // ——— Read the suggestion fixture for this state ———
  useEffect(() => {
    let cancelled = false
    setLoadingSugg(true)

    loadTopDistricts()
      .then((fixture) => {
        if (cancelled) return
        const forState = fixture?.states?.[state] || []
        setSuggestions(
          forState.slice(0, SUGGESTION_COUNT).map((d) => ({
            leaid: d.leaid,
            lea_name: d.name,
            state,
            observed_arrests: d.arrests,
          })),
        )
      })
      .catch((err) => {
        console.error('Failed to load suggested districts:', err)
        if (!cancelled) setSuggestions([])  // degrade gracefully — just show search box
      })
      .finally(() => {
        if (!cancelled) setLoadingSugg(false)
      })

    return () => { cancelled = true }
  }, [state])

  // ——— Live search as user types (debounced by React's natural event batching) ———
  useEffect(() => {
    if (!query.trim()) { setSearchResults([]); return }

    const timer = setTimeout(async () => {
      setLoadingSearch(true)
      try {
        const data = await searchDistricts(query, state)
        setSearchResults(data || [])
      } catch (err) {
        console.error('District search failed:', err)
        setSearchResults([])
      } finally {
        setLoadingSearch(false)
      }
    }, 300)

    return () => clearTimeout(timer)
  }, [query, state])

  // ——— Render a district card (used for both suggestions and search results) ———
  const renderDistrictCard = (dist) => (
    <button
      key={dist.leaid}
      className="cv-card"
      style={{ textAlign: 'left', padding: 'var(--space-2)' }}
      onClick={() => onSelect(dist)}
    >
      <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'baseline' }}>
        <span style={{ fontWeight: 600, color: 'var(--cv-navy-700)', fontSize: '0.95rem' }}>
          {dist.lea_name || dist.name}
        </span>
        {dist.observed_arrests !== undefined && (
          <span className="stat-label accent" style={{ marginTop: 0 }}>
            {dist.observed_arrests.toLocaleString()} arrests in 2021–22
          </span>
        )}
      </div>
    </button>
  )

  return (
    <div style={{ padding: 'var(--space-5) 0 var(--space-7)' }}>
      {/* Back button */}
      <button className="btn-outline" onClick={onBack} style={{ marginBottom: 'var(--space-3)' }}>
        ← Change state
      </button>

      <h2 style={{ marginTop: 0, marginBottom: 'var(--space-1)' }}>
        {state === 'DC' ? "District of Columbia" : `Find a district in ${getStateName(state)}`}
      </h2>
      <p style={{ color: 'var(--cv-ink-2)', marginBottom: 'var(--space-3)' }}>
        Search by district name, or try one of the suggested districts with the highest arrest counts.
      </p>

      {/* "Interesting" suggestions */}
      {!query && (
        <div style={{ marginTop: 'var(--space-4)' }}>
          <span className="eyebrow">Suggested districts — most arrests in 2021–22</span>
          {loadingSugg ? (
            <p style={{ color: 'var(--cv-ink-3)', padding: 'var(--space-2) 0' }}>Loading suggestions…</p>
          ) : suggestions.length > 0 ? (
            <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fill, minmax(280px, 1fr))', gap: 'var(--space-1)' }}>
              {suggestions.map(renderDistrictCard)}
            </div>
          ) : (
            <p style={{ color: 'var(--cv-ink-3)', padding: 'var(--space-2) 0' }}>
              No districts with reported arrests found in this state. Try searching by name below.
            </p>
          )}
        </div>
      )}

      {/* Live search */}
      <div style={{ marginTop: query ? 0 : 'var(--space-5)' }}>
        <label htmlFor="district-search" className="stat-label">Search district name:</label>
        <input
          id="district-search"
          type="text"
          placeholder="Type a district name… (e.g., Madison, Derby, Paterson)"
          value={query}
          onChange={(e) => setQuery(e.target.value)}
          style={{
            width: '100%', padding: 'var(--space-2)', fontSize: '1rem',
            border: '1px solid var(--cv-rule)', borderRadius: 'var(--radius-md)',
            fontFamily: 'var(--font-sans)'
          }}
        />

        {query && (
          <div style={{ marginTop: 'var(--space-2)' }}>
            {loadingSearch ? (
              <p style={{ color: 'var(--cv-ink-3)' }}>Searching…</p>
            ) : searchResults.length > 0 ? (
              <div style={{ display: 'grid', gap: 'var(--space-1)' }}>
                {searchResults.slice(0, 20).map(renderDistrictCard)}
              </div>
            ) : (
              <p style={{ color: 'var(--cv-ink-3)' }}>No districts found matching "{query}".</p>
            )}

            {/* Back to suggestions */}
            {searchResults.length > 0 && (
              <button className="btn-outline" onClick={() => setQuery('')} style={{ marginTop: 'var(--space-2)' }}>
                ← Show suggested districts again
              </button>
            )}
          </div>
        )}
      </div>
    </div>
  )
}

function getStateName(code) {
  const names = {
    AL:'Alabama',AK:'Alaska',AZ:'Arizona',AR:'Arkansas',CA:'California',CO:'Colorado',CT:'Connecticut',DE:'Delaware',DC:'District of Columbia',FL:'Florida',GA:'Georgia',HI:'Hawaii',ID:'Idaho',IL:'Illinois',IN:'Indiana',IA:'Iowa',KS:'Kansas',KY:'Kentucky',LA:'Louisiana',ME:'Maine',MD:'Maryland',MA:'Massachusetts',MI:'Michigan',MN:'Minnesota',MS:'Mississippi',MO:'Missouri',MT:'Montana',NE:'Nebraska',NV:'Nevada',NH:'New Hampshire',NJ:'New Jersey',NM:'New Mexico',NY:'New York',NC:'North Carolina',ND:'North Dakota',OH:'Ohio',OK:'Oklahoma',OR:'Oregon',PA:'Pennsylvania',RI:'Rhode Island',SC:'South Carolina',SD:'South Dakota',TN:'Tennessee',TX:'Texas',UT:'Utah',VT:'Vermont',VA:'Virginia',WA:'Washington',WV:'West Virginia',WI:'Wisconsin',WY:'Wyoming'
  }
  return names[code] || code
}