feat(WHE-23): add hybrid purchase parser with persisted parse metadata

packages/application/src/purchase-parser.ts

@@ -0,0 +1,132 @@
+export type PurchaseParserMode = 'rules' | 'llm'
+
+export interface ParsedPurchaseResult {
+  amountMinor: bigint
+  currency: 'GEL' | 'USD'
+  itemDescription: string
+  confidence: number
+  parserMode: PurchaseParserMode
+  needsReview: boolean
+}
+
+export type PurchaseParserLlmFallback = (rawText: string) => Promise<ParsedPurchaseResult | null>
+
+export interface ParsePurchaseInput {
+  rawText: string
+}
+
+export interface ParsePurchaseOptions {
+  llmFallback?: PurchaseParserLlmFallback
+}
+
+const CURRENCY_PATTERN = '(?:₾|gel|lari|лари|usd|\\$|доллар(?:а|ов)?)'
+const AMOUNT_WITH_OPTIONAL_CURRENCY = new RegExp(
+  `(?<amount>\\d+(?:[.,]\\d{1,2})?)\\s*(?<currency>${CURRENCY_PATTERN})?`,
+  'giu'
+)
+
+function normalizeCurrency(raw: string | undefined): 'GEL' | 'USD' | null {
+  if (!raw) {
+    return null
+  }
+
+  const value = raw.trim().toLowerCase()
+  if (value === '₾' || value === 'gel' || value === 'lari' || value === 'лари') {
+    return 'GEL'
+  }
+
+  if (value === 'usd' || value === '$' || value.startsWith('доллар')) {
+    return 'USD'
+  }
+
+  return null
+}
+
+function toMinorUnits(rawAmount: string): bigint {
+  const normalized = rawAmount.replace(',', '.')
+  const [wholePart, fractionalPart = ''] = normalized.split('.')
+  const cents = fractionalPart.padEnd(2, '0').slice(0, 2)
+
+  return BigInt(`${wholePart}${cents}`)
+}
+
+function normalizeDescription(rawText: string, matchedFragment: string): string {
+  const cleaned = rawText.replace(matchedFragment, ' ').replace(/\s+/g, ' ').trim()
+
+  if (cleaned.length === 0) {
+    return 'shared purchase'
+  }
+
+  return cleaned
+}
+
+function parseWithRules(rawText: string): ParsedPurchaseResult | null {
+  const matches = Array.from(rawText.matchAll(AMOUNT_WITH_OPTIONAL_CURRENCY))
+
+  if (matches.length !== 1) {
+    return null
+  }
+
+  const [match] = matches
+  if (!match?.groups?.amount) {
+    return null
+  }
+
+  const currency = normalizeCurrency(match.groups.currency)
+  const amountMinor = toMinorUnits(match.groups.amount)
+
+  const explicitCurrency = currency !== null
+  const resolvedCurrency = currency ?? 'GEL'
+  const confidence = explicitCurrency ? 92 : 78
+
+  return {
+    amountMinor,
+    currency: resolvedCurrency,
+    itemDescription: normalizeDescription(rawText, match[0] ?? ''),
+    confidence,
+    parserMode: 'rules',
+    needsReview: !explicitCurrency
+  }
+}
+
+function validateLlmResult(result: ParsedPurchaseResult | null): ParsedPurchaseResult | null {
+  if (!result) {
+    return null
+  }
+
+  if (result.amountMinor <= 0n) {
+    return null
+  }
+
+  if (result.confidence < 0 || result.confidence > 100) {
+    return null
+  }
+
+  if (result.itemDescription.trim().length === 0) {
+    return null
+  }
+
+  return result
+}
+
+export async function parsePurchaseMessage(
+  input: ParsePurchaseInput,
+  options: ParsePurchaseOptions = {}
+): Promise<ParsedPurchaseResult | null> {
+  const rawText = input.rawText.trim()
+  if (rawText.length === 0) {
+    return null
+  }
+
+  const rulesResult = parseWithRules(rawText)
+  if (rulesResult) {
+    return rulesResult
+  }
+
+  if (!options.llmFallback) {
+    return null
+  }
+
+  const llmResult = await options.llmFallback(rawText)
+  return validateLlmResult(llmResult)
+}