New Base func

lib/core/tax/tax-code-service.ts

@@ -0,0 +1,167 @@
+import { createClient } from '@/lib/supabase/server'
+import type { TaxCode } from '@/types'
+
+/**
+ * Tax Code Service
+ *
+ * Manages decoupled tax codes for momsdeklaration.
+ * Tax codes map journal entry lines to specific moms rutor (boxes)
+ * on the Swedish VAT declaration form.
+ */
+
+/**
+ * Get all active tax codes for a user (including system codes)
+ */
+export async function getTaxCodes(userId: string): Promise<TaxCode[]> {
+  const supabase = await createClient()
+
+  const { data, error } = await supabase
+    .from('tax_codes')
+    .select('*')
+    .or(`user_id.eq.${userId},user_id.is.null`)
+    .order('code')
+
+  if (error) {
+    throw new Error(`Failed to fetch tax codes: ${error.message}`)
+  }
+
+  return (data as TaxCode[]) || []
+}
+
+/**
+ * Get a single tax code by code string
+ */
+export async function getTaxCodeByCode(
+  userId: string,
+  code: string
+): Promise<TaxCode | null> {
+  const supabase = await createClient()
+
+  // Prefer user-specific code over system code
+  const { data, error } = await supabase
+    .from('tax_codes')
+    .select('*')
+    .eq('code', code)
+    .or(`user_id.eq.${userId},user_id.is.null`)
+    .order('user_id', { ascending: false, nullsFirst: false })
+    .limit(1)
+    .single()
+
+  if (error) {
+    return null
+  }
+
+  return data as TaxCode
+}
+
+/**
+ * Moms box result from tax code aggregation
+ */
+export interface MomsBoxResult {
+  /** Ruta number (e.g. '05', '10', '48') */
+  box: string
+  /** Sum of amounts for this box */
+  amount: number
+}
+
+/**
+ * Calculate momsdeklaration from journal entry lines grouped by tax_code,
+ * then mapped via the tax_codes table to moms boxes.
+ *
+ * This is the new, tax-code-driven approach that replaces the hardcoded
+ * category-based VAT calculation.
+ */
+export async function calculateMomsFromTaxCodes(
+  userId: string,
+  periodStart: string,
+  periodEnd: string
+): Promise<MomsBoxResult[]> {
+  const supabase = await createClient()
+
+  // Fetch journal entry lines with tax_code in the period
+  const { data: lines, error: linesError } = await supabase
+    .from('journal_entry_lines')
+    .select(`
+      tax_code,
+      debit_amount,
+      credit_amount,
+      journal_entry_id,
+      journal_entries!inner (
+        user_id,
+        entry_date,
+        status,
+        fiscal_period_id
+      )
+    `)
+    .not('tax_code', 'is', null)
+    .eq('journal_entries.user_id', userId)
+    .eq('journal_entries.status', 'posted')
+    .gte('journal_entries.entry_date', periodStart)
+    .lte('journal_entries.entry_date', periodEnd)
+
+  if (linesError) {
+    throw new Error(`Failed to fetch journal lines: ${linesError.message}`)
+  }
+
+  // Fetch all tax codes for lookup
+  const taxCodes = await getTaxCodes(userId)
+  const taxCodeMap = new Map<string, TaxCode>()
+  for (const tc of taxCodes) {
+    // User codes take precedence over system codes
+    if (!taxCodeMap.has(tc.code) || tc.user_id) {
+      taxCodeMap.set(tc.code, tc)
+    }
+  }
+
+  // Aggregate amounts by moms box
+  const boxTotals = new Map<string, number>()
+
+  for (const line of lines || []) {
+    if (!line.tax_code) continue
+
+    const taxCode = taxCodeMap.get(line.tax_code)
+    if (!taxCode) continue
+
+    const netAmount = Number(line.debit_amount || 0) - Number(line.credit_amount || 0)
+    const absAmount = Math.abs(netAmount)
+
+    // For output VAT: debit_amount goes to basis boxes, tax amount to tax boxes
+    // For input VAT: the amount goes to input boxes
+    const allBoxes = [
+      ...taxCode.moms_basis_boxes,
+      ...taxCode.moms_tax_boxes,
+      ...taxCode.moms_input_boxes,
+    ]
+
+    for (const box of allBoxes) {
+      const current = boxTotals.get(box) || 0
+      boxTotals.set(box, current + absAmount)
+    }
+  }
+
+  // Convert to result array
+  const results: MomsBoxResult[] = []
+  for (const [box, amount] of boxTotals) {
+    results.push({
+      box,
+      amount: Math.round(amount * 100) / 100,
+    })
+  }
+
+  return results.sort((a, b) => a.box.localeCompare(b.box))
+}
+
+/**
+ * Seed tax codes for a user by calling the database function
+ */
+export async function seedTaxCodes(userId: string): Promise<void> {
+  const supabase = await createClient()
+
+  const { error } = await supabase.rpc('seed_tax_codes_for_user', {
+    p_user_id: userId,
+  })
+
+  if (error) {
+    throw new Error(`Failed to seed tax codes: ${error.message}`)
+  }
+}