import { useState, useEffect, useCallback } from 'react'
import Sidebar from './components/Sidebar.jsx'
import StatusBar from './components/StatusBar.jsx'
import Setup from './views/Setup.jsx'
import Baseline from './views/Baseline.jsx'
import Forecast from './views/Forecast.jsx'

export default function App() {
  const [view, setView] = useState(() => localStorage.getItem('pf_view') || 'forecast')
  const [sidebarExpanded, setSidebarExpanded] = useState(() => localStorage.getItem('pf_sidebar') !== 'collapsed')

  const [sources,   setSources]   = useState([])
  const [sourcesLoaded, setSourcesLoaded] = useState(false)
  const [sourceId,  setSourceId]  = useState(() => localStorage.getItem('pf_sourceId')  || '')
  const [versions,  setVersions]  = useState([])
  const [versionsLoaded, setVersionsLoaded] = useState(false)
  const [versionId, setVersionId] = useState(() => localStorage.getItem('pf_versionId') || '')

  useEffect(() => { localStorage.setItem('pf_view', view) }, [view])
  useEffect(() => { localStorage.setItem('pf_sidebar', sidebarExpanded ? 'expanded' : 'collapsed') }, [sidebarExpanded])
  useEffect(() => { localStorage.setItem('pf_sourceId',  sourceId  || '') }, [sourceId])
  useEffect(() => { localStorage.setItem('pf_versionId', versionId || '') }, [versionId])

  const refreshSources = useCallback(async () => {
    const data = await fetch('/api/sources').then(r => r.json())
    const list = Array.isArray(data) ? data : []
    setSources(list)
    setSourcesLoaded(true)
    return list
  }, [])

  const refreshVersions = useCallback(async (sid) => {
    const id = sid ?? sourceId
    if (!id) { setVersions([]); setVersionsLoaded(true); return [] }
    const data = await fetch(`/api/sources/${id}/versions`).then(r => r.json())
    const list = Array.isArray(data) ? data : []
    setVersions(list)
    setVersionsLoaded(true)
    return list
  }, [sourceId])

  useEffect(() => { refreshSources() }, [])

  // The selection is restored from localStorage and survives a deregister, so it
  // has to be re-checked against the list itself rather than only at mount:
  // deleting the selected source otherwise leaves a dead id behind and every
  // call 404s "Source not found" until the page is reloaded.
  useEffect(() => {
    if (!sourcesLoaded) return
    if (sources.length === 0) { setSourceId(''); return }
    if (!sourceId || !sources.some(s => String(s.id) === String(sourceId))) {
      setSourceId(String(sources[0].id))
    }
  }, [sources, sourcesLoaded, sourceId])

  useEffect(() => {
    if (!sourceId) { setVersions([]); setVersionId(''); setVersionsLoaded(true); return }
    // The list belongs to the previous source until the fetch lands.
    setVersionsLoaded(false)
    refreshVersions(sourceId)
  }, [sourceId])

  // Same reasoning as sources: a deleted version must not stay selected.
  //
  // versionsLoaded matters more than it looks: without it, the empty initial
  // state reads as "this source has no versions", so a versionId restored from
  // localStorage is cleared and then set straight back when the fetch lands.
  // Forecast's load effect is keyed on that id, so the round trip made every
  // page load fetch and aggregate the whole version twice.
  useEffect(() => {
    if (!sourceId || !versionsLoaded) return
    if (versions.length === 0) { setVersionId(''); return }
    if (!versionId || !versions.some(v => String(v.id) === String(versionId))) {
      setVersionId(String(versions[0].id))
    }
  }, [versions, versionsLoaded, sourceId, versionId])

  const ctx = {
    sources, sourceId, setSourceId,
    versions, versionId, setVersionId,
    refreshSources, refreshVersions, setVersions,
  }

  return (
    <div className="flex h-screen w-full text-sm overflow-hidden">
      <Sidebar view={view} setView={setView} expanded={sidebarExpanded} setExpanded={setSidebarExpanded} />
      <div className="flex flex-col flex-1 overflow-hidden min-w-0">
        <StatusBar view={view} {...ctx} />
        <div className="flex-1 overflow-hidden">
          {view === 'setup'    && <Setup    {...ctx} />}
          {view === 'baseline' && <Baseline {...ctx} />}
          {view === 'forecast' && <Forecast {...ctx} />}
        </div>
      </div>
    </div>
  )
}