###########################################################################
#
# GreenstoneSQLPlugin.pm -- reads into doc_obj from SQL db and docsql.xml
# Metadata and/or fulltext are stored in SQL db, the rest may be stored in
# the docsql .xml files.
# A component of the Greenstone digital library software
# from the New Zealand Digital Library Project at the 
# University of Waikato, New Zealand.
#
# Copyright (C) 2001 New Zealand Digital Library Project
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
###########################################################################

package GreenstoneSQLPlugin;


use strict;
no strict 'refs'; # allow filehandles to be variables and viceversa

use DBI;
use docprint; # for new unescape_text() subroutine
use GreenstoneXMLPlugin;
use gssql;


# TODO:
# - Run TODOs here, in Plugout and in gssql.pm by Dr Bainbridge.
# - Have not yet tested writing out just meta or just fulltxt to sql db and reading just that 
# back in from the sql db while the remainder is to be read back in from the docsql .xml files.

# TODO: deal with incremental vs removeold. If docs removed from import folder, then import step
# won't delete it from archives but buildcol step will. Need to implement this with this database plugin or wherever the actual flow is

# TODO Q: is "reindex" = del from db + add to db?
# - is this okay for reindexing, or will it need to modify existing values (update table)
# - if it's okay, what does reindex need to accomplish (and how) if the OID changes because hash id produced is different?
# - delete is accomplished in GS SQL Plugin, during buildcol.pl. When should reindexing take place?
# during SQL plugout/import.pl or during plugin? If adding is done by GSSQLPlugout, does it need to
# be reimplemented in GSSQLPlugin to support the adding portion of reindexing.

# TODO: Add public instructions on using this plugin and its plugout: start with installing mysql binary, changing pwd, running the server (and the client against it for checking: basic cmds like create and drop). Then discuss db name, table names (per coll), db cols and col types, and how the plugout and plugin work.
# Discuss the plugin/plugout parameters.


# DONE:
# + TODO: Incremental delete can't work until GSSQLPlugout has implemented build_mode = incremental
# (instead of tossing away db on every build)
# + Ask about docsql naming convention adopted to identify OID. Better way?
# collection names -> table names: it seems hyphens not allowed. Changed to underscores.
# + Startup parameters (except removeold/build_mode)
# + how do we detect we're to do removeold during plugout in import.pl phase
# + incremental building: where do we need to add code to delete rows from our sql table after
# incrementally importing a coll with fewer docs (for instance)? What about deleted/modified meta?
# + Ask if I can assume that all SQL dbs (not just MySQL) will preserve the order of inserted nodes
# (sections) which in this case had made it easy to reconstruct the doc_obj in memory in the correct order.
# YES: Otherwise for later db types (drivers), can set order by primary key column and then order by did column
# + NOTTODO: when db is not running GLI is paralyzed -> can we set timeout on DBI connection attempt?
#   NOT A PROBLEM: Tested to find DBI connection attempt fails immediately when MySQL server not 
# running. The GLI "paralyzing" incident last time was not because of the gs sql connection code,
# but because my computer was freezing on-and-off.
# + "Courier" demo documents in lucene-sql collection: character (degree symbol) not preserved in title. Is this because we encode in utf8 when putting into db and reading back in?
# Test doc with meta and text like macron in Maori text.
# + TODO Q: During import, the GS SQL Plugin is called before the GS SQL Plugout with undesirable side
# effect that if the db doesn't exist, gssql::use_db() fails, as it won't create db.
#   This got fixed when GSSQLPlugin stopped connecting on init().


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

# GreenstoneSQLPlugin inherits from GreenstoneXMLPlugin so that it if meta or fulltext
# is still written out to doc.xml (docsql .xml), that will be processed as usual,
# whereas GreenstoneSQLPlugin will process all the rest (full text and/or meta, whichever
# is written out by GreenstoneSQLPlugout into the SQL db).


sub BEGIN {
    @GreenstoneSQLPlugin::ISA = ('GreenstoneXMLPlugin');
}

# This plugin must be in the document plugins pipeline IN PLACE OF GreenstoneXMLPlugin
# So we won't have a process exp conflict here.
# The structure of docsql.xml files is identical to doc.xml and the contents are similar except:
#   - since metadata and/or fulltxt are stored in mysql db instead, just XML comments indicating
#   this are left inside docsql.xml within the <Description> (for meta) and/or <Content> (for txt)
#   - the root element Archive now has a docoid attribute: <Archive docoid="OID">
sub get_default_process_exp {
    my $self = shift (@_);

    return q^(?i)docsql(-\d+)?\.xml$^; # regex based on this method in GreenstoneXMLPlugin
    #return q^(?i)docsql(-.+)?\.xml$^; # no longer storing the OID embedded in docsql .xml filename
}

my $process_mode_list =
    [ { 'name' => "meta_only",
        'desc' => "{GreenstoneSQLPlug.process_mode.meta_only}" },      
      { 'name' => "text_only",
        'desc' => "{GreenstoneSQLPlug.process_mode.text_only}" },
      { 'name' => "all",
        'desc' => "{GreenstoneSQLPlug.process_mode.all}" } ];

my $arguments =
    [ { 'name' => "process_exp",
	'desc' => "{BaseImporter.process_exp}",
	'type' => "regexp",
	'deft' => &get_default_process_exp(),
	'reqd' => "no" },
      { 'name' => "process_mode", 
	'desc' => "{GreenstoneSQLPlug.process_mode}",
	'type' => "enum",
	'list' => $process_mode_list,
	'deft' => "all",
	'reqd' => "no"},
      { 'name' => "db_driver", 
	'desc' => "{GreenstoneSQLPlug.db_driver}",
	'type' => "string",	
	'deft' => "mysql",
	'reqd' => "yes"},
      { 'name' => "db_client_user", 
	'desc' => "{GreenstoneSQLPlug.db_client_user}",
	'type' => "string",	
	'deft' => "root",
	'reqd' => "yes"},
      { 'name' => "db_client_pwd", 
	'desc' => "{GreenstoneSQLPlug.db_client_pwd}",
	'type' => "string",
	'deft' => "",
	'reqd' => "yes"}, # pwd required?
      { 'name' => "db_host", 
	'desc' => "{GreenstoneSQLPlug.db_host}",
	'type' => "string",
	'deft' => "127.0.0.1",
	'reqd' => "yes"},
    ];

my $options = { 'name'     => "GreenstoneSQLPlugin",
		'desc'     => "{GreenstoneSQLPlugin.desc}",
		'abstract' => "no",
		'inherits' => "yes",
	        'args'     => $arguments };


# TODO: For on cancel, add a SIGTERM handler or so to call end()
# or to explicitly call gs_sql->close_connection if $gs_sql def

sub new {
    my ($class) = shift (@_);
    my ($pluginlist,$inputargs,$hashArgOptLists) = @_;
    push(@$pluginlist, $class);

    push(@{$hashArgOptLists->{"ArgList"}},@{$arguments});
    push(@{$hashArgOptLists->{"OptList"}},$options);

    my $self = new GreenstoneXMLPlugin($pluginlist, $inputargs, $hashArgOptLists);

    
    #return bless $self, $class;
    $self = bless $self, $class;
    if ($self->{'info_only'}) {
	# If running pluginfo, we don't need to go further.
	return $self;
    }

    # do anything else that needs to be done here when not pluginfo
    
    return $self;
}

# This is called once if removeold is set with import.pl. Most plugins will do
# nothing but if a plugin does any stuff outside of creating doc obj, then 
# it may need to clear something.
# In the case of GreenstoneSQL plugs: this is the first time we have a chance
# to purge the tables of the current collection from the current site's database
sub remove_all {
    my $self = shift (@_);
    my ($pluginfo, $base_dir, $processor, $maxdocs) = @_;

    print STDERR "   Building with removeold option set, so deleting current collection's tables if they exist\n" if($self->{'verbosity'});
    
    # if we're in here, we'd already have run 'use database <site_name>;' during sub init()
    # so we can go ahead and delete the collection's tables
    my $gs_sql = $self->{'gs_sql'};
    $gs_sql->delete_collection_tables(); # will delete them if they exist

    # and recreate tables? No. Tables' existence is ensured in GreenstoneSQLPlugout::begin()
    my $proc_mode = $self->{'process_mode'};
    if($proc_mode ne "text_only") {
	$gs_sql->ensure_meta_table_exists();
    }
    if($proc_mode ne "meta_only") {
	$gs_sql->ensure_fulltxt_table_exists();
    }
}

# This is called per document for docs that have been deleted from the 
# collection. Most plugins will do nothing
# but if a plugin does any stuff outside of creating doc obj, then it may need
# to clear something.
# remove the doc(s) denoted by oids from GS SQL db
# This takes care of incremental deletes (docs marked D by ArchivesInfPlugin when building
# incrementally) as well as cases of "Non-icremental Delete", see ArchivesInfPlugin.pm
sub remove_one {
    my $self = shift (@_);
    
    my ($file, $oids, $archivedir) = @_;

    print STDERR "@@@ IN SQLPLUG::REMOVE_ONE: $file\n";
    
    #return undef unless $self->can_process_this_file($file); # NO, DON'T DO THIS: 
           # WE DON'T CARE IF IT'S AN IMAGE FILE THAT WAS DELETED.
           # WE CARE ABOUT REMOVING THE DOCOID OF THAT IMAGE FILE FROM THE DB

    print STDERR "*****************************\nAsked to remove_one oid\n***********************\n";
    
    my $gs_sql = $self->{'gs_sql'} || return 0; # couldn't make the connection or no db etc
    if(scalar @$oids > 1) {
	print STDERR "TODO: We now have reason to optimise GreenstoneSQLPlugin::remove_one() by using prepare and execute.\n";
    }
    
    my $proc_mode = $self->{'process_mode'};
    foreach my $oid (@$oids) {	
	if($proc_mode eq "all" || $proc_mode eq "meta_only") {
	    print STDERR "@@@@@@@@ Deleting $oid from meta table\n" if $self->{'verbosity'} > 2;
	    $gs_sql->delete_recs_from_metatable_with_docid($oid);
	}
	if($proc_mode eq "all" || $proc_mode eq "text_only") {
	    print STDERR "@@@@@@@@ Deleting $oid from fulltxt table\n" if $self->{'verbosity'} > 2;
	    $gs_sql->delete_recs_from_texttable_with_docid($oid);
	}
    }
    return 1;
}


sub xml_start_tag {
    my $self = shift(@_);
    my ($expat, $element) = @_;

    my $outhandle = $self->{'outhandle'};
    
    $self->{'element'} = $element;
    if ($element eq "Archive") { # docsql.xml files contain a OID attribute on Archive element
	# the element's attributes are in %_ as per ReadXMLFile::xml_start_tag() (while $_
	# contains the tag)

	# Don't access %_{'docoid'} directly: keep getting a warning message to 
	# use $_{'docoid'} for scalar contexts, but %_ is the element's attr hashmap 
	# whereas $_ has the tag info. So we don't want to do $_{'docoid'}.
	my %attr_hash = %_; # right way, see OAIPlugin.pm
	$self->{'doc_oid'} = $attr_hash{'docoid'};
	##print STDERR "XXXXXXXXXXXXXX in SQLPlugin::xml_start_tag()\n";
	print $outhandle "Extracted OID from docsql.xml: ".$self->{'doc_oid'}."\n"
	    if $self->{'verbosity'} > 2;

    }
    else { # let superclass GreenstoneXMLPlugin continue to process <Section> and <Metadata> elements
	$self->SUPER::xml_start_tag(@_);
    }
}

# TODO Q: Why are there 4 passes when we're only indexing at doc and section level (2 passes)? What's the dummy pass, why is there a pass for infodb?

# We should only ever get here during the buildcol.pl phase
# At the end of superclass GreenstoneXMLPlugin.pm's close_document() method,
# the doc_obj in memory is processed (indexed) and then made undef.
# So we have to work with doc_obj before superclass close_document() is finished.
sub close_document {
    my $self = shift(@_);

    ##print STDERR "XXXXXXXXX in SQLPlugin::close_doc()\n";
    
    my $gs_sql = $self->{'gs_sql'};
    
    my $outhandle = $self->{'outhandle'};
    my $doc_obj = $self->{'doc_obj'};

    my $oid = $self->{'doc_oid'}; # we stored current doc's OID during sub xml_start_tag()
    my $proc_mode = $self->{'process_mode'};
    
    # For now, we have access to doc_obj (until just before super::close_document() terminates)
    
    # no need to call $self->{'doc_obj'}->set_OID($oid);
    # because either the OID is stored in the SQL db as meta 'Identifier' alongside other metadata
    # or it's stored in the doc.xml as metadata 'Identifier' alongside other metadata
    # Either way, Identifier meta will be read into the docobj automatically with other meta.

    print STDERR "   GreenstoneSQLPlugin processing doc $oid (reading into docobj from SQL db)\n"
	if $self->{'verbosity'} > 0;
    
    if($proc_mode eq "all" || $proc_mode eq "meta_only") {
	# read in meta for the collection (i.e. select * from <col>_metadata table
	
	my $sth = $gs_sql->select_from_metatable_matching_docid($oid);
	print $outhandle "### SQL select stmt: ".$sth->{'Statement'}."\n"
	    if $self->{'verbosity'} > 2;
	
	print $outhandle "----------SQL DB contains meta-----------\n" if $self->{'verbosity'} > 2;
	# https://www.effectiveperlprogramming.com/2010/07/set-custom-dbi-error-handlers/
	while( my @row = $sth->fetchrow_array() ) {	    
	    #print $outhandle "row: @row\n";
	    my ($primary_key, $did, $sid, $metaname, $metaval) = @row;
	    
	    # get rid of the artificial "root" introduced in section id when saving to sql db
	    $sid =~ s@^root@@;
	    $sid = $doc_obj->get_top_section() unless $sid;
	    print $outhandle "### did: $did, sid: |$sid|, meta: $metaname, val: $metaval\n"
		if $self->{'verbosity'} > 2;
	    
	    # TODO:  we accessed the db in utf8 mode, so, we can call doc_obj->add_utf8_meta directly:
	    $doc_obj->add_utf8_metadata($sid, $metaname, &docprint::unescape_text($metaval));
	}
	print $outhandle "----------FIN READING DOC's META FROM SQL DB------------\n"
	    if $self->{'verbosity'} > 2;
    }
    
    if($proc_mode eq "all" || $proc_mode eq "text_only") {
	# read in fulltxt for the collection (i.e. select * from <col>_fulltxt table
	
	my $fulltxt_table = $gs_sql->get_fulltext_table_name();
	
	
	my $sth = $gs_sql->select_from_texttable_matching_docid($oid);
	print $outhandle "### stmt: ".$sth->{'Statement'}."\n" if $self->{'verbosity'} > 2;
	
	print $outhandle "----------\nSQL DB contains txt entries for-----------\n"
	    if $self->{'verbosity'} > 2;
	while( my ($primary_key, $did, $sid, $text) = $sth->fetchrow_array() ) {	   
	    
	    # get rid of the artificial "root" introduced in section id when saving to sql db
	    #$sid =~ s@^root@@;
	    $sid = $doc_obj->get_top_section() if ($sid eq "root");
	    print $outhandle "### did: $did, sid: |$sid|, fulltext: <TXT>\n"
		if $self->{'verbosity'} > 2;
	    
	    # TODO - pass by ref?
	    # TODO: we accessed the db in utf8 mode, so, we can call doc_obj->add_utf8_text directly:
	    $doc_obj->add_utf8_text($sid, &docprint::unescape_text($text));
	}	
	print $outhandle "----------FIN READING DOC's TXT FROM SQL DB------------\n"
	    if $self->{'verbosity'} > 2;
    }
    
    # done reading into docobj from SQL db
    
    # don't forget to clean up on close() in superclass
    # It will get the doc_obj indexed then make it undef
    $self->SUPER::close_document(@_);
}


# TODO: only want to work with sql db if buildcol.pl. Unfortunately, also runs on import.pl.
# During import, the GS SQL Plugin is called before the GS SQL Plugout with undesirable side
# effect that if the db doesn't exist, gssql::use_db() fails, as it won't create db.

# GS SQL Plugin::init() (and deinit()) is called by import.pl and also by buildcol.pl
# This means it connects and deconnects during import.pl as well. This is okay
# as removeold, which should drop the collection tables, happens during the import phase
# and therefore also requires a db connection.
# TODO: Eventually can try moving get_gssql_instance into gssql.pm? That way both GS SQL Plugin
# and Plugout would be using one connection during import.pl phase when both plugs exist.

# Call init() not begin() because there can be multiple plugin passes and begin() called for
# each pass (one for doc level and another for section level indexing), whereas init() should
# be called before any and all passes.
# This way, we can connect to the SQL database once per buildcol run.
sub init {
    my ($self) = shift (@_);
    ##print STDERR "@@@@@@@@@@ INIT CALLED\n";
    
    $self->SUPER::init(@_); # super (GreenstoneXMLPlugin) will not yet be trying to read from doc.xml (docsql .xml) files in init().

    ####################
#    print "@@@ SITE NAME: ". $self->{'site_name'} . "\n" if defined $self->{'site_name'};
#    print "@@@ COLL NAME: ". $ENV{'GSDLCOLLECTION'} . "\n";

#    print STDERR "@@@@ db_pwd: " . $self->{'db_client_pwd'} . "\n";
#    print STDERR "@@@@ user: " . $self->{'db_client_user'} . "\n";
#    print STDERR "@@@@ db_host: " . $self->{'db_host'} . "\n";
#    print STDERR "@@@@ db_driver: " . $self->{'db_driver'} . "\n";
    ####################

    # create gssql object.
    # collection name will be used for naming tables (site name will be used for naming database)
    my $gs_sql = new gssql({
	'collection_name' => $ENV{'GSDLCOLLECTION'},
	'verbosity' => $self->{'verbosity'}
			   });

    # try connecting to the mysql db, if that fails it will die
    if(!$gs_sql->connect_to_db({
	'db_driver' => $self->{'db_driver'},
	'db_client_user' => $self->{'db_client_user'},
	'db_client_pwd' => $self->{'db_client_pwd'},
	'db_host' => $self->{'db_host'}
			       })
	)
    {
	# This is fatal for the plugout, let's terminate here
	# PrintError would already have displayed the warning message on connection fail	
	die("Could not connect to db. Can't proceed.\n");
    }
    
    my $db_name = $self->{'site_name'} || "greenstone2"; # one database per GS3 site, for GS2 the db is called greenstone2

    # Attempt to use the db, create it if it doesn't exist (but don't create the tables yet)
    # Bail if we can't use the database
    if(!$gs_sql->use_db($db_name)) {
	
	# This is fatal for the plugout, let's terminate here after disconnecting again
	# PrintError would already have displayed the warning message on load fail
	$gs_sql->disconnect_from_db()
	    || warn("Unable to disconnect from database.\n");
	die("Could not use db $db_name. Can't proceed.\n");
    }
    
    
    # store db handle now that we're connected
    $self->{'gs_sql'} = $gs_sql;    
}


# This method also runs on import.pl if gs_sql has a value. But we just want to run it on buildcol
# Call deinit() not end() because there can be multiple plugin passes:
# one for doc level and another for section level indexing
# and deinit() should be called before all passes
# This way, we can close the SQL database once per buildcol run.
sub deinit {
    my ($self) = shift (@_);
    
    ##print STDERR "@@@@@@@@@@ GreenstoneSQLPlugin::DEINIT CALLED\n";
    
    if($self->{'gs_sql'}) { # only want to work with sql db if buildcol.pl, gs_sql won't have
	# a value except during buildcol, so when processor =~ m/buildproc$/.
	$self->{'gs_sql'}->disconnect_from_db()
	    || warn("Unable to disconnect from database " . $self->{'site_name'} . "\n");

	# explicitly delete gs_sql key (setting key to undef has a different meaning from deleting)
	# so all future use has to make the connection again
	delete $self->{'gs_sql'};
    }

    $self->SUPER::deinit(@_);
}