text: import { iterateObject, iterateArray, hasOwnProperty } from '../../utils';
  import { executeMixinWatchers } from './executeMixinWatchers';
  import { InternalMixin } from './InternalMixin';
  
  export function calculateAttrs({
    newAttrs, currentAttrs, currentMixins,
    elem, parentBlock, firstTime
  }) {
    iterateObject(currentAttrs, (value, attr) => {
      if (!hasOwnProperty(newAttrs, attr)) {
        if (value instanceof InternalMixin) {
          currentMixins[attr].$$.remove();
          delete currentMixins[attr];
        } else {
          elem.removeAttr(attr);
        }
  
        delete currentAttrs[attr];
      }
    });
  
    const mixins = [];
  
    iterateObject(newAttrs, (value, attr) => {
      const prevValue = currentAttrs[attr];
  
      if (prevValue === value) {
        return;
      }
  
      if (value instanceof InternalMixin) {
        const {
          parentScope,
          Mixin,
          value: evalFn
        } = value;
  
        if (prevValue) {
          const mixin = currentMixins[attr];
          const { $$ } = mixin;
          let newValue;
  
          $$.internal = value;
  
          if ($$.internals.indexOf(value) === -1) {
            $$.internals.push(value);
  
            if (Mixin.evaluate) {
              newValue = parentScope.$$.evaluate(
                evalFn,
                constructMixinWatcher(mixin, value),
                mixin
              );
            }
          } else if (Mixin.evaluate) {
            newValue = parentScope.$$.evaluate(evalFn);
          }
  
          if (Mixin.evaluate) {
            executeMixinWatchers(mixin, newValue);
          }
        } else {
          const buildMixin = () => {
            const mixin = new Mixin({
              ...value,
              parentBlock,
              elem,
              internal: value
            });
            const { $$ } = mixin;
  
            $$.internal = value;
            $$.internals = [value];
            currentMixins[attr] = mixin;
  
            if (Mixin.evaluate) {
              const afterUpdate = (newValue, oldValue) => {
                try {
                  mixin.afterUpdate(newValue, oldValue);
                } catch (err) {
                  console.error(`Uncaught error in ${ $$.name }#afterUpdate:`, err);
                }
              };
  
              $$.value = parentScope.$$.evaluate(
                evalFn,
                constructMixinWatcher(mixin, value),
                mixin
              );
              afterUpdate($$.evaluate(afterUpdate));
            }
          };
  
          if (firstTime) {
            mixins.push(buildMixin);
          } else {
            buildMixin();
          }
        }
      } else {
        elem.attr(attr, value);
      }
  
      currentAttrs[attr] = value;
    });
  
    if (firstTime) {
      return () => {
        iterateArray(mixins, buildMixin);
      };
    }
  }
  
  function constructMixinWatcher(mixin, internalMixin) {
    return function (newValue) {
      if (mixin.$$.internal === internalMixin) {
        executeMixinWatchers(mixin, newValue);
      }
    };
  }
  
  function buildMixin(builder) {
    builder();
  }
  