package DBIx::Custom::SQLTemplate;

use strict;

use warnings;

use base 'Object::Simple';

use Carp 'croak';

use DBIx::Custom::Query;

use DBIx::Custom::SQLTemplate::TagProcessor;

__PACKAGE__->attr('tag_processors' => sub { {} });

__PACKAGE__->attr(tag_start => '{');

__PACKAGE__->attr(tag_end   => '}');

__PACKAGE__->attr('tag_syntax' => <<'EOS');

[tag]                     [expand]

{? name}                  ?

{= name}                  name = ?

{<> name}                 name <> ?

{< name}                  name < ?

{> name}                  name > ?

{>= name}                 name >= ?

{<= name}                 name <= ?

{like name}               name like ?

{in name number}          name in [?, ?, ..]

{insert key1 key2} (key1, key2) values (?, ?)

{update key1 key2}    set key1 = ?, key2 = ?

EOS

sub new {

    my $self = shift->SUPER::new;

    $self->register_tag_processor(

        '?'      => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_placeholder_tag,

        '='      => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        '<>'     => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        '>'      => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        '<'      => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        '>='     => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        '<='     => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        'like'   => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_basic_tag,

        'in'     => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_in_tag,

        'insert' => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_insert_tag,

        'update' => \&DBIx::Custom::SQLTemplate::TagProcessors::expand_update_tag

    );

    return $self;

}

sub register_tag_processor {

    my $self = shift;

    my $tag_processors = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    $self->tag_processors({%{$self->tag_processors}, %{$tag_processors}});

    return $self;

}

sub create_query {

    my ($self, $template)  = @_;

    # Parse template

    my $tree = $self->_parse_template($template);

    # Build query

    my $query = $self->_build_query($tree);

    return $query;

}

sub _parse_template {

    my ($self, $template) = @_;

    if (ref $template eq 'ARRAY') {

        $template = $template->[1];

    }

    $template ||= '';

    my $tree = [];

    # Tags

    my $tag_start = quotemeta $self->tag_start;

    my $tag_end   = quotemeta $self->tag_end;

    # Tokenize

    my $state = 'text';

    # Save original template

    my $original_template = $template;

    # Parse template

    while ($template =~ s/([^$tag_start]*?)$tag_start([^$tag_end].*?)$tag_end//sm) {

        my $text = $1;

        my $tag  = $2;

        # Parse tree

        push @$tree, {type => 'text', tag_args => [$text]} if $text;

        if ($tag) {

            # Get tag name and arguments

            my ($tag_name, @tag_args) = split /\s+/, $tag;

            # Tag processor is exist?

            unless ($self->tag_processors->{$tag_name}) {

                my $tag_syntax = $self->tag_syntax;

                croak("Tag '{$tag}' in SQL template is not exist.\n\n" .

                      "<SQL template tag syntax>\n" .

                      "$tag_syntax\n" .

                      "<Your SQL template>\n" .

                      "$original_template\n\n");

            }

            # Check tag arguments

            foreach my $tag_arg (@tag_args) {

                # Cannot cantain placehosder '?'

                croak("Tag '{t }' arguments cannot contain '?'")

                  if $tag_arg =~ /\?/;

            }

            # Add tag to parsing tree

            push @$tree, {type => 'tag', tag_name => $tag_name, tag_args => [@tag_args]};

        }

    }

    # Add text to parsing tree 

    push @$tree, {type => 'text', tag_args => [$template]} if $template;

    return $tree;

}

sub _build_query {

    my ($self, $tree) = @_;

    # SQL

    my $sql = '';

    # All parameter key infomation

    my $all_columns = [];

    # Build SQL 

    foreach my $node (@$tree) {

        # Get type, tag name, and arguments

        my $type     = $node->{type};

        my $tag_name = $node->{tag_name};

        my $tag_args = $node->{tag_args};

        # Text

        if ($type eq 'text') {

            # Join text

            $sql .= $tag_args->[0];

        }

        # Tag

        elsif ($type eq 'tag') {

            # Get tag processor

            my $tag_processor = $self->tag_processors->{$tag_name};

            # Tag processor is code ref?

            croak("Tag processor '$tag_name' must be code reference")

              unless ref $tag_processor eq 'CODE';

            # Expand tag using tag processor

            my ($expand, $columns) = $tag_processor->($tag_name, $tag_args);

            # Check tag processor return value

            croak("Tag processor '$tag_name' must return (\$expand, \$columns)")

              if !defined $expand || ref $columns ne 'ARRAY';

            # Check placeholder count

            croak("Placeholder count in SQL created by tag processor '$tag_name' " .

                  "must be same as key informations count")

              unless $self->_placeholder_count($expand) eq @$columns;

            # Add key information

            push @$all_columns, @$columns;

            # Join expand tag to SQL

            $sql .= $expand;

        }

    }

    # Add semicolon

    $sql .= ';' unless $sql =~ /;$/;

    # Query

    my $query = DBIx::Custom::Query->new(sql => $sql, columns => $all_columns);

    return $query;

}

sub _placeholder_count {

    my ($self, $expand) = @_;

    $expand ||= '';

    my $count = 0;

    my $pos   = -1;

    while (($pos = index($expand, '?', $pos + 1)) != -1) {

        $count++;

    }

    return $count;

}

1;

=head1 NAME

DBIx::Custom::SQLTemplate - DBIx::Custom SQL Template

=head1 SYNOPSIS

    my $sql_tmpl = DBIx::Custom::SQLTemplate->new;

    my $tmpl   = "select from table {= k1} && {<> k2} || {like k3}";

    my $param = {k1 => 1, k2 => 2, k3 => 3};

    my $query = $sql_template->create_query($tmpl);

=head1 ATTRIBUTES

=head2 C<tag_processors>

    $sql_tmpl       = $sql_tmpl->tag_processors($name1 => $tag_processor1

                                                $name2 => $tag_processor2);

    $tag_processors = $sql_tmpl->tag_processors;

=head2 C<tag_start>

    $sql_tmpl  = $sql_tmpl->tag_start('{');

    $tag_start = $sql_tmpl->tag_start;

Default is '{'

=head2 C<tag_end>

    $sql_tmpl    = $sql_tmpl->tag_start('}');

    $tag_end = $sql_tmpl->tag_start;

Default is '}'

=head2 C<tag_syntax>

    $sql_tmpl   = $sql_tmpl->tag_syntax($tag_syntax);

    $tag_syntax = $sql_tmpl->tag_syntax;

=head1 METHODS

This class is L<Object::Simple> subclass.

You can use all methods of L<Object::Simple>

=head2 C<new>

=head2 C<create_query>

Create L<DBIx::Custom::Query> object parsing SQL template

    $query = $sql_tmpl->create_query($tmpl);

    # Sample

    $query = $sql_tmpl->create_sql(

         "select * from table where {= title} && {like author} || {<= price}")

    # Expanded

    $qeury->sql : "select * from table where title = ? && author like ? price <= ?;"

    $query->key_infos : [['title'], ['author'], ['price']]

    # Sample with table name

    ($sql, @bind_values) = $sql_tmpl->create_sql(

            "select * from table where {= table.title} && {like table.author}",

            {table => {title => 'Perl', author => '%Taro%'}}

        )

    # Expanded

    $query->sql : "select * from table where table.title = ? && table.title like ?;"

    $query->key_infos :[ [['table.title'],['table', 'title']],

                         [['table.author'],['table', 'author']] ]

This method create query using by L<DBIx::Custom>.

query has two infomation

    1. sql       : SQL

    2. key_infos : Parameter access key information

=head2 C<register_tag_processor>

Add tag processor

    $sql_tmpl = $sql_tmpl->register_tag_processor($tag_processor);

The following is register_tag_processor sample

    $sql_tmpl->register_tag_processor(

        '?' => sub {

            my ($tag_name, $tag_args) = @_;

            my $key1 = $tag_args->[0];

            my $key2 = $tag_args->[1];

            my $key_infos = [];

            # Expand tag and create key informations

            # Return expand tags and key informations

            return ($expand, $key_infos);

        }

    );

Tag processor recieve 2 argument

    1. Tag name            (?, =, <>, or etc)

    2. Tag arguments       (arg1 and arg2 in {tag_name arg1 arg2})

Tag processor return 2 value

    1. Expanded Tag (For exsample, '{= title}' is expanded to 'title = ?')

    2. Key infomations

You must be return expanded tag and key infomations.

Key information is a little complex. so I will explan this in future.

If you want to know more, Please see DBIx::Custom::SQLTemplate source code.

=head2 C<clone>

Clone DBIx::Custom::SQLTemplate object

    $clone = $sql_tmpl->clone;

=head1 Available Tags

Available Tags

    [tag]            [expand]

    {? name}         ?

    {= name}         name = ?

    {<> name}        name <> ?

    {< name}         name < ?

    {> name}         name > ?

    {>= name}        name >= ?

    {<= name}        name <= ?

    {like name}      name like ?

    {in name}        name in [?, ?, ..]

    {insert}         (key1, key2, key3) values (?, ?, ?)

    {update}         set key1 = ?, key2 = ?, key3 = ?

The following is insert SQL sample

    $query = $sql_tmpl->create_sql(

        "insert into table {insert key1 key2}"

    );

    # Expanded

    $query->sql : "insert into table (key1, key2) values (?, ?)"

The following is update SQL sample

    $query = $sql_tmpl->create_sql(

        "update table {update key1 key2} where {= key3}"

    );

    # Expanded

    $query->sql : "update table set key1 = ?, key2 = ? where key3 = ?;"

=cut