<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright (C) 2014-2023 Ryan Specialty, LLC.

  This file is part of tame-core.

  tame-core 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 3 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, see <http://www.gnu.org/licenses/>.
-->
<package xmlns="http://www.lovullo.com/rater"
         xmlns:t="http://www.lovullo.com/rater/apply-template"
         xmlns:c="http://www.lovullo.com/calc"
         core="true"
         desc="Date and time">

  <import package="base" />

  <import package="assert" />
  <import package="vector/cmatch" />


  Providing the current timestamp externally allows the system to be
    wholly deterministic.
  It also captures the state of the data in time,
    so re-calculating in the future (e.g. using the summary pages)
    will yield the same result.

  <param name="timestamp_current" type="integer" default="0"
         desc="Unix timestamp representing the current time of the
               system (clock time), as it should be perceived" />

  <t:assert failure="Missing Unix timestamp for timestamp_current">
    <t:match-gt on="timestamp_current" value="ZERO" />
  </t:assert>


  This system does not handle its own arthiemtic to figure out the
    current date components from the given timestamp.

  <param name="timestamp_year" type="integer" default="0"
         desc="Current year (clock time), as it should be perceived" />

  <param name="timestamp_month" type="integer" default="0"
         desc="Current month (clock time), as it should be perceived;
               1-indexed" />

  <param name="timestamp_day" type="integer" default="0"
         desc="Current day (clock time), as it should be perceived;
               1-indexed" />


  <!--
    Determines how many years the given date is relative to the current date

    Note that a positive number will be returned if the given date is
    in the past, negative if in the future.
  -->
  <template name="_age-years_" desc="Age in years of the given date relative to the current">
    <param name="@generates@" desc="Generator variable, per index" />
    <param name="@yearset@"   desc="Set of years to iterate on" />
    <param name="@sym@"       desc="Generator symbol" />
    <param name="@when@"      desc="Only when this boolean value is true" />
    <param name="@default@"   desc="Default age when yearset values are empty" />

    <param name="@yields@" desc="Variable to yield into">
      <text>_</text>
      <param-value name="@generates@" />
    </param>


    <rate yields="@yields@">
      <c:sum of="@yearset@" index="k" generates="@generates@" desc="Relative age" sym="@sym@">
        <c:cases>
          <if name="@when@">
            <c:case>
              <c:when name="@when@" index="k">
                <c:eq>
                  <c:value-of name="FALSE" />
                </c:eq>
              </c:when>

              <!-- return a default, or 0 if no default is provided -->
              <if name="@default@">
                <c:value-of name="@default@" index="k" />
              </if>
              <unless name="@default@">
                <c:const value="0" desc="Condition not met, but no default" />
              </unless>
            </c:case>
          </if>

          <!-- if no @when@, then we'll always do this -->
          <c:otherwise>
            <c:cases>
              <c:case>
                <c:when name="@yearset@" index="k">
                  <c:gt>
                    <c:const value="0" desc="Only calculate difference if a value is available" />
                  </c:gt>
                </c:when>

                <c:sum label="Calculate by subtracting the given year from the current year">
                  <c:value-of name="timestamp_year" />

                  <c:product>
                    <c:value-of name="NEGATE" />
                    <c:value-of name="@yearset@" index="k" />
                  </c:product>
                </c:sum>
              </c:case>

              <!-- we don't have a value; just use the default age we were given -->
              <if name="@default@">
                <c:otherwise>
                  <c:value-of name="@default@" index="k" />
                </c:otherwise>
              </if>
            </c:cases>
          </c:otherwise>
        </c:cases>
      </c:sum>
    </rate>
  </template>
</package>

