'use client'

import { useState, useCallback, useMemo } from 'react'
import Link from 'next/link'
import Papa from 'papaparse'
import { trpc } from '@/lib/trpc/client'
import { Button } from '@/components/ui/button'
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from '@/components/ui/card'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'
import { Badge } from '@/components/ui/badge'
import { Progress } from '@/components/ui/progress'
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from '@/components/ui/select'
import {
  Table,
  TableBody,
  TableCell,
  TableHead,
  TableHeader,
  TableRow,
} from '@/components/ui/table'
import {
  ArrowLeft,
  ArrowRight,
  AlertCircle,
  CheckCircle2,
  Loader2,
  Users,
  X,
  Plus,
  FileSpreadsheet,
  UserPlus,
} from 'lucide-react'
import { cn } from '@/lib/utils'

type Step = 'input' | 'preview' | 'sending' | 'complete'
type Role = 'JURY_MEMBER' | 'MENTOR' | 'OBSERVER'

interface MemberRow {
  id: string
  name: string
  email: string
  role: Role
  expertiseTags: string[]
  tagInput: string
}

interface ParsedUser {
  email: string
  name?: string
  role: Role
  expertiseTags?: string[]
  isValid: boolean
  error?: string
  isDuplicate?: boolean
}

const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/

const ROLE_LABELS: Record<Role, string> = {
  JURY_MEMBER: 'Jury Member',
  MENTOR: 'Mentor',
  OBSERVER: 'Observer',
}

let rowIdCounter = 0
function nextRowId(): string {
  return `row-${++rowIdCounter}`
}

function createEmptyRow(role: Role = 'JURY_MEMBER'): MemberRow {
  return { id: nextRowId(), name: '', email: '', role, expertiseTags: [], tagInput: '' }
}

// Common expertise tags for suggestions
const SUGGESTED_TAGS = [
  'Marine Biology',
  'Ocean Conservation',
  'Coral Reef Restoration',
  'Sustainable Fisheries',
  'Marine Policy',
  'Ocean Technology',
  'Climate Science',
  'Biodiversity',
  'Blue Economy',
  'Coastal Management',
  'Oceanography',
  'Marine Pollution',
  'Plastic Reduction',
  'Renewable Energy',
  'Business Development',
  'Impact Investment',
  'Social Entrepreneurship',
  'Startup Mentoring',
]

export default function MemberInvitePage() {
  const [step, setStep] = useState<Step>('input')
  const [inputMethod, setInputMethod] = useState<'manual' | 'csv'>('manual')
  const [rows, setRows] = useState<MemberRow[]>([createEmptyRow()])
  const [parsedUsers, setParsedUsers] = useState<ParsedUser[]>([])
  const [sendProgress, setSendProgress] = useState(0)
  const [result, setResult] = useState<{
    created: number
    skipped: number
  } | null>(null)

  const utils = trpc.useUtils()
  const bulkCreate = trpc.user.bulkCreate.useMutation({
    onSuccess: () => {
      // Invalidate user list to refresh the members table when navigating back
      utils.user.list.invalidate()
    },
  })

  // --- Manual entry helpers ---
  const updateRow = (id: string, field: keyof MemberRow, value: string | string[]) => {
    setRows((prev) =>
      prev.map((r) => (r.id === id ? { ...r, [field]: value } : r))
    )
  }

  const removeRow = (id: string) => {
    setRows((prev) => {
      const filtered = prev.filter((r) => r.id !== id)
      return filtered.length === 0 ? [createEmptyRow()] : filtered
    })
  }

  const addRow = () => {
    const lastRole = rows[rows.length - 1]?.role || 'JURY_MEMBER'
    setRows((prev) => [...prev, createEmptyRow(lastRole)])
  }

  // Per-row tag management
  const addTagToRow = (id: string, tag: string) => {
    const trimmed = tag.trim()
    if (!trimmed) return
    setRows((prev) =>
      prev.map((r) => {
        if (r.id !== id) return r
        if (r.expertiseTags.includes(trimmed)) return r
        return { ...r, expertiseTags: [...r.expertiseTags, trimmed], tagInput: '' }
      })
    )
  }

  const removeTagFromRow = (id: string, tag: string) => {
    setRows((prev) =>
      prev.map((r) =>
        r.id === id
          ? { ...r, expertiseTags: r.expertiseTags.filter((t) => t !== tag) }
          : r
      )
    )
  }

  // Get suggestions that haven't been added yet for a specific row
  const getSuggestionsForRow = (row: MemberRow) => {
    return SUGGESTED_TAGS.filter(
      (tag) =>
        !row.expertiseTags.includes(tag) &&
        tag.toLowerCase().includes(row.tagInput.toLowerCase())
    ).slice(0, 5)
  }

  // --- CSV helpers ---
  const handleCSVUpload = useCallback(
    (e: React.ChangeEvent<HTMLInputElement>) => {
      const file = e.target.files?.[0]
      if (!file) return
      Papa.parse<Record<string, string>>(file, {
        header: true,
        skipEmptyLines: true,
        complete: (results) => {
          const seenEmails = new Set<string>()
          const users: ParsedUser[] = results.data.map((row) => {
            const emailKey = Object.keys(row).find(
              (key) =>
                key.toLowerCase() === 'email' ||
                key.toLowerCase().includes('email')
            )
            const nameKey = Object.keys(row).find(
              (key) =>
                key.toLowerCase() === 'name' ||
                key.toLowerCase().includes('name')
            )
            const roleKey = Object.keys(row).find(
              (key) =>
                key.toLowerCase() === 'role' ||
                key.toLowerCase().includes('role')
            )
            const email = emailKey ? row[emailKey]?.trim().toLowerCase() : ''
            const name = nameKey ? row[nameKey]?.trim() : undefined
            const rawRole = roleKey ? row[roleKey]?.trim().toUpperCase() : ''
            const role: Role =
              rawRole === 'MENTOR'
                ? 'MENTOR'
                : rawRole === 'OBSERVER'
                  ? 'OBSERVER'
                  : 'JURY_MEMBER'
            const isValidFormat = emailRegex.test(email)
            const isDuplicate = email ? seenEmails.has(email) : false
            if (isValidFormat && !isDuplicate && email) seenEmails.add(email)
            return {
              email,
              name,
              role,
              isValid: isValidFormat && !isDuplicate,
              isDuplicate,
              error: !email
                ? 'No email found'
                : !isValidFormat
                  ? 'Invalid email format'
                  : isDuplicate
                    ? 'Duplicate email'
                    : undefined,
            }
          })
          setParsedUsers(users.filter((u) => u.email))
          setStep('preview')
        },
      })
    },
    []
  )

  // --- Parse manual rows into ParsedUser format ---
  const parseManualRows = (): ParsedUser[] => {
    const seenEmails = new Set<string>()
    return rows
      .filter((r) => r.email.trim())
      .map((r) => {
        const email = r.email.trim().toLowerCase()
        const isValidFormat = emailRegex.test(email)
        const isDuplicate = seenEmails.has(email)
        if (isValidFormat && !isDuplicate) seenEmails.add(email)
        return {
          email,
          name: r.name.trim() || undefined,
          role: r.role,
          expertiseTags: r.expertiseTags.length > 0 ? r.expertiseTags : undefined,
          isValid: isValidFormat && !isDuplicate,
          isDuplicate,
          error: !isValidFormat
            ? 'Invalid email format'
            : isDuplicate
              ? 'Duplicate email'
              : undefined,
        }
      })
  }

  const handleManualProceed = () => {
    const parsed = parseManualRows()
    if (parsed.length === 0) return
    setParsedUsers(parsed)
    setStep('preview')
  }

  // --- Summary ---
  const summary = useMemo(() => {
    const validUsers = parsedUsers.filter((u) => u.isValid)
    const invalidUsers = parsedUsers.filter((u) => !u.isValid)
    return {
      total: parsedUsers.length,
      valid: validUsers.length,
      invalid: invalidUsers.length,
      validUsers,
      invalidUsers,
    }
  }, [parsedUsers])

  const removeInvalidUsers = () =>
    setParsedUsers(parsedUsers.filter((u) => u.isValid))

  // --- Send ---
  const handleSendInvites = async () => {
    if (summary.valid === 0) return
    setStep('sending')
    setSendProgress(0)
    try {
      const result = await bulkCreate.mutateAsync({
        users: summary.validUsers.map((u) => ({
          email: u.email,
          name: u.name,
          role: u.role,
          expertiseTags: u.expertiseTags,
        })),
      })
      setSendProgress(100)
      setResult(result)
      setStep('complete')
    } catch {
      setStep('preview')
    }
  }

  const resetForm = () => {
    setStep('input')
    setRows([createEmptyRow()])
    setParsedUsers([])
    setResult(null)
    setSendProgress(0)
  }

  const hasManualData = rows.some((r) => r.email.trim() || r.name.trim())

  const steps: Array<{ key: Step; label: string }> = [
    { key: 'input', label: 'Input' },
    { key: 'preview', label: 'Preview' },
    { key: 'sending', label: 'Send' },
    { key: 'complete', label: 'Done' },
  ]
  const currentStepIndex = steps.findIndex((s) => s.key === step)

  const renderStep = () => {
    switch (step) {
      case 'input':
        return (
          <Card>
            <CardHeader>
              <CardTitle>Invite Members</CardTitle>
              <CardDescription>
                Add members individually or upload a CSV file
              </CardDescription>
            </CardHeader>
            <CardContent className="space-y-6">
              {/* Method toggle */}
              <div className="flex gap-2">
                <Button
                  type="button"
                  variant={inputMethod === 'manual' ? 'default' : 'outline'}
                  size="sm"
                  onClick={() => setInputMethod('manual')}
                >
                  <UserPlus className="mr-2 h-4 w-4" />
                  Add Manually
                </Button>
                <Button
                  type="button"
                  variant={inputMethod === 'csv' ? 'default' : 'outline'}
                  size="sm"
                  onClick={() => setInputMethod('csv')}
                >
                  <FileSpreadsheet className="mr-2 h-4 w-4" />
                  Upload CSV
                </Button>
              </div>

              {inputMethod === 'manual' ? (
                <div className="space-y-4">
                  {/* Member cards */}
                  {rows.map((row, index) => (
                    <div
                      key={row.id}
                      className="rounded-lg border p-4 space-y-3"
                    >
                      <div className="flex items-center justify-between">
                        <span className="text-sm font-medium text-muted-foreground">
                          Member {index + 1}
                        </span>
                        <Button
                          type="button"
                          variant="ghost"
                          size="sm"
                          onClick={() => removeRow(row.id)}
                          className="text-muted-foreground hover:text-destructive h-8 w-8 p-0"
                        >
                          <X className="h-4 w-4" />
                        </Button>
                      </div>

                      <div className="grid gap-3 sm:grid-cols-[1fr_1fr_140px]">
                        <Input
                          placeholder="Full name"
                          value={row.name}
                          onChange={(e) =>
                            updateRow(row.id, 'name', e.target.value)
                          }
                        />
                        <Input
                          type="email"
                          placeholder="email@example.com"
                          value={row.email}
                          onChange={(e) =>
                            updateRow(row.id, 'email', e.target.value)
                          }
                        />
                        <Select
                          value={row.role}
                          onValueChange={(v) =>
                            updateRow(row.id, 'role', v)
                          }
                        >
                          <SelectTrigger>
                            <SelectValue />
                          </SelectTrigger>
                          <SelectContent>
                            <SelectItem value="JURY_MEMBER">
                              Jury Member
                            </SelectItem>
                            <SelectItem value="MENTOR">Mentor</SelectItem>
                            <SelectItem value="OBSERVER">Observer</SelectItem>
                          </SelectContent>
                        </Select>
                      </div>

                      {/* Per-member expertise tags */}
                      <div className="space-y-2">
                        <Label className="text-xs text-muted-foreground">
                          Expertise Tags (optional)
                        </Label>
                        <div className="relative">
                          <Input
                            placeholder="Type tag and press Enter or comma..."
                            value={row.tagInput}
                            onChange={(e) =>
                              updateRow(row.id, 'tagInput', e.target.value)
                            }
                            onKeyDown={(e) => {
                              if (e.key === 'Enter' || e.key === ',') {
                                e.preventDefault()
                                addTagToRow(row.id, row.tagInput)
                              }
                            }}
                          />
                        </div>

                        {/* Tag suggestions */}
                        {row.tagInput && getSuggestionsForRow(row).length > 0 && (
                          <div className="flex flex-wrap gap-1">
                            {getSuggestionsForRow(row).map((suggestion) => (
                              <Button
                                key={suggestion}
                                type="button"
                                variant="outline"
                                size="sm"
                                className="h-6 text-xs"
                                onClick={() => addTagToRow(row.id, suggestion)}
                              >
                                + {suggestion}
                              </Button>
                            ))}
                          </div>
                        )}

                        {/* Quick suggestions when empty */}
                        {!row.tagInput && row.expertiseTags.length === 0 && (
                          <div className="flex flex-wrap gap-1">
                            <span className="text-xs text-muted-foreground mr-1">
                              Suggestions:
                            </span>
                            {SUGGESTED_TAGS.slice(0, 5).map((suggestion) => (
                              <Button
                                key={suggestion}
                                type="button"
                                variant="ghost"
                                size="sm"
                                className="h-6 text-xs px-2"
                                onClick={() => addTagToRow(row.id, suggestion)}
                              >
                                + {suggestion}
                              </Button>
                            ))}
                          </div>
                        )}

                        {/* Added tags */}
                        {row.expertiseTags.length > 0 && (
                          <div className="flex flex-wrap gap-1.5">
                            {row.expertiseTags.map((tag) => (
                              <Badge
                                key={tag}
                                variant="secondary"
                                className="gap-1 pr-1"
                              >
                                {tag}
                                <button
                                  type="button"
                                  onClick={() => removeTagFromRow(row.id, tag)}
                                  className="ml-1 hover:text-destructive rounded-full"
                                >
                                  <X className="h-3 w-3" />
                                </button>
                              </Badge>
                            ))}
                          </div>
                        )}
                      </div>
                    </div>
                  ))}

                  <Button
                    type="button"
                    variant="outline"
                    size="sm"
                    onClick={addRow}
                    className="w-full"
                  >
                    <Plus className="mr-2 h-4 w-4" />
                    Add another member
                  </Button>
                </div>
              ) : (
                <div className="space-y-2">
                  <Label>CSV File</Label>
                  <p className="text-xs text-muted-foreground">
                    CSV should have columns: name, email, role (optional)
                  </p>
                  <div
                    className={cn(
                      'border-2 border-dashed rounded-lg p-6 text-center cursor-pointer transition-colors',
                      'hover:border-primary/50'
                    )}
                    onClick={() =>
                      document.getElementById('csv-input')?.click()
                    }
                  >
                    <FileSpreadsheet className="mx-auto h-10 w-10 text-muted-foreground" />
                    <p className="mt-2 font-medium">
                      Drop CSV file here or click to browse
                    </p>
                    <Input
                      id="csv-input"
                      type="file"
                      accept=".csv"
                      onChange={handleCSVUpload}
                      className="hidden"
                    />
                  </div>
                </div>
              )}

              {/* Actions */}
              <div className="flex justify-between pt-4">
                <Button variant="outline" asChild>
                  <Link href="/admin/members">
                    <ArrowLeft className="mr-2 h-4 w-4" />
                    Cancel
                  </Link>
                </Button>
                {inputMethod === 'manual' && (
                  <Button
                    onClick={handleManualProceed}
                    disabled={!hasManualData}
                  >
                    Preview
                    <ArrowRight className="ml-2 h-4 w-4" />
                  </Button>
                )}
              </div>
            </CardContent>
          </Card>
        )

      case 'preview':
        return (
          <Card>
            <CardHeader>
              <CardTitle>Preview Invitations</CardTitle>
              <CardDescription>
                Review the list of members to invite
              </CardDescription>
            </CardHeader>
            <CardContent className="space-y-6">
              <div className="grid gap-4 sm:grid-cols-3">
                <div className="rounded-lg bg-muted p-4 text-center">
                  <p className="text-3xl font-bold">{summary.total}</p>
                  <p className="text-sm text-muted-foreground">Total</p>
                </div>
                <div className="rounded-lg bg-green-500/10 p-4 text-center">
                  <p className="text-3xl font-bold text-green-600">
                    {summary.valid}
                  </p>
                  <p className="text-sm text-muted-foreground">Valid</p>
                </div>
                <div className="rounded-lg bg-red-500/10 p-4 text-center">
                  <p className="text-3xl font-bold text-red-600">
                    {summary.invalid}
                  </p>
                  <p className="text-sm text-muted-foreground">Invalid</p>
                </div>
              </div>

              {summary.invalid > 0 && (
                <div className="flex items-start gap-3 rounded-lg bg-amber-500/10 p-4 text-amber-700">
                  <AlertCircle className="h-5 w-5 shrink-0 mt-0.5" />
                  <div className="flex-1">
                    <p className="font-medium">
                      {summary.invalid} email(s) have issues
                    </p>
                  </div>
                  <Button
                    variant="outline"
                    size="sm"
                    onClick={removeInvalidUsers}
                    className="shrink-0"
                  >
                    Remove Invalid
                  </Button>
                </div>
              )}

              <div className="rounded-lg border max-h-80 overflow-y-auto">
                <Table>
                  <TableHeader>
                    <TableRow>
                      <TableHead>Name</TableHead>
                      <TableHead>Email</TableHead>
                      <TableHead>Role</TableHead>
                      <TableHead>Status</TableHead>
                    </TableRow>
                  </TableHeader>
                  <TableBody>
                    {parsedUsers.map((user, index) => (
                      <TableRow
                        key={index}
                        className={cn(!user.isValid && 'bg-red-500/5')}
                      >
                        <TableCell>{user.name || '-'}</TableCell>
                        <TableCell className="font-mono text-sm">
                          {user.email}
                        </TableCell>
                        <TableCell>
                          <Badge variant="outline">
                            {ROLE_LABELS[user.role]}
                          </Badge>
                        </TableCell>
                        <TableCell>
                          {user.isValid ? (
                            <Badge
                              variant="outline"
                              className="text-green-600"
                            >
                              <CheckCircle2 className="mr-1 h-3 w-3" />
                              Valid
                            </Badge>
                          ) : (
                            <Badge variant="destructive">{user.error}</Badge>
                          )}
                        </TableCell>
                      </TableRow>
                    ))}
                  </TableBody>
                </Table>
              </div>

              <div className="flex justify-between pt-4">
                <Button
                  variant="outline"
                  onClick={() => {
                    setParsedUsers([])
                    setStep('input')
                  }}
                >
                  <ArrowLeft className="mr-2 h-4 w-4" />
                  Back
                </Button>
                <Button
                  onClick={handleSendInvites}
                  disabled={summary.valid === 0 || bulkCreate.isPending}
                >
                  {bulkCreate.isPending ? (
                    <Loader2 className="mr-2 h-4 w-4 animate-spin" />
                  ) : (
                    <Users className="mr-2 h-4 w-4" />
                  )}
                  Create & Invite {summary.valid} Member
                  {summary.valid !== 1 ? 's' : ''}
                </Button>
              </div>

              {bulkCreate.error && (
                <div className="flex items-center gap-2 rounded-lg bg-destructive/10 p-4 text-destructive">
                  <AlertCircle className="h-5 w-5" />
                  <span>{bulkCreate.error.message}</span>
                </div>
              )}
            </CardContent>
          </Card>
        )

      case 'sending':
        return (
          <Card>
            <CardContent className="flex flex-col items-center justify-center py-12">
              <Loader2 className="h-12 w-12 animate-spin text-primary" />
              <p className="mt-4 font-medium">
                Creating members and sending invitations...
              </p>
              <Progress value={sendProgress} className="mt-4 w-48" />
            </CardContent>
          </Card>
        )

      case 'complete':
        return (
          <Card>
            <CardContent className="flex flex-col items-center justify-center py-12">
              <div className="flex h-16 w-16 items-center justify-center rounded-full bg-green-500/10">
                <CheckCircle2 className="h-8 w-8 text-green-600" />
              </div>
              <p className="mt-4 text-xl font-semibold">
                Invitations Sent!
              </p>
              <p className="text-muted-foreground text-center max-w-sm mt-2">
                {result?.created} member{result?.created !== 1 ? 's' : ''}{' '}
                created and invited.
                {result?.skipped
                  ? ` ${result.skipped} skipped (already exist).`
                  : ''}
              </p>
              <div className="mt-6 flex gap-3">
                <Button variant="outline" asChild>
                  <Link href="/admin/members">View Members</Link>
                </Button>
                <Button onClick={resetForm}>Invite More</Button>
              </div>
            </CardContent>
          </Card>
        )
    }
  }

  return (
    <div className="space-y-6">
      <div className="flex items-center gap-4">
        <Button variant="ghost" asChild className="-ml-4">
          <Link href="/admin/members">
            <ArrowLeft className="mr-2 h-4 w-4" />
            Back to Members
          </Link>
        </Button>
      </div>

      <div>
        <h1 className="text-2xl font-semibold tracking-tight">
          Invite Members
        </h1>
        <p className="text-muted-foreground">
          Add new members to the platform
        </p>
      </div>

      {/* Step indicator */}
      <div className="flex items-center justify-center gap-2">
        {steps.map((s, index) => (
          <div key={s.key} className="flex items-center">
            {index > 0 && (
              <div
                className={cn(
                  'h-0.5 w-8 mx-1',
                  index <= currentStepIndex ? 'bg-primary' : 'bg-muted'
                )}
              />
            )}
            <div
              className={cn(
                'flex h-8 w-8 items-center justify-center rounded-full text-sm font-medium',
                index === currentStepIndex
                  ? 'bg-primary text-primary-foreground'
                  : index < currentStepIndex
                    ? 'bg-primary/20 text-primary'
                    : 'bg-muted text-muted-foreground'
              )}
            >
              {index + 1}
            </div>
          </div>
        ))}
      </div>

      {renderStep()}
    </div>
  )
}