<?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/>.

namespace core_courseformat;

use core_courseformat\stateupdates;
use core\event\course_module_updated;
use cm_info;
use section_info;
use stdClass;
use course_modinfo;
use moodle_exception;
use context_module;
use context_course;

/**
 * Contains the core course state actions.
 *
 * The methods from this class should be executed via "core_courseformat_edit" web service.
 *
 * Each format plugin could extend this class to provide new actions to the editor.
 * Extended classes should be locate in "format_XXX\course" namespace and
 * extends core_courseformat\stateactions.
 *
 * @package    core_courseformat
 * @copyright  2021 Ferran Recio <ferran@moodle.com>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class stateactions {

    /**
     * Move course modules to another location in the same course.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the list of affected course module ids
     * @param int $targetsectionid optional target section id
     * @param int $targetcmid optional target cm id
     */
    public function cm_move(
        stateupdates $updates,
        stdClass $course,
        array $ids,
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        // Validate target elements.
        if (!$targetsectionid && !$targetcmid) {
            throw new moodle_exception("Action cm_move requires targetsectionid or targetcmid");
        }

        $this->validate_cms($course, $ids, __FUNCTION__);

        // Check capabilities on every activity context.
        foreach ($ids as $cmid) {
            $modcontext = context_module::instance($cmid);
            require_capability('moodle/course:manageactivities', $modcontext);
        }

        $modinfo = get_fast_modinfo($course);

        // Target cm has more priority than target section.
        if (!empty($targetcmid)) {
            $this->validate_cms($course, [$targetcmid], __FUNCTION__);
            $targetcm = $modinfo->get_cm($targetcmid);
            $targetsection = $modinfo->get_section_info_by_id($targetcm->section, MUST_EXIST);
        } else {
            $this->validate_sections($course, [$targetsectionid], __FUNCTION__);
            $targetcm = null;
            $targetsection = $modinfo->get_section_info_by_id($targetsectionid, MUST_EXIST);
        }

        // The origin sections must be updated as well.
        $originalsections = [];

        $cms = $this->get_cm_info($modinfo, $ids);
        foreach ($cms as $cm) {
            $currentsection = $modinfo->get_section_info_by_id($cm->section, MUST_EXIST);
            moveto_module($cm, $targetsection, $targetcm);
            $updates->add_cm_put($cm->id);
            if ($currentsection->id != $targetsection->id) {
                $originalsections[$currentsection->id] = true;
            }
            // If some of the original sections are also target sections, we don't need to update them.
            if (array_key_exists($targetsection->id, $originalsections)) {
                unset($originalsections[$targetsection->id]);
            }
        }

        // Use section_state to return the full affected section and activities updated state.
        $this->cm_state($updates, $course, $ids, $targetsectionid, $targetcmid);

        foreach (array_keys($originalsections) as $sectionid) {
            $updates->add_section_put($sectionid);
        }
    }

    /**
     * Move course sections to another location in the same course.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the list of affected course module ids
     * @param int $targetsectionid optional target section id
     * @param int $targetcmid optional target cm id
     */
    public function section_move(
        stateupdates $updates,
        stdClass $course,
        array $ids,
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        // Validate target elements.
        if (!$targetsectionid) {
            throw new moodle_exception("Action cm_move requires targetsectionid");
        }

        $this->validate_sections($course, $ids, __FUNCTION__);

        $coursecontext = context_course::instance($course->id);
        require_capability('moodle/course:movesections', $coursecontext);

        $modinfo = get_fast_modinfo($course);

        // Target section.
        $this->validate_sections($course, [$targetsectionid], __FUNCTION__);
        $targetsection = $modinfo->get_section_info_by_id($targetsectionid, MUST_EXIST);

        $affectedsections = [$targetsection->section => true];

        $sections = $this->get_section_info($modinfo, $ids);
        foreach ($sections as $section) {
            $affectedsections[$section->section] = true;
            move_section_to($course, $section->section, $targetsection->section);
        }

        // Use section_state to return the section and activities updated state.
        $this->section_state($updates, $course, $ids, $targetsectionid);

        // All course sections can be renamed because of the resort.
        $allsections = $modinfo->get_section_info_all();
        foreach ($allsections as $section) {
            // Ignore the affected sections because they are already in the updates.
            if (isset($affectedsections[$section->section])) {
                continue;
            }
            $updates->add_section_put($section->id);
        }
        // The section order is at a course level.
        $updates->add_course_put();
    }

    /**
     * Create a course section.
     *
     * This method follows the same logic as changenumsections.php.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids not used
     * @param int $targetsectionid optional target section id (if not passed section will be appended)
     * @param int $targetcmid not used
     */
    public function section_add(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {

        $coursecontext = context_course::instance($course->id);
        require_capability('moodle/course:update', $coursecontext);

        // Get course format settings.
        $format = course_get_format($course->id);
        $lastsectionnumber = $format->get_last_section_number();
        $maxsections = $format->get_max_sections();

        if ($lastsectionnumber >= $maxsections) {
            throw new moodle_exception('maxsectionslimit', 'moodle', $maxsections);
        }

        $modinfo = get_fast_modinfo($course);

        // Get target section.
        if ($targetsectionid) {
            $this->validate_sections($course, [$targetsectionid], __FUNCTION__);
            $targetsection = $modinfo->get_section_info_by_id($targetsectionid, MUST_EXIST);
            // Inserting sections at any position except in the very end requires capability to move sections.
            require_capability('moodle/course:movesections', $coursecontext);
            $insertposition = $targetsection->section + 1;
        } else {
            // Get last section.
            $insertposition = 0;
        }

        course_create_section($course, $insertposition);

        // Adding a section affects the full course structure.
        $this->course_state($updates, $course);
    }

    /**
     * Delete course sections.
     *
     * This method follows the same logic as editsection.php.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids section ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function section_delete(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {

        $coursecontext = context_course::instance($course->id);
        require_capability('moodle/course:update', $coursecontext);
        require_capability('moodle/course:movesections', $coursecontext);

        $modinfo = get_fast_modinfo($course);

        foreach ($ids as $sectionid) {
            $section = $modinfo->get_section_info_by_id($sectionid, MUST_EXIST);
            // Send all activity deletions.
            if (!empty($modinfo->sections[$section->section])) {
                foreach ($modinfo->sections[$section->section] as $modnumber) {
                    $cm = $modinfo->cms[$modnumber];
                    $updates->add_cm_remove($cm->id);
                }
            }
            course_delete_section($course, $section, true, true);
            $updates->add_section_remove($sectionid);
        }

        // Removing a section affects the full course structure.
        $this->course_state($updates, $course);
    }

    /**
     * Hide course sections.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids section ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function section_hide(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        $this->set_section_visibility($updates, $course, $ids, 0);
    }

    /**
     * Show course sections.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids section ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function section_show(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        $this->set_section_visibility($updates, $course, $ids, 1);
    }

    /**
     * Show course sections.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids section ids
     * @param int $visible the new visible value
     */
    protected function set_section_visibility (
        stateupdates $updates,
        stdClass $course,
        array $ids,
        int $visible
    ) {
        $this->validate_sections($course, $ids, __FUNCTION__);
        $coursecontext = context_course::instance($course->id);
        require_all_capabilities(['moodle/course:update', 'moodle/course:sectionvisibility'], $coursecontext);

        $modinfo = get_fast_modinfo($course);

        foreach ($ids as $sectionid) {
            $section = $modinfo->get_section_info_by_id($sectionid, MUST_EXIST);
            course_update_section($course, $section, ['visible' => $visible]);
        }
        $this->section_state($updates, $course, $ids);
    }

    /**
     * Show course cms.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids cm ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function cm_show(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        $this->set_cm_visibility($updates, $course, $ids, 1, 1);
    }

    /**
     * Hide course cms.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids cm ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function cm_hide(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        $this->set_cm_visibility($updates, $course, $ids, 0, 1);
    }

    /**
     * Stealth course cms.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids cm ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function cm_stealth(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        $this->set_cm_visibility($updates, $course, $ids, 1, 0);
    }

    /**
     * Internal method to define the cm visibility.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids cm ids
     * @param int $visible the new visible value
     * @param int $coursevisible the new course visible value
     */
    protected function set_cm_visibility(
        stateupdates $updates,
        stdClass $course,
        array $ids,
        int $visible,
        int $coursevisible
    ): void {
        global $CFG;

        $this->validate_cms($course, $ids, __FUNCTION__);

        // Check capabilities on every activity context.
        foreach ($ids as $cmid) {
            $modcontext = context_module::instance($cmid);
            require_all_capabilities(['moodle/course:manageactivities', 'moodle/course:activityvisibility'], $modcontext);
        }

        $format = course_get_format($course->id);
        $modinfo = get_fast_modinfo($course);

        $cms = $this->get_cm_info($modinfo, $ids);
        foreach ($cms as $cm) {
            // Check stealth availability.
            if (!$coursevisible) {
                $section = $cm->get_section_info();
                $allowstealth = !empty($CFG->allowstealth) && $format->allow_stealth_module_visibility($cm, $section);
                $coursevisible = ($allowstealth) ? 0 : 1;
            }
            set_coursemodule_visible($cm->id, $visible, $coursevisible);
            course_module_updated::create_from_cm($cm, $modcontext)->trigger();
            $updates->add_cm_put($cm->id);
        }
    }

    /**
     * Extract several cm_info from the course_modinfo.
     *
     * @param course_modinfo $modinfo the course modinfo.
     * @param int[] $ids the course modules $ids
     * @return cm_info[] the extracted cm_info objects
     */
    protected function get_cm_info (course_modinfo $modinfo, array $ids): array {
        $cms = [];
        foreach ($ids as $cmid) {
            $cms[$cmid] = $modinfo->get_cm($cmid);
        }
        return $cms;
    }

    /**
     * Extract several section_info from the course_modinfo.
     *
     * @param course_modinfo $modinfo the course modinfo.
     * @param int[] $ids the course modules $ids
     * @return section_info[] the extracted section_info objects
     */
    protected function get_section_info(course_modinfo $modinfo, array $ids): array {
        $sections = [];
        foreach ($ids as $sectionid) {
            $sections[$sectionid] = $modinfo->get_section_info_by_id($sectionid);
        }
        return $sections;
    }

    /**
     * Update the course content section collapsed value.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the collapsed section ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function section_content_collapsed(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        if (!empty($ids)) {
            $this->validate_sections($course, $ids, __FUNCTION__);
        }
        $format = course_get_format($course->id);
        $format->set_sections_preference('contentcollapsed', $ids);
    }

    /**
     * Update the course index section collapsed value.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the collapsed section ids
     * @param int $targetsectionid not used
     * @param int $targetcmid not used
     */
    public function section_index_collapsed(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {
        if (!empty($ids)) {
            $this->validate_sections($course, $ids, __FUNCTION__);
        }
        $format = course_get_format($course->id);
        $format->set_sections_preference('indexcollapsed', $ids);
    }

    /**
     * Add the update messages of the updated version of any cm and section related to the cm ids.
     *
     * This action is mainly used by legacy actions to partially update the course state when the
     * result of core_course_edit_module is not enough to generate the correct state data.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the list of affected course module ids
     * @param int $targetsectionid optional target section id
     * @param int $targetcmid optional target cm id
     */
    public function cm_state(
        stateupdates $updates,
        stdClass $course,
        array $ids,
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {

        // Collect all section and cm to return.
        $cmids = [];
        foreach ($ids as $cmid) {
            $cmids[$cmid] = true;
        }
        if ($targetcmid) {
            $cmids[$targetcmid] = true;
        }

        $sectionids = [];
        if ($targetsectionid) {
            $this->validate_sections($course, [$targetsectionid], __FUNCTION__);
            $sectionids[$targetsectionid] = true;
        }

        $this->validate_cms($course, array_keys($cmids), __FUNCTION__);

        $modinfo = course_modinfo::instance($course);

        foreach (array_keys($cmids) as $cmid) {

            // Add this action to updates array.
            $updates->add_cm_put($cmid);

            $cm = $modinfo->get_cm($cmid);
            $sectionids[$cm->section] = true;
        }

        foreach (array_keys($sectionids) as $sectionid) {
            $updates->add_section_put($sectionid);
        }
    }

    /**
     * Add the update messages of the updated version of any cm and section related to the section ids.
     *
     * This action is mainly used by legacy actions to partially update the course state when the
     * result of core_course_edit_module is not enough to generate the correct state data.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the list of affected course section ids
     * @param int $targetsectionid optional target section id
     * @param int $targetcmid optional target cm id
     */
    public function section_state(
        stateupdates $updates,
        stdClass $course,
        array $ids,
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {

        $cmids = [];
        if ($targetcmid) {
            $this->validate_cms($course, [$targetcmid], __FUNCTION__);
            $cmids[$targetcmid] = true;
        }

        $sectionids = [];
        foreach ($ids as $sectionid) {
            $sectionids[$sectionid] = true;
        }
        if ($targetsectionid) {
            $sectionids[$targetsectionid] = true;
        }

        $this->validate_sections($course, array_keys($sectionids), __FUNCTION__);

        $modinfo = course_modinfo::instance($course);

        foreach (array_keys($sectionids) as $sectionid) {
            $sectioninfo = $modinfo->get_section_info_by_id($sectionid);
            $updates->add_section_put($sectionid);
            // Add cms.
            if (empty($modinfo->sections[$sectioninfo->section])) {
                continue;
            }

            foreach ($modinfo->sections[$sectioninfo->section] as $modnumber) {
                $mod = $modinfo->cms[$modnumber];
                if ($mod->is_visible_on_course_page()) {
                    $cmids[$mod->id] = true;
                }
            }
        }

        foreach (array_keys($cmids) as $cmid) {
            // Add this action to updates array.
            $updates->add_cm_put($cmid);
        }
    }

    /**
     * Add all the update messages from the complete course state.
     *
     * This action is mainly used by legacy actions to partially update the course state when the
     * result of core_course_edit_module is not enough to generate the correct state data.
     *
     * @param stateupdates $updates the affected course elements track
     * @param stdClass $course the course object
     * @param int[] $ids the list of affected course module ids (not used)
     * @param int $targetsectionid optional target section id (not used)
     * @param int $targetcmid optional target cm id (not used)
     */
    public function course_state(
        stateupdates $updates,
        stdClass $course,
        array $ids = [],
        ?int $targetsectionid = null,
        ?int $targetcmid = null
    ): void {

        $modinfo = course_modinfo::instance($course);

        $updates->add_course_put();

        // Add sections updates.
        $sections = $modinfo->get_section_info_all();
        $sectionids = [];
        foreach ($sections as $sectioninfo) {
            $sectionids[] = $sectioninfo->id;
        }
        if (!empty($sectionids)) {
            $this->section_state($updates, $course, $sectionids);
        }
    }

    /**
     * Checks related to sections: course format support them, all given sections exist and topic 0 is not included.
     *
     * @param stdClass $course The course where given $sectionids belong.
     * @param array $sectionids List of sections to validate.
     * @param string|null $info additional information in case of error (default null).
     * @throws moodle_exception if any id is not valid
     */
    protected function validate_sections(stdClass $course, array $sectionids, ?string $info = null): void {
        global $DB;

        if (empty($sectionids)) {
            throw new moodle_exception('emptysectionids', 'core', null, $info);
        }

        // No section actions are allowed if course format does not support sections.
        $courseformat = course_get_format($course->id);
        if (!$courseformat->uses_sections()) {
            throw new moodle_exception('sectionactionnotsupported', 'core', null, $info);
        }

        list($insql, $inparams) = $DB->get_in_or_equal($sectionids, SQL_PARAMS_NAMED);

        // Check if all the given sections exist.
        $couintsections = $DB->count_records_select('course_sections', "id $insql", $inparams);
        if ($couintsections != count($sectionids)) {
            throw new moodle_exception('unexistingsectionid', 'core', null, $info);
        }
    }

    /**
     * Checks related to course modules: all given cm exist.
     *
     * @param stdClass $course The course where given $cmids belong.
     * @param array $cmids List of course module ids to validate.
     * @param string $info additional information in case of error.
     * @throws moodle_exception if any id is not valid
     */
    protected function validate_cms(stdClass $course, array $cmids, ?string $info = null): void {

        if (empty($cmids)) {
            throw new moodle_exception('emptycmids', 'core', null, $info);
        }

        $moduleinfo = get_fast_modinfo($course->id);
        $intersect = array_intersect($cmids, array_keys($moduleinfo->get_cms()));
        if (count($cmids) != count($intersect)) {
            throw new moodle_exception('unexistingcmid', 'core', null, $info);
        }
    }
}
