'use client'

import { useEffect, useMemo, useState, useTransition } from 'react'
import Link from 'next/link'
import { usePathname, useRouter } from 'next/navigation'
import { Pin, PinOff, Archive, Search, X, PanelLeftOpen, PanelLeftClose } from 'lucide-react'
import { cn } from '@/lib/utils'
import { useAgentSheet } from './AgentSheetProvider'
import AgentAvatar from './AgentAvatar'

interface ConversationRow {
  id: string
  intent_id: string
  context_ref: string | null
  title: string | null
  pinned: boolean
  archived: boolean
  last_message_at: string | null
  last_message_preview: string | null
  created_at: string
}

interface Props {
  initialConversations: ConversationRow[]
}

// Time buckets for date grouping. Computed once per render against now().
// Mirrors the Idag / Igår / Denna vecka / Äldre pattern users know from
// Mail and iMessage.
type DateBucket = 'pinned' | 'today' | 'yesterday' | 'thisWeek' | 'older'

const BUCKET_LABELS: Record<DateBucket, string> = {
  pinned: 'Fästade',
  today: 'Idag',
  yesterday: 'Igår',
  thisWeek: 'Denna vecka',
  older: 'Äldre',
}

function bucketFor(c: ConversationRow): DateBucket {
  if (c.pinned) return 'pinned'
  const when = c.last_message_at ?? c.created_at
  if (!when) return 'older'
  const t = new Date(when)
  const now = new Date()
  const todayStart = new Date(now.getFullYear(), now.getMonth(), now.getDate())
  const yesterdayStart = new Date(todayStart.getTime() - 24 * 60 * 60 * 1000)
  const weekStart = new Date(todayStart.getTime() - 6 * 24 * 60 * 60 * 1000)
  if (t >= todayStart) return 'today'
  if (t >= yesterdayStart) return 'yesterday'
  if (t >= weekStart) return 'thisWeek'
  return 'older'
}

// Compact relative-time label shown to the right of each row. Locale-tuned
// to feel native in Swedish without going full date-fns.
function relativeTime(iso: string | null | undefined): string {
  if (!iso) return ''
  const t = new Date(iso).getTime()
  const now = Date.now()
  const diffMin = Math.round((now - t) / 60000)
  if (diffMin < 1) return 'nu'
  if (diffMin < 60) return `${diffMin} min`
  const diffHr = Math.round(diffMin / 60)
  if (diffHr < 24) return `${diffHr} h`
  const diffDay = Math.round(diffHr / 24)
  if (diffDay < 7) return `${diffDay} d`
  return new Date(iso).toLocaleDateString('sv-SE', { month: 'short', day: 'numeric' })
}

export default function ChatSidebar({ initialConversations }: Props) {
  const router = useRouter()
  const pathname = usePathname()
  const { openAgentSheet, identity } = useAgentSheet()
  const agentName = identity.displayName?.trim() || null
  const [conversations, setConversations] = useState<ConversationRow[]>(initialConversations)
  const [query, setQuery] = useState('')
  const [, startTransition] = useTransition()
  // Collapsed by default; persisted across reloads so power users keep
  // their preference. Hidden behind a thin rail when collapsed so the
  // conversation pane runs nearly edge-to-edge.
  const [collapsed, setCollapsed] = useState(true)
  useEffect(() => {
    const stored = localStorage.getItem('Accounted:chat-sidebar-collapsed')
    if (stored === 'false') setCollapsed(false)
  }, [])
  const toggleCollapsed = () => {
    setCollapsed(c => {
      const next = !c
      try { localStorage.setItem('Accounted:chat-sidebar-collapsed', next ? 'true' : 'false') } catch {}
      return next
    })
  }

  const activeId = pathname?.startsWith('/chat/') ? pathname.split('/')[2] : null
  const isConversationOpen = !!activeId

  const filtered = useMemo(() => {
    const q = query.trim().toLowerCase()
    if (!q) return conversations
    return conversations.filter((c) => {
      return (
        (c.title ?? '').toLowerCase().includes(q) ||
        (c.last_message_preview ?? '').toLowerCase().includes(q) ||
        (c.context_ref ?? '').toLowerCase().includes(q) ||
        c.intent_id.toLowerCase().includes(q)
      )
    })
  }, [conversations, query])

  // Group filtered into ordered buckets, preserving the sort order already
  // applied server-side (pinned first, then last_message_at desc).
  const grouped = useMemo(() => {
    const buckets: Record<DateBucket, ConversationRow[]> = {
      pinned: [],
      today: [],
      yesterday: [],
      thisWeek: [],
      older: [],
    }
    for (const c of filtered) buckets[bucketFor(c)].push(c)
    const order: DateBucket[] = ['pinned', 'today', 'yesterday', 'thisWeek', 'older']
    return order
      .map((b) => ({ bucket: b, rows: buckets[b] }))
      .filter((g) => g.rows.length > 0)
  }, [filtered])

  async function togglePin(id: string, current: boolean) {
    setConversations((prev) =>
      prev.map((c) => (c.id === id ? { ...c, pinned: !current } : c)),
    )
    await fetch(`/api/agent/conversations/${id}`, {
      method: 'PATCH',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ pinned: !current }),
    })
  }

  async function archive(id: string) {
    setConversations((prev) => prev.filter((c) => c.id !== id))
    await fetch(`/api/agent/conversations/${id}`, {
      method: 'PATCH',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ archived: true }),
    })
    if (activeId === id) startTransition(() => router.push('/chat'))
  }

  // Collapsed rail (desktop only). Mobile keeps the existing behavior where
  // the sidebar IS the page when no conversation is open, so the rail is
  // hidden below md. On desktop the rail keeps a thin column with toggle
  // + new-chat buttons so the conversation pane runs near-edge-to-edge.
  const railAside = collapsed ? (
    <aside
      className="hidden md:flex md:w-12 flex-col items-center border-r border-border bg-card/40 shrink-0 py-3 gap-2"
      aria-label="Konversationer (hopfälld)"
    >
      <button
        type="button"
        onClick={toggleCollapsed}
        aria-label="Visa konversationer"
        title="Visa konversationer"
        className="inline-flex h-9 w-9 items-center justify-center rounded-md text-muted-foreground hover:text-foreground hover:bg-secondary/60 transition-colors"
      >
        <PanelLeftOpen className="h-4 w-4" />
      </button>
      <div className="h-px w-6 bg-border" />
      <button
        type="button"
        onClick={() => openAgentSheet({ intentId: 'general.help' })}
        aria-label="Ny konversation"
        title="Ny konversation"
        className="inline-flex h-9 w-9 items-center justify-center rounded-md text-muted-foreground hover:text-foreground hover:bg-secondary/60 transition-colors text-lg"
      >
        +
      </button>
    </aside>
  ) : null

  return (
    <>
    {railAside}
    <aside
      className={cn(
        'flex-col border-r border-border bg-card/40 shrink-0',
        // Mobile: sidebar IS the page when no conversation; hidden otherwise.
        isConversationOpen ? 'hidden' : 'flex w-full',
        // Desktop: hidden if collapsed (rail takes its place); else 320px.
        collapsed ? 'md:hidden' : 'md:flex md:w-80',
      )}
    >
      <div className="border-b border-border px-5 py-4 space-y-3">
        <div className="flex items-center gap-2">
          <AgentAvatar avatarId={identity.avatarId} size="sm" alt={agentName ?? 'Assistent'} />
          <div className="flex-1 min-w-0">
            <h2 className="font-display text-base tracking-tight truncate">
              {agentName ?? 'Din assistent'}
            </h2>
            <p className="text-[11px] text-muted-foreground">Konversationer</p>
          </div>
          <button
            onClick={toggleCollapsed}
            aria-label="Dölj konversationer"
            title="Dölj konversationer"
            className="hidden md:inline-flex h-8 w-8 items-center justify-center rounded text-muted-foreground hover:text-foreground hover:bg-secondary/60 transition-colors"
          >
            <PanelLeftClose className="h-4 w-4" />
          </button>
          <button
            onClick={() => openAgentSheet({ intentId: 'general.help' })}
            className="text-xs uppercase tracking-wider text-muted-foreground hover:text-foreground transition-colors"
          >
            + Ny
          </button>
        </div>
        <div className="relative">
          <Search className="absolute left-2.5 top-1/2 -translate-y-1/2 h-3.5 w-3.5 text-muted-foreground" />
          <input
            type="text"
            value={query}
            onChange={(e) => setQuery(e.target.value)}
            placeholder="Sök…"
            className="w-full rounded-md border border-border bg-background pl-8 pr-7 py-1.5 text-sm focus:outline-none focus:ring-2 focus:ring-ring"
          />
          {query.length > 0 && (
            <button
              type="button"
              onClick={() => setQuery('')}
              aria-label="Rensa sökning"
              className="absolute right-1 top-1/2 -translate-y-1/2 inline-flex h-8 w-8 items-center justify-center rounded text-muted-foreground hover:bg-secondary hover:text-foreground"
            >
              <X className="h-3 w-3" />
            </button>
          )}
        </div>
      </div>

      <div className="flex-1 overflow-y-auto">
        {grouped.length === 0 ? (
          <div className="p-6 text-sm text-muted-foreground">
            {conversations.length === 0
              ? 'Inga konversationer ännu. Klicka på + Ny för att börja.'
              : 'Inga träffar.'}
          </div>
        ) : (
          grouped.map(({ bucket, rows }) => (
            <section key={bucket} className="py-2">
              <p className="px-4 pb-1 text-[10px] uppercase tracking-wider text-muted-foreground">
                {BUCKET_LABELS[bucket]}
              </p>
              <ul>
                {rows.map((c) => (
                  <li key={c.id}>
                    <Link
                      href={`/chat/${c.id}`}
                      className={cn(
                        'group flex items-start gap-2 px-4 py-2 hover:bg-secondary/60 transition-colors border-l-2',
                        activeId === c.id
                          ? 'bg-secondary/50 border-foreground'
                          : 'border-transparent',
                      )}
                    >
                      <div className="flex-1 min-w-0">
                        <div className="flex items-center gap-1.5">
                          <p className="text-sm font-medium truncate flex-1 min-w-0">
                            {c.title ?? intentLabel(c.intent_id)}
                          </p>
                          <p className="text-[11px] text-muted-foreground tabular-nums shrink-0">
                            {relativeTime(c.last_message_at ?? c.created_at)}
                          </p>
                        </div>
                        <p className="text-xs text-muted-foreground line-clamp-1 mt-0.5">
                          {c.last_message_preview ?? intentLabel(c.intent_id)}
                        </p>
                      </div>
                      {/* Always-visible action icons. Touch-friendly, no
                          hover-only invisibility on mobile. */}
                      <div className="flex flex-col gap-1 shrink-0 -mr-1">
                        <button
                          onClick={(e) => {
                            e.preventDefault()
                            e.stopPropagation()
                            void togglePin(c.id, c.pinned)
                          }}
                          title={c.pinned ? 'Avfäst' : 'Fäst'}
                          aria-label={c.pinned ? 'Avfäst konversation' : 'Fäst konversation'}
                          className={cn(
                            'inline-flex h-8 w-8 items-center justify-center rounded transition-colors',
                            c.pinned
                              ? 'text-foreground'
                              : 'text-muted-foreground/50 hover:text-foreground hover:bg-secondary',
                          )}
                        >
                          {c.pinned ? (
                            <Pin className="h-3 w-3" fill="currentColor" />
                          ) : (
                            <PinOff className="h-3 w-3" />
                          )}
                        </button>
                        <button
                          onClick={(e) => {
                            e.preventDefault()
                            e.stopPropagation()
                            void archive(c.id)
                          }}
                          title="Arkivera"
                          aria-label="Arkivera konversation"
                          className="inline-flex h-8 w-8 items-center justify-center rounded text-muted-foreground/50 hover:text-foreground hover:bg-secondary transition-colors"
                        >
                          <Archive className="h-3 w-3" />
                        </button>
                      </div>
                    </Link>
                  </li>
                ))}
              </ul>
            </section>
          ))
        )}
      </div>
    </aside>
    </>
  )
}

function intentLabel(intentId: string): string {
  switch (intentId) {
    case 'general.help':
      return 'Fråga din assistent'
    case 'transaction.categorization':
      return 'Hjälp med transaktion'
    case 'invoice.draft':
      return 'Hjälp med faktura'
    case 'supplier_invoice.review':
      return 'Granska leverantörsfaktura'
    case 'vat.review':
      return 'Granska moms­deklaration'
    case 'bokslut.step':
      return 'Hjälp med bokslut'
    case 'verifikation.draft':
      return 'Hjälp med verifikation'
    case 'kpi.explain':
      return 'Förklara nyckeltal'
    default:
      return intentId
  }
}