package DBIx::Custom::QueryBuilder;

use strict;

use warnings;

use base 'Object::Simple';

use Carp 'croak';

use DBIx::Custom::Query;

use DBIx::Custom::QueryBuilder::TagProcessors;

__PACKAGE__->dual_attr('tag_processors', default => sub { {} }, inherit => 'hash_copy');

__PACKAGE__->register_tag_processor(

    '?'      => \&DBIx::Custom::QueryBuilder::TagProcessors::placeholder,

    '='      => \&DBIx::Custom::QueryBuilder::TagProcessors::equal,

    '<>'     => \&DBIx::Custom::QueryBuilder::TagProcessors::not_equal,

    '>'      => \&DBIx::Custom::QueryBuilder::TagProcessors::greater_than,

    '<'      => \&DBIx::Custom::QueryBuilder::TagProcessors::lower_than,

    '>='     => \&DBIx::Custom::QueryBuilder::TagProcessors::greater_than_equal,

    '<='     => \&DBIx::Custom::QueryBuilder::TagProcessors::lower_than_equal,

    'like'   => \&DBIx::Custom::QueryBuilder::TagProcessors::like,

    'in'     => \&DBIx::Custom::QueryBuilder::TagProcessors::in,

    'insert' => \&DBIx::Custom::QueryBuilder::TagProcessors::insert,

    'update' => \&DBIx::Custom::QueryBuilder::TagProcessors::update

);

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

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

sub register_tag_processor {

    my $self = shift;

    # Merge tag processor

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

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

    return $self;

}

sub build_query {

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

    # Parse

    my $tree = $self->_parse($source);

    # Build query

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

    return $query;

}

sub _parse {

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

    # Source

    $source ||= '';

    # Tree

    my $tree = [];

    # Start tag

    my $tag_start = quotemeta $self->tag_start;

    croak qq{tag_start must be a charactor}

      if !$tag_start || length $tag_start == 1;

    # End tag

    my $tag_end   = quotemeta $self->tag_end;

    croak qq{tag_end must be a charactor}

      if !$tag_end || length $tag_end == 1;

    # Tokenize

    my $state = 'text';

    # Save original source

    my $original = $source;

    # Parse

    while ($source =~ s/([^$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 not registerd

            croak qq{Tag "$tag" in "$original" is not registerd}

               unless $self->tag_processors->{$tag_name};

            # Check tag arguments

            foreach my $tag_arg (@tag_args) {

                # Cannot cantain placehosder '?'

                croak qq{Tag cannot contains "?"}

                  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 @$tree, {type => 'text', tag_args => [$source]}

      if $source;

    return $tree;

}

sub _build_query {

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

    # SQL

    my $sql = '';

    # All Columns

    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 not sub reference

            croak qq{Tag processor "$tag_name" must be sub reference}

              unless ref $tag_processor eq 'CODE';

            # Execute tag processor

            my ($part, $columns) = @{$tag_processor->(@$tag_args)};

            # Check tag processor return value

            croak qq{Tag processor "$tag_name" must return [STRING, ARRAY_REFERENCE]}

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

            # Check placeholder count

            croak qq{Count of Placeholders must be same as count of columns in "$tag_name"}

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

            # Add columns

            push @$all_columns, @$columns;

            # Join part tag to SQL

            $sql .= $part;

        }

    }

    # 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) = @_;

    # Count

    $expand ||= '';

    my $count = 0;

    my $pos   = -1;

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

        $count++;

    }

    return $count;

}

1;

=head1 NAME

DBIx::Custom::QueryBuilder - Query builder

=head1 SYNOPSIS

    my $builder = DBIx::Custom::QueryBuilder->new;

    my $query = $builder->build_query(

        "select from table {= k1} && {<> k2} || {like k3}"

    );

=head1 ATTRIBUTES

=head2 C<tag_processors>

    my $tag_processors = $builder->tag_processors;

    $builder           = $builder->tag_processors(\%tag_processors);

Tag processors.

=head2 C<tag_start>

    my $tag_start = $builder->tag_start;

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

Tag start charactor.

Default to '{'.

=head2 C<tag_end>

    my $tag_end = $builder->tag_start;

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

Tag end charactor.

Default to '}'.

=head1 METHODS

L<DBIx::Custom::QueryBuilder> inherits all methods from L<Object::Simple>

and implements the following new ones.

=head2 C<build_query>

    my $query = $builder->build_query($source);

Create a new L<DBIx::Custom::Query> object from SQL source.

SQL source contains tags, such as {= title}, {like author}.

B<Example:>

SQL source

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

Query

    {

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

        columns => ['title', 'author', 'price']

    }

=head2 C<register_tag_processor>

    $builder->register_tag_processor(\%tag_processors);

    $builder->register_tag_processor(%tag_processors);

Register tag processor.

B<Examples:>

    $builder->register_tag_processor(

        '?' => sub {

            my $column = shift;

            return ['?', [$column]];

        }

    );

See L<DBIx::Custom::QueryBuilder::TagProcessors> about tag processor.

=head1 Tags

You can use the following tags in SQL source.

    [Tags]           [Replaced]

    {? NAME}    ->   ?

    {= NAME}    ->   NAME = ?

    {<> NAME}   ->   NAME <> ?

    {< NAME}    ->   NAME < ?

    {> NAME}    ->   NAME > ?

    {>= NAME}   ->   NAME >= ?

    {<= NAME}   ->   NAME <= ?

    {like NAME}       ->   NAME like ?

    {in NAME COUNT}   ->   NAME in [?, ?, ..]

    {insert NAME1 NAME2}   ->   (NAME1, NAME2) values (?, ?)

    {update NAME1 NAME2}   ->   set NAME1 = ?, NAME2 = ?