import React, { useState, useEffect, useRef } from 'react'
import { useNavigate } from '@tanstack/react-router'
import { useProjects } from '../features/projects/useProjects'
import { useSessions } from '../features/home/useSessions'
import { useSavedSearches } from '../features/settings/useSavedSearches'

interface PaletteProps {
  open: boolean
  onClose: () => void
}

interface JumpItem {
  kind: 'jump'
  label: string
  hint: string
  path: string
}

interface ProjectItem {
  kind: 'project'
  label: string
  hint?: string
  cwd: string
}

interface SessionItem {
  kind: 'session'
  label: string
  hint?: string
  tool: string
  host: string
  sessionId: string
}

interface SavedItem {
  kind: 'saved'
  label: string
  hint?: string
  query: string
}

type PaletteItem = JumpItem | ProjectItem | SessionItem | SavedItem

const JUMP_ITEMS: JumpItem[] = [
  { kind: 'jump', label: 'Recent',   hint: 'g h', path: '/' },
  { kind: 'jump', label: 'Projects', hint: 'g p', path: '/projects' },
  { kind: 'jump', label: 'Stats',    hint: 'g s', path: '/stats' },
  { kind: 'jump', label: 'Health',   hint: 'g i', path: '/health' },
  { kind: 'jump', label: 'Settings', hint: '',    path: '/settings' },
]

export function Palette({ open, onClose }: PaletteProps): React.JSX.Element {
  const navigate = useNavigate()
  const [query, setQuery] = useState('')
  const [cursor, setCursor] = useState(0)
  const inputRef = useRef<HTMLInputElement>(null)

  // Autofocus when palette opens; reset state when it closes
  useEffect(() => {
    if (open) {
      setQuery('')
      setCursor(0)
      // Small defer so the element is visible before focus
      requestAnimationFrame(() => {
        inputRef.current?.focus()
      })
    }
  }, [open])

  // Reset cursor when query changes
  useEffect(() => {
    setCursor(0)
  }, [query])

  // Always call hooks unconditionally (React rules); enabled+staleTime gate
  // network activity so closed-palette renders don't trigger refetches.
  const { data: projects } = useProjects({ since: 'all' }, { enabled: open, staleTime: 30_000 })
  const { data: sessions } = useSessions({}, { enabled: open, staleTime: 30_000 })
  const { data: savedSearches } = useSavedSearches({ enabled: open, staleTime: 30_000 })

  if (!open) return <></>

  const q = query.trim()

  const filteredJumps: JumpItem[] = q === ''
    ? JUMP_ITEMS
    : JUMP_ITEMS.filter(item =>
        item.label.toLowerCase().includes(q.toLowerCase()),
      )

  const filteredProjects: ProjectItem[] = (projects ?? [])
    .map(p => ({ kind: 'project' as const, label: p.cwd, cwd: p.cwd }))
    .filter(item => q === '' || item.label.toLowerCase().includes(q.toLowerCase()))

  const filteredSessions: SessionItem[] = (sessions ?? [])
    .slice(0, 50)
    .map(s => ({
      kind: 'session' as const,
      label: `${s.tool} · ${s.host} · ${s.summary || s.sessionId}`,
      tool: s.tool,
      host: s.host,
      sessionId: s.sessionId,
    }))
    .filter(item => q === '' || item.label.toLowerCase().includes(q.toLowerCase()))

  const filteredSaved: SavedItem[] = (savedSearches ?? [])
    .map(ss => ({ kind: 'saved' as const, label: ss.name, hint: ss.query, query: ss.query }))
    .filter(item => q === '' || item.label.toLowerCase().includes(q.toLowerCase()))

  const filtered: PaletteItem[] = [
    ...filteredJumps,
    ...filteredProjects,
    ...filteredSessions,
    ...filteredSaved,
  ]

  const showSearch = q !== '' && filtered.length === 0
  const total = filtered.length + (showSearch ? 1 : 0)

  function fire(idx: number): void {
    if (showSearch && idx === 0) {
      void navigate({ to: '/search', search: { q: query } })
      onClose()
      return
    }
    const item = filtered[showSearch ? idx - 1 : idx]
    if (item) {
      switch (item.kind) {
        case 'jump':
          void navigate({ to: item.path })
          break
        case 'project':
          void navigate({ to: '/project/$', params: { _splat: item.cwd } })
          break
        case 'session':
          void navigate({
            to: '/session/$tool/$host/$id',
            params: { tool: item.tool, host: item.host, id: item.sessionId },
          })
          break
        case 'saved':
          void navigate({ to: '/search', search: { q: item.query } })
          break
      }
      onClose()
    }
  }

  function onKeyDown(e: React.KeyboardEvent<HTMLInputElement>): void {
    if (e.key === 'Escape') {
      e.preventDefault()
      onClose()
    } else if (e.key === 'ArrowDown') {
      e.preventDefault()
      setCursor(c => Math.min(total - 1, c + 1))
    } else if (e.key === 'ArrowUp') {
      e.preventDefault()
      setCursor(c => Math.max(0, c - 1))
    } else if (e.key === 'Enter') {
      e.preventDefault()
      fire(cursor)
    }
  }

  // Build grouped render list with section headers
  interface Group {
    key: string
    head: string
    items: PaletteItem[]
    startIdx: number
  }

  const offset = showSearch ? 1 : 0
  const groups: Group[] = [
    { key: 'jump',     head: 'jump',     items: filteredJumps,    startIdx: offset },
    { key: 'projects', head: 'projects', items: filteredProjects,  startIdx: offset + filteredJumps.length },
    { key: 'sessions', head: 'sessions', items: filteredSessions,  startIdx: offset + filteredJumps.length + filteredProjects.length },
    { key: 'saved',    head: 'saved',    items: filteredSaved,     startIdx: offset + filteredJumps.length + filteredProjects.length + filteredSessions.length },
  ]

  return (
    <div className="scrim" onClick={onClose}>
      <div className="palette" onClick={e => e.stopPropagation()}>
        {/* Input row */}
        <div className="palette-input-row">
          <span className="palette-hint-badge mono muted">⌘K</span>
          <input
            ref={inputRef}
            className="palette-input"
            value={query}
            onChange={e => setQuery(e.target.value)}
            onKeyDown={onKeyDown}
            placeholder="search turns, jump to a page, pick a session…"
          />
        </div>

        {/* Item list */}
        <div className="palette-list">
          {showSearch && (
            <div
              className={'palette-row' + (cursor === 0 ? ' cursor' : '')}
              onClick={() => fire(0)}
            >
              <span className="kind accent-c">search</span>
              <span className="label">"{query}"</span>
              <span className="row-hint mono muted">↵</span>
            </div>
          )}
          {groups.map(group => {
            if (group.items.length === 0) return null
            return (
              <React.Fragment key={group.key}>
                <div className="palette-group-head muted mono">{group.head}</div>
                {group.items.map((item, i) => {
                  const idx = group.startIdx + i
                  return (
                    <div
                      key={`${item.kind}:${item.label}:${i}`}
                      className={'palette-row' + (idx === cursor ? ' cursor' : '')}
                      onClick={() => fire(idx)}
                    >
                      <span className="kind">{item.kind}</span>
                      <span className="label">{item.label}</span>
                      {item.hint !== undefined && item.hint !== '' && (
                        <span className="row-hint mono muted">{item.hint}</span>
                      )}
                    </div>
                  )
                })}
              </React.Fragment>
            )
          })}
          {filtered.length === 0 && !showSearch && (
            <div className="palette-empty muted">no matches</div>
          )}
        </div>

        {/* Footer */}
        <div className="palette-hint">
          <span>↑↓ navigate</span>
          <span>↵ open</span>
          <span>esc close</span>
          <span className="spacer" />
          <span>g h · g p · g s · g i</span>
        </div>
      </div>
    </div>
  )
}
