import { Config } from '../Config';
import { BaseHandler, BaseDecider } from '../entities';

const validator = {
  validate(config: Config, workflow: any) {
    if (workflow.type !== 'decision') {
      return 'top level workflow item must be decision task';
    }
    const leftToCheck = [workflow];
    while (leftToCheck.length) {
      const toCheck = leftToCheck.shift();
      if (typeof toCheck !== 'object') {
        return 'task is malformed';
      }
      if (!toCheck.name) {
        return `task ${toCheck.id} does not have a name`;
      }
      if (!toCheck.id) {
        return `task ${toCheck.name} does not have an id`;
      }
      if (!toCheck.handler) {
        return `task id: ${toCheck.id} name: ${toCheck.name} does not define a handler`;
      }
      if (!toCheck.parameters) {
        return `task id: ${toCheck.id} name: ${toCheck.name} does not define parameters`;
      }
      if (toCheck.maxRetry && typeof toCheck.maxRetry !== 'number') {
        return `task id: ${toCheck.id} name: ${toCheck.name} gave a maxRetry but of an invalid type`;
      }
      if (typeof toCheck.parameters !== 'object') {
        return `task id: ${toCheck.id} name: ${toCheck.name} does not object for parameters`;
      }

      let handler: BaseHandler | null = null;
      if (toCheck.type === 'decision') {
        handler = config.deciders.getModule(toCheck.handler);
      } else if (toCheck.type === 'activity') {
        let actType = config.activities.getModule(toCheck.handler);
        if (actType) {
          handler = actType.ActivityHandler;
        }
      } else {
        return `task id: ${toCheck.id}, name: ${toCheck.name} gave an invalid type`;
      }

      if (!handler) {
        return `${toCheck.type || 'activity'} node name: ${toCheck.name},
       id: ${toCheck.id} did not define a known handler, gave ${toCheck.handler}`;
      }

      let invalidReason = handler.validateTask(toCheck.parameters);
      if (invalidReason) {
        return `task ${toCheck.name}, id: ${toCheck.id}, handler: ${toCheck.handler}, was invalid: ${invalidReason}`;
      }

      if (toCheck.type === 'decision') {
        let decisionHandler = handler as typeof BaseDecider;
        let children = decisionHandler.getChildren(toCheck.parameters);
        if (!Array.isArray(children)) {
          children = [children];
        }
        leftToCheck.push(...children);
      }
    }
    return null;
  }
};

export { validator }