<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle 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.
//
// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Base class for a single availability condition.
 *
 * All condition types must extend this class.
 *
 * @package core_availability
 * @copyright 2014 The Open University
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace core_availability;

defined('MOODLE_INTERNAL') || die();

/**
 * Base class for a single availability condition.
 *
 * All condition types must extend this class.
 *
 * The structure of a condition in JSON input data is:
 *
 * { type:'date', ... }
 *
 * where 'date' is the name of the plugin (availability_date in this case) and
 * ... is arbitrary extra data to be used by the plugin.
 *
 * Conditions require a constructor with one parameter: $structure. This will
 * contain all the JSON data for the condition. If the structure of the data
 * is incorrect (e.g. missing fields) then the constructor may throw a
 * coding_exception. However, the constructor should cope with all data that
 * was previously valid (e.g. if the format changes, old data may still be
 * present in a restore, so there should be a default value for any new fields
 * and old ones should be handled correctly).
 *
 * @package core_availability
 * @copyright 2014 The Open University
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
abstract class condition extends tree_node {

    /**
     * Determines whether a particular item is currently available
     * according to this availability condition.
     *
     * If implementations require a course or modinfo, they should use
     * the get methods in $info.
     *
     * The $not option is potentially confusing. This option always indicates
     * the 'real' value of NOT. For example, a condition inside a 'NOT AND'
     * group will get this called with $not = true, but if you put another
     * 'NOT OR' group inside the first group, then a condition inside that will
     * be called with $not = false. We need to use the real values, rather than
     * the more natural use of the current value at this point inside the tree,
     * so that the information displayed to users makes sense.
     *
     * @param bool $not Set true if we are inverting the condition
     * @param info $info Item we're checking
     * @param bool $grabthelot Performance hint: if true, caches information
     *   required for all course-modules, to make the front page and similar
     *   pages work more quickly (works only for current user)
     * @param int $userid User ID to check availability for
     * @return bool True if available
     */
    public abstract function is_available($not, info $info, $grabthelot, $userid);

    public function check_available($not, info $info, $grabthelot, $userid) {
        // Use is_available, and we always display (at this stage).
        $allow = $this->is_available($not, $info, $grabthelot, $userid);
        return new result($allow, $this);
    }

    public function is_available_for_all($not = false) {
        // Default is that all conditions may make something unavailable.
        return false;
    }

    /**
     * Display a representation of this condition (used for debugging).
     *
     * @return string Text representation of condition
     */
    public function __toString() {
        return '{' . $this->get_type() . ':' . $this->get_debug_string() . '}';
    }

    /**
     * Gets the type name (e.g. 'date' for availability_date) of plugin.
     *
     * @return string The type name for this plugin
     */
    protected function get_type() {
        return preg_replace('~^availability_(.*?)\\\\condition$~', '$1', get_class($this));
    }

    /**

>      * Returns a marker indicating that an activity name should be placed in a description.
     * Obtains a string describing this restriction (whether or not
>      *
     * it actually applies). Used to obtain information that is displayed to
>      * Gets placeholder text which will be decoded by info::format_info later when we can safely
     * students if the activity is not available to them, and for staff to see
>      * display names.
     * what conditions are.
>      *
     *
>      * @param int $cmid Course-module id
     * The $full parameter can be used to distinguish between 'staff' cases
>      * @return string Placeholder text
     * (when displaying all information about the activity) and 'student' cases
>      * @since Moodle 4.0
     * (when displaying only conditions they don't meet).
>      */
     *
>     public static function description_cm_name(int $cmid): string {
     * If implementations require a course or modinfo, they should use
>         return '<AVAILABILITY_CMNAME_' . $cmid . '/>';
     * the get methods in $info.
>     }
     *
> 
     * The special string <AVAILABILITY_CMNAME_123/> can be returned, where
>     /**
     * 123 is any number. It will be replaced with the correctly-formatted
>      * Returns a marker indicating that formatted text should be placed in a description.
     * name for that activity.
>      *
     *
>      * Gets placeholder text which will be decoded by info::format_info later when we can safely
     * @param bool $full Set true if this is the 'full information' view
>      * call format_string.
     * @param bool $not Set true if we are inverting the condition
>      *
     * @param info $info Item we're checking
>      * @param string $str Text to be processed with format_string
     * @return string Information string (for admin) about all restrictions on
>      * @return string Placeholder text
     *   this item
>      * @since Moodle 4.0
     */
>      */
    public abstract function get_description($full, $not, info $info);
>     public static function description_format_string(string $str): string {

>         return '<AVAILABILITY_FORMAT_STRING>' . htmlspecialchars($str, ENT_NOQUOTES) .
    /**
>                 '</AVAILABILITY_FORMAT_STRING>';
     * Obtains a string describing this restriction, used when there is only
>     }
     * a single restriction to display. (I.e. this provides a 'short form'
> 
     * rather than showing in a list.)
>     /**
     *
>      * Returns a marker indicating that some of the description text should be computed at display
     * Default behaviour sticks the prefix text, normally displayed above
>      * time.
     * the list, in front of the standard get_description call.
>      *
     *
>      * This will result in a call to the get_description_callback_value static function within
     * If implementations require a course or modinfo, they should use
>      * the condition class.
     * the get methods in $info.
>      *
     *
>      * Gets placeholder text which will be decoded by info::format_info later when we can safely
     * The special string <AVAILABILITY_CMNAME_123/> can be returned, where
>      * call most Moodle functions.
     * 123 is any number. It will be replaced with the correctly-formatted
>      *
     * name for that activity.
>      * @param string[] $params Array of arbitrary parameters
     *
>      * @return string Placeholder text
     * @param bool $full Set true if this is the 'full information' view
>      * @since Moodle 4.0
     * @param bool $not Set true if we are inverting the condition
>      */
     * @param info $info Item we're checking
>     public function description_callback(array $params): string {
     * @return string Information string (for admin) about all restrictions on
>         $out = '<AVAILABILITY_CALLBACK type="' . $this->get_type() . '">';
     *   this item
>         $first = true;
     */
>         foreach ($params as $param) {
    public function get_standalone_description($full, $not, info $info) {
>             if ($first) {
        return get_string('list_root_and', 'availability') . ' ' .
>                 $first = false;
                $this->get_description($full, $not, $info);
>             } else {
    }
>                 $out .= '<P/>';

>             }
    /**
>             $out .= htmlspecialchars($param, ENT_NOQUOTES);
     * Obtains a representation of the options of this condition as a string,
>         }
     * for debugging.
>         $out .= '</AVAILABILITY_CALLBACK>';
     *
>         return $out;
     * @return string Text representation of parameters
>     }
     */
> 
    protected abstract function get_debug_string();
>     /**



<      * the get methods in $info.



>      * the get methods in $info. They should not use any other functions that
>      * might rely on modinfo, such as format_string.
>      *
>      * To work around this limitation, use the functions:
>      *
>      * description_cm_name()
>      * description_format_string()
>      * description_callback()



<      * The special string <AVAILABILITY_CMNAME_123/> can be returned, where
<      * 123 is any number. It will be replaced with the correctly-formatted
<      * name for that activity.



>      * These return special markers which will be added to the string and processed
>      * later after modinfo is complete.



<      * the get methods in $info.



>      * the get methods in $info. They should not use any other functions that
>      * might rely on modinfo, such as format_string.
>      *
>      * To work around this limitation, use the functions:
>      *
>      * description_cm_name()
>      * description_format_string()
>      * description_callback()



<      * The special string <AVAILABILITY_CMNAME_123/> can be returned, where
<      * 123 is any number. It will be replaced with the correctly-formatted
<      * name for that activity.



>      * These return special markers which will be added to the string and processed
>      * later after modinfo is complete.


     * completion value, it should return true here. (This is necessary so that
     * we know the course page needs to update when that activity becomes
     * complete.)
     *
     * Default implementation returns false.
     *
     * @param \stdClass $course Moodle course object
     * @param int $cmid ID of activity whose completion value is considered
     * @return boolean True if the availability of something else may rely on it
     */
    public static function completion_value_used($course, $cmid) {
        return false;
    }
}