obscenity/dist/transformer/collapse-duplicates/index.d.ts

Robust, extensible profanity filter.

/**
 * Creates a transformer that collapses duplicate characters. This is useful for
 * detecting variants of patterns in which a character is repeated to bypass
 * detection.
 *
 * As an example, the pattern `hi` does not match `hhiii` by default, as the
 * frequency of the characters does not match. With this transformer, `hhiii`
 * would become `hi`, and would therefore match the pattern.
 *
 * **Application order**
 *
 * It is recommended that this transformer be applied after all other
 * transformers. Using it before other transformers may have the effect of not
 * catching duplicates of certain characters that were originally different but
 * became the same after a series of transformations.
 *
 * **Warning**
 *
 * This transformer should be used with caution, as while it can make certain
 * patterns match text that wouldn't have been matched before, it can also go
 * the other way. For example, the pattern `hello` clearly matches `hello`, but
 * with this transformer, by default, `hello` would become `helo` which does
 * _not_ match. In this cases, the `customThresholds` option can be used to
 * allow two `l`s in a row, making it leave `hello` unchanged.
 *
 * @example
 * ```typescript
 * // Collapse runs of the same character.
 * const transformer = collapseDuplicatesTransformer();
 * const matcher = new RegExpMatcher({ ..., blacklistMatcherTransformers: [transformer] });
 * ```
 * @example
 * ```typescript
 * // Collapse runs of characters other than 'a'.
 * const transformer = collapseDuplicatesTransformer({ customThresholds: new Map([['a', Infinity]]) });
 * const matcher = new RegExpMatcher({ ..., blacklistMatcherTransformers: [transformer] });
 * ```
 * @param options - Options for the transformer.
 * @returns A container holding the transformer, which can then be passed to the
 * [[RegExpMatcher]].
 */
export declare function collapseDuplicatesTransformer({ defaultThreshold, customThresholds, }?: CollapseDuplicatesTransformerOptions): import("../Transformers").StatefulTransformerContainer;
export interface ProcessedCollapseDuplicatesTransformerOptions {
    customThresholds: Map<number, number>;
    defaultThreshold: number;
}
/**
 * Options for the collapse duplicates transformer.
 */
export interface CollapseDuplicatesTransformerOptions {
    /**
     * Custom thresholds for characters. If a character has an entry
     * corresponding to it, the value of tne entry will be used as the maximum
     * length of character runs comprised of said character before they are
     * collapsed.
     *
     * The intended use-case for this option is for characters which appear
     * more than once in a row in patterns. For example, the word `book` has
     * two `o`s in a row, and matches `book`. With this transformer, though,
     * `book` would become `bok`, meaning that `book` would no longer match `book`.
     * The fix would be to add an entry corresponding to `o` that overrides its
     * threshold to be `2`, with the effect of leaving `book` unchanged.
     *
     * @default new Map()
     */
    customThresholds?: Map<string, number>;
    /**
     * The maximum number of characters in a run that will be accepted before
     * they will be collapsed.
     *
     * For example, if this value was `2`, `aa` would stay the same but `aaa`
     * would be transformed to `aa`.
     *
     * @default 1
     */
    defaultThreshold?: number;
}