Function explainDrop

explainDrop(title: string, ast: SearchAst, fuzzyWords: boolean): string[]

Explains why a title failed an AST predicate: missing phrases are listed verbatim, and a NOT branch that excluded the title is reported as NOT <phrase>. Every drop gets at least one reason, so the dropped table is never blank.

Parameters

title: string
The rejected title.
ast: SearchAst
The parsed query tree.
fuzzyWords: boolean
Whether per-word fuzzy presence counts.

Returns string[]

The phrases responsible for the drop.

Example

const { ast } = parseSearchQuery("sodium AND NOT borohydride");
explainDrop("Potassium Chloride", ast, true);     // => ["sodium"]
explainDrop("Sodium Borohydride 98%", ast, true); // => ["NOT borohydride"]

Source

export function explainDrop(title: string, ast: SearchAst, fuzzyWords: boolean): string[] {
  switch (ast.type) {
    case 'term':
      return isPhrasePresent(title, ast.value, fuzzyWords) ? [] : [ast.value];
    case 'and':
      return [
        ...explainDrop(title, ast.left, fuzzyWords),
        ...explainDrop(title, ast.right, fuzzyWords),
      ];
    case 'or': {
      const left = explainDrop(title, ast.left, fuzzyWords);
      const right = explainDrop(title, ast.right, fuzzyWords);
      // An OR only fails when both branches fail; if either matched, nothing is missing.
      return left.length > 0 && right.length > 0 ? [...left, ...right] : [];
    }
    case 'not':
      // The NOT held (operand absent), so it isn't the reason; otherwise it is.
      return matchesAst(title, ast.operand, fuzzyWords) ? [`NOT ${renderAst(ast.operand)}`] : [];
    default:
      return [];
  }
}