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Overview

src/services/rulesFilter.ts implements the first layer of the hybrid filter pipeline. It is a pure function — no I/O, no side effects, and no external calls. All state required for deduplication is injected by the caller (dealsService.ts).

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Exported function

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applyHardFilters

export function applyHardFilters(
  deals: Deal[],
  options: RulesFilterOptions,
  notifiedIds: Set<string>,
): Deal[]
Filters a raw list of Deal objects returned by CheapShark against a set of hard thresholds and a deduplication set.
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deals
Deal[]
required
Raw deals fetched from the CheapShark API.
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options
RulesFilterOptions
required
Threshold values for each filter criterion. See the interface section below.
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notifiedIds
Set<string>
required
Set of steamAppID strings already notified within the deduplication window. Built by dealsService using getNotifiedIds() and injected here to keep this module side-effect-free.

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RulesFilterOptions interface

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minDiscountPercent
number
required
Minimum required savings percentage. Deals with savings < minDiscountPercent are rejected.
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minMetacriticScore
number
required
Minimum Metacritic score for the quality gate. Used in the OR condition together with minSteamRatingPercent.
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minSteamRatingPercent
number
required
Minimum Steam user rating percentage for the quality gate. A deal passes if steamRatingPercent >= minSteamRatingPercent even if it has no Metacritic score.
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maxPriceUSD
number
required
Maximum sale price in USD. Deals with salePrice > maxPriceUSD are rejected regardless of discount or quality.

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Filter logic

Each deal is evaluated against two categories of criteria: Rejection criteria — any one of these causes the deal to be dropped:
  • savings < minDiscountPercent
  • salePrice > maxPriceUSD
  • steamAppID is present in notifiedIds (deduplication)
Quality gate — deal must pass at least one of:
  • metacriticScore >= minMetacriticScore (only evaluated when a non-zero score is present)
  • steamRatingPercent >= minSteamRatingPercent
The quality gate uses an OR condition so games without a Metacritic score can still pass on Steam community ratings alone.

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Source code

export function applyHardFilters(
  deals: Deal[],
  options: RulesFilterOptions,
  notifiedIds: Set<string>,
): Deal[] {
  return deals.filter((deal) => {
    const savings = parseFloat(deal.savings);
    const salePrice = parseFloat(deal.salePrice);
    const metacritic = parseInt(deal.metacriticScore) || 0;
    const steamRating = parseInt(deal.steamRatingPercent) || 0;

    if (savings < options.minDiscountPercent) return false;
    if (salePrice > options.maxPriceUSD) return false;
    if (notifiedIds.has(deal.steamAppID)) return false;

    const hasGoodMetacritic = metacritic > 0 && metacritic >= options.minMetacriticScore;
    const hasGoodSteamRating = steamRating >= options.minSteamRatingPercent;

    return hasGoodMetacritic || hasGoodSteamRating;
  });
}
This module is intentionally pure — no disk access, no network calls, no global state. The deduplication set is constructed by dealsService and injected as a Set<string>, keeping rulesFilter independently testable with zero mocking.

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