const meta = {
  messages: {
    readonlySpread:
      'Flow type with spread property and all readonly properties must be '
    + 'wrapped in \'$ReadOnly<…>\' to prevent accidental loss of readonly-ness.',
  },
};

const create = (context) => ({
  TypeAlias(node) {
    if (node.right.type === 'GenericTypeAnnotation' && node.right.id.name === '$ReadOnly') {
      // it's already $ReadOnly<…>, nothing to do
    } else if (node.right.type === 'ObjectTypeAnnotation') {
      // let's iterate all props and if everything is readonly then throw
      let shouldThrow = false;
      let hasSpread = false;
      for (const property of node.right.properties) {
        if (property.type === 'ObjectTypeProperty') {
          if (property.variance && property.variance.kind === 'plus') {
            shouldThrow = true;
          } else {
            shouldThrow = false;
            break;
          }
        } else if (property.type === 'ObjectTypeSpreadProperty') {
          hasSpread = true;
        }
      }

      if (hasSpread === true && shouldThrow === true) {
        context.report({
          messageId: 'readonlySpread',
          node: node.right,
        });
      }
    }
  },
});

export default {
  create,
  meta,
};