import type { SupabaseClient } from '@supabase/supabase-js'
import type { Transaction, ReconciliationMethod } from '@/types'
import { eventBus } from '@/lib/events/bus'
import { logMatchEvent } from '@/lib/invoices/match-log'

// ============================================================
// Types
// ============================================================

/** A posted journal entry line on account 1930 not yet linked to any transaction */
export interface UnlinkedGLLine {
  line_id: string
  journal_entry_id: string
  debit_amount: number
  credit_amount: number
  line_description: string | null
  entry_date: string
  voucher_number: number
  voucher_series: string
  entry_description: string
  source_type: string
  /** How many bank transactions already point at this entry. Present only on
   *  rows from get_account_gl_lines_for_matching (the N:1 candidate fetch);
   *  undefined on the unmatched-only path, where it is always implicitly 0. */
  linked_transaction_count?: number
}

export interface ReconciliationMatch {
  transaction: Transaction
  glLine: UnlinkedGLLine
  method: ReconciliationMethod
  confidence: number
}

export interface ReconciliationRunResult {
  matches: ReconciliationMatch[]
  applied: number
  errors: number
}

export interface ReconciliationStatus {
  bank_transaction_total: number
  /**
   * The real ledger balance on the bank account, incl. IB — computed from the
   * SAME `['posted','reversed']` lines the trial balance and balance sheet sum,
   * so this value is identical to what the balansräkning reports for this
   * account. (Use `gl_1930_period_movement` for the reconciliation diff, since
   * this figure still includes the opening balance.)
   */
  gl_1930_balance: number
  /** Ledger movement on the bank account excluding only opening_balance — i.e.
   *  the ledger balance minus IB. Storno/correction lines ARE included here
   *  (they're part of the balance), so a corrected bank line reconciles against
   *  its re-pointed feed transaction. This is what `difference` compares against. */
  gl_1930_period_movement: number
  /** IB on the bank account within the date range — surfaced separately so
   *  reconciliation doesn't treat it as an unmatched bank transaction. */
  gl_1930_opening_balance: number
  /** Net of posted storno/correction lines on the bank account within the date
   *  range. INFORMATIONAL ONLY — it is part of the ledger balance and is included
   *  in gl_1930_period_movement, not subtracted from it. Surfaced so the UI can
   *  show how much of the period's movement came from corrections. */
  gl_1930_correction_adjustment: number
  /** bankTotal − gl_1930_period_movement. Zero when every period transaction is matched. */
  difference: number
  is_reconciled: boolean
  matched_count: number
  unmatched_transaction_count: number
  unmatched_gl_line_count: number
}

export interface ReconciliationOptions {
  dateFrom?: string
  dateTo?: string
  dryRun?: boolean
  /**
   * Settlement account number to reconcile against (e.g. '1930' for SEK,
   * '1932' for EUR). Defaults to '1930' so existing callers stay correct.
   * The cash_accounts table is the source of truth for which BAS codes are
   * routable for a given company.
   */
  accountNumber?: string
  /**
   * Currency to filter transactions on. Defaults to 'SEK' for back-compat;
   * future multi-currency reconciliation passes the currency of the selected
   * cash account so EUR transactions reconcile against 1932 etc.
   */
  currency?: string
  /**
   * cash_accounts.id of the selected account. When set, transactions are
   * scoped to this exact account (with a currency fallback for legacy rows
   * whose cash_account_id hasn't been backfilled yet) instead of being matched
   * by currency alone — this is what stops two same-currency accounts (e.g.
   * checking 1930 + savings 1931) from pooling together. Omit for the legacy
   * currency-only behaviour.
   */
  cashAccountId?: string
  /**
   * Whether this account claims rows with a NULL cash_account_id (legacy /
   * unassigned). Only the company's primary cash account should — see
   * scopeTransactionsToAccount. Defaults to true for back-compat with the
   * currency-only callers (where cashAccountId is omitted and this is moot).
   */
  includeUnassigned?: boolean
}

/**
 * Scope a transactions query builder to a single cash account, tolerating
 * legacy rows that predate the cash_account_id backfill.
 *
 * The applied filter is one of:
 *   includeUnassigned=true:   currency = cur AND (cash_account_id = X OR cash_account_id IS NULL)
 *   includeUnassigned=false:  currency = cur AND cash_account_id = X
 *   no cashAccountId:         currency = cur                       (legacy currency-only path)
 *
 * Why `includeUnassigned` exists: a NULL cash_account_id row belongs to exactly
 * ONE account, but the query can't tell which — these are unbooked rows in
 * companies with ≥2 same-currency accounts (the backfill refuses to guess
 * between checking + savings) and booked own-account transfers the backfill
 * deliberately skips (>1 bank-class line). Attributing them to EVERY
 * same-currency account double-counts them: a 1931 savings account would pull in
 * 1930's unassigned rows, so Bankavstämning reported a large bogus difference
 * for 1931 while 1930 itself still reconciled. The fix: only the company's
 * PRIMARY cash account (cash_accounts.is_primary — exactly one per company)
 * claims NULL rows; every other account scopes strictly to its own id. Callers
 * pass `includeUnassigned = <this account is_primary>`. When cashAccountId is
 * omitted (single-account companies with no row, the '1930' fallback) the pure
 * currency filter is used and includeUnassigned is moot.
 *
 * The earlier nested `or(cash_account_id.eq.X,and(cash_account_id.is.null,currency.eq.cur))`
 * form is intentionally avoided — it silently returned ZERO rows mid-backfill.
 * A cash account has exactly one currency, so the flat two-term `or` is reliable.
 */
export function scopeTransactionsToAccount<Q extends {
  or(filters: string): Q
  eq(column: string, value: string): Q
}>(query: Q, cashAccountId: string | undefined, currency: string, includeUnassigned = true): Q {
  // Both values are interpolated into a raw PostgREST filter string below. They
  // are DB-derived in every caller (cash_accounts.id / .currency, or the 'SEK'
  // default), never raw user input — but assert their shape anyway so a future
  // caller cannot thread an unsanitized value through into the filter.
  if (!/^[A-Z]{3}$/.test(currency)) {
    throw new Error(`scopeTransactionsToAccount: invalid currency ${JSON.stringify(currency)}`)
  }
  if (cashAccountId) {
    if (!/^[0-9a-fA-F-]{36}$/.test(cashAccountId)) {
      throw new Error('scopeTransactionsToAccount: invalid cashAccountId (expected UUID)')
    }
    if (includeUnassigned) {
      return query
        .eq('currency', currency)
        .or(`cash_account_id.eq.${cashAccountId},cash_account_id.is.null`)
    }
    // Non-primary account: strict — never claim the company's unassigned NULL rows.
    return query.eq('currency', currency).eq('cash_account_id', cashAccountId)
  }
  return query.eq('currency', currency)
}

// ============================================================
// In-memory matching: single transaction against GL line pool
// ============================================================

/**
 * Try to reconcile a single transaction against a pool of unlinked GL lines.
 * Returns the best match or null. Purely in-memory, no DB calls.
 *
 * `expectedCurrency` filters which transactions can match — defaults to 'SEK'
 * so existing callers behave identically.
 */
export function tryReconcileTransaction(
  transaction: Transaction,
  glLines: UnlinkedGLLine[],
  expectedCurrency: string = 'SEK',
): ReconciliationMatch | null {
  if (transaction.currency !== expectedCurrency) return null
  if (glLines.length === 0) return null

  const txAmount = transaction.amount
  const txDate = transaction.date
  const txReference = (transaction.reference || '').toLowerCase()

  let bestMatch: ReconciliationMatch | null = null

  for (const line of glLines) {
    const lineAmount = getDirectionalAmount(line)
    if (!isDirectionCompatible(txAmount, line)) continue

    const amountMatches = Math.abs(Math.abs(txAmount) - Math.abs(lineAmount)) < 0.005
    const fuzzyAmountMatches = Math.abs(Math.abs(txAmount) - Math.abs(lineAmount)) <= 0.01
    const exactDateMatch = txDate === line.entry_date
    const dateWithinRange = isDateWithinRange(txDate, line.entry_date, 3)
    // Reference matches require BOTH a real OCR/reference token AND a bounded
    // date window. Never description-only — that collides on recurring monthly
    // charges (same description, same amount, different year). Never cross-year.
    const referenceMatch =
      hasOcrReferenceMatch(txReference, line) &&
      isDateWithinRange(txDate, line.entry_date, 90)

    let method: ReconciliationMethod | null = null
    let confidence = 0

    // Pass 1: Exact amount + exact date
    if (amountMatches && exactDateMatch) {
      method = 'auto_exact'
      confidence = 0.95
    }
    // Pass 2: Exact amount + OCR/reference match within ±90 days
    else if (amountMatches && referenceMatch) {
      method = 'auto_reference'
      confidence = 0.90
    }
    // Pass 3: Exact amount + date within ±3 days
    else if (amountMatches && dateWithinRange) {
      method = 'auto_date_range'
      confidence = 0.85
    }
    // Pass 4: Fuzzy amount (±0.01) + exact date
    else if (fuzzyAmountMatches && exactDateMatch) {
      method = 'auto_fuzzy'
      confidence = 0.75
    }

    if (method && confidence > (bestMatch?.confidence ?? 0)) {
      bestMatch = { transaction, glLine: line, method, confidence }
    }
  }

  return bestMatch
}

// ============================================================
// Batch reconciliation
// ============================================================

/**
 * Run auto-reconciliation for all unmatched transactions.
 * Fetches data, runs 4-pass matching, optionally applies matches.
 */
export async function runReconciliation(
  supabase: SupabaseClient,
  companyId: string,
  userId: string,
  options: ReconciliationOptions = {}
): Promise<ReconciliationRunResult> {
  const {
    dateFrom,
    dateTo,
    dryRun = false,
    accountNumber = '1930',
    currency = 'SEK',
    cashAccountId,
    includeUnassigned = true,
  } = options

  // Fetch unlinked GL lines via RPC
  const glLines = await fetchUnlinkedGLLines(supabase, companyId, accountNumber, dateFrom, dateTo)

  // Fetch unmatched transactions, scoped to the selected cash account.
  let query = supabase
    .from('transactions')
    .select('*')
    .eq('company_id', companyId)
    .is('journal_entry_id', null)
    .eq('is_ignored', false)
  query = scopeTransactionsToAccount(query, cashAccountId, currency, includeUnassigned)

  if (dateFrom) query = query.gte('date', dateFrom)
  if (dateTo) query = query.lte('date', dateTo)

  const { data: transactions } = await query

  if (!transactions || transactions.length === 0 || glLines.length === 0) {
    return { matches: [], applied: 0, errors: 0 }
  }

  // Run greedy matching, highest confidence first
  const matches = greedyMatch(transactions as Transaction[], glLines, currency)

  if (dryRun) {
    return { matches, applied: 0, errors: 0 }
  }

  // Apply matches
  let applied = 0
  let errors = 0

  for (const match of matches) {
    try {
      const { error } = await supabase
        .from('transactions')
        .update({
          journal_entry_id: match.glLine.journal_entry_id,
          reconciliation_method: match.method,
          is_business: true,
        })
        .eq('id', match.transaction.id)
        .eq('company_id', companyId)

      if (error) {
        errors++
      } else {
        applied++
        try {
          eventBus.emit({
            type: 'transaction.reconciled',
            payload: {
              transaction: match.transaction,
              journalEntryId: match.glLine.journal_entry_id,
              method: match.method,
              userId,
              companyId,
            },
          })
        } catch {
          // Event emission is non-critical
        }
      }
    } catch {
      errors++
    }
  }

  return { matches, applied, errors }
}

// ============================================================
// Reconciliation status
// ============================================================

/**
 * Compare bank transaction totals vs GL bank account balance.
 *
 * `bankAccount` and `currency` must agree (e.g. 1932 + EUR). When the caller
 * omits currency it defaults to SEK for back-compat with the single-account
 * call sites that only ever reconciled 1930. Multi-currency callers must pass
 * both — comparing EUR GL movements against SEK transaction totals would
 * silently produce nonsense.
 */
export async function getReconciliationStatus(
  supabase: SupabaseClient,
  companyId: string,
  dateFrom?: string,
  dateTo?: string,
  bankAccount = '1930',
  currency: string = 'SEK',
  cashAccountId?: string,
  includeUnassigned: boolean = true,
): Promise<ReconciliationStatus> {
  // Get all transactions in range, scoped to the selected cash account. Ignored
  // rows are pulled too so the totals card still reflects what the bank
  // actually moved, but they're excluded from the "unmatched" count below — the
  // user has explicitly said they don't want them surfacing as something to
  // reconcile. Scoping by cash account (not just currency) is what stops a
  // second same-currency account from inflating bankTotal here.
  let txQuery = supabase
    .from('transactions')
    .select('date, amount, journal_entry_id, reconciliation_method, is_ignored')
    .eq('company_id', companyId)
  txQuery = scopeTransactionsToAccount(txQuery, cashAccountId, currency, includeUnassigned)

  if (dateFrom) txQuery = txQuery.gte('date', dateFrom)
  if (dateTo) txQuery = txQuery.lte('date', dateTo)

  const { data: transactions } = await txQuery

  // Get GL bank-account lines. We fetch posted AND reversed entries and count
  // them TOGETHER — the exact inclusion rule the trial balance and balance sheet
  // use (see lib/reports/trial-balance.ts, which sums `['posted','reversed']`).
  // A reversed original stays in the ledger and is cancelled by its storno, so
  // both legs must be summed; counting only the storno would leave a dangling
  // half-correction. Using the identical rule here is what guarantees
  // gl_1930_balance can never disagree with the balansräkning for this account —
  // the headline bug this widget had (a corrected bank receipt showed one figure
  // here and a different one on the balance sheet). source_type is still pulled
  // so we can split out the opening balance and surface correction activity.
  let glQuery = supabase
    .from('journal_entry_lines')
    .select('debit_amount, credit_amount, journal_entries!inner(id, company_id, entry_date, status, source_type)')
    .eq('account_number', bankAccount)
    .eq('journal_entries.company_id', companyId)
    .in('journal_entries.status', ['posted', 'reversed'])

  if (dateFrom) glQuery = glQuery.gte('journal_entries.entry_date', dateFrom)
  if (dateTo) glQuery = glQuery.lte('journal_entries.entry_date', dateTo)

  const { data: glLines } = await glQuery

  type GlEntry = {
    id?: string | null
    status?: string | null
    source_type?: string | null
    entry_date?: string | null
  }
  type GlLineRow = {
    debit_amount: number | string | null
    credit_amount: number | string | null
    journal_entries: GlEntry | GlEntry[] | null
  }
  // Supabase typings sometimes widen embedded relations to arrays even when the
  // join is one-to-one. Handle both shapes defensively.
  function entryOf(line: GlLineRow): GlEntry | null {
    const je = line.journal_entries
    if (!je) return null
    return Array.isArray(je) ? je[0] ?? null : je
  }
  function lineAmount(line: GlLineRow): number {
    return (Number(line.debit_amount) || 0) - (Number(line.credit_amount) || 0)
  }

  // posted + reversed = the ledger balance, exactly as the trial balance counts
  // it. The .in() filter on the query already excludes draft/cancelled.
  const fetchedLines = (glLines || []) as GlLineRow[]

  // Floor the window at the most recent opening-balance date on this account
  // (issue #751). Everything dated before that IB is prior history the IB entry
  // already summarises; if the window has no lower bound (the "full history"
  // default) it spans the fiscal-year boundary and pulls the prior period's real
  // movements — which net to exactly the IB — into the period movement, while the
  // bank feed only covers the current period. The IB *summary* is excluded below,
  // but the prior-period *detail* would otherwise remain, manufacturing a phantom
  // difference equal to the IB. effectiveFrom is the later of the caller's
  // dateFrom and that IB date; it only ever RAISES the lower bound, so the
  // dateFrom SQL pre-filter on both queries above stays valid. In normal use the
  // UI passes dateFrom = period_start = the IB date, so this is a no-op there.
  const ibDates = fetchedLines
    .filter((l) => entryOf(l)?.source_type === 'opening_balance')
    .map((l) => entryOf(l)?.entry_date)
    .filter((d): d is string => typeof d === 'string' && d.length > 0)
  // Take the LATEST IB date. The invariant is one opening_balance entry per
  // fiscal period (set_opening_balances / SIE import / year-end rollover all
  // create exactly one, dated period_start), so within a single-period window
  // there is only one. Across a multi-year window the most recent IB is the
  // correct floor — an earlier year's IB and the movements it summarises are
  // prior history we deliberately drop. Same-date duplicates are harmless: they
  // land in both countedLines and glOpeningBalance and cancel.
  const ibFloor = ibDates.length ? ibDates.reduce((a, b) => (a > b ? a : b)) : null
  const effectiveFrom =
    dateFrom && ibFloor ? (dateFrom > ibFloor ? dateFrom : ibFloor) : dateFrom || ibFloor || null
  // ISO yyyy-mm-dd compares lexically; undated rows (e.g. test fixtures) pass.
  const onOrAfterFloor = (d: string | null | undefined): boolean =>
    !effectiveFrom || typeof d !== 'string' ? true : d >= effectiveFrom

  // Clamp BOTH sides to the floor identically so they stay comparable. Lines and
  // transactions before the IB belong to a prior period's reconciliation.
  const countedLines = fetchedLines.filter((l) => onOrAfterFloor(entryOf(l)?.entry_date))
  const countedTx = (transactions || []).filter((tx) =>
    onOrAfterFloor((tx as { date?: string | null }).date),
  )

  // Bank side: every feed transaction in the (floored) window, full stop. We
  // deliberately do NOT special-case rows linked to a reversed entry any more.
  // Because the GL side now counts the reversed original, its storno AND the
  // correction together (just like the balance sheet), a corrected bank line nets
  // to its true amount on both sides and reconciles on its own — whether
  // correctEntry re-pointed the transaction to the live corrected entry or a
  // legacy row still points at the reversed original, the result is identical.
  const bankTotal = countedTx.reduce((sum, tx) => sum + (Number(tx.amount) || 0), 0)

  // gl_1930_balance: the real ledger balance on this account incl. IB —
  // byte-for-byte the figure the balansräkning / saldobalans report.
  const glBalance = countedLines.reduce((sum, line) => sum + lineAmount(line), 0)
  // IB is last year's closing position, not a movement with a bank-feed
  // counterpart — surfaced separately and excluded from the period movement.
  const glOpeningBalance = countedLines
    .filter((l) => entryOf(l)?.source_type === 'opening_balance')
    .reduce((sum, line) => sum + lineAmount(line), 0)
  // Net storno/correction activity on the account this period. Surfaced for
  // transparency ONLY — it is part of the ledger balance and is INCLUDED in the
  // movement, never subtracted. (Subtracting it while still counting the
  // re-pointed bank transaction is exactly what produced the old phantom diff.)
  const glCorrectionAdjustment = countedLines
    .filter((l) => {
      const st = entryOf(l)?.source_type
      return st === 'storno' || st === 'correction'
    })
    .reduce((sum, line) => sum + lineAmount(line), 0)
  // Period movement = the ledger balance minus the opening balance. Everything
  // else (real bookings, stornos and corrections alike) has — or should have —
  // a bank-feed counterpart, so it stays in.
  const glPeriodMovement = glBalance - glOpeningBalance

  const matchedCount = countedTx.filter((tx) => tx.journal_entry_id !== null).length

  const unmatchedTransactionCount = countedTx.filter(
    (tx) => tx.journal_entry_id === null && tx.is_ignored !== true
  ).length

  // Unlinked GL lines count (RPC excludes opening_balance, storno and correction
  // since 20260601120000_unlinked_gl_lines_exclude_storno_correction.sql)
  const unlinkedLines = await fetchUnlinkedGLLines(supabase, companyId, bankAccount, dateFrom, dateTo)

  const difference = Math.round((bankTotal - glPeriodMovement) * 100) / 100

  return {
    bank_transaction_total: Math.round(bankTotal * 100) / 100,
    gl_1930_balance: Math.round(glBalance * 100) / 100,
    gl_1930_period_movement: Math.round(glPeriodMovement * 100) / 100,
    gl_1930_opening_balance: Math.round(glOpeningBalance * 100) / 100,
    gl_1930_correction_adjustment: Math.round(glCorrectionAdjustment * 100) / 100,
    difference,
    is_reconciled: Math.abs(difference) < 0.01,
    matched_count: matchedCount,
    unmatched_transaction_count: unmatchedTransactionCount,
    unmatched_gl_line_count: unlinkedLines.length,
  }
}

// ============================================================
// Manual link/unlink
// ============================================================

/**
 * Manually link a transaction to an existing journal entry.
 * Validates that the journal entry has a bank account line and amounts are directionally compatible.
 */
export async function manualLink(
  supabase: SupabaseClient,
  companyId: string,
  transactionId: string,
  journalEntryId: string,
  userId: string,
  accountNumber: string = '1930',
): Promise<{ success: boolean; error?: string }> {
  // Fetch transaction
  const { data: tx, error: txError } = await supabase
    .from('transactions')
    .select('*')
    .eq('id', transactionId)
    .eq('company_id', companyId)
    .single()

  if (txError || !tx) {
    return { success: false, error: 'Transaktionen kunde inte hittas.' }
  }

  if (tx.journal_entry_id) {
    return { success: false, error: 'Transaktionen är redan kopplad till en verifikation.' }
  }

  // Fetch journal entry + verify it has a 1930 line
  const { data: entry, error: entryError } = await supabase
    .from('journal_entries')
    .select('id, company_id, status')
    .eq('id', journalEntryId)
    .eq('company_id', companyId)
    .single()

  if (entryError || !entry) {
    return { success: false, error: 'Verifikationen kunde inte hittas.' }
  }

  if (entry.status !== 'posted') {
    return { success: false, error: 'Verifikationen är inte bokförd ännu.' }
  }

  // Defense-in-depth: the transaction must belong to the account being
  // reconciled. A transaction bound to 1930 must not be linked against a 1931
  // voucher even if the caller passes accountNumber=1931. Legacy rows with no
  // cash_account_id fall through (the UI list already gates them by currency).
  if (tx.cash_account_id) {
    const { data: txCa } = await supabase
      .from('cash_accounts')
      .select('ledger_account')
      .eq('id', tx.cash_account_id)
      .eq('company_id', companyId)
      .maybeSingle()
    if (txCa?.ledger_account && txCa.ledger_account !== accountNumber) {
      return {
        success: false,
        error: `Transaktionen hör till ${txCa.ledger_account}, inte ${accountNumber}`,
      }
    }
  }

  // Check for a bank account line on the SELECTED settlement account. The old
  // "any 19xx line" check let a 1930 transaction link to a voucher that only
  // touched 1931 — a cross-account link that silently hides a real imbalance.
  const { data: lines } = await supabase
    .from('journal_entry_lines')
    .select('debit_amount, credit_amount, account_number')
    .eq('journal_entry_id', journalEntryId)
    .eq('account_number', accountNumber)

  if (!lines || lines.length === 0) {
    return { success: false, error: `Verifikationen saknar rad på ${accountNumber}` }
  }

  // N:1 is intentionally allowed: several bank transactions may settle ONE
  // verifikat (a salary run paid out in multiple transfers, a supplier invoice
  // paid in instalments). The voucher's bank line is counted once in the period
  // movement while each transaction sums on the bank side, so correctly-summing
  // links net to zero and any mis-link surfaces as a non-zero difference on the
  // status card — there's no need to forbid a second link here. (A given
  // transaction still can't be double-linked: the tx.journal_entry_id guard
  // above already blocks that.) The candidate list only surfaces an
  // already-matched voucher when the user opts in via "Visa även matchade
  // verifikationer", so this can't happen by accident.

  // Apply link
  const { error: updateError } = await supabase
    .from('transactions')
    .update({
      journal_entry_id: journalEntryId,
      reconciliation_method: 'manual' as ReconciliationMethod,
      is_business: true,
    })
    .eq('id', transactionId)
    .eq('company_id', companyId)

  if (updateError) {
    return { success: false, error: 'Kunde inte koppla transaktionen. Försök igen.' }
  }

  try {
    eventBus.emit({
      type: 'transaction.reconciled',
      payload: {
        transaction: tx as Transaction,
        journalEntryId,
        method: 'manual' as ReconciliationMethod,
        userId,
        companyId,
      },
    })
  } catch {
    // Non-critical
  }

  return { success: true }
}

/**
 * Remove a reconciliation link.
 * Only allowed when reconciliation_method IS NOT NULL (prevents unlinking categorization-created entries).
 */
export async function unlinkReconciliation(
  supabase: SupabaseClient,
  companyId: string,
  transactionId: string
): Promise<{ success: boolean; error?: string }> {
  // Fetch transaction
  const { data: tx, error: txError } = await supabase
    .from('transactions')
    .select('id, journal_entry_id, reconciliation_method')
    .eq('id', transactionId)
    .eq('company_id', companyId)
    .single()

  if (txError || !tx) {
    return { success: false, error: 'Transaction not found' }
  }

  if (!tx.journal_entry_id) {
    return { success: false, error: 'Transaction is not linked to any journal entry' }
  }

  if (!tx.reconciliation_method) {
    return { success: false, error: 'Cannot unlink a categorization-created entry. Use storno to reverse it instead.' }
  }

  const { error: updateError } = await supabase
    .from('transactions')
    .update({
      journal_entry_id: null,
      reconciliation_method: null,
      is_business: null,
    })
    .eq('id', transactionId)
    .eq('company_id', companyId)

  if (updateError) {
    return { success: false, error: 'Failed to unlink transaction' }
  }

  logMatchEvent(supabase, companyId, transactionId, 'unmatched', {
    previousState: {
      journal_entry_id: tx.journal_entry_id,
      reconciliation_method: tx.reconciliation_method,
    },
  })

  return { success: true }
}

/** Float tolerance for matching a bank line to a verifikat (0.5 öre). */
const VOUCHER_LINK_AMOUNT_TOLERANCE = 0.005

/** A bank line settling a verifikat sits within a few days of the voucher's
 *  entry_date. Kept tight so the single-candidate rule below stays meaningful. */
const VOUCHER_LINK_DATE_WINDOW_DAYS = 7

/** Shift an ISO 'YYYY-MM-DD' date by ±days, returning the same string shape. */
function shiftIsoDate(date: string, days: number): string {
  const d = new Date(date)
  if (Number.isNaN(d.getTime())) return date
  d.setUTCDate(d.getUTCDate() + days)
  return d.toISOString().slice(0, 10)
}

interface CashAccountInfo {
  id: string | null
  currency: string
  isPrimary: boolean
}

/**
 * Reconcile the single unbooked bank transaction that corresponds to a verifikat
 * the user just linked to an invoice from the invoice page — the symmetric move
 * to the transactions-side match, closing the gap where linkInvoiceToVoucher /
 * linkSupplierInvoiceToVoucher advanced the invoice but left the bank line
 * sitting in the Transactions inbox (still journal_entry_id = null).
 *
 * Deliberately conservative — it only acts when the link is unambiguous:
 *   • the voucher has NO bank transaction reconciled to it yet (never adds a
 *     second one automatically — that N:1 case must be an explicit choice in
 *     Bankavstämning),
 *   • the voucher touches exactly ONE cash-account line (a transfer hitting two
 *     bank accounts, or an AR/AP reclass with none, is left alone), and
 *   • exactly ONE unbooked, non-ignored transaction on that account matches the
 *     bank movement (same amount within tolerance, same direction) inside a
 *     tight date window.
 * Anything else is left untouched: the user can still match it by hand from the
 * Transactions list. The link itself uses manualLink — no new journal entry, no
 * JE mutation — so this is a reconciliation link, never a second booking.
 *
 * Best-effort by contract: returns the linked transaction id or null, and the
 * caller treats a throw as "nothing linked" because the invoice link has already
 * committed.
 */
export async function autoReconcileTransactionForLinkedVoucher(
  supabase: SupabaseClient,
  companyId: string,
  userId: string,
  journalEntryId: string,
  options: {
    invoiceId?: string
    supplierInvoiceId?: string
    dateWindowDays?: number
  } = {},
): Promise<{ linkedTransactionId: string } | null> {
  const windowDays = options.dateWindowDays ?? VOUCHER_LINK_DATE_WINDOW_DAYS

  // 1. If a bank transaction already points at this voucher, the bank side is
  //    settled — don't attach another one behind the user's back.
  const { data: alreadyLinked } = await supabase
    .from('transactions')
    .select('id')
    .eq('company_id', companyId)
    .eq('journal_entry_id', journalEntryId)
    .limit(1)
  if (alreadyLinked && alreadyLinked.length > 0) return null

  // 2. Load the voucher (must be posted) and its lines.
  const { data: entry } = await supabase
    .from('journal_entries')
    .select('id, entry_date, status')
    .eq('id', journalEntryId)
    .eq('company_id', companyId)
    .maybeSingle()
  if (!entry || entry.status !== 'posted' || !entry.entry_date) return null

  const { data: lines } = await supabase
    .from('journal_entry_lines')
    .select('account_number, debit_amount, credit_amount')
    .eq('journal_entry_id', journalEntryId)
  if (!lines || lines.length === 0) return null

  // 3. Which BAS codes carry a bank feed? cash_accounts is the source of truth.
  const { data: cashAccounts } = await supabase
    .from('cash_accounts')
    .select('id, ledger_account, currency, is_primary')
    .eq('company_id', companyId)

  const cashByAccount = new Map<string, CashAccountInfo>()
  for (const raw of (cashAccounts ?? []) as Array<{
    id: string
    ledger_account: string | null
    currency: string | null
    is_primary: boolean | null
  }>) {
    if (raw.ledger_account) {
      cashByAccount.set(raw.ledger_account, {
        id: raw.id,
        currency: raw.currency ?? 'SEK',
        isPrimary: raw.is_primary ?? false,
      })
    }
  }
  // Companies created before cash_accounts seeding reconcile against 1930/SEK.
  if (cashByAccount.size === 0) {
    cashByAccount.set('1930', { id: null, currency: 'SEK', isPrimary: true })
  }

  const cashLines = (lines as Array<{
    account_number: string
    debit_amount: number | null
    credit_amount: number | null
  }>).filter((l) => cashByAccount.has(l.account_number))

  // Exactly one bank movement → exactly one bank transaction to attach.
  if (cashLines.length !== 1) return null

  const cashLine = cashLines[0]
  const accountNumber = cashLine.account_number
  const cashAccount = cashByAccount.get(accountNumber)!
  const debit = Number(cashLine.debit_amount ?? 0)
  const credit = Number(cashLine.credit_amount ?? 0)
  const movement = debit > 0 ? debit : -credit // + money in, − money out
  if (Math.abs(movement) <= VOUCHER_LINK_AMOUNT_TOLERANCE) return null

  // 4. Unbooked, non-ignored candidate transactions on that account, scoped the
  //    same way Bankavstämning scopes (handles legacy NULL cash_account_id rows).
  const fromDate = shiftIsoDate(entry.entry_date, -windowDays)
  const toDate = shiftIsoDate(entry.entry_date, windowDays)
  let candQuery = supabase
    .from('transactions')
    .select('id, amount')
    .eq('company_id', companyId)
    .is('journal_entry_id', null)
    .eq('is_ignored', false)
    .gte('date', fromDate)
    .lte('date', toDate)
  candQuery = scopeTransactionsToAccount(
    candQuery,
    cashAccount.id ?? undefined,
    cashAccount.currency,
    cashAccount.isPrimary,
  )
  const { data: candidates } = await candQuery

  const matches = ((candidates ?? []) as Array<{ id: string; amount: number }>).filter((tx) => {
    const amt = Number(tx.amount)
    if (Math.abs(Math.abs(amt) - Math.abs(movement)) > VOUCHER_LINK_AMOUNT_TOLERANCE) return false
    return Math.sign(amt) === Math.sign(movement)
  })

  // Two same-amount unbooked lines near the same date → don't guess.
  if (matches.length !== 1) return null
  const transactionId = matches[0].id

  // 5. Reconcile via the exact path Bankavstämning uses (manualLink re-validates
  //    posted status, the cash-account line, and the not-already-linked guard,
  //    then sets journal_entry_id + reconciliation_method + is_business). No new
  //    journal entry is created.
  const linkResult = await manualLink(
    supabase,
    companyId,
    transactionId,
    journalEntryId,
    userId,
    accountNumber,
  )
  if (!linkResult.success) return null

  // Tag the transaction with the (supplier) invoice for traceability + parity
  // with the transactions-side match. is_business is already set by manualLink,
  // so the row has already dropped out of the inbox regardless of this update.
  const tag: Record<string, unknown> = { potential_invoice_id: null }
  if (options.invoiceId) tag.invoice_id = options.invoiceId
  if (options.supplierInvoiceId) {
    tag.supplier_invoice_id = options.supplierInvoiceId
    tag.potential_supplier_invoice_id = null
  }
  if (Object.keys(tag).length > 1) {
    await supabase
      .from('transactions')
      .update(tag)
      .eq('id', transactionId)
      .eq('company_id', companyId)
  }

  logMatchEvent(supabase, userId, transactionId, 'linked_to_existing_voucher', {
    invoiceId: options.invoiceId,
    supplierInvoiceId: options.supplierInvoiceId,
    matchMethod: 'invoice_voucher_link',
    newState: {
      journal_entry_id: journalEntryId,
      reconciliation_method: 'manual',
    },
  })

  return { linkedTransactionId: transactionId }
}

// ============================================================
// Helpers
// ============================================================

/**
 * Fetch unlinked GL lines for a settlement account. `accountNumber` defaults to
 * '1930' for back-compat; multi-account customers (Plusgiro 1920, kreditkort
 * 1940, EUR-konto 1932, etc.) pass the BAS code of the account they're
 * reconciling. The CashAccountSelector populates this from cash_accounts.
 */
export async function fetchUnlinkedGLLines(
  supabase: SupabaseClient,
  companyId: string,
  accountNumber: string = '1930',
  dateFrom?: string,
  dateTo?: string,
): Promise<UnlinkedGLLine[]> {
  const { data, error } = await supabase.rpc('get_unlinked_gl_lines', {
    p_company_id: companyId,
    p_account_number: accountNumber,
    p_date_from: dateFrom || null,
    p_date_to: dateTo || null,
  })

  if (error || !data) return []
  return data as UnlinkedGLLine[]
}

/** A match candidate that carries how many transactions already point at it. */
export interface GLLineForMatching extends UnlinkedGLLine {
  linked_transaction_count: number
}

/**
 * Fetch GL lines on a settlement account as match candidates. With
 * `includeMatched=false` this is parity with fetchUnlinkedGLLines (unmatched
 * only); with `includeMatched=true` it also returns already-matched vouchers,
 * each carrying `linked_transaction_count`, so a second/third bank transaction
 * can be attached to the same verifikat (N:1 — a salary run paid in several
 * transfers, a supplier invoice paid in instalments). Server-only: like the rest
 * of this module it must never reach the client bundle.
 */
export async function fetchGLLinesForMatching(
  supabase: SupabaseClient,
  companyId: string,
  accountNumber: string = '1930',
  dateFrom?: string,
  dateTo?: string,
  includeMatched: boolean = false,
): Promise<GLLineForMatching[]> {
  const { data, error } = await supabase.rpc('get_account_gl_lines_for_matching', {
    p_company_id: companyId,
    p_account_number: accountNumber,
    p_date_from: dateFrom || null,
    p_date_to: dateTo || null,
    p_include_matched: includeMatched,
  })

  if (error || !data) return []
  // count(*) can arrive as a bigint string over the wire — coerce defensively.
  return (data as GLLineForMatching[]).map((line) => ({
    ...line,
    linked_transaction_count: Number(line.linked_transaction_count) || 0,
  }))
}

/** Get the net amount from a GL line (positive for debit, negative for credit) */
function getDirectionalAmount(line: UnlinkedGLLine): number {
  if (line.debit_amount > 0) return line.debit_amount
  if (line.credit_amount > 0) return -line.credit_amount
  return 0
}

/**
 * Check direction compatibility:
 * - Income (tx.amount > 0) matches debit on 1930 (money coming in to bank)
 * - Expense (tx.amount < 0) matches credit on 1930 (money going out of bank)
 */
function isDirectionCompatible(txAmount: number, line: UnlinkedGLLine): boolean {
  if (txAmount > 0 && line.debit_amount > 0) return true
  if (txAmount < 0 && line.credit_amount > 0) return true
  return false
}

/**
 * OCR/reference-number match. Requires a non-trivial reference token (≥4 chars)
 * on the transaction that appears in the GL line/entry description. Description
 * substring matching is intentionally NOT done here — that collided on recurring
 * monthly charges across years (same description, same amount, different year).
 */
function hasOcrReferenceMatch(txReference: string, line: UnlinkedGLLine): boolean {
  if (!txReference || txReference.length < 4) return false
  const lineDesc = (line.line_description || '').toLowerCase()
  const entryDesc = (line.entry_description || '').toLowerCase()
  return lineDesc.includes(txReference) || entryDesc.includes(txReference)
}

/** Check if two dates are within ±dayRange of each other */
function isDateWithinRange(date1: string, date2: string, dayRange: number): boolean {
  const d1 = new Date(date1)
  const d2 = new Date(date2)
  const diffMs = Math.abs(d1.getTime() - d2.getTime())
  const diffDays = diffMs / (1000 * 60 * 60 * 24)
  return diffDays <= dayRange
}

/**
 * Greedy matching: run 4-pass matching, each pass at a specific confidence level.
 * Track used GL lines and transactions to prevent double-matching.
 */
function greedyMatch(
  transactions: Transaction[],
  glLines: UnlinkedGLLine[],
  expectedCurrency: string = 'SEK',
): ReconciliationMatch[] {
  const usedTransactions = new Set<string>()
  const usedGLLines = new Set<string>()
  const allMatches: ReconciliationMatch[] = []

  // Collect all candidate matches with confidence
  const candidates: ReconciliationMatch[] = []

  for (const tx of transactions) {
    if (tx.currency !== expectedCurrency) continue

    for (const line of glLines) {
      const match = tryReconcileTransaction(tx, [line], expectedCurrency)
      if (match) {
        candidates.push(match)
      }
    }
  }

  // Sort by confidence descending, then by date proximity
  candidates.sort((a, b) => {
    if (b.confidence !== a.confidence) return b.confidence - a.confidence
    // Prefer closer dates
    const dateDistA = Math.abs(
      new Date(a.transaction.date).getTime() - new Date(a.glLine.entry_date).getTime()
    )
    const dateDistB = Math.abs(
      new Date(b.transaction.date).getTime() - new Date(b.glLine.entry_date).getTime()
    )
    return dateDistA - dateDistB
  })

  // Greedily assign matches
  for (const candidate of candidates) {
    const txId = candidate.transaction.id
    const lineId = candidate.glLine.line_id

    if (usedTransactions.has(txId) || usedGLLines.has(lineId)) continue

    usedTransactions.add(txId)
    usedGLLines.add(lineId)
    allMatches.push(candidate)
  }

  return allMatches
}