@c  This document is part of the Liza Data Collection Framework manual.
@c  Copyright (C) 2017 R-T Specialty, LLC.
@c
@c    Permission is granted to copy, distribute and/or modify this document
@c    under the terms of the GNU Free Documentation License, Version 1.3
@c    or any later version published by the Free Software Foundation;
@c    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
@c    Texts.  A copy of the license is included in the section entitled ``GNU
@c    Free Documentation License''.


@node Program
@chapter Program
@maintstart
@footnote{
  The @code{Program} class was one of the first prototypes created,
    and has evolved poorly with the rest of the system.
  It is the base class for all compiled programs,
    and it glues together too many other systems with a terrible
    API and little to no encapsulation.

  With that said, it is one of the least touched classes (thus its
    state); developers rarely have the need to touch @code{Program}.}
@maintend


@cindex Program
The @dfn{Program} is a declarative representation of an entire system.
It is the highest level of abstraction from a data perspective.
The user observes and interacts with a Program using the
  @ref{Program UI,,Program@tie{}UI}.

@cindex Program, XML
Programs contain a lot of metadata that is not in a convenience
  human-readable (or modifiable) format,
    some of which are redundant.
Programs are ideally compiled from a @ref{Program XML,,Program@tie{}XML}
  document.

@menu
* Program UI::
* Program XML::
@end menu

@node Program UI
@section Program UI
@maintenance{
  The @code{Ui} class,
    in addition to @srcref{src/client/Client,Client} (@pxref{Client}),
    represent the two monoliths of the system.
  This mediates all UI-related tasks,
    and still has far too many concerns with far too many
      dependencies.
  Code is to be extracted out of this class as it is touched.
}


@cindex Program, User Interface
@cindex User Interface, Program
The @dfn{Program UI} renders a @ref{Program} as a form.

@cindex Step
@cindex Group
At the highest level,
  steps are rendered in a tab-like manner,
  above the main form content.
A step contains groups,
  which in turn contain elements such as questions.
Groups are delimited in some manner defined by their style
  (@pxref{Group Styles}).

@cindex Question
@cindex Question, Value Formatting
@cindex Bucket, Updating
Questions are rendered as form fields.
Any time the respective @ref{Bucket} field is changed,
  the form field is updated to reflect those changes,
    after having first been formatted with the appropriate validator
    (@pxref{Formatting Values}).
When a question is changed by the user,
  the value is expected to be propagated to the Bucket
  (@pxref{Bucket Assignment}).

@cindex Navigation Bar
@cindex User Interface, Navigation Bar
@cindex User Interface, Button Navigation
Navigation between steps can be done via the
  @dfn{Navigation Bar} above the step@tie{}content,
  or using ``Go@tie{}Back'' and ``Continue'' buttons at the foot of the
  step@tie{}content.

@cindex Sidebar
A @dfn{Sidebar} is rendered adjacent to the step content.
It displays the name of the Program,
  as well as configurable metadata (usually through the @samp{sidebar}
  node of the @ref{Program XML,,Program@tie{}XML}).
It also displays question help text (also configured through the XML)
  and any error messages (@pxref{Error Handling}).

@menu
* Group Styles:: Different ways of displaying groups of questions to
                 the user.
@end menu


@node Group Styles
@subsection Group Styles
@refactor{
  Some group styles still use jQuery;
    they should be modified to use modern formatters and Liza DOM
    abstractions (see @srcrefraw{src/ui/field}
      and @srcrefraw{src/ui/styler}).}

@cindex Group, Styling
Groups support a number of @dfn{group styles} that determine how
  they are delimited from other groups;
  how the elements they contain are rendered and laid out;
  and how multiple indexes are displayed, added, and removed.
A list of available styles is detailed in @ref{t:group-styles}.

@float Table, t:group-styles
@multitable @columnfractions 0.15 0.65 0.10 0.10
  @headitem Name @tab Description @tab Multi-Index? @tab Add/Remove Index?

  @item @samp{default}
  @tab
  Groups are unstyled by default@mdash{
    }they render elements as flat fields like a traditional form.
  Only the first index of elements is rendered.
  @tab@center N
  @tab@center N

  @item @samp{collapsetable}
  @tab
  Renders element label in the leftmost column like @samp{sidetable}.
  Indexes are groups of rows delimited by headings,
    which collapse the respective group of rows when clicked.
  @tab@center Y
  @tab@center Add

  @item @samp{sidetable}
  @tab
  Renders elements as rows with label in the leftmost column rather
    than the top row.
  Each index is rendered as a column.
  @tab@center Y
  @tab@center Add

  @item @samp{tabbedblock}
  @tab
  Each group is rendered as a block,
    with each index rendered as a tab to the right of it.
  Clicking a tab toggles the body content to the associated index.
  Elements are rendered within the box.
  @tab@center Y
  @tab@center N

  @item @samp{tabbed}
  @tab
  Like @samp{default},
    but each index has a tab at the top of the group.
  Clicking a tab toggles the body content to the associated index.
  @tab@center Y
  @tab@center Y

  @item @samp{table}
  @tab
  A vanilla table with elements as columns,
    their labels across the top row.
  Each index is rendered in its own row.
  @tab@center Y
  @tab@center Y
@end multitable
@caption{Group styles and index support}
@end float



@node Program XML
@section Program XML
@helpwanted

@menu
* Specifying Predicates::
@end menu


@node Specifying Predicates
@subsection Specifying Predicates

Object predicates (@pxref{Predicate System}) are specified using the
  @xmlattr{when} attribute of certain nodes.
It must contain a string of references understood by the system
  (see domain of discourse, @ref{Predicate System}),
    all of which much match for the predicate to be true.

@float Figure, f:pred-when
@example
  <question id="describe" type="noyes"
            label="Any special notes for this location?" />

  <question id="vacant_desc" type="textarea"
            when="q:describe vacant property"
            label="Show only when a vacant property with the
                   question 'describe' non-empty and non-zero" />
@end example
@caption{Using the @xmlattr{when} attribute}
@end float

In @ref{f:pred-when} above,
  question @samp{vacant_desc} will be applicable when @emph{all} of
  the values of @samp{vacant}, @samp{property},
  and@tie{}@samp{q:describe} are true.@footnote{
    @xref{Predicate System} for what ``true'' means for a particular
      variable in the domain of discourse.}
Within the context of the @progxml,
  this concretely means that the classifications
  @samp{vacant} and@tie{}@samp{property} are true,
    and that the question @samp{describe} is answered ``yes''.
It reads as a sentence:
  ``@samp{vacant_desc}'' is applicable when we should @tie{}``describe
  a vacant property''.