import { Sum, HandlerSetter, ItemSelector } from 'interfaces';
import Operation from '../Operation';
import checkCondition from './checkCondition';

export default function getSumHandlers(
  parentEntityType: string,
  propKey: string,
  propValue: Sum
): {selfHandlerSetters: Array<HandlerSetter>, childHandlerSetters: Array<HandlerSetter>} {
  // ---------- selfHandler ----------
  const selfHandlerSetter: HandlerSetter = {
    handlerHolder: 'SELF', // 'SELF' = parent
    onAdd: [{
      updatingParentType: null,
      operationModifier: (parentOperation: Operation) => { // so, selfOperation = parentOperation
        parentOperation.modify({ [propKey]: 0 });
      }
    }],
    onUpdate: [],
    onDelete: []
  };

  // ---------- childHandler ----------
  const { childEntityType, childPropKey, conditions } = propValue;

  const checkNeedUpdatingParents = (childOperation: Operation, beforeParentItemSelectors: ItemSelector[], afterParentItemSelectors: ItemSelector[] ) => {
    let needUpdate: boolean = false;
    const deltas = {};
    beforeParentItemSelectors.forEach(s => deltas[s.id] = 0);
    afterParentItemSelectors.forEach(s => deltas[s.id] = 0);

    const beforeChildNum = +childOperation.before[childPropKey] || 0;
    const isBeforeChildOnCondition = checkCondition(childOperation.before, conditions);
    if (isBeforeChildOnCondition) {
      beforeParentItemSelectors.forEach(s => deltas[s.id] -= beforeChildNum);
    }
    const afterChildNum = +childOperation.after[childPropKey] || 0;
    const isAfterChildOnCondition = checkCondition(childOperation.after, conditions);
    if (isAfterChildOnCondition) {
      afterParentItemSelectors.forEach(s => deltas[s.id] += afterChildNum);
    }
    Object.keys(deltas).forEach(parentId => {
      if (deltas[parentId] !== 0) needUpdate = true;
    });
    return needUpdate;
  }

  const updateSumOfParentOperations = (
    childOperation: Operation,
    beforeParentOperations: Array<Operation>,
    afterParentOperations: Array<Operation>
  ) => {
    const beforeChildNum = +childOperation.before[childPropKey] || 0;
    const isBeforeChildOnCondition = checkCondition(childOperation.before, conditions);
    if (isBeforeChildOnCondition) {
      beforeParentOperations.forEach((parentOperation) => {
        parentOperation.addNumToProp(propKey, -beforeChildNum);
      });
    }

    const afterChildNum = +childOperation.after[childPropKey] || 0;
    const isAfterChildOnCondition = checkCondition(childOperation.after, conditions);
    if (isAfterChildOnCondition) {
      afterParentOperations.forEach((parentOperation) => {
        parentOperation.addNumToProp(propKey, afterChildNum);
      });
    }
  };

  const childHandlerSetter: HandlerSetter = {
    handlerHolder: childEntityType,
    onAdd: [{
      checkNeedUpdatingParents,
      updatingParentType: parentEntityType,
      operationModifier: (
        childOperation: Operation,
        beforeParentOperations: Array<Operation>,
        afterParentOperations: Array<Operation>
      ) => {
        updateSumOfParentOperations(childOperation, beforeParentOperations, afterParentOperations);
      }
    }],
    onUpdate: [{
      checkNeedUpdatingParents,
      updatingParentType: parentEntityType,
      operationModifier: (
        childOperation: Operation,
        beforeParentOperations: Array<Operation>,
        afterParentOperations: Array<Operation>
      ) => {
        updateSumOfParentOperations(childOperation, beforeParentOperations, afterParentOperations);
      }
    }],
    onDelete: [{
      checkNeedUpdatingParents,
      updatingParentType: parentEntityType,
      operationModifier: (
        childOperation: Operation,
        beforeParentOperations: Array<Operation>,
        afterParentOperations: Array<Operation>
      ) => {
        updateSumOfParentOperations(childOperation, beforeParentOperations, afterParentOperations);
      }
    }]
  };

  return { selfHandlerSetters: [selfHandlerSetter], childHandlerSetters: [childHandlerSetter] };
}