import React from 'react';
import graphql from 'graphql-anywhere';
import mapValues from 'lodash/mapValues';
import hoistStatics from 'recompose/hoistStatics';
import {getShallowChanges} from 'coral-framework/utils';
import PropTypes from 'prop-types';
import union from 'lodash/union';

// TODO: Should not depend on `props.data`
// Currently necessary because of this https://github.com/apollographql/graphql-anywhere/issues/38
function filter(doc, data, variables) {
  const resolver = (
    fieldName,
    root,
    args,
    context,
    info,
  ) => {
    return root[info.resultKey];
  };

  return graphql(resolver, doc, data, null, variables);
}

// filterProps returns only the property as defined in the fragments.
// TODO: Should not depend on `props.data`
function filterProps(props, fragments) {
  const filtered = {};
  Object.keys(fragments).forEach((key) => {
    if (!(key in props)) {
      return;
    }
    filtered[key] = props.data
      ? filter(fragments[key], props[key], props.data.variables)
      : props[key];
  });
  return filtered;
}

// hasEqualLeaves compares two different apollo query result for equality.
function hasEqualLeaves(a, b, path = '') {
  for (const key of union(Object.keys(a), Object.keys(b))) {
    if (!(key in a) || !(key in b)) {
      return false;
    }
    if (typeof a[key] === 'object' && a[key] && b[key]) {
      if (Array.isArray(a[key])) {
        if (a[key].length !== b[key].length) {
          return false;
        }
      }
      if (!hasEqualLeaves(a[key], b[key], `${path}.${key}`)) {
        return false;
      }
      continue;
    }
    if (a[key] !== b[key]) {
      return false;
    }
  }
  return true;
}

export default (fragments) => hoistStatics((BaseComponent) => {
  class WithFragments extends React.Component {
    static contextTypes = {
      graphqlRegistry: PropTypes.object,
    };

    get graphqlRegistry() {
      return this.context.graphqlRegistry;
    }

    resolveDocument(documentOrCallback) {
      const document = typeof documentOrCallback === 'function'
        ? documentOrCallback(this.props, this.context)
        : documentOrCallback;
      return this.graphqlRegistry.resolveFragments(document);
    }

    fragments = mapValues(fragments, (val) => this.resolveDocument(val));
    fragmentKeys = Object.keys(fragments).sort();

    // Cache variables between lifecycles to speed up render.
    filteredProps = filterProps(this.props, this.fragments)
    queryDataHasChanged = false;
    shallowChanges = null;

    componentWillReceiveProps(next) {
      this.shallowChanges = getShallowChanges(this.props, next);

      if (this.fragmentKeys.some((key) => this.shallowChanges.indexOf(key) >= 0)) {
        const nextFilteredProps = filterProps(next, this.fragments);
        this.queryDataHasChanged = !hasEqualLeaves(this.filteredProps, nextFilteredProps);
        if (this.queryDataHasChanged) {

          // Only changed props when query data has changed.
          this.filteredProps = filterProps(next, this.fragments);
        }
      }
    }

    shouldComponentUpdate(next) {
      const onlyQueryDataChanges = this.shallowChanges.every((key) => this.fragmentKeys.indexOf(key) >= 0);

      if (onlyQueryDataChanges) {
        return this.queryDataHasChanged;
      }

      return this.shallowChanges.length !== 0;
    }

    render() {
      const queryProps = this.filteredProps;
      return <BaseComponent
        {...this.props}
        {...queryProps}
      />;
    }
  }

  WithFragments.fragments = fragments;
  return WithFragments;
});