protected function findUseDeclarations()

in src/Migrations/HSLMigration.hack [503:590]
75 lines of code
16 McCabe index (conditional complexity)

  protected function findUseDeclarations(
    vec<INamespaceUseDeclaration> $declarations,
  ): (vec<INamespaceUseDeclaration>, vec<HslNamespace>) {

    $search = vec['HH', 'Lib'];
    $nodes = vec[];
    $suffixes = vec[];
    foreach ($declarations as $decl) {
      // we only care about "use namespace" directives
      if (!($decl->getKind() is NamespaceToken)) {
        continue;
      }

      if ($decl is NamespaceGroupUseDeclaration) {
        // group declarations: does prefix match?
        $parts = $decl->getPrefix()
          ->getParts()
          ->getChildrenOfItemsOfType(NameToken::class);
        if (C\count($parts) !== 2) {
          continue;
        }
        $found_prefix = true;
        foreach ($parts as $i => $token) {
          if ($token?->getText() === $search[$i]) {
            continue;
          }
          $found_prefix = false;
          break;
        }

        // prefix didn't match? skip this declaration
        if (!$found_prefix) {
          continue;
        }

        // prefix matches: add node to list of nodes
        $nodes[] = $decl;

        $clauses = $decl->getClauses()
          ->getDescendantsByType<NamespaceUseClause>();
        $suffixes = $clauses
          |> Vec\map(
            $$,
            $c ==> {
              $n = $c->getName();
              return $n is NameToken
                ? HslNamespace::coerce($n->getText())
                : null;
            },
          )
          |> Vec\filter_nulls($$)
          |> Vec\concat($suffixes, $$);
      } else {
        invariant(
          $decl is NamespaceUseDeclaration,
          'Unhandled declaration type',
        );

        $clauses = $decl->getClauses()->getChildrenOfItems();
        foreach ($clauses as $clause) {
          $name = $clause->getName();
          if ($name is QualifiedName) {
            $parts = $name->getParts()
              ->getChildrenOfItemsOfType(NameToken::class);
            if (C\count($parts) !== 3) {
              continue;
            }

            foreach ($parts as $i => $token) {
              if ($i < 2 && $token?->getText() !== $search[$i]) {
                break;
              }

              if ($i === 2) {
                // we found an HH\Lib\* use statement, add the node and suffix
                $nodes[] = $decl;
                $ns = HslNamespace::coerce($token?->getText());
                if ($ns !== null) {
                  $suffixes[] = $ns;
                }
              }
            }
          }
        }
      }
    }
    return tuple($nodes, $suffixes);
  }