import { useState } from 'react'
import { createFileRoute, useNavigate } from '@tanstack/react-router'
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
import {
  lessonPlanTemplateDetailOptions, lessonPlanTemplateMutations, lessonPlanTemplateKeys,
  enrollmentListOptions,
} from '@/api/lessons'
import { globalMemberListOptions } from '@/api/members'
import { TemplateSectionBuilder, type TemplateSectionRow } from '@/components/lessons/template-section-builder'
import { Button } from '@/components/ui/button'
import { Badge } from '@/components/ui/badge'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'
import { Textarea } from '@/components/ui/textarea'
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select'
import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
import { Dialog, DialogContent, DialogHeader, DialogTitle } from '@/components/ui/dialog'
import { ArrowLeft, Search, X, Zap } from 'lucide-react'
import { toast } from 'sonner'
import { useAuthStore } from '@/stores/auth.store'
import type { Enrollment, LessonPlanTemplate } from '@/types/lesson'
import type { MemberWithAccount } from '@/api/members'

export const Route = createFileRoute('/_authenticated/lessons/templates/$templateId')({
  component: TemplateDetailPage,
})

function TemplateDetailPage() {
  const { templateId } = Route.useParams()
  const navigate = useNavigate()
  const queryClient = useQueryClient()
  const hasPermission = useAuthStore((s) => s.hasPermission)
  const canAdmin = hasPermission('lessons.admin')

  const { data: template, isLoading } = useQuery(lessonPlanTemplateDetailOptions(templateId))

  const [instantiateOpen, setInstantiateOpen] = useState(false)

  if (isLoading) return <div className="text-sm text-muted-foreground">Loading...</div>
  if (!template) return <div className="text-sm text-destructive">Template not found.</div>

  return (
    <div className="space-y-6 max-w-3xl">
      <div className="flex items-center gap-3">
        <Button variant="ghost" size="sm" onClick={() => navigate({ to: '/lessons/templates', search: { page: 1, limit: 25, q: undefined, sort: undefined, order: 'asc' as const } })}>
          <ArrowLeft className="h-4 w-4" />
        </Button>
        <div className="flex-1">
          <h1 className="text-2xl font-bold">{template.name}</h1>
          {template.instrument && <p className="text-sm text-muted-foreground">{template.instrument}</p>}
        </div>
        <Badge variant={template.isActive ? 'default' : 'secondary'}>{template.isActive ? 'Active' : 'Inactive'}</Badge>
      </div>

      <div className="flex gap-2">
        <Button onClick={() => setInstantiateOpen(true)}>
          <Zap className="h-4 w-4 mr-2" />Instantiate for Student
        </Button>
      </div>

      {canAdmin && (
        <EditTemplateForm template={template} templateId={templateId} queryClient={queryClient} />
      )}

      {/* Read-only curriculum preview */}
      {!canAdmin && (
        <Card>
          <CardHeader><CardTitle className="text-lg">Curriculum</CardTitle></CardHeader>
          <CardContent className="space-y-4">
            {template.sections.map((section) => (
              <div key={section.id}>
                <p className="font-semibold text-sm">{section.title}</p>
                <ul className="mt-1 space-y-0.5 pl-4">
                  {section.items.map((item) => (
                    <li key={item.id} className="text-sm text-muted-foreground list-disc">{item.title}</li>
                  ))}
                </ul>
              </div>
            ))}
          </CardContent>
        </Card>
      )}

      <InstantiateDialog
        template={template}
        templateId={templateId}
        open={instantiateOpen}
        onClose={() => setInstantiateOpen(false)}
      />
    </div>
  )
}

// ─── Edit Form ────────────────────────────────────────────────────────────────

function EditTemplateForm({ template, templateId, queryClient }: { template: LessonPlanTemplate; templateId: string; queryClient: ReturnType<typeof useQueryClient> }) {
  const [name, setName] = useState(template.name)
  const [description, setDescription] = useState(template.description ?? '')
  const [instrument, setInstrument] = useState(template.instrument ?? '')
  const [skillLevel, setSkillLevel] = useState<'beginner' | 'intermediate' | 'advanced' | 'all_levels'>(template.skillLevel)
  const [sections, setSections] = useState<TemplateSectionRow[]>(
    template.sections.map((s) => ({
      id: s.id,
      title: s.title,
      description: s.description ?? '',
      items: s.items.map((i) => ({ id: i.id, title: i.title, description: i.description ?? '' })),
    })),
  )

  const updateMutation = useMutation({
    mutationFn: () =>
      lessonPlanTemplateMutations.update(templateId, {
        name,
        description: description || undefined,
        instrument: instrument || undefined,
        skillLevel,
        sections: sections.map((s, sIdx) => ({
          title: s.title,
          description: s.description || undefined,
          sortOrder: sIdx,
          items: s.items.map((item, iIdx) => ({
            title: item.title,
            description: item.description || undefined,
            sortOrder: iIdx,
          })),
        })),
      }),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: lessonPlanTemplateKeys.detail(templateId) })
      toast.success('Template updated')
    },
    onError: (err: Error) => toast.error(err.message),
  })

  const allValid = name.trim() && sections.every((s) => s.title.trim() && s.items.every((i) => i.title.trim()))

  return (
    <form
      onSubmit={(e) => { e.preventDefault(); updateMutation.mutate() }}
      className="space-y-6"
    >
      <Card>
        <CardHeader><CardTitle className="text-lg">Details</CardTitle></CardHeader>
        <CardContent className="space-y-4">
          <div className="space-y-2">
            <Label>Name *</Label>
            <Input value={name} onChange={(e) => setName(e.target.value)} required />
          </div>
          <div className="space-y-2">
            <Label>Description</Label>
            <Textarea value={description} onChange={(e) => setDescription(e.target.value)} rows={2} />
          </div>
          <div className="grid grid-cols-2 gap-4">
            <div className="space-y-2">
              <Label>Instrument</Label>
              <Input value={instrument} onChange={(e) => setInstrument(e.target.value)} placeholder="e.g. Piano" />
            </div>
            <div className="space-y-2">
              <Label>Skill Level</Label>
              <Select value={skillLevel} onValueChange={(v) => setSkillLevel(v as 'beginner' | 'intermediate' | 'advanced' | 'all_levels')}>
                <SelectTrigger><SelectValue /></SelectTrigger>
                <SelectContent>
                  <SelectItem value="beginner">Beginner</SelectItem>
                  <SelectItem value="intermediate">Intermediate</SelectItem>
                  <SelectItem value="advanced">Advanced</SelectItem>
                  <SelectItem value="all_levels">All Levels</SelectItem>
                </SelectContent>
              </Select>
            </div>
          </div>
        </CardContent>
      </Card>

      <Card>
        <CardHeader><CardTitle className="text-lg">Curriculum</CardTitle></CardHeader>
        <CardContent>
          <TemplateSectionBuilder sections={sections} onChange={setSections} />
        </CardContent>
      </Card>

      <Button type="submit" disabled={updateMutation.isPending || !allValid}>
        {updateMutation.isPending ? 'Saving...' : 'Save Changes'}
      </Button>
    </form>
  )
}

// ─── Instantiate Dialog ───────────────────────────────────────────────────────

function InstantiateDialog({ template, templateId, open, onClose }: {
  template: LessonPlanTemplate
  templateId: string
  open: boolean
  onClose: () => void
}) {
  const navigate = useNavigate()
  const [memberSearch, setMemberSearch] = useState('')
  const [showDropdown, setShowDropdown] = useState(false)
  const [selectedMember, setSelectedMember] = useState<MemberWithAccount | null>(null)
  const [selectedEnrollmentId, setSelectedEnrollmentId] = useState('')
  const [customTitle, setCustomTitle] = useState('')

  const { data: membersData } = useQuery(
    globalMemberListOptions({ page: 1, limit: 20, q: memberSearch || undefined, order: 'asc', sort: 'first_name' }),
  )

  const { data: enrollmentsData } = useQuery({
    ...enrollmentListOptions({ memberId: selectedMember?.id ?? '', status: 'active', page: 1, limit: 50 }),
    enabled: !!selectedMember?.id,
  })

  const mutation = useMutation({
    mutationFn: () =>
      lessonPlanTemplateMutations.createPlan(templateId, {
        memberId: selectedMember!.id,
        enrollmentId: selectedEnrollmentId || undefined,
        title: customTitle || undefined,
      }),
    onSuccess: (plan) => {
      toast.success('Plan created from template')
      navigate({ to: '/lessons/plans/$planId', params: { planId: plan.id }, search: { page: 1, limit: 25, q: undefined, sort: undefined, order: 'asc' as const } })
    },
    onError: (err) => toast.error(err.message),
  })

  const members = membersData?.data ?? []
  const enrollments = enrollmentsData?.data ?? []

  function reset() {
    setMemberSearch('')
    setSelectedMember(null)
    setSelectedEnrollmentId('')
    setCustomTitle('')
  }

  return (
    <Dialog open={open} onOpenChange={(o) => { if (!o) { reset(); onClose() } }}>
      <DialogContent className="max-w-md">
        <DialogHeader>
          <DialogTitle>Create Plan from "{template.name}"</DialogTitle>
        </DialogHeader>
        <div className="space-y-4">
          {/* Member select */}
          {!selectedMember ? (
            <div className="relative">
              <Label>Student *</Label>
              <div className="relative mt-1">
                <Search className="absolute left-3 top-1/2 -translate-y-1/2 h-4 w-4 text-muted-foreground" />
                <Input
                  placeholder="Search member..."
                  value={memberSearch}
                  onChange={(e) => { setMemberSearch(e.target.value); setShowDropdown(true) }}
                  onFocus={() => setShowDropdown(true)}
                  className="pl-9"
                />
              </div>
              {showDropdown && memberSearch && (
                <div className="absolute z-50 mt-1 w-full rounded-md border bg-popover shadow-lg max-h-48 overflow-auto">
                  {members.length === 0 ? (
                    <div className="p-3 text-sm text-muted-foreground">No members found</div>
                  ) : (
                    members.map((m) => (
                      <button
                        key={m.id}
                        type="button"
                        className="w-full text-left px-3 py-2 text-sm hover:bg-accent"
                        onClick={() => { setSelectedMember(m); setShowDropdown(false); setMemberSearch('') }}
                      >
                        <span className="font-medium">{m.firstName} {m.lastName}</span>
                        {m.accountName && <span className="text-muted-foreground ml-2">— {m.accountName}</span>}
                      </button>
                    ))
                  )}
                </div>
              )}
            </div>
          ) : (
            <div>
              <Label>Student</Label>
              <div className="flex items-center justify-between mt-1 p-2 rounded-md border bg-muted/30">
                <p className="text-sm font-medium">{selectedMember.firstName} {selectedMember.lastName}</p>
                <Button type="button" variant="ghost" size="sm" onClick={() => { setSelectedMember(null); setSelectedEnrollmentId('') }}>
                  <X className="h-4 w-4" />
                </Button>
              </div>
            </div>
          )}

          {selectedMember && enrollments.length > 0 && (
            <div className="space-y-2">
              <Label>Enrollment (optional)</Label>
              <Select value={selectedEnrollmentId || 'none'} onValueChange={(v) => setSelectedEnrollmentId(v === 'none' ? '' : v)}>
                <SelectTrigger><SelectValue placeholder="Not linked to enrollment" /></SelectTrigger>
                <SelectContent>
                  <SelectItem value="none">Not linked to enrollment</SelectItem>
                  {enrollments.map((e: Enrollment) => (
                    <SelectItem key={e.id} value={e.id}>Enrollment {e.id.slice(-6)}</SelectItem>
                  ))}
                </SelectContent>
              </Select>
            </div>
          )}

          <div className="space-y-2">
            <Label>Custom Title</Label>
            <Input value={customTitle} onChange={(e) => setCustomTitle(e.target.value)} placeholder={`Leave blank to use "${template.name}"`} />
          </div>

          <Button
            onClick={() => mutation.mutate()}
            disabled={!selectedMember || mutation.isPending}
            className="w-full"
          >
            {mutation.isPending ? 'Creating...' : 'Create Plan'}
          </Button>
        </div>
      </DialogContent>
    </Dialog>
  )
}
