"use strict";

const systemPath = require(`path`);

const normalize = require(`normalize-path`);

const _ = require(`lodash`);

const {
  GraphQLList,
  getNullableType,
  getNamedType,
  Kind
} = require(`graphql`);

const {
  getValueAt
} = require(`../utils/get-value-at`);

const findMany = typeName => (source, args, context, info) => context.nodeModel.runQuery({
  query: args,
  firstOnly: false,
  type: info.schema.getType(typeName)
}, {
  path: context.path,
  connectionType: typeName
});

const findOne = typeName => (source, args, context, info) => context.nodeModel.runQuery({
  query: {
    filter: args
  },
  firstOnly: true,
  type: info.schema.getType(typeName)
}, {
  path: context.path
});

const findManyPaginated = typeName => async (source, args, context, info) => {
  // Peek into selection set and pass on the `field` arg of `group` and
  // `distinct` which might need to be resolved.
  const group = getProjectedField(info, `group`);
  const distinct = getProjectedField(info, `distinct`);
  const extendedArgs = Object.assign({}, args, {
    group: group || [],
    distinct: distinct || []
  });
  const result = await findMany(typeName)(source, extendedArgs, context, info);
  return paginate(result, {
    skip: args.skip,
    limit: args.limit
  });
};

const distinct = (source, args, context, info) => {
  const {
    field
  } = args;
  const {
    edges
  } = source;
  const values = edges.reduce((acc, {
    node
  }) => {
    const value = getValueAt(node, field);
    return value != null ? acc.concat(value instanceof Date ? value.toISOString() : value) : acc;
  }, []);
  return Array.from(new Set(values)).sort();
};

const group = (source, args, context, info) => {
  const {
    field
  } = args;
  const {
    edges
  } = source;
  const groupedResults = edges.reduce((acc, {
    node
  }) => {
    const value = getValueAt(node, field);
    const values = Array.isArray(value) ? value : [value];
    values.filter(value => value != null).forEach(value => {
      const key = value instanceof Date ? value.toISOString() : value;
      acc[key] = (acc[key] || []).concat(node);
    });
    return acc;
  }, {});
  return Object.keys(groupedResults).sort().reduce((acc, fieldValue) => {
    acc.push(Object.assign({}, paginate(groupedResults[fieldValue], args), {
      field,
      fieldValue
    }));
    return acc;
  }, []);
};

const paginate = (results = [], {
  skip = 0,
  limit
}) => {
  if (results === null) {
    results = [];
  }

  const count = results.length;
  const items = results.slice(skip, limit && skip + limit);
  const pageCount = limit ? Math.ceil(skip / limit) + Math.ceil((count - skip) / limit) : skip ? 2 : 1;
  const currentPage = limit ? Math.ceil(skip / limit) + 1 : skip ? 2 : 1;
  const hasPreviousPage = currentPage > 1;
  const hasNextPage = skip + limit < count;
  return {
    totalCount: count,
    edges: items.map((item, i, arr) => {
      return {
        node: item,
        next: arr[i + 1],
        previous: arr[i - 1]
      };
    }),
    nodes: items,
    pageInfo: {
      currentPage,
      hasPreviousPage,
      hasNextPage,
      itemCount: items.length,
      pageCount,
      perPage: limit
    }
  };
};

const link = (options = {}, fieldConfig) => async (source, args, context, info) => {
  const resolver = fieldConfig.resolve || context.defaultFieldResolver;
  const fieldValue = await resolver(source, args, context, Object.assign({}, info, {
    from: options.from || info.from,
    fromNode: options.from ? options.fromNode : info.fromNode
  }));
  if (fieldValue == null || _.isPlainObject(fieldValue)) return fieldValue;

  if (Array.isArray(fieldValue) && (fieldValue[0] == null || _.isPlainObject(fieldValue[0]))) {
    return fieldValue;
  }

  const returnType = getNullableType(options.type || info.returnType);
  const type = getNamedType(returnType);

  if (options.by === `id`) {
    if (Array.isArray(fieldValue)) {
      return context.nodeModel.getNodesByIds({
        ids: fieldValue,
        type: type
      }, {
        path: context.path
      });
    } else {
      return context.nodeModel.getNodeById({
        id: fieldValue,
        type: type
      }, {
        path: context.path
      });
    }
  }

  const equals = value => {
    return {
      eq: value
    };
  };

  const oneOf = value => {
    return {
      in: value
    };
  };

  const operator = Array.isArray(fieldValue) ? oneOf : equals;
  args.filter = options.by.split(`.`).reduceRight((acc, key, i, {
    length
  }) => {
    return {
      [key]: i === length - 1 ? operator(acc) : acc
    };
  }, fieldValue);
  const result = await context.nodeModel.runQuery({
    query: args,
    firstOnly: !(returnType instanceof GraphQLList),
    type
  }, {
    path: context.path
  });

  if (returnType instanceof GraphQLList && Array.isArray(fieldValue) && Array.isArray(result)) {
    return fieldValue.map(value => result.find(obj => getValueAt(obj, options.by) === value));
  } else {
    return result;
  }
};

const fileByPath = (options = {}, fieldConfig) => async (source, args, context, info) => {
  const resolver = fieldConfig.resolve || context.defaultFieldResolver;
  const fieldValue = await resolver(source, args, context, Object.assign({}, info, {
    from: options.from || info.from,
    fromNode: options.from ? options.fromNode : info.fromNode
  }));
  if (fieldValue == null || _.isPlainObject(fieldValue)) return fieldValue;

  if (Array.isArray(fieldValue) && (fieldValue[0] == null || _.isPlainObject(fieldValue[0]))) {
    return fieldValue;
  }

  const findLinkedFileNode = relativePath => {
    // Use the parent File node to create the absolute path to
    // the linked file.
    const fileLinkPath = normalize(systemPath.resolve(parentFileNode.dir, relativePath)); // Use that path to find the linked File node.

    const linkedFileNode = _.find(context.nodeModel.getAllNodes({
      type: `File`
    }), n => n.absolutePath === fileLinkPath);

    return linkedFileNode;
  }; // Find the File node for this node (we assume the node is something
  // like markdown which would be a child node of a File node).


  const parentFileNode = context.nodeModel.findRootNodeAncestor(source, node => node.internal && node.internal.type === `File`);
  return resolveValue(findLinkedFileNode, fieldValue);
};

const resolveValue = (resolve, value) => Array.isArray(value) ? value.map(v => resolveValue(resolve, v)) : resolve(value);

const getProjectedField = (info, fieldName) => {
  const selectionSet = info.fieldNodes[0].selectionSet;
  const fieldNodes = getFieldNodeByNameInSelectionSet(selectionSet, fieldName, info);
  const fieldEnum = getNullableType(getNullableType(info.returnType).getFields()[fieldName].args.find(arg => arg.name === `field`).type);
  return fieldNodes.reduce((acc, fieldNode) => {
    const fieldArg = fieldNode.arguments.find(arg => arg.name.value === `field`);

    if (fieldArg) {
      const enumKey = fieldArg.value.value;
      return [...acc, fieldEnum.getValue(enumKey).value];
    } else {
      return acc;
    }
  }, []);
};

const getFieldNodeByNameInSelectionSet = (selectionSet, fieldName, info) => selectionSet.selections.reduce((acc, selection) => {
  if (selection.kind === Kind.FRAGMENT_SPREAD) {
    const fragmentDef = info.fragments[selection.name.value];

    if (fragmentDef) {
      return [...acc, ...getFieldNodeByNameInSelectionSet(fragmentDef.selectionSet, fieldName, info)];
    }
  } else if (selection.kind === Kind.INLINE_FRAGMENT) {
    return [...acc, ...getFieldNodeByNameInSelectionSet(selection.selectionSet, fieldName, info)];
  }
  /* FIELD_NODE */
  else {
      if (selection.name.value === fieldName) {
        return [...acc, selection];
      }
    }

  return acc;
}, []);

const defaultFieldResolver = (source, args, context, info) => {
  if (!source || typeof source !== `object`) return null;

  if (info.from) {
    if (info.fromNode) {
      const node = context.nodeModel.findRootNodeAncestor(source);
      if (!node) return null;
      return getValueAt(node, info.from);
    }

    return getValueAt(source, info.from);
  }

  return source[info.fieldName];
};

module.exports = {
  defaultFieldResolver,
  findManyPaginated,
  findOne,
  fileByPath,
  link,
  distinct,
  group,
  paginate
};
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