add (unfinished) db migration script

migrate.pl

@@ -0,0 +1,79 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use 5.020;
+
+use DBI;
+
+my $dbname = $ENV{TRAVELYNX_DB_FILE} // 'travelynx.sqlite';
+my $dbh = DBI->connect( "dbi:SQLite:dbname=${dbname}", q{}, q{} );
+
+my $has_version_query = $dbh->prepare(qq{
+	select name from sqlite_master
+	where type = 'table' and name = 'schema_version';
+});
+
+sub get_schema_version {
+	$has_version_query->execute();
+	my $rows = $has_version_query->fetchall_arrayref;
+	if (@{$rows} == 1) {
+		my $get_version_query = $dbh->prepare(qq{
+			select version from schema_version;
+		});
+		$get_version_query->execute();
+		my $rows = $get_version_query->fetchall_arrayref;
+		if (@{$rows} == 0) {
+			return -1;
+		}
+		return $rows->[0][0];
+	}
+	return 0;
+}
+
+my @migrations = (
+	# v0 -> v1
+	sub {
+		$dbh->do(qq{
+			begin transaction;
+		});
+		$dbh->do(qq{
+			create table schema_version (
+				version integer primary key
+			);
+		});
+		$dbh->do(qq{
+			insert into schema_version (version) values (1);
+		});
+		$dbh->do(qq{
+			create table new_users (
+				id integer primary key,
+				name char(64) not null unique,
+				status int not null,
+				email char(256),
+				password text,
+				registered_at datetime,
+				last_login datetime
+			);
+		});
+		my $get_users_query = $dbh->prepare(qq{
+			select * from users;
+		});
+		$dbh->do(qq{
+			commit;
+		});
+	},
+);
+
+my $schema_version = get_schema_version();
+
+say "Found travelynx schema v${schema_version}";
+
+if ($schema_version == @migrations) {
+	say "Database schema is up-to-date";
+}
+
+for my $i ($schema_version .. $#migrations) {
+	printf("Updating to v%d\n", $i + 1);
+	$migrations[$i]();
+}