function transform(file, { j }, options) {
  const root = j(file.source);

  const dirty = transformArrayMethod('concat-map', 'flatMap', root, j);

  return dirty ? root.toSource(options) : file.source;
}

export default transform;

function transformArrayMethod(method, identifierName, root, j) {
  const { identifier, dirtyFlag: importDirtyFlag } = removeImport(
    method,
    root,
    j
  );

  let dirtyFlag = importDirtyFlag;

  root
    .find(j.CallExpression, {
      callee: {
        type: "Identifier",
        name: identifier,
      },
    })
    .forEach((path) => {
      const [arrayArg, ...otherArgs] = path.node.arguments;
      if (j.Identifier.check(arrayArg) || j.ArrayExpression.check(arrayArg)) {
        path.replace(
          j.callExpression(
            j.memberExpression(arrayArg, j.identifier(identifierName)),
            otherArgs
          )
        );
        dirtyFlag = true;
      }
    });

  return dirtyFlag;
}

function removeImport(name, root, j) {
  // Find the import or require statement for 'is-boolean-object'
  const importDeclaration = root.find(j.ImportDeclaration, {
    source: {
      value: name,
    },
  });

  const requireDeclaration = root
    .find(j.CallExpression, {
      callee: {
        name: "require",
      },
      arguments: [
        {
          value: name,
        },
      ],
    })
    .closest(j.VariableDeclarator);

  // Require statements without declarations like `Object.is = require("object-is");`
  const requireAssignment = root.find(j.AssignmentExpression, {
    operator: "=",
    right: {
      callee: {
        name: "require",
      },
      arguments: [
        {
          value: name,
        },
      ],
    },
  });

  // Side effect requires statements like `require("error-cause/auto");`
  const sideEffectRequireExpression = root.find(j.ExpressionStatement, {
    expression: {
      callee: {
        name: "require",
      },
      arguments: [
        {
          value: name,
        },
      ],
    },
  });

  // Return the identifier name, e.g. 'fn' in `import { fn } from 'is-boolean-object'`
  // or `var fn = require('is-boolean-object')`
  const identifier =
    importDeclaration.paths().length > 0
      ? importDeclaration.get().node.specifiers[0].local.name
      : requireDeclaration.paths().length > 0
      ? requireDeclaration.find(j.Identifier).get().node.name
      : requireAssignment.paths().length > 0
      ? requireAssignment.find(j.Identifier).get().node.name
      : null;

  importDeclaration.remove();
  requireDeclaration.remove();
  requireAssignment.remove();
  sideEffectRequireExpression.remove();

  const dirtyFlag =
    importDeclaration.length > 0 ||
    requireDeclaration.length > 0 ||
    requireAssignment.length > 0 ||
    sideEffectRequireExpression.length > 0;

  return { identifier, dirtyFlag };
}

export default transform;