#!/usr/bin/perl -w
###############################################################################
=pod

=head1 NAME

mig-env - This tool is for tracking and setting environment variables used by
B<mig> and its sub-tools.

=head1 SYNOPSIS

B<mig-env> <create|use> <migration_schema>

B<mig-env> <show> [migration_schema]

B<mig-env> <list>

B<mig-env> <help>

=head1 DESCRIPTION

For most invocations, B<mig-env> will either create or use a migration-specific
file (~/.mig/<migration_schema>.env) for setting the following environment
variables:

=over 15

=item MIGSCHEMA

The name of the migration schema.  Convention has this being a single lowercased
word or acronym identifying the library, prefixed with 'm_'.

=item MIGWORKDIR

The base working directory for containing migration data, scripts, and other
files.

=item PGHOST

The IP address or hostname for the PostgreSQL database used for a migration.

=item PGPORT

The TCP port for the PostgreSQL database.

=item PGUSER

The PostgreSQL user to use for the database.

=item PGDATABASE

The name of the actual database containing the migration schema.

=back

This script may also setup a symlink from a specified Git repository to a
scripts/ directory within the migration work directory.  The default for this is
~/git/migration-work/past_migrations/MIGSCHEMA --> MIGWORKDIR/scripts

It may also create the migration work directory if necessary.

=head1 COMMANDS

=over 15

=item B<create> <schema>

This invocation will prompt for various values and create a .env file for the
specified migration schema, and a symlink between the specified Git repository
and migration work directory (which will also be created if needed).

=item B<use> <schema>

This command will spawn a bash shell that executes the corresponding
~/.mig/<schema>.env script for setting up environment variables encoded during
B<create>.

=item B<show> [schema]

This command will show the contents of the corresponding ~/.mig/<schema>.env
script, or, if no schema is specified, then it will list pertinent variables in
the current environment if they exist.

=item B<list>

This command will list migration schemas found in ~/.mig

=item B<help>

Display the documentation you're reading now.

=back

=cut

###############################################################################

use strict;
use 5.012;
use Switch;
use Env qw(
    HOME PGHOST PGPORT PGUSER PGDATABASE MIGSCHEMA
    MIGBASEWORKDIR MIGBASEGITDIR MIGGITDIR MIGWORKDIR
);
use Pod::Usage;
use File::Path qw(make_path);
use FindBin;
my $mig_bin = "$FindBin::Bin/";
use lib "$FindBin::Bin/";

pod2usage(-verbose => 2) if ! $ARGV[0];

my $migration_schema = $ARGV[1] || '';
my $filename = "$HOME/.mig/$migration_schema.env";
switch($ARGV[0]) {
    case "--help" {
        pod2usage(-verbose => 2);
    }
    case "help" {
        pod2usage(-verbose => 2);
    }
    case "create" {
        pod2usage(-verbose => 1) if ! $ARGV[1];
        mig_env_create();
    }
    case "use" {
        pod2usage(-verbose => 1) if ! $ARGV[1];
        if (-e $filename) {
            exec '/bin/bash', '--init-file', $filename;
        } else {
            die "\n$filename does not exist\n";
        }
    }
    case "show" {
        if (-e $filename) {
            exec '/bin/cat', $filename;
        } else {
            print `env | sort | egrep 'MIG|PG'`;
        }
    }
    case "list" {
        opendir(my $dh, "$HOME/.mig") || die "can't open $HOME/.mig: $!";
        while (readdir $dh) {
            if (/^(.*)\.env$/) {
                print "$1\n";
            }
        }
        closedir $dh;
    }
    else {
        pod2usage(1);
    }
}

sub mig_env_create {
    if (-e $filename) {
        print "Re-Creating $filename\n";
        print `cat $filename`;
    } else {
        print "Creating $filename\n";
    }
    print "\n";

    # directories

    $MIGBASEWORKDIR = "$HOME/data/" unless $MIGBASEWORKDIR;
    my $migworkdir_default = "$MIGBASEWORKDIR$migration_schema/";
    print "Main work directory (default $migworkdir_default): ";
    my $MIGWORKDIR = <STDIN>;
    chomp $MIGWORKDIR;
    if (! $MIGWORKDIR) {
        $MIGWORKDIR = $migworkdir_default;
    }
    $MIGBASEGITDIR = "$HOME/git/migration-work/" unless $MIGBASEGITDIR;
    my $miggitdir_default = "${MIGBASEGITDIR}past_migrations/$migration_schema/";
    print "git repo for migration-specific scripts (default $miggitdir_default): ";
    my $MIGGITDIR = <STDIN>;
    chomp $MIGGITDIR;
    if (! $MIGGITDIR) {
        $MIGGITDIR = $miggitdir_default;
    }

    # PostgreSQL

    $PGHOST = 'localhost' unless $PGHOST;
    my $pghost_default = $PGHOST;
    print "PGHOST (default $pghost_default): ";
    $PGHOST = <STDIN>;
    chomp $PGHOST;
    if (! $PGHOST) {
        $PGHOST = $pghost_default;
    }
    $PGPORT = 5432 unless $PGPORT;
    my $pgport_default = $PGPORT;
    print "PGPORT (default $pgport_default): ";
    $PGPORT = <STDIN>;
    chomp $PGPORT;
    if (! $PGPORT) {
        $PGPORT = $pgport_default;
    }
    $PGDATABASE = 'evergreen' unless $PGDATABASE;
    my $pgdatabase_default = $PGDATABASE;
    print "PGDATABASE (default $pgdatabase_default): ";
    $PGDATABASE = <STDIN>;
    chomp $PGDATABASE;
    if (! $PGDATABASE) {
        $PGDATABASE = $pgdatabase_default;
    }
    $PGUSER = $PGDATABASE unless $PGUSER;
    my $pguser_default = $PGUSER;
    print "PGUSER (default $pguser_default): ";
    my $PGUSER = <STDIN>;
    chomp $PGUSER;
    if (! $PGUSER) {
        $PGUSER = $pguser_default;
    }

    # create files and directories if needed

    mkdir "$HOME/.mig";
    make_path($MIGGITDIR, { verbose => 1 });
    `touch $MIGGITDIR/README`;
    make_path($MIGWORKDIR, { verbose => 1 });
    symlink $MIGGITDIR, "$MIGWORKDIR/scripts";
    open FILE, ">$filename";
    print FILE "export PGHOST=$PGHOST\n";
    print FILE "export PGPORT=$PGPORT\n";
    print FILE "export PGDATABASE=$PGDATABASE\n";
    print FILE "export PGUSER=$PGUSER\n";
    print FILE "export MIGENVPROMPT=$migration_schema\n";
    print FILE "export MIGSCHEMA=$migration_schema\n";
    print FILE "export MIGBASEWORKDIR=$MIGBASEWORKDIR\n";
    print FILE "export MIGWORKDIR=$MIGWORKDIR\n";
    print FILE "export MIGBASEGITDIR=$MIGBASEGITDIR\n";
    print FILE "export MIGGITDIR=$MIGGITDIR\n";
    print FILE "alias wcd='cd `mig wdir`'\n";
    print FILE "alias gcd='cd `mig gdir`'\n";
    print FILE "alias scd='cd `mig sdir`'\n";
    print FILE "source ~/.profile\n";
    print FILE "env | sort | egrep 'PG|MIG'\n";
    print FILE 'echo shell PID = $$' . "\n";
    close FILE;
}