Add history attributes to ChargeVersionModel (#1272)

https://eaflood.atlassian.net/browse/WATER-4560

> Part of the work to display NALD mod log records as history in WRLS

So, we are now importing mod logs from NALD and have added a model linked to charge, licence and return version models to allow us to retrieve them from the database.

We are in the process of building [a new licence history page](#1182) and we need to update the view of the charge version in the future.

Because of this, we believe adding a modifier and instance methods to the `ChargeVersionModel` that will handle fetching the mod logs and determining this information is valuable.

This change updates the `ChargeVersionModel` with these properties. This is similar to the work we did in [Add history attributes to ReturnVersionModel](#1267) and [Add history attributes to LicenceVersionModel](#1271).

app/models/charge-version.model.js

@@ -14,6 +14,14 @@ class ChargeVersionModel extends BaseModel {
     return 'chargeVersions'
   }
 
+  // Defining which fields contain json allows us to insert an object without needing to stringify it first
+  static get jsonAttributes () {
+    return [
+      'approvedBy',
+      'createdBy'
+    ]
+  }
+
   static get relationMappings () {
     return {
       billingAccount: {
@@ -82,6 +90,190 @@ class ChargeVersionModel extends BaseModel {
       }
     }
   }
+
+  /**
+   * Modifiers allow us to reuse logic in queries, eg. select the charge version, note, and/or all mod log records:
+   *
+   * return ChargeVersionModel.query()
+   *   .findById(chargeVersionId)
+   *   .modify('history')
+   *
+   * See {@link https://vincit.github.io/objection.js/recipes/modifiers.html | Modifiers} for more details
+   */
+  static get modifiers () {
+    return {
+      // history modifier fetches all the related records needed to determine history properties, for example, created
+      // at, and created by from the record, plus its note, change reason, and NALD mod logs (where they exist)
+      history (query) {
+        query
+          .select(['createdBy'])
+          .withGraphFetched('modLogs')
+          .modifyGraph('modLogs', (builder) => {
+            builder.select([
+              'id',
+              'naldDate',
+              'note',
+              'reasonDescription',
+              'userId'
+            ])
+              .orderBy('externalId', 'asc')
+          })
+          .withGraphFetched('changeReason')
+          .modifyGraph('changeReason', (builder) => {
+            builder.select([
+              'id',
+              'description'
+            ])
+          })
+          .withGraphFetched('chargeVersionNote')
+          .modifyGraph('chargeVersionNote', (builder) => {
+            builder.select([
+              'id',
+              'note'
+            ])
+          })
+      }
+    }
+  }
+
+  /**
+   * Determine the created at date of the 'source' record using history
+   *
+   * > We recommend adding the `history` modifier to your query to support this determination
+   *
+   * NALD has a concept called 'mod log'. When someone creates a new licence, charge, or return version, they can
+   * provide a reason and a note, which is saved as the 'mod log'. Who created the 'mod log' and when is also captured.
+   *
+   * It was intended to record a history of changes to the licence.
+   *
+   * Unfortunately, NALD doesn't enforce it's creation. But as the NALD version records don't capture the who and when,
+   * they are the best 'source' we have to determine this information for imported records.
+   *
+   * If there are mod logs for this record, it extracts the date from the first entry, for example, `2019-06-02`, and
+   * returns it. Else, it falls back to using the return version's `createdAt` time stamp.
+   *
+   * > The NALD date takes priority, because all records will have a created at date. But in the case of imported
+   * > records this will be when it was imported to WRLS, which can be some time after it was created in NALD.
+   *
+   * @returns {Date} the date the 'source' record was created
+   */
+  $createdAt () {
+    const firstModLog = this._firstModLog()
+
+    return firstModLog?.naldDate ?? this.createdAt
+  }
+
+  /**
+   * Determine which user created the 'source' record using history
+   *
+   * > We recommend adding the `history` modifier to your query to support this determination
+   *
+   * NALD has a concept called 'mod log'. When someone creates a new licence, charge, or return version, they can
+   * provide a reason and a note, which is saved as the 'mod log'. Who created the 'mod log' and when is also captured.
+   *
+   * It was intended to record a history of changes to the licence.
+   *
+   * Unfortunately, NALD doesn't enforce it's creation. But as the NALD version records don't capture the who and when,
+   * they are the best 'source' we have to determine this information for imported records.
+   *
+   * If a `createdBy` is populated for this version then it was created in WRLS and it is the 'source'. It extracts the
+   * user name, for example, `carol.shaw@wrls.gov.uk`.
+   *
+   * If `createdBy` is not populated, it falls back to attempting to extract the user ID from the first mod log record,
+   * for example, `JSMITH`. If one exists it is the 'source'.
+   *
+   * If neither `createdBy` nor any mod logs exist it will return `null`.
+   *
+   * @returns {string} the user name of the user that created the 'source' record, else `null` if it cannot be
+   * determined
+   */
+  $createdBy () {
+    if (this.createdBy) {
+      return this.createdBy.email
+    }
+
+    const firstModLog = this._firstModLog()
+
+    return firstModLog?.userId ?? null
+  }
+
+  /**
+   * Determine the notes for the record using its history
+   *
+   * > We recommend adding the `history` modifier to your query to support this determination
+   *
+   * NALD has a concept called 'mod log'. When someone creates a new licence, charge, or return version, they can
+   * provide a reason and a note, which is saved as the 'mod log'. Who created the 'mod log' and when is also captured.
+   *
+   * It was intended to record a history of changes to the licence.
+   *
+   * In NALD a charge version can have multiple mod logs, each with their own note.
+   *
+   * In WRLS only a single note can be captured in `charge_version_notes` and linked to the charge version (we believe
+   * the intent was to allow multiples but the final research/design determined only 1 was needed: the code was never
+   * refactored).
+   *
+   * In short, if the record was created in WRLS we return an array containing the single note. For imported records,
+   * the mod log notes are extracted and return as an array. If a record has neither an empty array is returned.
+   *
+   * @returns {string[]} an array of all the notes in ascending date order taken from the record's history
+   */
+  $notes () {
+    if (this.chargeVersionNote) {
+      return [this.chargeVersionNote.note]
+    }
+
+    const notes = []
+
+    for (const modLog of this.modLogs) {
+      if (modLog.note) {
+        notes.push(modLog.note)
+      }
+    }
+
+    return notes
+  }
+
+  /**
+   * Determine the reason the 'source' record was created using history
+   *
+   * > We recommend adding the `history` modifier to your query to support this determination
+   *
+   * NALD has a concept called 'mod log'. When someone creates a new licence, charge, or return version, they can
+   * provide a reason and a note, which is saved as the 'mod log'. Who created the 'mod log' and when is also captured.
+   *
+   * It was intended to record a history of changes to the licence.
+   *
+   * Unfortunately, NALD doesn't enforce it's creation. But as the NALD version records don't capture the who and when,
+   * they are the best 'source' we have to determine this information for imported records.
+   *
+   * If the record has a reason, either it was created in WRLS or we have mapped the NALD 'source' reason to a WRLS one.
+   * The version record is the 'source'.
+   *
+   * If a reason doesn't exist, it falls back to attempting to extract the reason description from the first mod log
+   * record, for example, `Record Loaded During Migration`. If one exists it is the 'source'.
+   *
+   * If neither 'source' records have a reason then it returns `null`
+   *
+   * @returns {string} the reason the 'source' record was created, else `null` if it cannot be determined
+   */
+  $reason () {
+    if (this.changeReason) {
+      return this.changeReason.description
+    }
+
+    const firstModLog = this._firstModLog()
+
+    return firstModLog?.reasonDescription ?? null
+  }
+
+  _firstModLog () {
+    if (this.modLogs.length > 0) {
+      return this.modLogs[0]
+    }
+
+    return null
+  }
 }
 
 module.exports = ChargeVersionModel