# All files / src/utils credibilityCheck.ts

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     /**
     * Data credibility checks for EP API values.
     *
     * Used by `scripts/generate-stats.ts --update` to prevent overwriting
     * curated statistics with incomplete EP API data.
     *
     * @module utils/credibilityCheck
     */

    /** API values below this are suspicious when stored value is much larger. */
    export const MIN_CREDIBLE_VALUE = 10;

    /**
     * Maximum allowed percentage drop from stored value before the API value
     * is treated as incomplete/unreliable.
     *
     * EP API endpoints sometimes return partial datasets due to:
     * - Server-side pagination issues or timeouts
     * - Data reorganisation or migration
     * - Incomplete database loads
     *
     * Set to 50% to catch clearly incomplete data (e.g. 80% drops in speeches,
     * 73% drops in documents) while still allowing genuine corrections.
     */
    export const MAX_ALLOWED_DROP_PERCENT = 50;

    /**
     * Minimum stored value before the "significant drop" guard activates.
     *
     * Small stored values (≤ 100) are allowed to fluctuate freely since
     * even large percentage changes represent small absolute differences.
     */
    export const MIN_STORED_FOR_DROP_CHECK = 100;

    /**
     * Check whether an API value is credible enough to overwrite the stored value.
     *
     * Returns false when the API clearly returned incomplete data:
     *
     * **Guard 1 — tiny API value:** API value is below {@link MIN_CREDIBLE_VALUE}
     * AND stored value is much larger (> 5× the API value).
     *
     * **Guard 2 — significant drop:** Stored value is substantial
     * (> {@link MIN_STORED_FOR_DROP_CHECK}) AND the API value represents a drop
     * of more than {@link MAX_ALLOWED_DROP_PERCENT}% from stored. This catches
     * scenarios where the EP API returns a plausible-looking number (e.g. 1998
     * speeches) that is nonetheless far below the known count (10000), indicating
     * incomplete pagination or partial data loads.
     *
     * Both guards protect curated data from being overwritten by incomplete
     * EP API responses while still allowing genuine corrections (increases
     * and small decreases).
     */
    export function isCredibleApiValue(apiValue: number, storedValue: number): boolean {
      if (apiValue < MIN_CREDIBLE_VALUE && storedValue > apiValue * 5) return false;

      if (
        storedValue > MIN_STORED_FOR_DROP_CHECK &&
        apiValue < storedValue &&
        ((storedValue - apiValue) / storedValue) * 100 > MAX_ALLOWED_DROP_PERCENT
      ) {
        return false;
      }

      return true;
    }