Holy Promises, Watman

wat.js

server.method('projects.remix', function(userId, remixData, done) {
  var project;
  var transaction;
  var transactionErr;

  getTransactionClient().then(function(t) {
    transaction = t;
    return begin(transaction);
  }).then(function() {
    return executeTransaction(transaction, queries.projects.create,
      [
        userId,
        remixData.id,
        server.methods.utils.version(),
        remixData.title,
        remixData.thumbnail
      ]
    );
  }).then(function(result) {
    project = server.methods.utils.formatProject(result.rows[0]);

    return Promise.resolve(remixData.pages.map(function(page) {
      return new Promise(function(resolve, reject) {
        var remixPage;
        executeTransaction(transaction, queries.pages.create,
          [
            project.id,
            page.x,
            page.y,
            page.styles
          ]
        ).then(function(result) {
          remixPage = result.rows[0];
          return Promise.resolve(page.elements.map(function(element) {
            return executeTransaction(transaction, queries.elements.create,
              [
                remixPage.id,
                element.type,
                element.attributes,
                element.styles
              ]
            );
          }));
        }).then(function(elementPromises) {
          return Promise.all(elementPromises);
        }).then(resolve)
        .catch(reject);
      });
    }));
  }).then(function(pagePromises) {
    return Promise.all(pagePromises);
  }).then(function() {
    return commit(transaction);
  }).then(function() {
    done(null, project);
  }).catch(function(err) {
    transactionErr = err;
    return rollback(transaction);
  }).then(function() {
    done(transactionErr);
  }).catch(function(err) {
    done(err);
  });
});