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package SL::PriceSource;
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use strict;
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use parent 'SL::DB::Object';
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use Rose::Object::MakeMethods::Generic (
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scalar => [ qw(record_item record fast) ],
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'scalar --get_set_init' => [ qw(
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best_price best_discount
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) ],
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'array --get_set_init' => [ qw(
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all_price_sources
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available_prices available_discounts
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) ],
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);
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use List::UtilsBy qw(min_by max_by);
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use SL::PriceSource::ALL;
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use SL::PriceSource::Price;
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use SL::Locale::String;
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sub init_all_price_sources {
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my ($self) = @_;
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[ map {
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$self->price_source_by_class($_);
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} SL::PriceSource::ALL->all_enabled_price_sources ]
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}
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sub price_source_by_class {
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my ($self, $class) = @_;
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return unless $class;
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$self->{price_source_by_name}{$class} //=
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$class->new(record_item => $self->record_item, record => $self->record, fast => $self->fast);
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}
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sub price_from_source {
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my ($self, $source) = @_;
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return empty_price() if !$source;
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${ $self->{price_from_source} //= {} }{$source} //= do {
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my ($source_name, $spec) = split m{/}, $source, 2;
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my $class = SL::PriceSource::ALL->price_source_class_by_name($source_name);
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my $source_object = $self->price_source_by_class($class);
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$source_object
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? $source_object->price_from_source($source, $spec)
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: empty_price();
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}
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}
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sub discount_from_source {
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my ($self, $source) = @_;
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return empty_discount() if !$source;
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${ $self->{discount_from_source} //= {} }{$source} //= do {
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my ($source_name, $spec) = split m{/}, $source, 2;
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my $class = SL::PriceSource::ALL->price_source_class_by_name($source_name);
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my $source_object = $self->price_source_by_class($class);
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$source_object
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? $source_object->discount_from_source($source, $spec)
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: empty_discount();
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}
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}
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sub init_available_prices {
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[ map { $_->available_prices } $_[0]->all_price_sources ];
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}
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sub init_available_discounts {
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return [] if $_[0]->record_item->part->not_discountable;
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[ map { $_->available_discounts } $_[0]->all_price_sources ];
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}
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sub init_best_price {
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min_by { $_->price } max_by { $_->priority } grep { $_->price > 0 } grep { $_ } map { $_->best_price } $_[0]->all_price_sources;
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}
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sub init_best_discount {
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max_by { $_->discount } max_by { $_->priority } grep { $_->discount } grep { $_ } map { $_->best_discount } $_[0]->all_price_sources;
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}
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sub empty_price {
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SL::PriceSource::Price->new(
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description => t8('None (PriceSource)'),
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);
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}
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sub empty_discount {
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SL::PriceSource::Discount->new(
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description => t8('None (PriceSource Discount)'),
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);
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}
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1;
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__END__
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=encoding utf-8
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=head1 NAME
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SL::PriceSource - mixin for price_sources in record items
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=head1 DESCRIPTION
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PriceSource is an interface that allows generic algorithms to be plugged
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together to calculate available prices for a position in a record.
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Each algorithm can access details of the record to realize dependencies on
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part, customer, vendor, date, quantity etc, which was previously not possible.
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=head1 BACKGROUND AND PHILOSOPHY
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sql ledger and subsequently Lx-Office had three prices per part: sellprice,
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listprice and lastcost. When adding an item to a record, the applicable price
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was copied and after that it was free to be changed.
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Later on additional things were added. Various types of discount, vendor pricelists
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and the infamous price groups. The problem was not that those didn't work, the
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problem was they had to guess too much when to change a price with the
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available price from the database, and when to leave the user entered price.
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The result was that the price of an item in a record seemed to change on a
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whim, and the origin of the price itself being opaque.
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Unrelated to that, users asked for more ways to store special prices, based on
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qty (block pricing, bulk discount), based on date (special offers), based on
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customers (special terms), up to full blown calculation modules.
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On a third front sales personnel asked for ways to see what price options a
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position in a quotation has, and wanted information available when prices
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changed to make better informed choices about sales later in the workflow.
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Price sources now extend the previous pricing by attaching a source to every
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price in records. The information it provides are:
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=over 4
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=item 1.
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Where did this price originate?
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=item 2.
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If this price would be calculated today, is it still the same as it was when
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this record was created?
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=item 3.
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If I want to price an item in this record now, which prices are available?
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=item 4.
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Which one is the "best"?
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=back
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=head1 GUARANTEES
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To ensure price source prices are comprehensible and reproducible, some
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invariants are guaranteed:
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=over 4
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=item 1.
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Price sources will never on their own change a price. They will offer options,
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and it is up to the user to change a price.
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=item 2.
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If a price is set from a source then the system will try to prevent the user
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from messing it up. By default this means the price will be read-only.
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Implementations can choose to make prices editable, but even then deviations
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from the calculatied price will be marked.
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A price that is not set from a source will not have any of this.
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=item 3.
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A price should be able to repeat the calculations done to arrive at the price
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when it was first used. If these calculations are no longer applicable (special
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offer expired) this should be signalled. If the calculations result in a
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different price, this should be signalled. If the calculations fail (needed
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information is no longer present) this must be signalled.
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=back
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The first point creates user security by never changing a price for them
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without their explicit consent, eliminating all problems originating from
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trying to be smart. The second and third one ensure that later on the
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calculation can be repeated so that invalid prices can be caught (because for
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example the special offer is no longer valid), and so that sales personnel have
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information about rising or falling prices.
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=head1 STRUCTURE
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Price sources are managed by this package (L<SL::PriceSource>), and all
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external access should be by using its interface.
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Each source is an instance of L<SL::PriceSource::Base> and the available
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implementations are recorded in L<SL::PriceSource::ALL>. Prices and discounts
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returned by interface methods are instances of L<SL::PriceSource::Price> and
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L<SL::PriceSource::Discount>.
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Returned prices and discounts should be checked for entries in C<invalid> and
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C<missing>, see documentation in their classes.
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=head1 INTERFACE METHODS
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=over 4
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=item C<new PARAMS>
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C<PARAMS> must contain both C<record> and C<record_item>. C<record_item> does
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not have to be registered in C<record>.
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=item C<price_from_source>
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Attempts to retrieve a formerly calculated price with the same conditions
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=item C<discount_from_source>
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Attempts to retrieve a formerly calculated discount with the same conditions
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=item C<available_prices>
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Returns all available prices.
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=item C<available_discounts>
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Returns all available discounts.
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=item C<best_price>
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Attempts to get the best available price. returns L<empty_price> if no price is
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found.
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=item C<best_discount>
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Attempts to get the best available discount. returns L<empty_discount> if no
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discount is found.
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=item C<empty_price>
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A special empty price that does not change the previously entered price and
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opens the price field to manual changes.
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=item C<empty_discount>
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A special empty discount that does not change the previously entered discount
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and opens the discount field to manual changes.
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=item C<fast>
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If set to true, indicates that calls may skip doing intensive work and instead
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return a price or discount flagged as unknown. The caller must be prepared to
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deal with those.
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Typically this is intended to delay expensive calculations until they can be
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done in a second batch pass. If the information is already present, it is still
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encouraged that implementations return the correct values.
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=back
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=head1 SEE ALSO
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L<SL::PriceSource::Base>,
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L<SL::PriceSource::Price>,
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L<SL::PriceSource::Discount>,
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L<SL::PriceSource::ALL>
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=head1 BUGS AND CAVEATS
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=over 4
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=item *
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The current model of price sources requires a record and a record_item for
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every price calculation. This means that price structures can never be used
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when no record is available, such as calculation the worth of assembly rows.
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A possible solution is to either split price sources into simple and complex
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ones (where the former do not require records).
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Another would be to have default values for the input normally taken from
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records (like qty defaulting to 1).
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A last one would be to provide an alternative input channel for needed
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properties.
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=item *
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Discount sources were implemented as a copy of the prices with slightly
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different semantics. Need to do a real design. A requirement is, that a single
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source can provide both prices and discounts (needed for price_rules).
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=item *
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Priorities are implemented ad hoc. The semantics which are chosen by the "best"
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accessors are unintuitive because they do not guarantee anything. Better
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terminology might help.
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=item *
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It is currently not possible to link a price to the price of the generating
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record_item (i.e. the price of a delivery order item to the order item it was
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generated from). This is crucial to enterprises that calculate all their prices
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in orders, and update those after they made delivery orders.
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=item *
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Currently it is only possible to provide additional prices, but not to restrict
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prices. Potential scenarios include credit limit customers which do not receive
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benefits from sales, or general ALLOW, DENY order calculation.
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=item *
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Composing price sources is disallowed for clarity, but all price sources need
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to be aware of units and price_factors. This is madness.
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=item *
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The current implementation of lastcost is useless. Since it's one of the
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master_data prices it will always compete with listprice. But in real scenarios
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the listprice tends to go up, while lastcost stays the same, so lastcost
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usually wins. Lastcost could be lower priority, but a better design would be
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nice.
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=item *
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Guarantee 1 states that price sources will never change prices on their own.
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Further testing in the wild has shown that this is desirable within a record,
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but not when copying items from one record to another within a workflow.
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Specifically when changing from sales to purchase records prices don't make
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sense anymore. The guarantees should be updated to reflect this and
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transposition guidelines should be documented.
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The previously mentioned linked prices can emulated by allowing price sources
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to set a new price when changing to a new record in the workflow. The decision
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about whether a price is eligable to be set can be suggested by the price
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source implementation but is ultimately up to the surrounding framework, which
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can make this configurable.
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=item *
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Prices were originally planned as a context element rather than a modal popup.
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It would be great to have this now with better framework.
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=item *
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Large records (30 positions or more) in combination with complicated price
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sources run into n+1 problems. There should be an extra hook that allows price
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source implementations to make bulk calculations before the actual position loop.
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=item *
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Prices have defined information channels for missing and invalid, but it would
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be deriable to have more information flow. For example a limited offer might
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expire in three days while the record is valid for 20 days. THis mismatch is
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impossible to resolve automatically, but informing the user about it would be a
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nice thing.
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This can also extend to diagnostics on class level, where implementations can
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call attention to likely misconfigurations.
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=back
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=head1 AUTHOR
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Sven Schoeling E<lt>s.schoeling@linet-services.deE<gt>
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=cut
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