node-redis/packages/search/lib/commands/SPELLCHECK.ts

import { RedisArgument, CommandArguments, Command, ReplyUnion } from '@redis/client/dist/lib/RESP/types';

export interface Terms {
  mode: 'INCLUDE' | 'EXCLUDE';
  dictionary: RedisArgument;
}

export interface FtSpellCheckOptions {
  DISTANCE?: number;
  TERMS?: Terms | Array<Terms>;
  DIALECT?: number;
}

export default {
  FIRST_KEY_INDEX: undefined,
  IS_READ_ONLY: true,
  transformArguments(index: RedisArgument, query: RedisArgument, options?: FtSpellCheckOptions) {
    const args = ['FT.SPELLCHECK', index, query];

    if (options?.DISTANCE) {
      args.push('DISTANCE', options.DISTANCE.toString());
    }

    if (options?.TERMS) {
      if (Array.isArray(options.TERMS)) {
        for (const term of options.TERMS) {
          pushTerms(args, term);
        }
      } else {
        pushTerms(args, options.TERMS);
      }
    }

    if (options?.DIALECT) {
      args.push('DIALECT', options.DIALECT.toString());
    }

    return args;
  },
  transformReply: {
    2: (rawReply: SpellCheckRawReply): SpellCheckReply => {
      return rawReply.map(([, term, suggestions]) => ({
        term,
        suggestions: suggestions.map(([score, suggestion]) => ({
          score: Number(score),
          suggestion
        }))
      }));
    },
    3: undefined as unknown as () => ReplyUnion,
  },
  unstableResp3: true
} as const satisfies Command;

type SpellCheckRawReply = Array<[
  _: string,
  term: string,
  suggestions: Array<[score: string, suggestion: string]>
]>;

type SpellCheckReply = Array<{
  term: string,
  suggestions: Array<{
    score: number,
    suggestion: string
  }>
}>;

function pushTerms(args: CommandArguments, { mode, dictionary }: Terms) {
  args.push('TERMS', mode, dictionary);
}