migrations.js

/**
 * Meteor Migration
 *
 * Simple database migrations for meteor
 *
 * @author idmontie
 */

/* global console */

// =================
// Meteor Migrations
// =================

Migrations = {
  /**
   * Meteor collection to store data in
   * TODO settings should dictate what db to use.
   */
  warehouse : new Meteor.Collection( 'meteor-migrations' ),
  /**
   * Add a migration.  Will run the given migration once and only
   * once, even when the app is restarted.
   *
   * Returns true if a migration of the same name is not already added.
   * Returns false if otherwise.
   *
   * Migration names should be globally unique.
   *
   * The order number is an optional parameter that sets what
   * order the migrations should be run in. Migrations are run
   * from smallest order number to largest order number.  If an
   * order number is not provided, the largest order number + 10
   * is used.
   *
   * @param String name Name of the migration
   * @param Function migrationCallback The function to run once and only once
   * @param Number order Optional order number
   * @return boolean
   */
  add : function ( name, migrationCallback, rollbackCallback, order ) {
    'use strict';

    // If we are called with less than 4 arguments, than assume
    // that we are being called with the following signature:
    // ( name, migrationCallback, order )
    if ( arguments.length < 4 ) {
      order = rollbackCallback;
      rollbackCallback = null;
    }

    var found = false

    for ( var i = 0; i < Migrations.migrations.length; i++ ) {
      if ( name == Migrations.migrations[i].name ) {
        found = true
        break
      }
    }

    if ( ! found ) {
      if ( order == null ) {
        order = Migrations.largestOrderNumber + 10
        Migrations.largestOrderNumber = order
      } else if ( order > Migrations.largestOrderNumber ) {
        Migrations.largestOrderNumber = order
      }

      Migrations.migrations.push( {
        migrationCallback: migrationCallback,
        rollbackCallback: rollbackCallback,
        name: name,
        order: order
      } )

      return true
    } else {
      return false
    }
  },
  /**
   * Removes the migration from the current queue.
   * This does NOT remove the migration from the collection of
   * previously run migrations.
   *
   * To remove a migration to allow it to rerun, use removeFromDatabase.
   *
   * @param String name Name of the migration
   */
  remove : function ( name ) {
    'use strict';

    for ( var i = 0; i < Migrations.migrations.length; i++ ) {
      if ( Migrations.migrations[i].name == name ) {
        delete Migrations.migrations[i];
      }
    }
  },
  /**
   * Removes the migration from the database, so that it can be run again.
   *
   * @param String name Name of the migration
   */
  removeFromDatabase : function ( name ) {
    'use strict';

    // TODO settings should dictate what db to use
    Migrations.warehouse.remove( {
      name : name
    } )
  },
  /**
   * Changes which function to run when the migration is performed.
   *
   * If the migration with the given name has already been run, this will
   * NOT force a re-run of the migration.  This is only available to override
   * which migration to run.
   *
   * @param String name Name of the migration
   * @param Function newMigrationCallback The new function to run once and only once
   */
  update : function ( name, newMigrationCallback, order ) {
    'use strict';

    for ( var i = 0; i < Migrations.migrations.length; i++ ) {
      if ( name == Migrations.migrations[i].name ) {
        if ( order == null ) {
          order = Migrations.migrations[i].order
        } else if ( order > Migrations.largestOrderNumber ) {
          Migrations.largestOrderNumber = order
        }
      }

      Migrations.migrations[i] = {
        migrationCallback: newMigrationCallback,
        name: name,
        order: order
      }
    }
  },
  /**
   * Rollback a given migration. The migration will be rerun on start up since
   * this also removes the migration from the database.
   *
   * @param String name The name of the migration to rollback
   */
  rollback : function ( name ) {
    for ( var i = 0; i < Migrations.migrations.length; i++ ) {
      if ( Migrations.migrations[i].name == name ) {

        if ( Migrations.migrations[i].rollbackCallback ) {
          Migrations.migrations[i].rollbackCallback();
        }
      }
    }

    Migrations.removeFromDatabase( name );
  },
  /**
   * Enables console logs for already run migrations.
   *
   * @type boolean
   */
  verbose : false,
  /**
   * Array of migration objects.  Do not use directly.
   *
   * Initially empty, no migrations to run
   *
   * Object structure:
   *
   * - orderNumber
   * - name
   * - migrationCallback
   *
   * @type Array
   */
  migrations : [],
  /**
   * Stores the largest order number
   *
   * @type Number
   */
  largestOrderNumber : 0
};

// ==============
// Meteor Startup
// ==============

Meteor.startup( function () {
  'use strict';

  /*
   * Migrations are unsorted.  Sort them and do them in order of
   * smallest to largest order number
   */

  Migrations.migrations.sort( function ( a, b ) {
    if ( a.order < b.order ) {
      return -1;
    } else if ( a.order > b.order ) {
      return 1;
    } else {
      return 0;
    }
  } )


  for ( var i = 0; i < Migrations.migrations.length; i++ ) {
    var migration = Migrations.migrations[i]
    // Do the migration
    var pastMigration = Migrations.warehouse.findOne( {
      name : migration.name
    } )

    if ( ! pastMigration ) {
      console.log ( '> Starting ' + migration.name + ' migration.' )

      migration.migrationCallback()

      Migrations.warehouse.insert( {
        name : migration.name
      } )

      console.log ( '> Finishing ' + migration.name + ' migration.' )
    } else {
      if ( Migrations.verbose ) {
        console.log( '> Skipping ' + migration.name + '.' )
      }
    }
  }
} )