import { useState } from 'react'
import { Plus, Pin, Trash2, MessageSquare, History, X } from 'lucide-react'
import { cn } from '@/lib/utils'
import type { ChatListItem } from '@/types/assistant-chat'

interface ChatSidebarProps {
  chats: ChatListItem[]
  activeChatId: string | null
  onSelectChat: (id: string) => void
  onNewChat: () => void
  onDeleteChat: (id: string) => void
  onTogglePin: (id: string, pinned: boolean) => void
  mobileOpen?: boolean
  onMobileClose?: () => void
  collapsed?: boolean
  onToggleCollapse?: () => void
}

export function ChatSidebar({
  chats,
  activeChatId,
  onSelectChat,
  onNewChat,
  onDeleteChat,
  onTogglePin,
  mobileOpen = false,
  onMobileClose,
  collapsed = false,
  onToggleCollapse,
}: ChatSidebarProps) {
  const pinnedChats = chats.filter(c => c.pinned)
  const unpinnedChats = chats.filter(c => !c.pinned)

  const handleSelectChat = (id: string) => {
    onSelectChat(id)
    onMobileClose?.()
  }

  const handleNewChat = () => {
    onNewChat()
    onMobileClose?.()
  }

  // When collapsed on desktop, render nothing — parent renders the top bar
  if (collapsed && !mobileOpen) {
    return null
  }

  return (
    <>
      {/* Mobile overlay */}
      {mobileOpen && (
        <div className="fixed inset-0 z-40 bg-black/50 sm:hidden" onClick={onMobileClose} />
      )}
      <div
        className={cn(
          'w-72 shrink-0 flex flex-col border-r h-full',
          'fixed inset-y-0 left-0 z-50 sm:static sm:z-auto',
          'transition-transform duration-200',
          mobileOpen ? 'translate-x-0' : '-translate-x-full sm:translate-x-0',
        )}
        style={{ background: 'var(--color-bg-sidebar)' }}
      >
      {/* Header */}
      <div className="px-3 py-3 border-b shrink-0 flex items-center gap-2" style={{ borderColor: 'var(--color-border-default)' }}>
        <button
          onClick={handleNewChat}
          className="flex-1 flex items-center justify-center gap-2 bg-primary text-white font-semibold text-sm rounded-lg px-4 py-2.5 hover:brightness-110 active:scale-[0.98] transition-all"
        >
          <Plus size={16} />
          New Chat
        </button>
        {onToggleCollapse && (
          <button
            onClick={onToggleCollapse}
            className="hidden sm:flex p-1.5 rounded-lg text-muted-foreground hover:text-heading hover:bg-elevated transition-colors"
            title="Collapse to top bar"
          >
            <X size={16} />
          </button>
        )}
      </div>

      {/* Chat list */}
      <div className="flex-1 overflow-y-auto py-2">
        {pinnedChats.length > 0 && (
          <div className="px-3 mb-1">
            <span className="font-sans text-[0.625rem] uppercase tracking-widest text-muted-foreground">
              Pinned
            </span>
          </div>
        )}
        {pinnedChats.map(chat => (
          <ChatItem
            key={chat.id}
            chat={chat}
            isActive={chat.id === activeChatId}
            onSelect={() => handleSelectChat(chat.id)}
            onDelete={() => onDeleteChat(chat.id)}
            onTogglePin={() => onTogglePin(chat.id, !chat.pinned)}
          />
        ))}

        {pinnedChats.length > 0 && unpinnedChats.length > 0 && (
          <div className="mx-3 my-2 border-b" style={{ borderColor: 'var(--color-border-default)' }} />
        )}

        {unpinnedChats.map(chat => (
          <ChatItem
            key={chat.id}
            chat={chat}
            isActive={chat.id === activeChatId}
            onSelect={() => handleSelectChat(chat.id)}
            onDelete={() => onDeleteChat(chat.id)}
            onTogglePin={() => onTogglePin(chat.id, !chat.pinned)}
          />
        ))}

        {chats.length === 0 && (
          <div className="px-4 py-8 text-center text-muted-foreground text-sm">
            No conversations yet
          </div>
        )}
      </div>
    </div>
    </>
  )
}

/** Collapsed top bar — rendered by the parent page above the chat area */
export function ChatSidebarCollapsedBar({
  chats,
  activeChatId,
  onNewChat,
  onExpand,
}: {
  chats: ChatListItem[]
  activeChatId: string | null
  onNewChat: () => void
  onExpand: () => void
}) {
  return (
    <div
      className="flex items-center gap-2 px-3 py-2 border-b shrink-0"
      style={{ background: 'var(--color-bg-sidebar)', borderColor: 'var(--color-border-default)' }}
    >
      <button
        onClick={onNewChat}
        className="flex items-center gap-1.5 bg-primary text-white font-semibold text-xs rounded-md px-3 py-1.5 hover:brightness-110 active:scale-[0.98] transition-all"
      >
        <Plus size={14} />
        New
      </button>
      <button
        onClick={onExpand}
        className="flex items-center gap-1.5 rounded-md px-2.5 py-1.5 text-xs text-muted-foreground hover:text-heading hover:bg-elevated transition-colors"
        title="Show chat history"
      >
        <History size={14} />
        <span>History</span>
        {chats.length > 0 && (
          <span className="text-[10px] bg-elevated rounded-full px-1.5 py-0.5 font-medium">{chats.length}</span>
        )}
      </button>
      <div className="flex-1" />
      {activeChatId && (
        <span className="text-xs text-muted-foreground truncate max-w-[300px]">
          {chats.find(c => c.id === activeChatId)?.title}
        </span>
      )}
    </div>
  )
}

function ChatItem({
  chat,
  isActive,
  onSelect,
  onDelete,
  onTogglePin,
}: {
  chat: ChatListItem
  isActive: boolean
  onSelect: () => void
  onDelete: () => void
  onTogglePin: () => void
}) {
  const [confirming, setConfirming] = useState(false)

  return (
    <div
      onClick={confirming ? e => e.stopPropagation() : onSelect}
      className={cn(
        'group flex items-center gap-2 px-3 py-2.5 mx-1.5 rounded-lg cursor-pointer transition-colors',
        confirming
          ? 'bg-danger-dim border border-danger/20'
          : isActive
            ? 'bg-accent-dim text-foreground'
            : 'text-muted-foreground hover:bg-input hover:text-foreground'
      )}
    >
      <MessageSquare size={14} className="shrink-0" />
      <div className="flex-1 min-w-0">
        {confirming ? (
          <div className="flex items-center gap-2">
            <span className="text-[0.75rem] text-danger font-medium">Delete?</span>
            <button
              onClick={e => { e.stopPropagation(); onDelete(); setConfirming(false) }}
              className="text-[0.6875rem] font-medium text-danger hover:text-danger px-1.5 py-0.5 rounded bg-danger/15 hover:bg-danger/25 transition-colors"
            >
              Yes
            </button>
            <button
              onClick={e => { e.stopPropagation(); setConfirming(false) }}
              className="text-[0.6875rem] text-muted-foreground hover:text-foreground px-1.5 py-0.5"
            >
              No
            </button>
          </div>
        ) : (
          <>
            <div className="flex items-center gap-1.5 min-w-0">
              <div className="text-[0.8125rem] font-medium truncate">{chat.title}</div>
              {chat.psa_ticket_id && (
                <span className="font-mono shrink-0 rounded-md bg-accent-dim px-1.5 py-0.5 text-[0.5625rem] text-accent-text">
                  #{chat.psa_ticket_id}
                </span>
              )}
              {(chat.status === 'escalated' || chat.status === 'requesting_escalation') && (
                <span className="font-sans shrink-0 rounded-md bg-warning-dim px-1.5 py-0.5 text-[0.5625rem] uppercase tracking-wider text-warning border border-warning/20">
                  Escalated
                </span>
              )}
            </div>
            {/* Secondary line: problem snippet when the title doesn't already
                carry it, otherwise the message count. Keeps untitled
                sessions from collapsing into identical-looking rows. */}
            {chat.problem_summary && chat.problem_summary !== chat.title ? (
              <div className="text-[0.6875rem] text-muted-foreground truncate">
                {chat.problem_summary}
              </div>
            ) : (
              <div className="text-[0.6875rem] text-muted-foreground">
                {chat.message_count} messages
              </div>
            )}
          </>
        )}
      </div>
      {!confirming && (
        <div className="flex items-center gap-0.5 opacity-0 group-hover:opacity-100 transition-opacity">
          <button
            onClick={e => { e.stopPropagation(); onTogglePin() }}
            className="p-1 rounded hover:bg-elevated"
            title={chat.pinned ? 'Unpin' : 'Pin'}
          >
            <Pin size={12} className={chat.pinned ? 'text-primary' : ''} />
          </button>
          <button
            onClick={e => { e.stopPropagation(); setConfirming(true) }}
            className="p-1 rounded hover:bg-elevated text-muted-foreground hover:text-danger"
            title="Delete"
          >
            <Trash2 size={12} />
          </button>
        </div>
      )}
    </div>
  )
}
