import { parse, print } from "graphql";

//
// 1. Parse the GraphQL tag.
// 2. From the parsed GraphQL query, get the AST definition.
// 3. From the AST definition, inject an import to that file inside the artifact directory
// 4. MD5 the printed source text
// 5. At runtime, if md5 !== import.md5, then warn the user that the query has changed
//    but the file hasn't been updated so it must be reloaded.
// 6. Replace the TemplateLiteral with the default identifier from the injected import
let artifactDirectory: string =
  process?.env?.BUN_MACRO_RELAY_ARTIFACT_DIRECTORY ??
  process?.env?.RELAY_ARTIFACT_DIRECTORY ??
  `__generated__`;

artifactDirectory = artifactDirectory.startsWith("/")
  ? artifactDirectory
  : Bun.cwd + artifactDirectory;

export function graphql(node) {
  let query;

  if (node instanceof <call />) {
    query = node.arguments[0].toString();
  } else if (node instanceof <template />) {
    query = node.toString();
  }

  if (typeof query !== "string" || query.length === 0) {
    throw new Error("BunMacroRelay: Unexpected empty graphql string.");
  }

  const ast = parse(query);

  if (ast.definitions.length === 0) {
    throw new Error("BunMacroRelay: Unexpected empty graphql tag.");
  }

  const definition = ast.definitions[0];

  if (
    definition.kind !== "FragmentDefinition" &&
    definition.kind !== "OperationDefinition"
  ) {
    throw new Error(
      `BunMacroRelay: Expected a fragment, mutation, query, or subscription, got "${definition.kind}"`
    );
  }

  const graphqlDefinition = definition;

  const definitionName = graphqlDefinition.name && graphqlDefinition.name.value;
  if (!definitionName) {
    throw new Error("GraphQL operations and fragments must contain names");
  }

  const importStmt = (
    <import
      default={definitionName}
      path={`${artifactDirectory}/${definitionName}`}
    />
  );

  try {
    const ret = (
      <>
        <inject>{importStmt}</inject>
        <id to={importStmt.namespace[definitionName]} pure />
      </>
    );
    return ret;
  } catch (exception) {
    console.error(exception);
  }
  return null;
}