All files combineIncludesLink.js

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85.19% Branches 23/27
92.86% Functions 13/14
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import { visit } from 'graphql'
import { print } from 'graphql/language/printer'
import { ApolloLink, Observable, createOperation } from 'apollo-link'
import { BatchLink } from 'apollo-link-batch'
 
const extractGroupInfo = operation => {
  const variables = {}
 
  for (let name in operation.variables) {
    if (operation.includes.indexOf(name) === -1) {
      variables[name] = operation.variables[name]
    }
  }
 
  return {
    key: `${print(operation.query)}|${JSON.stringify(variables)}`,
    includes: operation.includes,
    operationName: operation.operationName,
    variables: variables,
    query: operation.query
  }
}
 
const batchHandler = (operations, forward) => {
  // Early exit in case only one operation is available.
  Iif (operations.length === 1) {
    return forward[0](operations[0]).map(result => [result])
  }
 
  const groups = {}
 
  for (let i in operations) {
    const {
      key,
      includes,
      variables,
      operationName,
      query,
      extensions = {}
    } = extractGroupInfo(operations[i])
 
    // Ensure group exists.
    groups[key] = groups[key] || {
      operations: [],
      includes: [],
      variables,
      operationName,
      query,
      extensions
    }
 
    // Attach operation info.
    groups[key].operations.push(operations[i])
 
    // Merge extensions.
    groups[key].extensions = { ...groups[key].extensions, ...extensions }
 
    // Enforce enabled includes.
    for (let j in includes) {
      groups[key].variables[includes[j]] =
        groups[key].variables[includes[j]] ||
        operations[i].variables[includes[j]]
    }
  }
 
  // Use first forward as default.
  // @TODO: this might break context usage from here on!
  const forwarder = forward[0]
 
  return new Observable(observer => {
    const results = []
 
    for (let key in groups) {
      const {
        operationName,
        query,
        variables,
        extensions,
        operations: groupOperations
      } = groups[key]
 
      const combinedContext = groupOperations.reduce(
        (combined, operation) => ({ ...combined, ...operation.getContext() }),
        {}
      )
 
      const combinedOperation = createOperation(combinedContext, {
        operationName,
        query,
        variables,
        extensions
      })
 
      // Dispatch operation
      // @TODO: handle errors down the link stream.
      forwarder(combinedOperation).subscribe(result => {
        groupOperations.forEach(operation => {
          const context = combinedOperation.getContext()
          context.httpResponse = context.response
          // Save response context.
          operation.setContext(context)
          // Register as many results as there were
          // original operations in this group.
          results.push(result)
        })
 
        if (results.length === operations.length) {
          observer.next(results)
          observer.complete()
        }
      })
    }
  })
}
 
/**
 * Group queries per operationName.
 */
const batchKey = ({ operationName }) => operationName || null
 
/**
 * Determines if an operation can be combined based on the existence
 * of both an operationName and @include directives.
 */
const defaultCanCombine = operation => {
  // Early exit when operation is not named.
  Iif (!operation.operationName) return false
 
  let hasIncludes = false
 
  visit(operation.query, {
    Directive: (
      { name: { value: name }, arguments: args },
      key,
      parent,
      path,
      ancestors
    ) => {
      Eif (name === 'include') {
        hasIncludes = true
 
        // Save include variables for further reference.
        operation.includes = (operation.includes || []).concat(
          args[0].value.name.value
        )
      }
    }
  })
 
  // Early exit when operation has no include directive.
  if (!hasIncludes) return false
 
  return true
}
 
export class CombineIncludesLink extends ApolloLink {
  /**
   * The batching link.
   */
  batcher
 
  /**
   * A callback to determine if an operation can be combined.
   */
  canCombine
 
  constructor ({
    /**
     * The interval at which to batch, in milliseconds.
     */
    batchInterval = 10,
 
    /**
     * The maximum number of operations to include in one fetch.
     */
    batchMax = 10,
 
    /**
     * A custom callback to determine if an operation can be combined.
     *
     * Defaults to accounting
     */
    canCombine = defaultCanCombine
  } = {}) {
    super()
 
    this.canCombine = canCombine
 
    this.batcher = new BatchLink({
      batchInterval,
      batchMax,
      batchHandler,
      batchKey
    })
  }
 
  normalizeResponse = operation => result => {
    const context = operation.getContext()
    context.response = context.httpResponse
    operation.setContext(context)
    return result
  }
 
  /**
   * Link query requester.
   */
  request = (operation, forward) =>
    // Can this operation be combined?
    this.canCombine(operation, defaultCanCombine)
      ? this.batcher
        .request(operation, forward)
        .map(this.normalizeResponse(operation))
      : forward(operation)
}