WritePointers Module.

This module is intended to provide write pointer autonumber indices for use in a data store that uses a lazy delete functionality. When a record is deleted, the index of the deleted record is recovered and re-used for the next available new record.

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NOTE: Version 1.2.0 fixed multiple delete bug.

You should obviate all earlier versions.

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NOTE: Version 1.0.0 small change to delete function return value.

In version 1.0.0, a delete command will return the id that was deleted OR -1 if no record can be found to be deleted.
In version 0.5.x, the return values were true or false. This should be a minor change to any using code OR you can just continue with the 0.5.x version.

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The Write Pointer functionality is provided as a class so that it can be embedded within a larger module or class and so multiple instances can be embedded in one structure if needed.

WritePointers contains two classes. WritePointer and WritePointerSafe. WritePointer will do no validation of the params for the inUse and delete functions. WritePointerSafe will ensure datatype for these. Use WritePointerSafe during development OR when your WritePointer instance is intended to be used by using authors or other end users.

WritePointers also contains a function ( writePointerAttachAsMixin) to attach a WritePointer or WritePointerSafe instance as a mixin to another class or object.

Commands:

next: gets the next available id
inUse: checks to see if an id is in use
idsInUse: shows all the ids currently in use as an array. delete: deletes an id from the system and makes it available for the next function for reuse
count: checks to see how many ids are in use OR the number of ids in use + those that have been deleted.

Usage

Instantiation:

import { WritePointer } from 'write-pointers';
writePointer = new WritePointer('dataPointers');
// or to start the index at a specific value ( MUST BE >=0 )
writePointer = new WritePointer('dataPointers', 20);
// or to do the same things with id validation.
import { WritePointerSafe } from 'write-pointers';
writePointer = new WritePointerSafe('dataPointersSafe');

Next Available Write Id:

let newId = writePointer.next()

Delete an in-use Write Id:

// returns the id that was deleted if an in-use record was deleted, 
// OR false if no record to be deleted 
let didThisDelete = writePointer.delete();

Check if an Id is being used for a record:

// if id === true runs idsInUse command shown just below. 
let isThisInUse = writePointer.inUse(<id>);

Show all the Ids in use

let idsInUse = writePointer.inUse(<id>);

How Many Records are in this system.

// return the number of records that are in use.
let count = writePointer.count();

// return the number of ALL records including ones that were deleted.
let count = writePointer.count(false);

Use as a Mixin

writePointerAttachAsMixin function will attach the four api commands to a parent or target class as public function proxy calls to the writePointer instance. The functions will appear on the parent class. By default, camelCase will be used, but underscore notation is also possible.

To use with CamelCase:

const writePointer = new WritePointer('index');
class targetClass {}
writePointerAttachAsMixin(writePointer, targetClass, <camelCase> = true);
/* 
	writePointer.next  .... targetClass.indexNext;
	writePointer.delete  .... targetClass.indexDelete;
	writePointer.inUse  .... targetClass.indexInUse;
	writePointer.count  .... targetClass.indexCount;
*/

To use with underscore:

const writePointer = new WritePointer('index');
class targetClass {}
writePointerAttachAsMixin(writePointer, targetClass, false);
/* 
	writePointer.next  .... targetClass.index_next;
	writePointer.delete  .... targetClass.index_delete;
	writePointer.inUse  .... targetClass.index_inUse;
	writePointer.count  .... targetClass.index_count;
*/