'use client'

import { useState, useEffect, Suspense } from 'react'
import { useRouter, useSearchParams } from 'next/navigation'
import { createClient } from '@/lib/supabase/client'
import { Progress } from '@/components/ui/progress'
import { useToast } from '@/components/ui/use-toast'
import { Loader2 } from 'lucide-react'
import { validatePeriodDuration } from '@/lib/bookkeeping/validate-period-duration'
import type { CompanySettings, EntityType, MomsPeriod } from '@/types'

import Step1EntityType from '@/components/onboarding/Step1EntityType'
import Step2CompanyDetails from '@/components/onboarding/Step2CompanyDetails'
import Step3TaxRegistration from '@/components/onboarding/Step3TaxRegistration'
import Step4PreliminaryTax from '@/components/onboarding/Step4PreliminaryTax'
import Step5ConnectBank from '@/components/onboarding/Step6ConnectBank'

const STEP_TITLES = [
  'Verksamhetsform',
  'Företagsuppgifter',
  'Skatteregistrering',
  'F-skatt',
  'Anslut bank',
]

function translatePeriodError(msg: string): string {
  if (msg.includes('end must be after')) return 'Slutdatumet måste vara efter startdatumet.'
  if (msg.includes('start must be the 1st')) return 'Startdatumet måste vara den 1:a i en månad.'
  if (msg.includes('end must be the last day')) return 'Slutdatumet måste vara sista dagen i en månad.'
  if (msg.includes('exceeds maximum 18 months')) return 'Räkenskapsåret får inte överstiga 18 månader (BFL 3 kap.).'
  return 'Ogiltigt räkenskapsår. Kontrollera datumen och försök igen.'
}

export default function OnboardingPage() {
  return (
    <Suspense fallback={<div className="flex items-center justify-center h-64"><Loader2 className="h-8 w-8 animate-spin text-primary" /></div>}>
      <OnboardingPageContent />
    </Suspense>
  )
}

function OnboardingPageContent() {
  const router = useRouter()
  const searchParams = useSearchParams()
  const { toast } = useToast()
  const supabase = createClient()

  const [isLoading, setIsLoading] = useState(true)
  const [isSaving, setIsSaving] = useState(false)
  const [currentStep, setCurrentStep] = useState(1)
  const [settings, setSettings] = useState<Partial<CompanySettings>>({})

  const totalSteps = 5
  const stepTitles = STEP_TITLES

  // Load existing settings on mount
  useEffect(() => {
    async function loadSettings() {
      const { data: { user } } = await supabase.auth.getUser()

      if (!user) {
        router.push('/login')
        return
      }

      const { data, error } = await supabase
        .from('company_settings')
        .select('*')
        .eq('user_id', user.id)
        .single()

      if (data) {
        setSettings(data)
        const step = data.onboarding_step || 1
        // Clamp to max steps (handles existing users mid-onboarding from old 7-step flow)
        setCurrentStep(step > totalSteps ? totalSteps : step)
      }

      setIsLoading(false)
    }

    loadSettings()
  }, [supabase, router, toast])

  // Handle bank_connected callback from PSD2 flow
  useEffect(() => {
    if (searchParams.get('bank_connected') === 'true') {
      toast({
        title: 'Bank ansluten!',
        description: 'Din bank har kopplats.',
      })
      // Complete onboarding after bank connection
      saveSettings({ onboarding_complete: true }, totalSteps).then((success) => {
        if (success) {
          toast({
            title: 'Välkommen!',
            description: 'Din profil är nu redo.',
          })
          router.push('/')
        }
      })
    }
  }, [searchParams])

  const saveSettings = async (updates: Partial<CompanySettings>, nextStep?: number) => {
    setIsSaving(true)

    const { data: { user } } = await supabase.auth.getUser()

    if (!user) {
      router.push('/login')
      return false
    }

    const updatedSettings = {
      ...settings,
      ...updates,
      onboarding_step: nextStep || currentStep,
    }

    // Remove read-only and transient fields before updating
    const {
      id: _id, user_id: _uid, created_at: _ca, updated_at: _ua,
      is_first_fiscal_year: _ify, first_year_start: _fys, first_year_end: _fye,
      ...settingsToSave
    } = updatedSettings as Record<string, unknown>

    const { error } = await supabase
      .from('company_settings')
      .upsert({ ...settingsToSave, user_id: user.id }, { onConflict: 'user_id' })

    if (error) {
      console.error('Error saving settings:', JSON.stringify(error), 'code:', error.code, 'message:', error.message, 'details:', error.details)
      console.error('Payload was:', JSON.stringify({ ...settingsToSave, user_id: user.id }))
      toast({
        title: 'Fel',
        description: error.message || 'Kunde inte spara. Försök igen.',
        variant: 'destructive',
      })
      setIsSaving(false)
      return false
    }

    setSettings(updatedSettings)
    setIsSaving(false)
    return true
  }

  const handleNext = async (stepData: Partial<CompanySettings>) => {
    // Fix org number bug: clear dependent fields when entity type changes
    if (currentStep === 1 && stepData.entity_type && stepData.entity_type !== settings.entity_type) {
      stepData = { ...stepData, org_number: '', company_name: '' }
    }

    const nextStep = currentStep + 1
    const success = await saveSettings(stepData, nextStep)

    if (success) {
      // After step 1 (entity type selection): seed chart of accounts
      if (currentStep === 1 && stepData.entity_type) {
        try {
          const { data: { user } } = await supabase.auth.getUser()
          if (user) {
            await supabase.rpc('seed_chart_of_accounts', {
              p_user_id: user.id,
              p_entity_type: stepData.entity_type,
            })
          }
        } catch (err) {
          console.error('Failed to seed chart of accounts:', err)
        }
      }

      // After step 3 (tax registration): create initial fiscal period
      if (currentStep === 3) {
        try {
          const { data: { user } } = await supabase.auth.getUser()
          if (user) {
            const isFirstYear = stepData.is_first_fiscal_year as boolean | undefined
            const firstYearStart = stepData.first_year_start as string | undefined
            const firstYearEnd = stepData.first_year_end as string | undefined

            let startStr: string
            let endStr: string
            let periodName: string

            if (isFirstYear && firstYearStart && firstYearEnd) {
              // First fiscal year: use exact dates provided
              startStr = firstYearStart
              endStr = firstYearEnd

              const startYear = new Date(firstYearStart).getFullYear()
              const endYear = new Date(firstYearEnd).getFullYear()
              periodName = startYear === endYear
                ? `Första räkenskapsåret ${startYear}`
                : `Första räkenskapsåret ${startYear}/${endYear}`
            } else {
              // Ongoing: compute 12-month period from fiscal_year_start_month
              let startMonth = stepData.fiscal_year_start_month || settings.fiscal_year_start_month || 1

              // For enskild firma: force calendar year
              if (settings.entity_type === 'enskild_firma') {
                startMonth = 1
              }

              const currentYear = new Date().getFullYear()
              startStr = `${currentYear}-${String(startMonth).padStart(2, '0')}-01`

              let endYear: number
              let endMonth: number
              if (startMonth === 1) {
                endYear = currentYear
                endMonth = 12
              } else {
                endYear = currentYear + 1
                endMonth = startMonth - 1
              }
              const lastDay = new Date(endYear, endMonth, 0).getDate()
              endStr = `${endYear}-${String(endMonth).padStart(2, '0')}-${String(lastDay).padStart(2, '0')}`

              periodName = startMonth === 1
                ? `Räkenskapsår ${currentYear}`
                : `Räkenskapsår ${currentYear}/${currentYear + 1}`
            }

            // Validate period duration
            const validationError = validatePeriodDuration(startStr, endStr)
            if (validationError) {
              toast({
                title: 'Ogiltigt räkenskapsår',
                description: translatePeriodError(validationError),
                variant: 'destructive',
              })
              setCurrentStep(3)
              return
            }

            // Delete any existing fiscal periods that have no journal entries,
            // so re-running onboarding with different dates doesn't create
            // overlapping periods (DB exclusion constraint would reject it).
            const { data: existingPeriods } = await supabase
              .from('fiscal_periods')
              .select('id')
              .eq('user_id', user.id)

            if (existingPeriods && existingPeriods.length > 0) {
              for (const ep of existingPeriods) {
                const { count } = await supabase
                  .from('journal_entries')
                  .select('id', { count: 'exact', head: true })
                  .eq('fiscal_period_id', ep.id)

                if (count === 0) {
                  await supabase
                    .from('fiscal_periods')
                    .delete()
                    .eq('id', ep.id)
                }
              }
            }

            await supabase.from('fiscal_periods').upsert({
              user_id: user.id,
              name: periodName,
              period_start: startStr,
              period_end: endStr,
            }, {
              onConflict: 'user_id,period_start,period_end',
            })
          }
        } catch (err) {
          toast({
            title: 'Kunde inte skapa räkenskapsår',
            description: 'Ett fel uppstod när räkenskapsåret skulle skapas. Försök igen.',
            variant: 'destructive',
          })
        }
      }

      if (nextStep > totalSteps) {
        await saveSettings({ onboarding_complete: true }, totalSteps)
        toast({
          title: 'Välkommen!',
          description: 'Din profil är nu redo.',
        })
        router.push('/')
      } else {
        setCurrentStep(nextStep)
      }
    }
  }

  const handleBack = () => {
    if (currentStep > 1) {
      setCurrentStep(currentStep - 1)
    }
  }

  const handleSkip = async () => {
    const nextStep = currentStep + 1
    const success = await saveSettings({}, nextStep)

    if (success) {
      setCurrentStep(nextStep)
    }
  }

  if (isLoading) {
    return (
      <div className="min-h-screen flex items-center justify-center">
        <Loader2 className="h-8 w-8 animate-spin text-primary" />
      </div>
    )
  }

  const progressPercent = ((currentStep - 1) / (totalSteps - 1)) * 100

  const renderSteps = () => (
    <>
      {currentStep === 1 && (
        <Step1EntityType
          initialData={{ entity_type: settings.entity_type as EntityType }}
          onNext={(data) => handleNext(data)}
          isSaving={isSaving}
        />
      )}

      {currentStep === 2 && (
        <Step2CompanyDetails
          key={settings.entity_type}
          initialData={{
            company_name: settings.company_name ?? undefined,
            org_number: settings.org_number ?? undefined,
            address_line1: settings.address_line1 ?? undefined,
            postal_code: settings.postal_code ?? undefined,
            city: settings.city ?? undefined,
          }}
          entityType={settings.entity_type as EntityType}
          onNext={(data) => handleNext(data)}
          onBack={handleBack}
          isSaving={isSaving}
        />
      )}

      {currentStep === 3 && (
        <Step3TaxRegistration
          initialData={{
            f_skatt: settings.f_skatt ?? undefined,
            fiscal_year_start_month: settings.fiscal_year_start_month ?? undefined,
            vat_registered: settings.vat_registered ?? undefined,
            vat_number: settings.vat_number ?? undefined,
            moms_period: settings.moms_period as MomsPeriod | undefined,
            accounting_method: (settings.accounting_method as 'accrual' | 'cash') ?? undefined,
          }}
          entityType={settings.entity_type as EntityType}
          orgNumber={settings.org_number ?? undefined}
          onNext={(data) => handleNext(data)}
          onBack={handleBack}
          isSaving={isSaving}
        />
      )}

      {currentStep === 4 && (
        <Step4PreliminaryTax
          initialData={{
            preliminary_tax_monthly: settings.preliminary_tax_monthly ?? undefined,
          }}
          onNext={(data) => handleNext(data)}
          onBack={handleBack}
          onSkip={handleSkip}
          isSaving={isSaving}
        />
      )}

      {currentStep === 5 && (
        <Step5ConnectBank
          initialData={{
            bank_name: settings.bank_name ?? undefined,
            clearing_number: settings.clearing_number ?? undefined,
            account_number: settings.account_number ?? undefined,
            iban: settings.iban ?? undefined,
            bic: settings.bic ?? undefined,
          }}
          onComplete={async (data) => {
            if (data) {
              await saveSettings(data, totalSteps)
            }
            await saveSettings({ onboarding_complete: true }, totalSteps)
            toast({
              title: 'Välkommen!',
              description: 'Din profil är nu redo.',
            })
            router.push('/')
          }}
          onBack={handleBack}
          onSkip={async () => {
            await saveSettings({ onboarding_complete: true }, totalSteps)
            toast({
              title: 'Välkommen!',
              description: 'Din profil är nu redo.',
            })
            router.push('/')
          }}
          isSaving={isSaving}
        />
      )}
    </>
  )

  return (
    <div className="min-h-screen bg-gradient-to-br from-primary/5 via-background to-primary/10">
      {/* Header */}
      <div className="sticky top-0 z-10 bg-background/80 backdrop-blur-sm border-b">
        <div className="max-w-2xl mx-auto px-4 py-4">
          <div className="flex items-center justify-between mb-2">
            <span className="text-sm font-medium text-muted-foreground">
              Steg {currentStep} av {totalSteps}
            </span>
            <span className="text-sm font-medium">
              {stepTitles[currentStep - 1]}
            </span>
          </div>
          <Progress value={progressPercent} className="h-2" />
        </div>
      </div>

      {/* Content */}
      <div className="max-w-2xl mx-auto px-4 py-8">
        {renderSteps()}
      </div>
    </div>
  )
}