'use client'

import { useState, useEffect, useMemo } from 'react'
import { useRouter } from 'next/navigation'
import { useTranslations } from 'next-intl'
import {
  Dialog,
  DialogContent,
  DialogHeader,
  DialogTitle,
  DialogFooter,
} from '@/components/ui/dialog'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'
import AccountCombobox from '@/components/bookkeeping/AccountCombobox'
import { AddAccountDialog } from '@/components/bookkeeping/AddAccountDialog'
import CorrectionPreview from '@/components/bookkeeping/CorrectionPreview'
import {
  autoCorrectionDescription,
  correctionDescriptionForSubmit,
} from '@/components/bookkeeping/correction-entry-description'
import { nextLineDescriptionForAccountChange } from '@/components/bookkeeping/correction-line-description'
import { useToast } from '@/components/ui/use-toast'
import { getErrorMessage } from '@/lib/errors/get-error-message'
import { Loader2, Plus, Trash2 } from 'lucide-react'
import { formatDate } from '@/lib/utils'
import { formatVoucher } from '@/lib/bookkeeping/voucher-series-resolver'
import {
  changeCorrectionLineAccount,
  getSelectableCorrectionCatalog,
} from '@/lib/bookkeeping/correction-line-account'
import { splitCreateAccountPrefill } from '@/lib/bookkeeping/create-account-prefill'
import { loadBasCatalog, type CatalogAccount } from '@/lib/bookkeeping/bas-catalog-client'
import type { JournalEntry, JournalEntryLine, BASAccount } from '@/types'

interface CorrectionLine {
  account_number: string
  debit_amount: string
  credit_amount: string
  line_description: string
}

interface Props {
  entry: JournalEntry
  open: boolean
  onOpenChange: (open: boolean) => void
  onCorrected: () => void
}

export default function CorrectionEntryDialog({ entry, open, onOpenChange, onCorrected }: Props) {
  const { toast } = useToast()
  const router = useRouter()
  const t = useTranslations('journal_detail')
  const [accounts, setAccounts] = useState<BASAccount[]>([])
  const [catalog, setCatalog] = useState<CatalogAccount[]>([])
  const [accountsStatus, setAccountsStatus] = useState<'loading' | 'ready' | 'error'>('loading')
  const [lines, setLines] = useState<CorrectionLine[]>([])
  const [description, setDescription] = useState('')
  const [isSubmitting, setIsSubmitting] = useState(false)
  // Index of the line whose combobox opened the create dialog, and the search
  // string it was showing. Null index = the dialog is closed.
  const [creatingAccountForLine, setCreatingAccountForLine] = useState<number | null>(null)
  const [createAccountPrefill, setCreateAccountPrefill] = useState('')

  const activeAccounts = useMemo(
    () => accounts.filter((account) => account.is_active),
    [accounts],
  )
  const selectableCatalog = useMemo(
    () => getSelectableCorrectionCatalog(accounts, catalog),
    [accounts, catalog],
  )
  const accountNameSources = useMemo(
    () => [...accounts, ...catalog],
    [accounts, catalog],
  )

  const originalLines = ((entry.lines || []) as JournalEntryLine[])
    .slice()
    .sort((a, b) => a.sort_order - b.sort_order)

  useEffect(() => {
    if (open) {
      // Pre-fill with original entry's lines
      setLines(
        originalLines.map((l) => ({
          account_number: l.account_number,
          debit_amount: Number(l.debit_amount) > 0 ? String(Number(l.debit_amount)) : '',
          credit_amount: Number(l.credit_amount) > 0 ? String(Number(l.credit_amount)) : '',
          line_description: l.line_description || '',
        }))
      )
      // Pre-fill the verifikationstext with the same auto text the server
      // would generate; only a user edit is sent along (see handleSubmit).
      setDescription(autoCorrectionDescription(entry.description))
      void fetchAccounts()
    }
  }, [open, entry.id]) // eslint-disable-line react-hooks/exhaustive-deps

  async function fetchAccounts() {
    setAccountsStatus('loading')
    try {
      const [res, basCatalog] = await Promise.all([
        fetch('/api/bookkeeping/accounts?active=false'),
        loadBasCatalog(),
      ])
      if (!res.ok) throw new Error(`accounts ${res.status}`)
      const { data } = await res.json()
      setAccounts(data || [])
      setCatalog(basCatalog)
      setAccountsStatus('ready')
    } catch {
      setAccounts([])
      setCatalog([])
      setAccountsStatus('error')
    }
  }

  const updateLine = (index: number, field: keyof CorrectionLine, value: string) => {
    setLines((prev) =>
      prev.map((l, i) => {
        if (i !== index) return l
        const next = { ...l, [field]: value }
        // When the account changes, refresh the auto-filled description to the
        // new account's name. Without this, a description carried over from the
        // original entry (e.g. 2393 "Lån från närstående personer, långfristig
        // del") stays stale on the newly chosen account (e.g. 2893, kortfristig).
        if (field === 'account_number' && value) {
          next.line_description = nextLineDescriptionForAccountChange(
            l.line_description,
            l.account_number,
            value,
            accounts,
          )
        }
        return next
      })
    )
  }

  const updateLineAccount = (index: number, accountNumber: string) => {
    setLines((prev) => prev.map((line, lineIndex) => (
      lineIndex === index
        ? changeCorrectionLineAccount(line, accountNumber, accountNameSources)
        : line
    )))
  }

  const addLine = () => {
    setLines((prev) => [...prev, { account_number: '', debit_amount: '', credit_amount: '', line_description: '' }])
  }

  const removeLine = (index: number) => {
    setLines((prev) => prev.filter((_, i) => i !== index))
  }

  const closeCreateAccount = () => {
    setCreatingAccountForLine(null)
    setCreateAccountPrefill('')
  }

  // A number that is neither in the company chart nor in BAS 2026 (a retired
  // account such as 8022, or a company-specific underkonto) would otherwise be
  // a dead end here: the rättelse can only post to accounts that exist in the
  // chart. Creating it inline keeps the half-finished rättelse intact.
  const handleAccountCreated = async (account: { account_number: string; account_name?: string }) => {
    await fetchAccounts()
    if (creatingAccountForLine != null) {
      // fetchAccounts' state update is not visible in this closure, so the
      // fresh account's own name is passed alongside the stale sources. The
      // reactivate path reports no name, but that account is already in
      // `accounts` (the fetch includes deactivated rows).
      const created = account.account_name
        ? [{ account_number: account.account_number, account_name: account.account_name }]
        : []
      setLines((prev) => prev.map((line, index) => (
        index === creatingAccountForLine
          ? changeCorrectionLineAccount(line, account.account_number, [...accountNameSources, ...created])
          : line
      )))
    }
    closeCreateAccount()
  }

  const totalDebit = lines.reduce((sum, l) => sum + (parseFloat(l.debit_amount) || 0), 0)
  const totalCredit = lines.reduce((sum, l) => sum + (parseFloat(l.credit_amount) || 0), 0)
  const roundedDebit = Math.round(totalDebit * 100) / 100
  const roundedCredit = Math.round(totalCredit * 100) / 100
  const isBalanced = roundedDebit === roundedCredit && roundedDebit > 0

  const hasValidLines = lines.length >= 2 && lines.every((l) => l.account_number.length === 4)

  async function handleSubmit() {
    if (!isBalanced || !hasValidLines) return

    setIsSubmitting(true)
    try {
      const apiLines = lines.map((l) => ({
        account_number: l.account_number,
        debit_amount: parseFloat(l.debit_amount) || 0,
        credit_amount: parseFloat(l.credit_amount) || 0,
        line_description: l.line_description || undefined,
      }))

      const res = await fetch(`/api/bookkeeping/journal-entries/${entry.id}/correct`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          lines: apiLines,
          // Only sent when the user changed the auto prefill: the server
          // fallback ("Rättelse: <original>") stays the source of truth.
          description: correctionDescriptionForSubmit(description, entry.description),
        }),
      })

      const result = await res.json()

      if (!res.ok) {
        const error = new Error('Failed to create correction') as Error & { body?: unknown; status?: number }
        error.body = result
        error.status = res.status
        throw error
      }

      const correctedId = result.data?.corrected?.id

      toast({
        title: 'Ändringsverifikation skapad',
        description: 'Storno och rättelse har bokförts.',
        action: correctedId ? (
          <Button variant="outline" size="sm" onClick={() => router.push(`/bookkeeping/${correctedId}`)}>
            Visa rättelsen
          </Button>
        ) : undefined,
      })
      onOpenChange(false)
      onCorrected()
    } catch (err) {
      const anyErr = err as { body?: unknown; status?: number }
      toast({
        title: 'Kunde inte spara ändringsverifikation',
        description: getErrorMessage(anyErr.body ?? err, { context: 'journal_entry', statusCode: anyErr.status }),
        variant: 'destructive',
      })
    } finally {
      setIsSubmitting(false)
    }
  }

  return (
    <Dialog open={open} onOpenChange={onOpenChange}>
      <DialogContent className="sm:max-w-3xl max-h-[95dvh] sm:max-h-[90vh] overflow-y-auto">
        <DialogHeader>
          <DialogTitle>Skapa ändringsverifikation</DialogTitle>
        </DialogHeader>

        {/* Storno explanation */}
        <div className="rounded-lg bg-muted/50 border p-3 text-sm text-muted-foreground">
          <p className="font-medium text-foreground mb-1">Hur fungerar en ändringsverifikation?</p>
          <p>En bokförd verifikation kan inte ändras direkt. Istället skapas automatiskt:</p>
          <ol className="list-decimal list-inside mt-1 space-y-0.5">
            <li>En <strong>stornoverifikation</strong> som nollställer den ursprungliga</li>
            <li>En ny verifikation med dina rättade uppgifter</li>
          </ol>
          <p className="mt-2">
            Rättelsen bokförs i samma räkenskapsperiod som originalet: du hittar den under originalets räkenskapsår.
          </p>
        </div>

        {/* Original entry metadata: lines live inside CorrectionPreview below */}
        <div className="space-y-1">
          <div className="flex items-center gap-2 text-sm text-muted-foreground flex-wrap">
            <span className="text-muted-foreground">Original</span>
            <span className="font-mono">{formatVoucher(entry)}</span>
            <span className="tabular-nums">{formatDate(entry.entry_date)}</span>
          </div>
          <p className="text-sm">{entry.description}</p>
        </div>

        {/* Live diff: original | storno | correction | förändring */}
        <CorrectionPreview originalLines={originalLines} correctedLines={lines} />

        {/* Verifikationstext for the new (corrected) entry. Pre-filled with
            the auto text; editable so a header named after the wrong account
            is not echoed on the correction (issue #1031). */}
        <div className="space-y-1">
          <Label htmlFor="correction-description">Verifikationstext</Label>
          <Input
            id="correction-description"
            value={description}
            onChange={(e) => setDescription(e.target.value)}
            placeholder={autoCorrectionDescription(entry.description)}
          />
          <p className="text-xs text-muted-foreground">
            Texten på den nya verifikationen. Ändra den om originalets beskrivning inte längre
            stämmer, till exempel när rättelsen byter konto.
          </p>
        </div>

        {/* Corrected lines (editable) */}
        <div className="space-y-2">
          <div className="space-y-1">
            <p className="text-sm font-medium">Rättade rader</p>
            <p className="text-xs text-muted-foreground">
              Det här är hela den nya verifikationen: alla konton som ska finnas kvar måste stå
              kvar. Tar du bort ett konto nollställs det (stornon återför det). Vill du bara återföra
              hela verifikatet utan att ersätta det, använd Återför (storno) istället.
            </p>
          </div>

          {accountsStatus !== 'ready' && (
            <div className="flex items-center justify-between gap-3 rounded-lg border bg-muted/50 p-3 text-sm text-muted-foreground">
              <span className="flex items-center gap-2">
                {accountsStatus === 'loading' && <Loader2 className="h-4 w-4 animate-spin" />}
                {accountsStatus === 'loading' ? t('accounts_loading') : t('accounts_load_failed')}
              </span>
              {accountsStatus === 'error' && (
                <Button variant="outline" size="sm" onClick={() => void fetchAccounts()}>
                  {t('accounts_retry')}
                </Button>
              )}
            </div>
          )}

          <div className="space-y-2">
            {lines.map((line, index) => (
              <div key={index} className="space-y-2 sm:space-y-0 sm:grid sm:grid-cols-[1fr_1fr_120px_120px_auto] sm:gap-2 sm:items-start border-b sm:border-0 pb-3 sm:pb-0 last:border-0">
                <div className="grid grid-cols-[1fr_auto] sm:contents gap-2">
                  <AccountCombobox
                    value={line.account_number}
                    accounts={activeAccounts}
                    catalog={selectableCatalog}
                    onChange={(v) => updateLineAccount(index, v)}
                    onCreateAccount={(prefill) => {
                      setCreatingAccountForLine(index)
                      setCreateAccountPrefill(prefill)
                    }}
                    disabled={accountsStatus !== 'ready'}
                  />
                  <Button
                    variant="ghost"
                    size="icon"
                    className="h-8 w-8 min-h-[44px] min-w-[44px] sm:order-last"
                    onClick={() => removeLine(index)}
                    disabled={lines.length <= 2}
                  >
                    <Trash2 className="h-4 w-4" />
                  </Button>
                </div>
                <Input
                  value={line.line_description}
                  onChange={(e) => updateLine(index, 'line_description', e.target.value)}
                  placeholder="Beskrivning"
                  className="h-8"
                />
                <div className="grid grid-cols-2 gap-2 sm:contents">
                  <Input
                    type="number"
                    value={line.debit_amount}
                    onChange={(e) => updateLine(index, 'debit_amount', e.target.value)}
                    placeholder="Debet"
                    className="h-8 text-right"
                    min={0}
                    step="0.01"
                  />
                  <Input
                    type="number"
                    value={line.credit_amount}
                    onChange={(e) => updateLine(index, 'credit_amount', e.target.value)}
                    placeholder="Kredit"
                    className="h-8 text-right"
                    min={0}
                    step="0.01"
                  />
                </div>
              </div>
            ))}
          </div>

          <Button variant="outline" size="sm" onClick={addLine}>
            <Plus className="h-4 w-4 mr-1" />
            Lägg till rad
          </Button>

          {/* Balance summary */}
          <div className="flex justify-end gap-6 text-sm pt-2 border-t">
            <div>
              <span className="text-muted-foreground mr-2">Debet:</span>
              <span className={!isBalanced ? 'text-destructive font-medium' : 'font-medium'}>
                {roundedDebit.toLocaleString('sv-SE', { minimumFractionDigits: 2 })}
              </span>
            </div>
            <div>
              <span className="text-muted-foreground mr-2">Kredit:</span>
              <span className={!isBalanced ? 'text-destructive font-medium' : 'font-medium'}>
                {roundedCredit.toLocaleString('sv-SE', { minimumFractionDigits: 2 })}
              </span>
            </div>
          </div>

          {!isBalanced && roundedDebit + roundedCredit > 0 && (
            <p className="text-sm text-destructive">
              Debet och kredit måste vara lika och större än 0.
            </p>
          )}
        </div>

        <DialogFooter>
          <Button variant="outline" onClick={() => onOpenChange(false)} disabled={isSubmitting}>
            Avbryt
          </Button>
          <Button
            onClick={handleSubmit}
            disabled={!isBalanced || !hasValidLines || isSubmitting}
          >
            {isSubmitting ? 'Skapar...' : 'Skapa ändringsverifikation'}
          </Button>
        </DialogFooter>
      </DialogContent>

      {/* Nested on purpose: closing this one (Esc, click-outside, Avbryt) must
          leave the half-filled ändringsverifikation behind it untouched. */}
      <AddAccountDialog
        open={creatingAccountForLine != null}
        onOpenChange={(next) => {
          if (!next) closeCreateAccount()
        }}
        onCreated={handleAccountCreated}
        {...splitCreateAccountPrefill(createAccountPrefill)}
      />
    </Dialog>
  )
}