sql.ts

const arrayMarker = Symbol("sql.array");

export interface ArraySqlReplacement {
  [arrayMarker]: true;
  array: any[];
  joiner: string;
}

const isArraySqlReplacement = (value: any): value is ArraySqlReplacement =>
  typeof value === "object" && value !== null && value[arrayMarker];

export function sql(
  fragments: TemplateStringsArray,
  ...values: any[]
): [string, any[]] {
  const fragmentsIt = fragments[Symbol.iterator]();
  const strings = [fragmentsIt.next().value];
  const bindings = [];

  let index = 1;
  for (const value of values) {
    if (isArraySqlReplacement(value)) {
      const { array, joiner } = value;
      strings.push(array.map(() => "$" + index++).join(joiner));
      bindings.push(...array);
    } else {
      strings.push("$" + index++);
      bindings.push(value);
    }

    strings.push(fragmentsIt.next().value);
  }

  return [strings.join(""), bindings];
}

sql.array = (array: any[], joiner: string = ", "): ArraySqlReplacement =>
  ({ [arrayMarker]: true, array, joiner });