/lib/blocklib.php

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<?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/>.

/**
 * Block Class and Functions
 *
 * This file defines the {@link block_manager} class,
 *
 * @package    core
 * @subpackage block
 * @copyright  1999 onwards Martin Dougiamas  http://dougiamas.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

/**#@+
 * Default names for the block regions in the standard theme.
 */
define('BLOCK_POS_LEFT',  'side-pre');
define('BLOCK_POS_RIGHT', 'side-post');
/**#@-*/

define('BUI_CONTEXTS_FRONTPAGE_ONLY', 0);
define('BUI_CONTEXTS_FRONTPAGE_SUBS', 1);
define('BUI_CONTEXTS_ENTIRE_SITE', 2);

define('BUI_CONTEXTS_CURRENT', 0);
define('BUI_CONTEXTS_CURRENT_SUBS', 1);

// Position of "Add block" control, to be used in theme config as a value for $THEME->addblockposition:
// - default: as a fake block that is displayed in editing mode
// - flatnav: "Add block" item in the flat navigation drawer in editing mode
// - custom: none of the above, theme will take care of displaying the control.
define('BLOCK_ADDBLOCK_POSITION_DEFAULT', 0);
define('BLOCK_ADDBLOCK_POSITION_FLATNAV', 1);
define('BLOCK_ADDBLOCK_POSITION_CUSTOM', -1);

/**
 * Exception thrown when someone tried to do something with a block that does
 * not exist on a page.
 *
 * @copyright 2009 Tim Hunt
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @since     Moodle 2.0
 */
class block_not_on_page_exception extends moodle_exception {
    /**
     * Constructor
     * @param int $instanceid the block instance id of the block that was looked for.
     * @param object $page the current page.
     */
    public function __construct($instanceid, $page) {
        $a = new stdClass;
        $a->instanceid = $instanceid;
        $a->url = $page->url->out();
        parent::__construct('blockdoesnotexistonpage', '', $page->url->out(), $a);
    }
}

/**
 * This class keeps track of the block that should appear on a moodle_page.
 *
 * The page to work with as passed to the constructor.
 *
 * @copyright 2009 Tim Hunt
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @since     Moodle 2.0
 */
class block_manager {
    /**
     * The UI normally only shows block weights between -MAX_WEIGHT and MAX_WEIGHT,
     * although other weights are valid.
     */
    const MAX_WEIGHT = 10;

/// Field declarations =========================================================

    /**
     * the moodle_page we are managing blocks for.
     * @var moodle_page
     */
    protected $page;

    /** @var array region name => 1.*/
    protected $regions = array();

    /** @var string the region where new blocks are added.*/
    protected $defaultregion = null;

    /** @var array will be $DB->get_records('blocks') */
    protected $allblocks = null;

    /**
     * @var array blocks that this user can add to this page. Will be a subset
     * of $allblocks, but with array keys block->name. Access this via the
     * {@link get_addable_blocks()} method to ensure it is lazy-loaded.
     */
    protected $addableblocks = null;

    /**
     * Will be an array region-name => array(db rows loaded in load_blocks);
     * @var array
     */
    protected $birecordsbyregion = null;

    /**
     * array region-name => array(block objects); populated as necessary by
     * the ensure_instances_exist method.
     * @var array
     */
    protected $blockinstances = array();

    /**
     * array region-name => array(block_contents objects) what actually needs to
     * be displayed in each region.
     * @var array
     */
    protected $visibleblockcontent = array();

    /**
     * array region-name => array(block_contents objects) extra block-like things
     * to be displayed in each region, before the real blocks.
     * @var array
     */
    protected $extracontent = array();

    /**
     * Used by the block move id, to track whether a block is currently being moved.
     *
     * When you click on the move icon of a block, first the page needs to reload with
     * extra UI for choosing a new position for a particular block. In that situation
     * this field holds the id of the block being moved.
     *
     * @var integer|null
     */
    protected $movingblock = null;

    /**
     * Show only fake blocks
     */
    protected $fakeblocksonly = false;

/// Constructor ================================================================

    /**
     * Constructor.
     * @param object $page the moodle_page object object we are managing the blocks for,
     * or a reasonable faxilimily. (See the comment at the top of this class
     * and {@link http://en.wikipedia.org/wiki/Duck_typing})
     */
    public function __construct($page) {
        $this->page = $page;
    }

/// Getter methods =============================================================

    /**
     * Get an array of all region names on this page where a block may appear
     *
     * @return array the internal names of the regions on this page where block may appear.
     */
    public function get_regions() {
        if (is_null($this->defaultregion)) {
            $this->page->initialise_theme_and_output();
        }
        return array_keys($this->regions);
    }

    /**
     * Get the region name of the region blocks are added to by default
     *
     * @return string the internal names of the region where new blocks are added
     * by default, and where any blocks from an unrecognised region are shown.
     * (Imagine that blocks were added with one theme selected, then you switched
     * to a theme with different block positions.)
     */
    public function get_default_region() {
        $this->page->initialise_theme_and_output();
        return $this->defaultregion;
    }

    /**
     * The list of block types that may be added to this page.
     *
     * @return array block name => record from block table.
     */
    public function get_addable_blocks() {
        $this->check_is_loaded();

        if (!is_null($this->addableblocks)) {
            return $this->addableblocks;
        }

        // Lazy load.
        $this->addableblocks = array();

        $allblocks = blocks_get_record();
        if (empty($allblocks)) {
            return $this->addableblocks;
        }

        $unaddableblocks = self::get_undeletable_block_types();
        $requiredbythemeblocks = $this->get_required_by_theme_block_types();
        $pageformat = $this->page->pagetype;
        foreach($allblocks as $block) {
            if (!$bi = block_instance($block->name)) {
                continue;
            }
            if ($block->visible && !in_array($block->name, $unaddableblocks) &&
                    !in_array($block->name, $requiredbythemeblocks) &&
                    ($bi->instance_allow_multiple() || !$this->is_block_present($block->name)) &&
                    blocks_name_allowed_in_format($block->name, $pageformat) &&
                    $bi->user_can_addto($this->page)) {
                $block->title = $bi->get_title();
                $this->addableblocks[$block->name] = $block;
            }
        }

        core_collator::asort_objects_by_property($this->addableblocks, 'title');
        return $this->addableblocks;
    }

    /**
     * Given a block name, find out of any of them are currently present in the page

     * @param string $blockname - the basic name of a block (eg "navigation")
     * @return boolean - is there one of these blocks in the current page?
     */
    public function is_block_present($blockname) {
        if (empty($this->blockinstances)) {
            return false;
        }

        $requiredbythemeblocks = $this->get_required_by_theme_block_types();
        foreach ($this->blockinstances as $region) {
            foreach ($region as $instance) {
                if (empty($instance->instance->blockname)) {
                    continue;
                }
                if ($instance->instance->blockname == $blockname) {
                    if ($instance->instance->requiredbytheme) {
                        if (!in_array($blockname, $requiredbythemeblocks)) {
                            continue;
                        }
                    }
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Find out if a block type is known by the system
     *
     * @param string $blockname the name of the type of block.
     * @param boolean $includeinvisible if false (default) only check 'visible' blocks, that is, blocks enabled by the admin.
     * @return boolean true if this block in installed.
     */
    public function is_known_block_type($blockname, $includeinvisible = false) {
        $blocks = $this->get_installed_blocks();
        foreach ($blocks as $block) {
            if ($block->name == $blockname && ($includeinvisible || $block->visible)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Find out if a region exists on a page
     *
     * @param string $region a region name
     * @return boolean true if this region exists on this page.
     */
    public function is_known_region($region) {
        if (empty($region)) {
            return false;
        }
        return array_key_exists($region, $this->regions);
    }

    /**
     * Get an array of all blocks within a given region
     *
     * @param string $region a block region that exists on this page.
     * @return array of block instances.
     */
    public function get_blocks_for_region($region) {
        $this->check_is_loaded();
        $this->ensure_instances_exist($region);
        return $this->blockinstances[$region];
    }

    /**
     * Returns an array of block content objects that exist in a region
     *
     * @param string $region a block region that exists on this page.
     * @return array of block block_contents objects for all the blocks in a region.
     */
    public function get_content_for_region($region, $output) {
        $this->check_is_loaded();
        $this->ensure_content_created($region, $output);
        return $this->visibleblockcontent[$region];
    }

    /**
     * Returns an array of block content objects for all the existings regions
     *
     * @param renderer_base $output the rendered to use
     * @return array of block block_contents objects for all the blocks in all regions.
     * @since  Moodle 3.3
     */
    public function get_content_for_all_regions($output) {
        $contents = array();
        $this->check_is_loaded();

        foreach ($this->regions as $region => $val) {
            $this->ensure_content_created($region, $output);
            $contents[$region] = $this->visibleblockcontent[$region];
        }
        return $contents;
    }

    /**
     * Helper method used by get_content_for_region.
     * @param string $region region name
     * @param float $weight weight. May be fractional, since you may want to move a block
     * between ones with weight 2 and 3, say ($weight would be 2.5).
     * @return string URL for moving block $this->movingblock to this position.
     */
    protected function get_move_target_url($region, $weight) {
        return new moodle_url($this->page->url, array('bui_moveid' => $this->movingblock,
                'bui_newregion' => $region, 'bui_newweight' => $weight, 'sesskey' => sesskey()));
    }

    /**
     * Determine whether a region contains anything. (Either any real blocks, or
     * the add new block UI.)
     *
     * (You may wonder why the $output parameter is required. Unfortunately,
     * because of the way that blocks work, the only reliable way to find out
     * if a block will be visible is to get the content for output, and to
     * get the content, you need a renderer. Fortunately, this is not a
     * performance problem, because we cache the output that is generated, and
     * in almost every case where we call region_has_content, we are about to
     * output the blocks anyway, so we are not doing wasted effort.)
     *
     * @param string $region a block region that exists on this page.
     * @param core_renderer $output a core_renderer. normally the global $OUTPUT.
     * @return boolean Whether there is anything in this region.
     */
    public function region_has_content($region, $output) {

        if (!$this->is_known_region($region)) {
            return false;
        }
        $this->check_is_loaded();
        $this->ensure_content_created($region, $output);
        // if ($this->page->user_is_editing() && $this->page->user_can_edit_blocks()) {
        // Mark Nielsen's patch - part 1
        if ($this->page->user_is_editing() && $this->page->user_can_edit_blocks() && $this->movingblock) {
            // If editing is on, we need all the block regions visible, for the
            // move blocks UI.
            return true;
        }
        return !empty($this->visibleblockcontent[$region]) || !empty($this->extracontent[$region]);
    }

    /**
     * Determine whether a region contains any fake blocks.
     *
     * (Fake blocks are typically added to the extracontent array per region)
     *
     * @param string $region a block region that exists on this page.
     * @return boolean Whether there are fake blocks in this region.
     */
    public function region_has_fakeblocks($region): bool {
        return !empty($this->extracontent[$region]);
    }

    /**
     * Get an array of all of the installed blocks.
     *
     * @return array contents of the block table.
     */
    public function get_installed_blocks() {
        global $DB;
        if (is_null($this->allblocks)) {
            $this->allblocks = $DB->get_records('block');
        }
        return $this->allblocks;
    }

    /**
     * @return array names of block types that must exist on every page with this theme.
     */
    public function get_required_by_theme_block_types() {
        $requiredbythemeblocks = false;
        if (isset($this->page->theme->requiredblocks)) {
            $requiredbythemeblocks = $this->page->theme->requiredblocks;
        }

        if ($requiredbythemeblocks === false) {
            return array('navigation', 'settings');
        } else if ($requiredbythemeblocks === '') {
            return array();
        } else if (is_string($requiredbythemeblocks)) {
            return explode(',', $requiredbythemeblocks);
        } else {
            return $requiredbythemeblocks;
        }
    }

    /**
     * Make this block type undeletable and unaddable.
     *
     * @param mixed $blockidorname string or int
     */
    public static function protect_block($blockidorname) {
        global $DB;

        $syscontext = context_system::instance();

        require_capability('moodle/site:config', $syscontext);

        $block = false;
        if (is_int($blockidorname)) {
            $block = $DB->get_record('block', array('id' => $blockidorname), 'id, name', MUST_EXIST);
        } else {
            $block = $DB->get_record('block', array('name' => $blockidorname), 'id, name', MUST_EXIST);
        }
        $undeletableblocktypes = self::get_undeletable_block_types();
        if (!in_array($block->name, $undeletableblocktypes)) {
            $undeletableblocktypes[] = $block->name;
            set_config('undeletableblocktypes', implode(',', $undeletableblocktypes));
            add_to_config_log('block_protect', "0", "1", $block->name);
        }
    }

    /**
     * Make this block type deletable and addable.
     *
     * @param mixed $blockidorname string or int
     */
    public static function unprotect_block($blockidorname) {
        global $DB;

        $syscontext = context_system::instance();

        require_capability('moodle/site:config', $syscontext);

        $block = false;
        if (is_int($blockidorname)) {
            $block = $DB->get_record('block', array('id' => $blockidorname), 'id, name', MUST_EXIST);
        } else {
            $block = $DB->get_record('block', array('name' => $blockidorname), 'id, name', MUST_EXIST);
        }
        $undeletableblocktypes = self::get_undeletable_block_types();
        if (in_array($block->name, $undeletableblocktypes)) {
            $undeletableblocktypes = array_diff($undeletableblocktypes, array($block->name));
            set_config('undeletableblocktypes', implode(',', $undeletableblocktypes));
            add_to_config_log('block_protect', "1", "0", $block->name);
        }

    }

    /**
     * Get the list of "protected" blocks via admin block manager ui.
     *
     * @return array names of block types that cannot be added or deleted. E.g. array('navigation','settings').
     */
    public static function get_undeletable_block_types() {
        global $CFG;
        $undeletableblocks = false;
        if (isset($CFG->undeletableblocktypes)) {
            $undeletableblocks = $CFG->undeletableblocktypes;
        }

        if (empty($undeletableblocks)) {
            return array();
        } else if (is_string($undeletableblocks)) {
            return explode(',', $undeletableblocks);
        } else {
            return $undeletableblocks;
        }
    }

/// Setter methods =============================================================

    /**
     * Add a region to a page
     *
     * @param string $region add a named region where blocks may appear on the current page.
     *      This is an internal name, like 'side-pre', not a string to display in the UI.
     * @param bool $custom True if this is a custom block region, being added by the page rather than the theme layout.
     */
    public function add_region($region, $custom = true) {
        global $SESSION;
        $this->check_not_yet_loaded();
        if ($custom) {
            if (array_key_exists($region, $this->regions)) {
                // This here is EXACTLY why we should not be adding block regions into a page. It should
                // ALWAYS be done in a theme layout.
                debugging('A custom region conflicts with a block region in the theme.', DEBUG_DEVELOPER);
            }
            // We need to register this custom region against the page type being used.
            // This allows us to check, when performing block actions, that unrecognised regions can be worked with.
            $type = $this->page->pagetype;
            if (!isset($SESSION->custom_block_regions)) {
                $SESSION->custom_block_regions = array($type => array($region));
            } else if (!isset($SESSION->custom_block_regions[$type])) {
                $SESSION->custom_block_regions[$type] = array($region);
            } else if (!in_array($region, $SESSION->custom_block_regions[$type])) {
                $SESSION->custom_block_regions[$type][] = $region;
            }
        }
        $this->regions[$region] = 1;

        // Checking the actual property instead of calling get_default_region as it ends up in a recursive call.
        if (empty($this->defaultregion)) {
            $this->set_default_region($region);
        }
    }

    /**
     * Add an array of regions
     * @see add_region()
     *
     * @param array $regions this utility method calls add_region for each array element.
     */
    public function add_regions($regions, $custom = true) {
        foreach ($regions as $region) {
            $this->add_region($region, $custom);
        }
    }

    /**
     * Finds custom block regions associated with a page type and registers them with this block manager.
     *
     * @param string $pagetype
     */
    public function add_custom_regions_for_pagetype($pagetype) {
        global $SESSION;
        if (isset($SESSION->custom_block_regions[$pagetype])) {
            foreach ($SESSION->custom_block_regions[$pagetype] as $customregion) {
                $this->add_region($customregion, false);
            }
        }
    }

    /**
     * Set the default region for new blocks on the page
     *
     * @param string $defaultregion the internal names of the region where new
     * blocks should be added by default, and where any blocks from an
     * unrecognised region are shown.
     */
    public function set_default_region($defaultregion) {
        $this->check_not_yet_loaded();
        if ($defaultregion) {
            $this->check_region_is_known($defaultregion);
        }
        $this->defaultregion = $defaultregion;
    }

    /**
     * Add something that looks like a block, but which isn't an actual block_instance,
     * to this page.
     *
     * @param block_contents $bc the content of the block-like thing.
     * @param string $region a block region that exists on this page.
     */
    public function add_fake_block($bc, $region) {
        $this->page->initialise_theme_and_output();
        if (!$this->is_known_region($region)) {
            $region = $this->get_default_region();
        }
        if (array_key_exists($region, $this->visibleblockcontent)) {
            throw new coding_exception('block_manager has already prepared the blocks in region ' .
                    $region . 'for output. It is too late to add a fake block.');
        }
        if (!isset($bc->attributes['data-block'])) {
            $bc->attributes['data-block'] = '_fake';
        }
        $bc->attributes['class'] .= ' block_fake';
        $this->extracontent[$region][] = $bc;
    }

    /**
     * Checks to see whether all of the blocks within the given region are docked
     *
     * @see region_uses_dock
     * @param string $region
     * @return bool True if all of the blocks within that region are docked
     *
     * Return false as from MDL-64506
     */
    public function region_completely_docked($region, $output) {
        return false;
    }

    /**
     * Checks to see whether any of the blocks within the given regions are docked
     *
     * @see region_completely_docked
     * @param array|string $regions array of regions (or single region)
     * @return bool True if any of the blocks within that region are docked
     *
     * Return false as from MDL-64506
     */
    public function region_uses_dock($regions, $output) {
        return false;
    }

/// Actions ====================================================================

    /**
     * This method actually loads the blocks for our page from the database.
     *
     * @param boolean|null $includeinvisible
     *      null (default) - load hidden blocks if $this->page->user_is_editing();
     *      true - load hidden blocks.
     *      false - don't load hidden blocks.
     */
    public function load_blocks($includeinvisible = null) {
        global $DB, $CFG;

        if (!is_null($this->birecordsbyregion)) {
            // Already done.
            return;
        }

        if ($CFG->version < 2009050619) {
            // Upgrade/install not complete. Don't try too show any blocks.
            $this->birecordsbyregion = array();
            return;
        }

        // Ensure we have been initialised.
        if (is_null($this->defaultregion)) {
            $this->page->initialise_theme_and_output();
            // If there are still no block regions, then there are no blocks on this page.
            if (empty($this->regions)) {
                $this->birecordsbyregion = array();
                return;
            }
        }

        // Check if we need to load normal blocks
        if ($this->fakeblocksonly) {
            $this->birecordsbyregion = $this->prepare_per_region_arrays();
            return;
        }

        // Exclude auto created blocks if they are not undeletable in this theme.
        $requiredbytheme = $this->get_required_by_theme_block_types();
        $requiredbythemecheck = '';
        $requiredbythemeparams = array();
        $requiredbythemenotparams = array();
        if (!empty($requiredbytheme)) {
            list($testsql, $requiredbythemeparams) = $DB->get_in_or_equal($requiredbytheme, SQL_PARAMS_NAMED, 'requiredbytheme');
            list($testnotsql, $requiredbythemenotparams) = $DB->get_in_or_equal($requiredbytheme, SQL_PARAMS_NAMED,
                                                                                'notrequiredbytheme', false);
            $requiredbythemecheck = 'AND ((bi.blockname ' . $testsql . ' AND bi.requiredbytheme = 1) OR ' .
                                ' (bi.blockname ' . $testnotsql . ' AND bi.requiredbytheme = 0))';
        } else {
            $requiredbythemecheck = 'AND (bi.requiredbytheme = 0)';
        }

        if (is_null($includeinvisible)) {
            $includeinvisible = $this->page->user_is_editing();
        }
        if ($includeinvisible) {
            $visiblecheck = '';
        } else {
            $visiblecheck = 'AND (bp.visible = 1 OR bp.visible IS NULL) AND (bs.visible = 1 OR bs.visible IS NULL)';
        }

        $context = $this->page->context;
        $contexttest = 'bi.parentcontextid IN (:contextid2, :contextid3)';
        $parentcontextparams = array();
        $parentcontextids = $context->get_parent_context_ids();
        if ($parentcontextids) {
            list($parentcontexttest, $parentcontextparams) =
                    $DB->get_in_or_equal($parentcontextids, SQL_PARAMS_NAMED, 'parentcontext');
            $contexttest = "($contexttest OR (bi.showinsubcontexts = 1 AND bi.parentcontextid $parentcontexttest))";
        }

        $pagetypepatterns = matching_page_type_patterns($this->page->pagetype);
        list($pagetypepatterntest, $pagetypepatternparams) =
                $DB->get_in_or_equal($pagetypepatterns, SQL_PARAMS_NAMED, 'pagetypepatterntest');

        $ccselect = ', ' . context_helper::get_preload_record_columns_sql('ctx');
        $ccjoin = "LEFT JOIN {context} ctx ON (ctx.instanceid = bi.id AND ctx.contextlevel = :contextlevel)";

        $systemcontext = context_system::instance();
        $params = array(
            'contextlevel' => CONTEXT_BLOCK,
            'subpage1' => $this->page->subpage,
            'subpage2' => $this->page->subpage,
            'subpage3' => $this->page->subpage,
            'contextid1' => $context->id,
            'contextid2' => $context->id,
            'contextid3' => $systemcontext->id,
            'contextid4' => $systemcontext->id,
            'pagetype' => $this->page->pagetype,
            'pagetype2' => $this->page->pagetype,
        );
        if ($this->page->subpage === '') {
            $params['subpage1'] = '';
            $params['subpage2'] = '';
            $params['subpage3'] = '';
        }
        $sql = "SELECT
                    bi.id,
                    COALESCE(bp.id, bs.id) AS blockpositionid,
                    bi.blockname,
                    bi.parentcontextid,
                    bi.showinsubcontexts,
                    bi.pagetypepattern,
                    bi.requiredbytheme,
                    bi.subpagepattern,
                    bi.defaultregion,
                    bi.defaultweight,
                    COALESCE(bp.visible, bs.visible, 1) AS visible,
                    COALESCE(bp.region, bs.region, bi.defaultregion) AS region,
                    COALESCE(bp.weight, bs.weight, bi.defaultweight) AS weight,
                    bi.configdata
                    $ccselect

                FROM {block_instances} bi
                JOIN {block} b ON bi.blockname = b.name
                LEFT JOIN {block_positions} bp ON bp.blockinstanceid = bi.id
                                                  AND bp.contextid = :contextid1
                                                  AND bp.pagetype = :pagetype
                                                  AND bp.subpage = :subpage1
                LEFT JOIN {block_positions} bs ON bs.blockinstanceid = bi.id
                                                  AND bs.contextid = :contextid4
                                                  AND bs.pagetype = :pagetype2
                                                  AND bs.subpage = :subpage3
                $ccjoin

                WHERE
                $contexttest
                AND bi.pagetypepattern $pagetypepatterntest
                AND (bi.subpagepattern IS NULL OR bi.subpagepattern = :subpage2)
                $visiblecheck
                AND b.visible = 1
                $requiredbythemecheck

                ORDER BY
                    COALESCE(bp.region, bs.region, bi.defaultregion),
                    COALESCE(bp.weight, bs.weight, bi.defaultweight),
                    bi.id";

        $allparams = $params + $parentcontextparams + $pagetypepatternparams + $requiredbythemeparams + $requiredbythemenotparams;
        $blockinstances = $DB->get_recordset_sql($sql, $allparams);

        $this->birecordsbyregion = $this->prepare_per_region_arrays();
        $unknown = array();
        foreach ($blockinstances as $bi) {
            context_helper::preload_from_record($bi);
            if ($this->is_known_region($bi->region)) {
                $this->birecordsbyregion[$bi->region][] = $bi;
            } else {
                $unknown[] = $bi;
            }
        }
        $blockinstances->close();

        // Pages don't necessarily have a defaultregion. The  one time this can
        // happen is when there are no theme block regions, but the script itself
        // has a block region in the main content area.
        if (!empty($this->defaultregion)) {
            $this->birecordsbyregion[$this->defaultregion] =
                    array_merge($this->birecordsbyregion[$this->defaultregion], $unknown);
        }
    }

    /**
     * Add a block to the current page, or related pages. The block is added to
     * context $this->page->contextid. If $pagetypepattern $subpagepattern
     *
     * @param string $blockname The type of block to add.
     * @param string $region the block region on this page to add the block to.
     * @param integer $weight determines the order where this block appears in the region.
     * @param boolean $showinsubcontexts whether this block appears in subcontexts, or just the current context.
     * @param string|null $pagetypepattern which page types this block should appear on. Defaults to just the current page type.
     * @param string|null $subpagepattern which subpage this block should appear on. NULL = any (the default), otherwise only the specified subpage.
     */
    public function add_block($blockname, $region, $weight, $showinsubcontexts, $pagetypepattern = NULL, $subpagepattern = NULL) {
        global $DB;
        // Allow invisible blocks because this is used when adding default page blocks, which
        // might include invisible ones if the user makes some default blocks invisible
        $this->check_known_block_type($blockname, true);
        $this->check_region_is_known($region);

        if (empty($pagetypepattern)) {
            $pagetypepattern = $this->page->pagetype;
        }

        $blockinstance = new stdClass;
        $blockinstance->blockname = $blockname;
        $blockinstance->parentcontextid = $this->page->context->id;
        $blockinstance->showinsubcontexts = !empty($showinsubcontexts);
        $blockinstance->pagetypepattern = $pagetypepattern;
        $blockinstance->subpagepattern = $subpagepattern;
        $blockinstance->defaultregion = $region;
        $blockinstance->defaultweight = $weight;
        $blockinstance->configdata = '';
        $blockinstance->timecreated = time();
        $blockinstance->timemodified = $blockinstance->timecreated;
        $blockinstance->id = $DB->insert_record('block_instances', $blockinstance);

        // Ensure the block context is created.
        context_block::instance($blockinstance->id);

        // If the new instance was created, allow it to do additional setup
        if ($block = block_instance($blockname, $blockinstance)) {
            $block->instance_create();
        }
    }

    public function add_block_at_end_of_default_region($blockname) {
        if (empty($this->birecordsbyregion)) {
            // No blocks or block regions exist yet.
            return;
        }
        $defaulregion = $this->get_default_region();

        $lastcurrentblock = end($this->birecordsbyregion[$defaulregion]);
        if ($lastcurrentblock) {
            $weight = $lastcurrentblock->weight + 1;
        } else {
            $weight = 0;
        }

        if ($this->page->subpage) {
            $subpage = $this->page->subpage;
        } else {
            $subpage = null;
        }

        // Special case. Course view page type include the course format, but we
        // want to add the block non-format-specifically.
        $pagetypepattern = $this->page->pagetype;
        if (strpos($pagetypepattern, 'course-view') === 0) {
            $pagetypepattern = 'course-view-*';
        }

        // We should end using this for ALL the blocks, making always the 1st option
        // the default one to be used. Until then, this is one hack to avoid the
        // 'pagetypewarning' message on blocks initial edition (MDL-27829) caused by
        // non-existing $pagetypepattern set. This way at least we guarantee one "valid"
        // (the FIRST $pagetypepattern will be set)

        // We are applying it to all blocks created in mod pages for now and only if the
        // default pagetype is not one of the available options
        if (preg_match('/^mod-.*-/', $pagetypepattern)) {
            $pagetypelist = generate_page_type_patterns($this->page->pagetype, null, $this->page->context);
            // Only go for the first if the pagetype is not a valid option
            if (is_array($pagetypelist) && !array_key_exists($pagetypepattern, $pagetypelist)) {
                $pagetypepattern = key($pagetypelist);
            }
        }
        // Surely other pages like course-report will need this too, they just are not important
        // enough now. This will be decided in the coming days. (MDL-27829, MDL-28150)

        $this->add_block($blockname, $defaulregion, $weight, false, $pagetypepattern, $subpage);
    }

    /**
     * Convenience method, calls add_block repeatedly for all the blocks in $blocks. Optionally, a starting weight
     * can be used to decide the starting point that blocks are added in the region, the weight is passed to {@link add_block}
     * and incremented by the position of the block in the $blocks array
     *
     * @param array $blocks array with array keys the region names, and values an array of block names.
     * @param string $pagetypepattern optional. Passed to {@link add_block()}
     * @param string $subpagepattern optional. Passed to {@link add_block()}
     * @param boolean $showinsubcontexts optional. Passed to {@link add_block()}
     * @param integer $weight optional. Determines the starting point that the blocks are added in the region.
     */
    public function add_blocks($blocks, $pagetypepattern = NULL, $subpagepattern = NULL, $showinsubcontexts=false, $weight=0) {
        $initialweight = $weight;
        $this->add_regions(array_keys($blocks), false);
        foreach ($blocks as $region => $regionblocks) {
            foreach ($regionblocks as $offset => $blockname) {
                $weight = $initialweight + $offset;
                $this->add_block($blockname, $region, $weight, $showinsubcontexts, $pagetypepattern, $subpagepattern);
            }
        }
    }

    /**
     * Move a block to a new position on this page.
     *
     * If this block cannot appear on any other pages, then we change defaultposition/weight
     * in the block_instances table. Otherwise we just set the position on this page.
     *
     * @param $blockinstanceid the block instance id.
     * @param $newregion the new region name.
     * @param $newweight the new weight.
     */
    public function reposition_block($blockinstanceid, $newregion, $newweight) {
        global $DB;

        $this->check_region_is_known($newregion);
        $inst = $this->find_instance($blockinstanceid);

        $bi = $inst->instance;
        if ($bi->weight == $bi->defaultweight && $bi->region == $bi->defaultregion &&
                !$bi->showinsubcontexts && strpos($bi->pagetypepattern, '*') === false &&
                (!$this->page->subpage || $bi->subpagepattern)) {

            // Set default position
            $newbi = new stdClass;
            $newbi->id = $bi->id;
            $newbi->defaultregion = $newregion;
            $newbi->defaultweight = $newweight;
            $newbi->timemodified = time();
            $DB->update_record('block_instances', $newbi);

            if ($bi->blockpositionid) {
                $bp = new stdClass;
                $bp->id = $bi->blockpositionid;
                $bp->region = $newregion;
                $bp->weight = $newweight;
                $DB->update_record('block_positions', $bp);
            }

        } else {
            // Just set position on this page.
            $bp = new stdClass;
            $bp->region = $newregion;
            $bp->weight = $newweight;

            if ($bi->blockpositionid) {
                $bp->id = $bi->blockpositionid;
                $DB->update_record('block_positions', $bp);

            } else {
                $bp->blockinstanceid = $bi->id;
                $bp->contextid = $this->page->context->id;
                $bp->pagetype = $this->page->pagetype;
                if ($this->page->subpage) {
                    $bp->subpage = $this->page->subpage;
                } else {
                    $bp->subpage = '';
                }
                $bp->visible = $bi->visible;
                $DB->insert_record('block_positions', $bp);
            }
        }
    }

    /**
     * Find a given block by its instance id
     *
     * @param integer $instanceid
     * @return block_base
     */
    public function find_instance($instanceid) {
        foreach ($this->regions as $region => $notused) {
            $this->ensure_instances_exist($region);
            foreach($this->blockinstances[$region] as $instance) {
                if ($instance->instance->id == $instanceid) {
                    return $instance;
                }
            }
        }
        throw new block_not_on_page_exception($instanceid, $this->page);
    }

/// Inner workings =============================================================

    /**
     * Check whether the page blocks have been loaded yet
     *
     * @return void Throws coding exception if already loaded
     */
    protected function check_not_yet_loaded() {
        if (!is_null($this->birecordsbyregion)) {
            throw new coding_exception('block_manager has already loaded the blocks, to it is too late to change things that might affect which blocks are visible.');
        }
    }

    /**
     * Check whether the page blocks have been loaded yet
     *
     * Nearly identical to the above function {@link check_not_yet_loaded()} except different message
     *
     * @return void Throws coding exception if already loaded
     */
    protected function check_is_loaded() {
        if (is_null($this->birecordsbyregion)) {
            throw new coding_exception('block_manager has not yet loaded the blocks, to it is too soon to request the information you asked for.');
        }
    }

    /**
     * Check if a block type is known and usable
     *
     * @param string $blockname The block type name to search for
     * @param bool $includeinvisible Include disabled block types in the initial pass
     * @return void Coding Exception thrown if unknown or not enabled
     */
    protected function check_known_block_type($blockname, $includeinvisible = false) {
        if (!$this->is_known_block_type($blockname, $includeinvisible)) {
            if ($this->is_known_block_type($blockname, true)) {
                throw new coding_exception('Unknown block type ' . $blockname);
            } else {
                throw new coding_exception('Block type ' . $blockname . ' has been disabled by the administrator.');
            }
        }
    }

    /**
     * Check if a region is known by its name
     *
     * @param string $region
     * @return void Coding Exception thrown if the region is not known
     */
    protected function check_region_is_known($region) {
        if (!$this->is_known_region($region)) {
            throw new coding_exception('Trying to reference an unknown block region ' . $region);
        }
    }

    /**
     * Returns an array of region names as keys and nested arrays for values
     *
     * @return array an array where the array keys are the region names, and the array
     * values are empty arrays.
     */
    protected function prepare_per_region_arrays() {
        $result = array();
        foreach ($this->regions as $region => $notused) {
            $result[$region] = array();
        }
        return $result;
    }

    /**
     * Create a set of new block instance from a record array
     *
     * @param array $birecords An array of block instance records
     * @return array An array of instantiated block_instance objects
     */
    protected function create_block_instances($birecords) {
        $results = array();
        foreach ($birecords as $record) {
            if ($blockobject = block_instance($record->blockname, $record, $this->page)) {
                $results[] = $blockobject;
            }
        }
        return $results;
    }

    /**
     * Create all the block instances for all the blocks that were loaded by
     * load_blocks. This is used, for example, to ensure that all blocks get a
     * chance to initialise themselves via the {@link block_base::specialize()}
     * method, before any output is done.
     *
     * It is also used to create any blocks that are "requiredbytheme" by the current theme.
     * These blocks that are auto-created have requiredbytheme set on the block instance
     * so they are only visible on themes that require them.
     */
    public function create_all_block_instances() {
        $missing = false;

        // If there are any un-removable blocks that were not created - force them.
        $requiredbytheme = $this->get_required_by_theme_block_types();
        if (!$this->fakeblocksonly) {
            foreach ($requiredbytheme as $forced) {
                if (empty($forced)) {
                    continue;
                }
                $found = false;
                foreach ($this->get_regions() as $region) {
                    foreach($this->birecordsbyregion[$region] as $instance) {
                        if ($instance->blockname == $forced) {
                            $found = true;
                        }
                    }
                }
                if (!$found) {
                    $this->add_block_required_by_theme($forced);
                    $missing = true;
                }
            }
        }

        if ($missing) {
            // Some blocks were missing. Lets do it again.
            $this->birecordsbyregion = null;
            $this->load_blocks();
        }
        foreach ($this->get_regions() as $region) {
            $this->ensure_instances_exist($region);
        }

    }

    /**
     * Add a block that is required by the current theme but has not been
     * created yet. This is a special type of block that only shows in themes that
     * require it (by listing it in undeletable_block_types).
     *
     * @param string $blockname the name of the block type.
     */
    protected function add_block_required_by_theme($blockname) {
        global $DB;

        if (empty($this->birecordsbyregion)) {
            // No blocks or block regions exist yet.
            return;
        }

        // Never auto create blocks when we are showing fake blocks only.
        if ($this->fakeblocksonly) {
            return;
        }

        // Never add a duplicate block required by theme.
        if ($DB->record_exists('block_instances', array('blockname' => $blockname, 'requiredbytheme' => 1))) {
            return;
        }

        $systemcontext = context_system::instance();
        $defaultregion = $this->get_default_region();
        // Add a special system wide block instance only for themes that require it.
        $blockinstance = new stdClass;
        $blockinstance->blockname = $blockname;
        $blockinstance->parentcontextid = $systemcontext->id;
        $blockinstance->showinsubcontexts = true;
        $blockinstance->requiredbytheme = true;
        $blockinstance->pagetypepattern = '*';
        $blockinstance->subpagepattern = null;
        $blockinstance->defaultregion = $defaultregion;
        $blockinstance->defaultweight = 0;
        $blockinstance->configdata = '';
        $blockinstance->timecreated = time();
        $blockinstance->timemodified = $blockinstance->timecreated;
        $blockinstance->id = $DB->insert_record('block_instances', $blockinstance);

        // Ensure the block context is created.
        context_block::instance($blockinstance->id);

        // If the new instance was created, allow it to do additional setup.
        if ($block = block_instance($blockname, $blockinstance)) {
            $block->instance_create();
        }
    }

    /**
     * Return an array of content objects from a set of block instances
     *
     * @param array $instances An array of block instances
     * @param renderer_base The renderer to use.
     * @param string $region the region name.
     * @return array An array of block_content (and possibly block_move_target) objects.
     */
    protected function create_block_contents($instances, $output, $region) {
        $results = array();

        $lastweight = 0;
        $lastblock = 0;
        if ($this->movingblock) {
            $first = reset($instances);
            if ($first) {
                $lastweight = $first->instance->weight - 2;
            }
        }

        foreach ($instances as $instance) {
            $content = $instance->get_content_for_output($output);
            if (empty($content)) {
                continue;
            }

            if ($this->movingblock && $lastweight != $instance->instance->weight &&
                    $content->blockinstanceid != $this->movingblock && $lastblock != $this->movingblock) {
                $results[] = new block_move_target($this->get_move_target_url($region, ($lastweight + $instance->instance->weight)/2));
            }

            if ($content->blockinstanceid == $this->movingblock) {
                $content->add_class('beingmoved');
                $content->annotation .= get_string('movingthisblockcancel', 'block',
                        html_writer::link($this->page->url, get_string('cancel')));
            }

            $results[] = $content;
            $lastweight = $instance->instance->weight;
            $lastblock = $instance->instance->id;
        }

        if ($this->movingblock && $lastblock != $this->movingblock) {
            $results[] = new block_move_target($this->get_move_target_url($region, $lastweight + 1));
        }
        return $results;
    }

    /**
     * Ensure block instances exist for a given region
     *
     * @param string $region Check for bi's with the instance with this name
     */
    protected function ensure_instances_exist($region) {
        $this->check_region_is_known($region);
        if (!array_key_exists($region, $this->blockinstances)) {
            $this->blockinstances[$region] =
                    $this->create_block_instances($this->birecordsbyregion[$region]);
        }
    }

    /**
     * Ensure that there is some content within the given region
     *
     * @param string $region The name of the region to check
     */
    public function ensure_content_created($region, $output) {
        $this->ensure_instances_exist($region);

        if (!has_capability('moodle/block:view', $this->page->context) ) {
            $this->visibleblockcontent[$region] = [];
            return;
        }

        if (!array_key_exists($region, $this->visibleblockcontent)) {
            $contents = array();
            if (array_key_exists($region, $this->extracontent)) {
                $contents = $this->extracontent[$region];
            }
            $contents = array_merge($contents, $this->create_block_contents($this->blockinstances[$region], $output, $region));
            if (($region == $this->defaultregion) && (!isset($this->page->theme->addblockposition) ||
                    $this->page->theme->addblockposition == BLOCK_ADDBLOCK_POSITION_DEFAULT)) {
                $addblockui = block_add_block_ui($this->page, $output);
                if ($addblockui) {
                    $contents[] = $addblockui;
                }
            }
            $this->visibleblockcontent[$region] = $contents;
        }
    }

/// Process actions from the URL ===============================================

    /**
     * Get the appropriate list of editing icons for a block. This is used
     * to set {@link block_contents::$controls} in {@link block_base::get_contents_for_output()}.
     *
     * @param $output The core_renderer to use when generating the output. (Need to get icon paths.)
     * @return an array in the format for {@link block_contents::$controls}
     */
    public function edit_controls($block) {
        global $CFG;

        $controls = array();
        $actionurl …

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