import { useState, useEffect, useRef } from 'react'
import { useNavigate } from 'react-router-dom'
import {
  ArrowRight, User, Mail, Lock, Building2, Coffee,
  UtensilsCrossed, Beer, ShoppingBag, CheckCircle2, ChevronRight, Hash,
} from 'lucide-react'
import client from '../api/client'
import Button from '../ui/Button'
import { LabelledInput } from '../ui/Input'

// ─── Step indicator ───────────────────────────────────────────────────────────

function StepDots({ total, current }) {
  return (
    <div className="flex items-center gap-2">
      {Array.from({ length: total }).map((_, i) => (
        <div
          key={i}
          className={`rounded-full transition-all duration-300 ${
            i < current
              ? 'w-2 h-2 bg-sky-400'
              : i === current
              ? 'w-6 h-2 bg-sky-500'
              : 'w-2 h-2 bg-slate-200'
          }`}
        />
      ))}
    </div>
  )
}

// ─── Venue type selector (multi-select) ───────────────────────────────────────

const VENUE_TYPES = [
  { id: 'restaurant',  label: 'Restaurant',   Icon: UtensilsCrossed },
  { id: 'bar',         label: 'Bar',           Icon: Beer },
  { id: 'coffee_shop', label: 'Coffee Shop',   Icon: Coffee },
  { id: 'fast_food',   label: 'Fast Food',     Icon: ShoppingBag },
]

function VenueTypeButton({ type, selected, onToggle }) {
  const { label, Icon } = type
  return (
    <button
      type="button"
      onClick={() => onToggle(type.id)}
      className={`relative flex flex-col items-center gap-2 rounded-xl border-2 p-4 text-[13px] font-medium transition-all ${
        selected
          ? 'border-sky-500 bg-sky-50 text-sky-700'
          : 'border-slate-200 bg-white text-slate-600 hover:border-slate-300 hover:bg-slate-50'
      }`}
    >
      {selected && (
        <div className="absolute top-2 right-2 flex h-4 w-4 items-center justify-center rounded-full bg-sky-500">
          <CheckCircle2 className="h-3 w-3 text-white" />
        </div>
      )}
      <Icon className={`h-6 w-6 ${selected ? 'text-sky-500' : 'text-slate-400'}`} />
      {label}
    </button>
  )
}

// ─── PIN pad ──────────────────────────────────────────────────────────────────

const PIN_DIGITS = ['1','2','3','4','5','6','7','8','9','','0','⌫']

function PinPad({ pin, onChange }) {
  function press(d) {
    if (d === '⌫') { onChange(p => p.slice(0, -1)); return }
    if (d === '') return
    if (pin.length >= 6) return
    onChange(p => p + d)
  }
  return (
    <div className="space-y-3">
      <div className="flex justify-center gap-3 py-1">
        {Array.from({ length: 4 }).map((_, i) => (
          <div
            key={i}
            className={`w-3.5 h-3.5 rounded-full border-2 transition-colors ${
              i < pin.length ? 'bg-sky-500 border-sky-500' : 'border-slate-300'
            }`}
          />
        ))}
      </div>
      <div className="grid grid-cols-3 gap-2">
        {PIN_DIGITS.map((d, i) => (
          <button
            key={i}
            type="button"
            onClick={() => press(d)}
            disabled={d === ''}
            className={`h-12 rounded-xl text-lg font-semibold transition-colors ${
              d === ''
                ? 'invisible'
                : d === '⌫'
                ? 'bg-slate-100 hover:bg-slate-200 text-slate-600'
                : 'bg-slate-100 hover:bg-sky-100 active:bg-sky-200 text-slate-800'
            }`}
          >
            {d}
          </button>
        ))}
      </div>
    </div>
  )
}

// ─── Steps ───────────────────────────────────────────────────────────────────

function StepWelcome({ onNext }) {
  return (
    <div className="flex flex-col items-center text-center gap-6">
      <div className="flex h-20 w-20 items-center justify-center rounded-2xl bg-sky-500 shadow-lg shadow-sky-200">
        <UtensilsCrossed className="h-10 w-10 text-white" />
      </div>

      <div className="space-y-2">
        <h1 className="text-2xl font-bold text-slate-900">Welcome to Xenia POS</h1>
        <p className="text-slate-500 text-[14px] leading-relaxed max-w-xs">
          The complete point-of-sale system for your venue. Let's get you set up
          in just a few steps — it won't take long.
        </p>
      </div>

      <div className="w-full rounded-xl border border-slate-100 bg-slate-50 p-4 text-left space-y-2">
        {[
          'Create your manager account',
          'Tell us about your venue',
          'You\'re ready to go',
        ].map((s, i) => (
          <div key={i} className="flex items-center gap-3 text-[13px] text-slate-600">
            <div className="flex h-5 w-5 items-center justify-center rounded-full bg-sky-100 text-sky-600 text-[11px] font-semibold flex-shrink-0">
              {i + 1}
            </div>
            {s}
          </div>
        ))}
      </div>

      <Button variant="primary" className="w-full py-3 justify-center" onClick={onNext}>
        Get Started <ArrowRight className="h-4 w-4" />
      </Button>

      <p className="text-[11px] text-slate-400">Thank you for choosing Xenia POS.</p>
    </div>
  )
}

function StepAccount({ data, onChange, onNext, onBack }) {
  const [errors, setErrors] = useState({})
  // Live password match: debounce 1s after confirm changes
  const confirmTimer = useRef(null)

  function handleConfirmChange(value) {
    onChange('confirm', value)
    clearTimeout(confirmTimer.current)
    confirmTimer.current = setTimeout(() => {
      if (value && data.password && value !== data.password) {
        setErrors(e => ({ ...e, confirm: 'Passwords do not match' }))
      } else {
        setErrors(e => { const next = { ...e }; delete next.confirm; return next })
      }
    }, 1000)
  }

  // Also clear the error immediately if they now match
  function handlePasswordChange(value) {
    onChange('password', value)
    if (data.confirm && value === data.confirm) {
      setErrors(e => { const next = { ...e }; delete next.confirm; return next })
    }
  }

  function validate() {
    const e = {}
    if (!data.username.trim()) e.username = 'Username is required'
    if (!data.fullName.trim()) e.fullName = 'Full name is required'
    if (!data.email.trim()) e.email = 'Email is required'
    else if (!/\S+@\S+\.\S+/.test(data.email)) e.email = 'Enter a valid email'
    if (data.password.length < 6) e.password = 'At least 6 characters'
    if (data.password !== data.confirm) e.confirm = 'Passwords do not match'
    setErrors(e)
    return Object.keys(e).length === 0
  }

  return (
    <div className="flex flex-col gap-5">
      <div className="space-y-1">
        <h2 className="text-xl font-bold text-slate-900">Create your manager account</h2>
        <p className="text-[13px] text-slate-500">This will be the primary administrator account.</p>
      </div>

      <div className="space-y-3">
        <div>
          <LabelledInput
            icon={User}
            placeholder="Username"
            value={data.username}
            onChange={e => onChange('username', e.target.value)}
            autoComplete="off"
            autoFocus
          />
          {errors.username && <p className="mt-1 text-[12px] text-rose-500">{errors.username}</p>}
        </div>

        <div>
          <LabelledInput
            icon={User}
            placeholder="Full Name"
            value={data.fullName}
            onChange={e => onChange('fullName', e.target.value)}
            autoComplete="off"
          />
          {errors.fullName && <p className="mt-1 text-[12px] text-rose-500">{errors.fullName}</p>}
        </div>

        <div>
          <LabelledInput
            icon={Mail}
            placeholder="Email address"
            value={data.email}
            onChange={e => onChange('email', e.target.value)}
            type="email"
            autoComplete="off"
          />
          {errors.email && <p className="mt-1 text-[12px] text-rose-500">{errors.email}</p>}
        </div>

        <div>
          <LabelledInput
            icon={Lock}
            placeholder="Password"
            value={data.password}
            onChange={e => handlePasswordChange(e.target.value)}
            type="password"
            autoComplete="new-password"
          />
          {errors.password && <p className="mt-1 text-[12px] text-rose-500">{errors.password}</p>}
        </div>

        <div>
          <LabelledInput
            icon={Lock}
            placeholder="Confirm Password"
            value={data.confirm}
            onChange={e => handleConfirmChange(e.target.value)}
            type="password"
            autoComplete="new-password"
          />
          {errors.confirm && <p className="mt-1 text-[12px] text-rose-500">{errors.confirm}</p>}
        </div>
      </div>

      <div className="flex gap-3">
        <Button variant="ghost" className="flex-1 justify-center py-3" onClick={onBack}>
          Back
        </Button>
        <Button variant="primary" className="flex-1 justify-center py-3" onClick={() => { if (validate()) onNext() }}>
          Continue <ChevronRight className="h-4 w-4" />
        </Button>
      </div>
    </div>
  )
}

function StepVenue({ data, onChange, onNext, onBack }) {
  const [errors, setErrors] = useState({})

  function toggleType(id) {
    const current = data.venueTypes
    const next = current.includes(id)
      ? current.filter(v => v !== id)
      : [...current, id]
    onChange('venueTypes', next)
  }

  function validate() {
    const e = {}
    if (data.venueTypes.length === 0) e.venueType = 'Please select at least one type'
    if (!data.venueName.trim()) e.venueName = 'Venue name is required'
    setErrors(e)
    return Object.keys(e).length === 0
  }

  return (
    <div className="flex flex-col gap-5">
      <div className="space-y-1">
        <h2 className="text-xl font-bold text-slate-900">Tell us about your venue</h2>
        <p className="text-[13px] text-slate-500">Select all that apply — you can always change this later.</p>
      </div>

      <div className="space-y-4">
        <div>
          <p className="text-[12px] font-medium text-slate-500 uppercase tracking-wider mb-2">Venue type</p>
          <div className="grid grid-cols-2 gap-2">
            {VENUE_TYPES.map(type => (
              <VenueTypeButton
                key={type.id}
                type={type}
                selected={data.venueTypes.includes(type.id)}
                onToggle={toggleType}
              />
            ))}
          </div>
          {errors.venueType && <p className="mt-1 text-[12px] text-rose-500">{errors.venueType}</p>}
        </div>

        <div>
          <p className="text-[12px] font-medium text-slate-500 uppercase tracking-wider mb-2">Venue name</p>
          <LabelledInput
            icon={Building2}
            placeholder="e.g. The Golden Fork"
            value={data.venueName}
            onChange={e => onChange('venueName', e.target.value)}
            autoComplete="off"
          />
          {errors.venueName && <p className="mt-1 text-[12px] text-rose-500">{errors.venueName}</p>}
        </div>
      </div>

      <div className="flex gap-3">
        <Button variant="ghost" className="flex-1 justify-center py-3" onClick={onBack}>
          Back
        </Button>
        <Button variant="primary" className="flex-1 justify-center py-3" onClick={() => { if (validate()) onNext() }}>
          Continue <ChevronRight className="h-4 w-4" />
        </Button>
      </div>
    </div>
  )
}

function StepPin({ pin, onChange, onNext, onBack }) {
  const hasPin = pin.length >= 4

  return (
    <div className="flex flex-col gap-5">
      <div className="space-y-1">
        <h2 className="text-xl font-bold text-slate-900">Set a quick-access PIN</h2>
        <p className="text-[13px] text-slate-500">
          Optional. Used to unlock the dashboard quickly when it's locked,
          without typing your full password.
        </p>
      </div>

      <div className="rounded-xl border border-slate-100 bg-slate-50 p-5">
        <PinPad pin={pin} onChange={onChange} />
      </div>

      {hasPin && (
        <p className="text-center text-[12px] text-emerald-600 font-medium">
          PIN set — {pin.length} digits
        </p>
      )}

      <div className="flex gap-3">
        <Button variant="ghost" className="flex-1 justify-center py-3" onClick={onBack}>
          Back
        </Button>
        <Button
          variant={hasPin ? 'primary' : 'secondary'}
          className="flex-1 justify-center py-3"
          onClick={onNext}
        >
          {hasPin ? <>Continue <ChevronRight className="h-4 w-4" /></> : 'Skip for now'}
        </Button>
      </div>
    </div>
  )
}

function StepDone({ onGoToLogin, loading, error }) {
  return (
    <div className="flex flex-col items-center text-center gap-6">
      <div className="flex h-20 w-20 items-center justify-center rounded-2xl bg-emerald-500 shadow-lg shadow-emerald-200">
        <CheckCircle2 className="h-10 w-10 text-white" />
      </div>

      <div className="space-y-2">
        <h2 className="text-2xl font-bold text-slate-900">You're all set!</h2>
        <p className="text-[14px] text-slate-500 leading-relaxed max-w-xs">
          Your manager account is ready. Log in and start configuring your
          products, tables, and staff.
        </p>
      </div>

      <div className="w-full rounded-xl border border-emerald-100 bg-emerald-50 p-4 text-left space-y-2">
        {['Add your menu and products', 'Set up tables and zones', 'Add your waiters'].map((tip, i) => (
          <div key={i} className="flex items-center gap-3 text-[13px] text-slate-600">
            <ChevronRight className="h-4 w-4 text-emerald-500 flex-shrink-0" />
            {tip}
          </div>
        ))}
      </div>

      {error && <p className="text-[13px] text-rose-500">{error}</p>}

      <Button
        variant="primary"
        className="w-full py-3 justify-center"
        onClick={onGoToLogin}
        disabled={loading}
      >
        {loading ? 'Setting up…' : 'Go to Login'}
        {!loading && <ArrowRight className="h-4 w-4" />}
      </Button>
    </div>
  )
}

// ─── Main wizard ──────────────────────────────────────────────────────────────

// Steps: 0=welcome, 1=account, 2=venue, 3=pin, 4=done
const INNER_STEPS = 3  // steps 1-3 show the dot indicator

export default function SetupWizard() {
  const navigate = useNavigate()
  const [step, setStep] = useState(0)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState('')

  const [account, setAccount] = useState({
    username: '', fullName: '', email: '', password: '', confirm: '',
  })
  const [venue, setVenue] = useState({ venueTypes: [], venueName: '' })
  const [pin, setPin] = useState('')

  function updateAccount(key, value) {
    setAccount(prev => ({ ...prev, [key]: value }))
  }
  function updateVenue(key, value) {
    setVenue(prev => ({ ...prev, [key]: value }))
  }

  async function handleFinish() {
    setLoading(true)
    setError('')
    try {
      await client.post('/api/setup/init', {
        username: account.username.trim(),
        password: account.password,
        email: account.email.trim(),
        full_name: account.fullName.trim(),
        venue_type: venue.venueTypes.join(','),
        venue_name: venue.venueName.trim(),
        pin: pin.length >= 4 ? pin : undefined,
      })
      navigate('/login', { replace: true })
    } catch (err) {
      setError(err.response?.data?.detail || 'Something went wrong. Please try again.')
      setLoading(false)
    }
  }

  return (
    <div className="min-h-screen bg-gradient-to-br from-slate-50 to-sky-50 flex items-center justify-center p-4">
      <div className="w-full max-w-md">
        <div className="bg-white rounded-2xl shadow-xl shadow-slate-200/60 border border-slate-100 p-8">
          {/* Dot indicator for inner steps only */}
          {step >= 1 && step <= INNER_STEPS && (
            <div className="flex justify-center mb-6">
              <StepDots total={INNER_STEPS} current={step - 1} />
            </div>
          )}

          {step === 0 && <StepWelcome onNext={() => setStep(1)} />}

          {step === 1 && (
            <StepAccount
              data={account}
              onChange={updateAccount}
              onNext={() => setStep(2)}
              onBack={() => setStep(0)}
            />
          )}

          {step === 2 && (
            <StepVenue
              data={venue}
              onChange={updateVenue}
              onNext={() => setStep(3)}
              onBack={() => setStep(1)}
            />
          )}

          {step === 3 && (
            <StepPin
              pin={pin}
              onChange={setPin}
              onNext={() => setStep(4)}
              onBack={() => setStep(2)}
            />
          )}

          {step === 4 && (
            <StepDone
              onGoToLogin={handleFinish}
              loading={loading}
              error={error}
            />
          )}
        </div>

        <p className="text-center text-[11px] text-slate-400 mt-4">
          Xenia POS · First-time Setup
        </p>
      </div>
    </div>
  )
}