'use client'

import { useCallback, useEffect, useMemo, useState } from 'react'
import {
  defaultFoundingWizardState,
  type FoundingWizardState,
  type Gesellschafter,
  type GFContract,
  type GeneratedDocument,
} from '@/lib/sdk/founding/types'

const STORAGE_KEY = 'breakpilot:founding-wizard:state:v1'

export const FOUNDING_WIZARD_STEPS = [
  { id: 1, name: 'Stage & Basics', description: 'Unternehmensname, Sitz, Gegenstand' },
  { id: 2, name: 'Gesellschafter', description: 'Gründer und ihre Anteile' },
  { id: 3, name: 'Geschäftsführer', description: 'GF-Bestellung und Rollen' },
  { id: 4, name: 'Kapital', description: 'Stammkapital und Einzahlung' },
  { id: 5, name: 'Notar', description: 'Notartermin und Beurkundung' },
  { id: 6, name: 'SHA-Optionen', description: 'Vesting, Drag-Along, Reserved Matters' },
  { id: 7, name: 'GF-Verträge', description: 'Vergütung, D&O, Kündigungsfristen' },
  { id: 8, name: 'Dokumente generieren', description: 'Auswahl und Word-Export' },
]

export function useFoundingWizardForm() {
  const [state, setState] = useState<FoundingWizardState>(defaultFoundingWizardState())
  const [hydrated, setHydrated] = useState(false)
  const [generating, setGenerating] = useState(false)
  const [error, setError] = useState<string | null>(null)

  // Hydrate from localStorage
  useEffect(() => {
    try {
      const raw = localStorage.getItem(STORAGE_KEY)
      if (raw) {
        const parsed = JSON.parse(raw)
        setState({ ...defaultFoundingWizardState(), ...parsed })
      }
    } catch {
      // ignore corrupted storage
    }
    setHydrated(true)
  }, [])

  // Persist on every change after hydration
  useEffect(() => {
    if (!hydrated) return
    try {
      localStorage.setItem(STORAGE_KEY, JSON.stringify(state))
    } catch {
      // quota exceeded - ignore
    }
  }, [state, hydrated])

  const update = useCallback(<K extends keyof FoundingWizardState>(
    key: K,
    value: FoundingWizardState[K] | ((prev: FoundingWizardState[K]) => FoundingWizardState[K])
  ) => {
    setState(prev => ({
      ...prev,
      [key]: typeof value === 'function' ? (value as Function)(prev[key]) : value,
    }))
  }, [])

  const setStep = useCallback((step: number) => {
    setState(prev => ({ ...prev, current_step: step }))
  }, [])

  const nextStep = useCallback(() => {
    setState(prev => ({ ...prev, current_step: Math.min(prev.current_step + 1, FOUNDING_WIZARD_STEPS.length) }))
  }, [])

  const prevStep = useCallback(() => {
    setState(prev => ({ ...prev, current_step: Math.max(prev.current_step - 1, 1) }))
  }, [])

  const reset = useCallback(() => {
    setState(defaultFoundingWizardState())
    try { localStorage.removeItem(STORAGE_KEY) } catch {}
  }, [])

  // Gesellschafter helpers
  const addGesellschafter = useCallback((gs: Omit<Gesellschafter, 'id' | 'anteil_nr'>) => {
    setState(prev => {
      const nextNr = (prev.gesellschafter.reduce((m, g) => Math.max(m, g.anteil_nr), 0)) + 1
      const id = `gs_${Date.now()}_${nextNr}`
      return { ...prev, gesellschafter: [...prev.gesellschafter, { ...gs, id, anteil_nr: nextNr }] }
    })
  }, [])

  const updateGesellschafter = useCallback((id: string, patch: Partial<Gesellschafter>) => {
    setState(prev => ({
      ...prev,
      gesellschafter: prev.gesellschafter.map(g => g.id === id ? { ...g, ...patch } : g),
    }))
  }, [])

  const removeGesellschafter = useCallback((id: string) => {
    setState(prev => ({
      ...prev,
      gesellschafter: prev.gesellschafter.filter(g => g.id !== id),
      gf_contracts: prev.gf_contracts.filter(c => c.gesellschafter_id !== id),
    }))
  }, [])

  // GF Contract helpers
  const upsertGFContract = useCallback((contract: GFContract) => {
    setState(prev => {
      const idx = prev.gf_contracts.findIndex(c => c.gesellschafter_id === contract.gesellschafter_id)
      const next = [...prev.gf_contracts]
      if (idx >= 0) next[idx] = contract
      else next.push(contract)
      return { ...prev, gf_contracts: next }
    })
  }, [])

  // Validation (canProceed for current step)
  const canProceed = useMemo(() => {
    switch (state.current_step) {
      case 1:
        return state.basics.company_name.trim().length > 1 &&
               state.basics.company_seat.trim().length > 1 &&
               state.basics.company_purpose_description.trim().length > 10
      case 2: {
        if (state.gesellschafter.length < 1) return false
        const sum = state.gesellschafter.reduce((s, g) => s + (g.nennbetrag_eur || 0), 0)
        return sum === state.capital.stammkapital_eur
      }
      case 3:
        return state.gesellschafter.some(g => g.is_geschaeftsfuehrer)
      case 4:
        return state.capital.stammkapital_eur >= 25000
      case 5:
        return state.notar.notary_name.trim().length > 1 && state.notar.notary_place.trim().length > 1
      case 6:
        return true
      case 7:
        return state.gesellschafter.filter(g => g.is_geschaeftsfuehrer)
          .every(g => state.gf_contracts.some(c => c.gesellschafter_id === g.id))
      case 8:
        return state.selected_documents.length > 0
      default:
        return false
    }
  }, [state])

  const generateDocuments = useCallback(async (): Promise<GeneratedDocument[]> => {
    setGenerating(true)
    setError(null)
    try {
      const response = await fetch('/api/v1/founding-wizard/generate', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(state),
      })
      if (!response.ok) {
        throw new Error(`Generierung fehlgeschlagen: ${response.status}`)
      }
      const data = await response.json()
      const docs: GeneratedDocument[] = data.documents || []
      setState(prev => ({ ...prev, generated_documents: docs }))
      return docs
    } catch (e: unknown) {
      const msg = e instanceof Error ? e.message : 'Unbekannter Fehler'
      setError(msg)
      throw e
    } finally {
      setGenerating(false)
    }
  }, [state])

  // Derived: hat zugehöriger GF einen Vertrag?
  const gf_list = useMemo(
    () => state.gesellschafter.filter(g => g.is_geschaeftsfuehrer),
    [state.gesellschafter]
  )

  return {
    state, hydrated, generating, error,
    update, setStep, nextStep, prevStep, reset,
    addGesellschafter, updateGesellschafter, removeGesellschafter,
    upsertGFContract,
    canProceed, generateDocuments,
    gf_list,
    steps: FOUNDING_WIZARD_STEPS,
  }
}