schema-loader.ts

import fs from "fs";
import type { DocumentNode, ObjectTypeDefinitionNode } from "graphql";
import { join } from "path";
import { parse } from "graphql/language/parser.js";

const { readdir, readFile } = fs.promises;

export default class SchemaLoader {
  originalTypeDefs: DocumentNode;
  queryDef: ObjectTypeDefinitionNode;
  resourceTypeDefs: Array<ObjectTypeDefinitionNode>;

  constructor(graphql: string) {
    this.originalTypeDefs = parse(graphql);

    const typeDefinitionNodes = this.originalTypeDefs.definitions.filter(
      (def): def is ObjectTypeDefinitionNode => {
        return def.kind === "ObjectTypeDefinition";
      }
    );

    const queryDef = typeDefinitionNodes.find(
      (def) => def.name.value === "Query"
    );
    if (!queryDef) {
      throw new Error("Query is not defined");
    }
    this.queryDef = queryDef;

    this.resourceTypeDefs = typeDefinitionNodes.filter(
      (def) => def.name.value !== "Query"
    );
  }

  static async loadFrom(baseDir: string): Promise<SchemaLoader> {
    let schema = "";

    for (const path of await readdir(baseDir)) {
      if (!/^[0-9a-zA-Z].*\.graphql$/.test(path)) {
        continue;
      }

      schema += await readFile(join(baseDir, path), "utf8");
    }

    return new SchemaLoader(schema);
  }
}