const runtimeOpts: any = {
    timeoutSeconds: 540, // 9 minutes
    memory: '2GB'
  }

  // Take the existing DB struct and restruct to accommodate this app's schema.
  exports.dbReconfig = functions
  .runWith(runtimeOpts)
  .https.onCall((data) => {
    // Get each record doc then each child from within the doc and save that child to
    // the top-level 'students' collection.
   return db.collection('records').get()
    .then((querySnapshot: QuerySnapshot) => {
                      querySnapshot.forEach((doc: QueryDocumentSnapshot) => {
                        const recordId = doc.id;
                        const _fatherEmail = doc.data().fatherEmail;
                        const _motherEmail = doc.data().motherEmail;
                        const children = doc.data().children;
                        if (children) {
                          const childrenArr = convertMapToArray(children);
                          childrenArr.forEach(child => {
                            const fDob = new Date(child.dob._seconds * 1000);
                            const childObj = {
                              dob: fDob,
                              recordId,
                              fatherEmail: _fatherEmail,
                              motherEmail: _motherEmail,
                              ...child,
                            }
                           return db.collection('students').doc(child.id).set(childObj)
                           .then( () => {
                             return db.collection('financials').get()
                              .then((qs: QuerySnapshot) => {
                                qs.forEach((fDoc: QueryDocumentSnapshot) => {
                                  // A way to filter out the unwanted properties and keep desired ones.
                                  // See https://codeburst.io/use-es2015-object-rest-operator-to-omit-properties-38a3ecffe90
                                  const {childFirstName, childLastName, fatherEmail, motherEmail, grade, ...keep} = fDoc.data();
                                  return db.collection('students').doc(fDoc.id).collection('financials').doc(fDoc.id).set(keep)
                                    .then(()=> {
                                      // Go to the top-level 'financials' collection and
                                      // get all the docs from each subcollection with each financial doc.
                                      const collections = ['extendedCareCharges',
                                                            'extendedCarePayments',
                                                            'lunchCharges',
                                                            'lunchPayments',
                                                            'miscCharges',
                                                            'miscPayments',
                                                            'tuitionCharges',
                                                            'tuitionPayments'];
                                      collections.forEach(collection => {
                                        return db.collection('financials').doc(fDoc.id).collection(collection)
                                        .get()
                                        .then((qss: QuerySnapshot) => {
                                          if (qss) { // collection may not exist.
                                            console.log(`MD: qss`, qss);
                                            // Write each subcollection and their docs to subcollections under the applicable doc in the students collection.
                                            qss.forEach((d: QueryDocumentSnapshot) => {
                                            console.log(`MD: d.data()`, d.data());
                                              return db.collection('students').doc(fDoc.id).collection('financials').doc(fDoc.id)
                                              .collection(collection).doc(d.id).set(d.data());
                                            })
                                          }

                                        })
                                      })
                                    })
                                })
                              })
                           });
                          }); // end forEach(child => ...)
                        } else {
                          console.log("No children for this record.");
                        }
                      });

  });
});