# Wallet::Object -- Parent class for any object stored in the wallet.
# $Id$
#
# Written by Russ Allbery <rra@stanford.edu>
# Copyright 2007 Board of Trustees, Leland Stanford Jr. University
#
# See README for licensing terms.

##############################################################################
# Modules and declarations
##############################################################################

package Wallet::Object;
require 5.006;

use strict;
use vars qw($VERSION);

use DBI;

# This version should be increased on any code change to this module.  Always
# use two digits for the minor version with a leading zero if necessary so
# that it will sort properly.
$VERSION = '0.01';

##############################################################################
# Constructors
##############################################################################

# Initialize an object from the database.  Verifies that the object already
# exists with the given type, and if it does, returns a new blessed object of
# the specified class.  Stores the database handle to use, the name, and the
# type in the object.  If the object doesn't exist, returns undef.  This will
# probably be usable as-is by most object types.
sub new {
    my ($class, $name, $type, $dbh) = shift;
    $dbh->{AutoCommit} = 0;
    $dbh->{RaiseError} = 1;
    $dbh->{PrintError} = 0;
    my $sql = 'select ob_name from objects where ob_name = ? and ob_type = ?';
    my $data = $dbh->selectrow_array ($sql, undef, $name, $type);
    return undef unless ($data and $data eq $name);
    my $self = {
        dbh  => $dbh,
        name => $name,
        type => $type,
    };
    bless ($self, $class);
    return $self;
}

# Create a new object in the database of the specified name and type, setting
# the ob_created_* fields accordingly, and returns a new blessed object of the
# specified class.  Stores the database handle to use, the name, and the type
# in the object.  Subclasses may need to override this to do additional setup.
sub create {
    my ($class, $name, $type, $dbh, $creator, $host, $time) = @_;
    $dbh->{AutoCommit} = 0;
    $dbh->{RaiseError} = 1;
    $dbh->{PrintError} = 0;
    $time ||= time;
    eval {
        my $sql = 'insert into objects (ob_name, ob_type, ob_created_by,
            ob_created_from, ob_created_on) values (?, ?, ?, ?, ?)';
        $dbh->do ($sql, undef, $name, $type, $creator, $host, $time);
        $dbh->commit;
    };
    if ($@) {
        $dbh->rollback;
        return undef;
    }
    my $self = {
        dbh  => $dbh,
        name => $name,
        type => $type,
    };
    bless ($self, $class);
    return $self;
}

##############################################################################
# History functions
##############################################################################

# Record a global object action for this object.  Takes the action (which must
# be one of get or store), and the trace information: user, host, and time.
# Returns true on success and false on failure, setting error appropriately.
#
# This function commits its transaction when complete and should not be called
# inside another transaction.
sub log_action {
    my ($self, $action, $user, $host, $time) = @_;
    unless ($action =~ /^(get|store)\z/) {
        $self->{error} = "invalid history action $action";
        return undef;
    }

    # We have two traces to record, one in the object_history table and one in
    # the object record itself.  Commit both changes as a transaction.  We
    # assume that AutoCommit is turned off.
    eval {
        my $sql = 'insert into object_history (oh_object, oh_type, oh_action,
            oh_by, oh_from, oh_on) values (?, ?, ?, ?, ?, ?)';
        $self->{dbh}->do ($sql, undef, $self->{name}, $self->{type}, $action,
                          $user, $host, $time);
        if ($action eq 'get') {
            $sql = 'update objects set ob_downloaded_by = ?,
                ob_downloaded_from = ?, ob_downloaded_on = ? where
                ob_name = ? and ob_type = ?';
            $self->{dbh}->do ($sql, undef, $user, $host, $time, $self->{name},
                              $self->{type});
        } elsif ($action eq 'store') {
            $sql = 'update objects set ob_stored_by = ?, ob_stored_from = ?,
                ob_stored_on = ? where ob_name = ? and ob_type = ?';
            $self->{dbh}->do ($sql, undef, $user, $host, $time, $self->{name},
                              $self->{type});
        }
        $self->{dbh}->commit;
    };
    if ($@) {
        my $id = $self->{type} . ':' . $self->{name};
        $self->{error} = "cannot update history for $id: $@";
        $self->{dbh}->rollback;
        return undef;
    }
    return 1;
}

# Record a setting change for this object.  Takes the field, the old value,
# the new value, and the trace information (user, host, and time).  The field
# may have the special value "type_data <field>" in which case the value after
# the whitespace is used as the type_field value.
#
# This function does not commit and does not catch exceptions.  It should
# normally be called as part of a larger transaction that implements the
# setting change and committed with that change.
sub log_set {
    my ($self, $field, $old, $new, $user, $host, $time) = @_;
    my $type_field;
    if ($field =~ /^type_data\s+/) {
        ($field, $type_field) = split (' ', $field, 2);
    }
    my %fields = map { $_ => 1 }
        qw(owner acl_get acl_store acl_show acl_destroy acl_flags expires
           flags type_data);
    unless ($fields{$field}) {
        die "invalid history field $field";
    }
    my $sql = "insert into object_history (oh_object, oh_type, oh_action,
        oh_field, oh_type_field, oh_from, oh_to, oh_by, oh_from, oh_on)
        values (?, ?, 'set', ?, ?, ?, ?, ?, ?, ?)";
    $self->{dbh}->do ($sql, undef, $self->{name}, $self->{type}, $field,
                      $type_field, $old, $new, $user, $host, $time);
}

##############################################################################
# Get/set values
##############################################################################

# Set a particular attribute.  Takes the attribute to set and its new value.
# Returns undef on failure and the new value on success.
sub _set_internal {
    my ($self, $attr, $value, $user, $host, $time) = @_;
    my $name = $self->{name};
    my $type = $self->{type};
    eval {
        my $sql = "select ob_$attr from objects where ob_name = ? and
            ob_type = ?";
        my $old = $self->{dbh}->selectrow_array ($sql, undef, $name, $type);
        $sql = "update objects set ob_$attr = ? where ob_name = ? and
            ob_type = ?";
        $self->{dbh}->do ($sql, undef, $value, $name, $type);
        $self->log_set ($attr, $old, $value, $user, $host, $time);
        $self->{dbh}->commit;
    };
    if ($@) {
        my $id = $self->{type} . ':' . $self->{name};
        $self->{error} = "cannot set $attr on $id: $@";
        $self->{dbh}->rollback;
        return;
    }
    return $value;
}

# Get a particular attribute.  Returns the attribute value.
sub _get_internal {
    my ($self, $attr) = @_;
    my $name = $self->{name};
    my $type = $self->{type};
    my $sql = "select $attr from objects where ob_name = ? and ob_type = ?";
    my $value = $self->{dbh}->selectrow_array ($sql, undef, $name, $type);
    return $value;
}

# Get or set the owner of an object.  If setting it, trace information must
# also be provided.
sub owner {
    my ($self, $owner, $user, $host, $time) = @_;
    if ($owner) {
        if ($owner !~ /^\d+\z/) {
            $self->{error} = "malformed owner ACL id $owner";
            return;
        }
        return $self->_set_internal ('owner', $owner, $user, $host, $time);
    } else {
        return $self->_get_internal ('owner');
    }
}

# Get or set an ACL on an object.  Takes the type of ACL and, if setting, the
# new ACL identifier.  If setting it, trace information must also be provided.
sub acl {
    my ($self, $type, $acl, $user, $host, $time) = @_;
    if ($type !~ /^(get|store|show|destroy|flags)\z/) {
        $self->{error} = "invalid ACL type $type";
        return;
    }
    my $attr = "acl_$type";
    if ($acl) {
        if ($acl !~ /^\d+\z/) {
            $self->{error} = "malformed ACL id $acl";
            return;
        }
        return $self->_set_internal ($attr, $acl, $user, $host, $time);
    } else {
        return $self->_get_internal ($attr);
    }
}

# Get or set the expires value of an object.  Expects an expiration time in
# seconds since epoch.  If setting the expiration, trace information must also
# be provided.
sub expires {
    my ($self, $expires, $user, $host, $time) = @_;
    if ($expires) {
        if ($expires !~ /^\d+\z/ || $expires == 0) {
            $self->{error} = "malformed expiration time $expires";
            return;
        }
        return $self->_set_internal ('expires', $expires, $user, $host, $time);
    } else {
        return $self->_get_internal ('expires');
    }
}

##############################################################################
# Object manipulation
##############################################################################

# The get methods must always be overridden by the subclass.
sub get { die "Do not instantiate Wallet::Object directly\n"; }

# Provide a default store implementation that returns an immutable object
# error so that auto-generated types don't have to provide their own.
sub store {
    my ($self, $data, $user, $host, $time) = @_;
    my $id = $self->{type} . ':' . $self->{name};
    $self->{error} = "cannot store $id: object type is immutable";
    return;
}

# The default show function.  This may be adequate for many types; types that
# have additional data should call this method, grab the results, and then add
# their data on to the end.
sub show {
    my ($self) = @_;
    my @attrs = ([ ob_type            => 'Type'            ],
                 [ ob_name            => 'Name'            ],
                 [ ob_owner           => 'Owner'           ],
                 [ ob_acl_get         => 'Get ACL'         ],
                 [ ob_acl_store       => 'Store ACL'       ],
                 [ ob_acl_show        => 'Show ACL'        ],
                 [ ob_acl_destroy     => 'Destroy ACL'     ],
                 [ ob_acl_flags       => 'Flags ACL'       ],
                 [ ob_expires         => 'Expires'         ],
                 [ ob_created_by      => 'Created by'      ],
                 [ ob_created_from    => 'Created from'    ],
                 [ ob_created_on      => 'Created on'      ],
                 [ ob_stored_by       => 'Stored by'       ],
                 [ ob_stored_from     => 'Stored from'     ],
                 [ ob_stored_on       => 'Stored on'       ],
                 [ ob_downloaded_by   => 'Downloaded by'   ],
                 [ ob_downloaded_from => 'Downloaded from' ],
                 [ ob_downloaded_on   => 'Downloaded on'   ]);
    my $fields = join (', ', map { $_->[0] } @attrs);
    my @data;
    eval {
        my $sql = "select $fields from objects where ob_name = ? and
            ob_type = ?";
        @data = $self->{dbh}->selectrow_array ($sql, undef, $name, $type);
    };
    if ($@) {
        my $id = $self->{type} . ':' . $self->{name};
        $self->{error} = "cannot retrieve data for $id: $@";
        return undef;
    }
    my $output = '';
    for (my $i = 0; $i < @data; $i++) {
        next unless defined $data[$i];
        $output .= sprintf ("%15s: %s\n", $attrs[$i][1], $data[$i]);
    }
    return $output;
}

# The default destroy function only destroys the database metadata.  Generally
# subclasses need to override this to destroy whatever additional information
# is stored about this object.
sub destroy {
    my ($self, $user, $host, $time) = @_;
    my $name = $self->{name};
    my $type = $self->{type};
    eval {
        my $sql = 'delete from flags where fl_object = ? and fl_type = ?';
        $self->{dbh}->do ($sql, undef, $name, $type);
        $sql = 'delete from objects where ob_name = ? and ob_type = ?';
        $self->{dbh}->do ($sql, undef, $name, $type);
        my $sql = "insert into object_history (oh_object, oh_type, 'destroy',
            oh_by, oh_from, oh_on) values (?, ?, ?, ?, ?)";
        $self->{dbh}->do ($sql, undef, $name, $type, $user, $host, $time);
        $self->{dbh}->commit;
    };
    if ($@) {
        my $id = $self->{type} . ':' . $self->{name};
        $self->{error} = "cannot destroy $id: $@";
        $self->{dbh}->rollback;
        return undef;
    }
    return 1;
}