'use client'

import { useSession } from 'next-auth/react'
import { trpc } from '@/lib/trpc/client'
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from '@/components/ui/card'
import { Skeleton } from '@/components/ui/skeleton'
import { MentorChat } from '@/components/shared/mentor-chat'
import { WorkspaceFilesPanel } from '@/components/mentor/workspace-files-panel'
import {
  MessageSquare,
  UserCircle,
  FileText,
} from 'lucide-react'

export default function ApplicantMentorPage() {
  const { data: session, status: sessionStatus } = useSession()
  const isAuthenticated = sessionStatus === 'authenticated'

  const { data: dashboardData, isLoading: dashLoading } = trpc.applicant.getMyDashboard.useQuery(
    undefined,
    { enabled: isAuthenticated }
  )

  const projectId = dashboardData?.project?.id

  const { data: mentorMessages, isLoading: messagesLoading } = trpc.applicant.getMentorMessages.useQuery(
    { projectId: projectId! },
    { enabled: !!projectId }
  )

  const utils = trpc.useUtils()
  const sendMessage = trpc.applicant.sendMentorMessage.useMutation({
    onSuccess: () => {
      utils.applicant.getMentorMessages.invalidate({ projectId: projectId! })
    },
  })

  if (dashLoading) {
    return (
      <div className="space-y-6">
        <div className="space-y-2">
          <Skeleton className="h-8 w-48" />
          <Skeleton className="h-4 w-64" />
        </div>
        <Skeleton className="h-96 w-full" />
      </div>
    )
  }

  if (!projectId) {
    return (
      <div className="space-y-6">
        <div>
          <h1 className="text-2xl font-semibold tracking-tight">Mentor</h1>
        </div>
        <Card>
          <CardContent className="flex flex-col items-center justify-center py-12">
            <FileText className="h-12 w-12 text-muted-foreground/50 mb-4" />
            <h2 className="text-xl font-semibold mb-2">No Project</h2>
            <p className="text-muted-foreground text-center">
              Submit a project first to communicate with your mentor.
            </p>
          </CardContent>
        </Card>
      </div>
    )
  }

  // TODO(PR8 Task 7): show ALL assigned mentors. For now we display only the
  // first one until the multi-mentor applicant UI ships.
  const primaryAssignment = dashboardData?.project?.mentorAssignments?.[0] ?? null
  const mentor = primaryAssignment?.mentor

  return (
    <div className="space-y-6">
      {/* Header */}
      <div>
        <h1 className="text-2xl font-semibold tracking-tight flex items-center gap-2">
          <MessageSquare className="h-6 w-6" />
          Mentor Communication
        </h1>
        <p className="text-muted-foreground">
          Chat with your assigned mentor
        </p>
      </div>

      {/* Mentor info */}
      {mentor ? (
        <Card className="bg-muted/50">
          <CardContent className="p-4">
            <div className="flex items-center gap-3">
              <UserCircle className="h-10 w-10 text-muted-foreground" />
              <div>
                <p className="font-medium">{mentor.name || 'Mentor'}</p>
                <p className="text-sm text-muted-foreground">{mentor.email}</p>
              </div>
            </div>
          </CardContent>
        </Card>
      ) : (
        <Card className="bg-muted/50">
          <CardContent className="flex flex-col items-center justify-center py-8">
            <UserCircle className="h-12 w-12 text-muted-foreground/50 mb-3" />
            <p className="text-muted-foreground text-center">
              No mentor has been assigned to your project yet.
              You&apos;ll be notified when a mentor is assigned.
            </p>
          </CardContent>
        </Card>
      )}

      {/* Chat */}
      {mentor && (
        <Card>
          <CardHeader>
            <CardTitle>Messages</CardTitle>
            <CardDescription>
              Your conversation history with {mentor.name || 'your mentor'}
            </CardDescription>
          </CardHeader>
          <CardContent>
            <MentorChat
              messages={mentorMessages || []}
              currentUserId={session?.user?.id || ''}
              onSendMessage={async (message) => {
                await sendMessage.mutateAsync({ projectId: projectId!, message })
              }}
              isLoading={messagesLoading}
              isSending={sendMessage.isPending}
            />
          </CardContent>
        </Card>
      )}

      {/* Files */}
      {primaryAssignment?.id && projectId && (
        <WorkspaceFilesPanel
          projectId={projectId}
          mentorAssignmentId={primaryAssignment.id}
          asApplicant
        />
      )}
    </div>
  )
}