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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)
}
|