finstream

  EXTRACT   ←  CSV files  |  Yahoo Finance REST API (live)  |  PostgreSQL

      ↓  DataFrame chunk (10,000 rows)

  CLEAN     DataCleaner — remove invalid amounts and unknown currencies

  TRANSFORM CurrencyNormalizer  — USD / GBP / CHF → EUR
            Deduplicator       — remove duplicate transaction IDs
            DateStandardizer   — normalize dates to ISO 8601

      ↓  clean DataFrame chunk

  VALIDATE  QualityEngine (5 rules)
            ├─ NotNullRule         required fields must not be null
            ├─ PositiveAmountRule  amount must be > 0
            ├─ ValidCurrencyRule   currency must be EUR/USD/GBP/CHF
            ├─ NoDuplicateRule     transaction id must be unique
            └─ DateRangeRule       date within acceptable range
            → quality score ≥ 80% to proceed

      ↓  validated DataFrame chunk

  LOAD      PostgreSQLStorage — bulk insert via psycopg2 execute_values
            ON CONFLICT DO NOTHING — idempotent runs