import { useState, useEffect } from 'react'
import StateSelector from './components/StateSelector.jsx'
import DistrictSearch from './components/DistrictSearch.jsx'
import LoadingAnimation from './components/LoadingAnimation.jsx'
import ChartPanel from './components/ChartPanel.jsx'
import Footer from './components/Footer.jsx'
import { fetchDistrictEstimates } from './hooks/useApi.js'

// Two-letter USPS state code. The deep-link value flows into API request URLs
// and into the Hugging Face parquet shard path duckdb-wasm reads, so it gets
// validated here at the boundary rather than propagated verbatim.
const STATE_CODE_PATTERN = /^[A-Z]{2}$/

/**
 * CRDC Arrests API Demo App — main router.
 * Flow: state → district search (with interesting suggestions) → loading animation → charts
 */
export default function App() {
  const [step, setStep] = useState('state')   // 'state' | 'search' | 'loading' | 'results'
  const [selectedState, setSelectedState] = useState(null)
  const [district, setDistrict] = useState(null)

  // On first load: check URL for ?leaid= and state to allow deep-linking
  useEffect(() => {
    const params = new URLSearchParams(window.location.search)
    const leaid = params.get('leaid')
    const rawState = params.get('state')
    const stateParam = rawState ? rawState.trim().toUpperCase() : null

    if (rawState && !STATE_CODE_PATTERN.test(stateParam)) {
      // Malformed deep link — drop it and start at the state selector rather
      // than passing an arbitrary string into fetch URLs and shard paths.
      console.warn('Ignoring deep link: `state` is not a two-letter state code.')
      return
    }

    if (leaid && stateParam) {
      // Deep link (including browser back/forward landing on this URL): resolve
      // the district name via a real estimates row, keyed by LEAID. The previous
      // version called searchDistricts(leaid, ...), a name/text search — passing
      // an LEAID as search text never matches, so it always fell back to "Unknown
      // District".
      setSelectedState(stateParam)

      fetchDistrictEstimates(leaid, { model: 'unified_m2_mod', year: '21-22' }).then(rows => {
        const row = rows?.[0]
        setDistrict(row
          ? { leaid: row.leaid, lea_name: row.lea_name, state: row.state }
          : { leaid, lea_name: 'Unknown District', state: stateParam })
        setStep('loading')
      }).catch(() => {
        // Fallback on error
        setDistrict({ leaid, lea_name: 'Unknown District', state: stateParam })
        setStep('loading')
      })
    }
  }, [])

  const handleStateChange = (stateCode) => {
    setSelectedState(stateCode)
    setStep('search')
  }

  const handleDistrictSelect = (dist) => {
    // Update URL for shareability
    const params = new URLSearchParams({ leaid: dist.leaid, state: selectedState })
    window.history.replaceState(null, '', `?${params}`)
    setDistrict(dist)
    setStep('loading')
  }

  return (
    <div className="cv-app">
      {/* Header */}
      <header className="cv-header cv-wrap">
        <a href="/crdc-demo" aria-label="Civilytics" style={{ display: 'block' }}>
          <img
            src={import.meta.env.BASE_URL + 'civilytics-wordmark.svg'}
            alt="Civilytics — social science for the public good"
            style={{ height: '2.5rem', width: 'auto' }}
          />
        </a>
      </header>

      {/* Main content */}
      <main style={{ maxWidth: '60rem', margin: '0 auto', padding: '0 var(--space-3)' }}>
        {step === 'state' && (
          <StateSelector onNext={handleStateChange} />
        )}

        {step === 'search' && selectedState && (
          <DistrictSearch
            state={selectedState}
            onSelect={handleDistrictSelect}
            onBack={() => setStep('state')}
          />
        )}

        {step === 'loading' && district && (
          <LoadingAnimation district={district} state={selectedState} />
        )}

        {/* ChartPanel listens for data-ready event from LoadingAnimation */}
        {step === 'results' && district && (
          <ChartPanel district={district} state={selectedState} />
        )}

        {(step === 'loading' || step === 'results') && (
          <button
            className="btn-outline"
            style={{ margin: 'var(--space-3) 0', display: 'block' }}
            onClick={() => { window.location.href = '/crdc-demo/' }}
          >
            ← Search another district
          </button>
        )}
      </main>

      <Footer />
    </div>
  )
}