/
TransformQuery.ts
122 lines (105 loc) · 3.43 KB
/
TransformQuery.ts
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import { visit, Kind, SelectionSetNode, FragmentDefinitionNode, GraphQLError } from 'graphql';
import { Transform, Request, ExecutionResult, relocatedError } from '@graphql-tools/utils';
export type QueryTransformer = (
selectionSet: SelectionSetNode,
fragments: Record<string, FragmentDefinitionNode>
) => SelectionSetNode;
export type ResultTransformer = (result: any) => any;
export type ErrorPathTransformer = (path: ReadonlyArray<string | number>) => Array<string | number>;
export default class TransformQuery implements Transform {
private readonly path: Array<string>;
private readonly queryTransformer: QueryTransformer;
private readonly resultTransformer: ResultTransformer;
private readonly errorPathTransformer: ErrorPathTransformer;
private readonly fragments: Record<string, FragmentDefinitionNode>;
constructor({
path,
queryTransformer,
resultTransformer = result => result,
errorPathTransformer = errorPath => [].concat(errorPath),
fragments = {},
}: {
path: Array<string>;
queryTransformer: QueryTransformer;
resultTransformer?: ResultTransformer;
errorPathTransformer?: ErrorPathTransformer;
fragments?: Record<string, FragmentDefinitionNode>;
}) {
this.path = path;
this.queryTransformer = queryTransformer;
this.resultTransformer = resultTransformer;
this.errorPathTransformer = errorPathTransformer;
this.fragments = fragments;
}
public transformRequest(originalRequest: Request): Request {
const pathLength = this.path.length;
let index = 0;
const document = visit(originalRequest.document, {
[Kind.FIELD]: {
enter: node => {
if (index === pathLength || node.name.value !== this.path[index]) {
return false;
}
index++;
if (index === pathLength) {
const selectionSet = this.queryTransformer(node.selectionSet, this.fragments);
return {
...node,
selectionSet,
};
}
},
leave: () => {
index--;
},
},
});
return {
...originalRequest,
document,
};
}
public transformResult(originalResult: ExecutionResult): ExecutionResult {
const data = this.transformData(originalResult.data);
const errors = originalResult.errors;
return {
data,
errors: errors != null ? this.transformErrors(errors) : undefined,
};
}
private transformData(data: any): any {
const leafIndex = this.path.length - 1;
let index = 0;
let newData = data;
if (newData) {
let next = this.path[index];
while (index < leafIndex) {
if (data[next]) {
newData = newData[next];
} else {
break;
}
index++;
next = this.path[index];
}
newData[next] = this.resultTransformer(newData[next]);
}
return newData;
}
private transformErrors(errors: ReadonlyArray<GraphQLError>): ReadonlyArray<GraphQLError> {
return errors.map(error => {
const path: ReadonlyArray<string | number> = error.path;
let match = true;
let index = 0;
while (index < this.path.length) {
if (path[index] !== this.path[index]) {
match = false;
break;
}
index++;
}
const newPath = match ? path.slice(0, index).concat(this.errorPathTransformer(path.slice(index))) : path;
return relocatedError(error, newPath);
});
}
}