<?php

namespace SilverStripe\ORM\Versioning;


use Exception;
use FieldList;
use SilverStripe\ORM\HasManyList;
use TextField;
use ReadonlyField;
use i18n;
use BadMethodCallException;
use LogicException;
use SilverStripe\ORM\ValidationException;
use SilverStripe\ORM\DB;
use SilverStripe\ORM\DataObject;
use SilverStripe\Security\Member;
use SilverStripe\Security\Permission;


/**
 * The ChangeSet model tracks several VersionedAndStaged objects for later publication as a single
 * atomic action
 *
 * @method HasManyList Changes()
 * @method Member Owner()
 * @property string $Name
 * @property string $State
 *
 * @package framework
 * @subpackage orm
 */
class ChangeSet extends DataObject {

	private static $singular_name = 'Campaign';

	private static $plural_name = 'Campaigns';

	/** An active changeset */
	const STATE_OPEN = 'open';

	/** A changeset which is reverted and closed */
	const STATE_REVERTED = 'reverted';

	/** A changeset which is published and closed */
	const STATE_PUBLISHED = 'published';

	private static $table_name = 'ChangeSet';

	private static $db = array(
		'Name'  => 'Varchar',
		'State' => "Enum('open,published,reverted','open')",
	);

	private static $has_many = array(
		'Changes' => 'SilverStripe\ORM\Versioning\ChangeSetItem',
	);

	private static $defaults = array(
		'State' => 'open'
	);

	private static $has_one = array(
		'Owner' => 'SilverStripe\\Security\\Member',
	);

	private static $casting = array(
		'Description' => 'Text',
	);

	/**
	 * List of classes to set apart in description
	 *
	 * @config
	 * @var array
	 */
	private static $important_classes = array(
		'SiteTree',
		'File',
	);

	/**
	 * Default permission to require for publishers.
	 * Publishers must either be able to use the campaign admin, or have all admin access.
	 *
	 * Also used as default permission for ChangeSetItem default permission.
	 *
	 * @config
	 * @var array
	 */
	private static $required_permission = array('CMS_ACCESS_CampaignAdmin', 'CMS_ACCESS_LeftAndMain');

	/**
	 * Publish this changeset, then closes it.
	 *
	 * @throws Exception
	 */
	public function publish() {
		// Logical checks prior to publish
		if($this->State !== static::STATE_OPEN) {
			throw new BadMethodCallException(
				"ChangeSet can't be published if it has been already published or reverted."
			);
		}
		if(!$this->isSynced()) {
			throw new ValidationException(
				"ChangeSet does not include all necessary changes and cannot be published."
			);
		}
		if(!$this->canPublish()) {
			throw new LogicException("The current member does not have permission to publish this ChangeSet.");
		}

		DB::get_conn()->withTransaction(function(){
			foreach($this->Changes() as $change) {
				/** @var ChangeSetItem $change */
				$change->publish();
			}

			$this->State = static::STATE_PUBLISHED;
			$this->write();
		});
	}

	/**
	 * Add a new change to this changeset. Will automatically include all owned
	 * changes as those are dependencies of this item.
	 *
	 * @param DataObject $object
	 */
	public function addObject(DataObject $object) {
		if(!$this->isInDB()) {
			throw new BadMethodCallException("ChangeSet must be saved before adding items");
		}

		$references = [
			'ObjectID'    => $object->ID,
			'ObjectClass' => $object->baseClass(),
		];

		// Get existing item in case already added
		$item = $this->Changes()->filter($references)->first();

		if (!$item) {
			$item = new ChangeSetItem($references);
			$this->Changes()->add($item);
		}

		$item->ReferencedBy()->removeAll();

		$item->Added = ChangeSetItem::EXPLICITLY;
		$item->write();


		$this->sync();
	}

	/**
	 * Remove an item from this changeset. Will automatically remove all changes
	 * which own (and thus depend on) the removed item.
	 *
	 * @param DataObject $object
	 */
	public function removeObject(DataObject $object) {
		$item = ChangeSetItem::get()->filter([
				'ObjectID' => $object->ID,
				'ObjectClass' => $object->baseClass(),
				'ChangeSetID' => $this->ID
			])->first();

		if ($item) {
			// TODO: Handle case of implicit added item being removed.

			$item->delete();
		}

		$this->sync();
	}

	/**
	 * Build identifying string key for this object
	 *
	 * @param DataObject $item
	 * @return string
	 */
	protected function implicitKey(DataObject $item) {
		if ($item instanceof ChangeSetItem) {
			return $item->ObjectClass.'.'.$item->ObjectID;
		}
		return $item->baseClass().'.'.$item->ID;
	}

	protected function calculateImplicit() {
		/** @var string[][] $explicit List of all items that have been explicitly added to this ChangeSet */
		$explicit = array();

		/** @var string[][] $referenced List of all items that are "referenced" by items in $explicit */
		$referenced = array();

		/** @var string[][] $references List of which explicit items reference each thing in referenced */
		$references = array();

		/** @var ChangeSetItem $item */
		foreach ($this->Changes()->filter(['Added' => ChangeSetItem::EXPLICITLY]) as $item) {
			$explicitKey = $this->implicitKey($item);
			$explicit[$explicitKey] = true;

			foreach ($item->findReferenced() as $referee) {
				/** @var DataObject $referee */
				$key = $this->implicitKey($referee);

				$referenced[$key] = [
					'ObjectID' => $referee->ID,
					'ObjectClass' => $referee->baseClass(),
				];

				$references[$key][] = $item->ID;
			}
		}

		/** @var string[][] $explicit List of all items that are either in $explicit, $referenced or both */
		$all = array_merge($referenced, $explicit);

		/** @var string[][] $implicit Anything that is in $all, but not in $explicit, is an implicit inclusion */
		$implicit = array_diff_key($all, $explicit);

		foreach($implicit as $key => $object) {
			$implicit[$key]['ReferencedBy'] = $references[$key];
		}

		return $implicit;
	}

	/**
	 * Add implicit changes that should be included in this changeset
	 *
	 * When an item is created or changed, all it's owned items which have
	 * changes are implicitly added
	 *
	 * When an item is deleted, it's owner (even if that owner does not have changes)
	 * is implicitly added
	 */
	public function sync() {
		// Start a transaction (if we can)
		DB::get_conn()->withTransaction(function() {

			// Get the implicitly included items for this ChangeSet
			$implicit = $this->calculateImplicit();

			// Adjust the existing implicit ChangeSetItems for this ChangeSet
			/** @var ChangeSetItem $item */
			foreach ($this->Changes()->filter(['Added' => ChangeSetItem::IMPLICITLY]) as $item) {
				$objectKey = $this->implicitKey($item);

				// If a ChangeSetItem exists, but isn't in $implicit, it's no longer required, so delete it
				if (!array_key_exists($objectKey, $implicit)) {
					$item->delete();
				}
				// Otherwise it is required, so update ReferencedBy and remove from $implicit
				else {
					$item->ReferencedBy()->setByIDList($implicit[$objectKey]['ReferencedBy']);
					unset($implicit[$objectKey]);
				}
			}

			// Now $implicit is all those items that are implicitly included, but don't currently have a ChangeSetItem.
			// So create new ChangeSetItems to match

			foreach ($implicit as $key => $props) {
				$item = new ChangeSetItem($props);
				$item->Added = ChangeSetItem::IMPLICITLY;
				$item->ChangeSetID = $this->ID;
				$item->ReferencedBy()->setByIDList($props['ReferencedBy']);
				$item->write();
			}
		});
	}

	/** Verify that any objects in this changeset include all owned changes */
	public function isSynced() {
		$implicit = $this->calculateImplicit();

		// Check the existing implicit ChangeSetItems for this ChangeSet

		foreach ($this->Changes()->filter(['Added' => ChangeSetItem::IMPLICITLY]) as $item) {
			$objectKey = $this->implicitKey($item);

			// If a ChangeSetItem exists, but isn't in $implicit -> validation failure
			if (!array_key_exists($objectKey, $implicit)) return false;
			// Exists, remove from $implicit
			unset($implicit[$objectKey]);
		}

		// If there's anything left in $implicit -> validation failure
		return empty($implicit);
	}

	public function canView($member = null) {
		return $this->can(__FUNCTION__, $member);
	}

	public function canEdit($member = null) {
		return $this->can(__FUNCTION__, $member);
	}

	public function canCreate($member = null, $context = array()) {
		return $this->can(__FUNCTION__, $member, $context);
	}

	public function canDelete($member = null) {
		return $this->can(__FUNCTION__, $member);
	}

	/**
	 * Check if this item is allowed to be published
	 *
	 * @param Member $member
	 * @return bool
	 */
	public function canPublish($member = null) {
		// All changes must be publishable
		foreach($this->Changes() as $change) {
			/** @var ChangeSetItem $change */
			if(!$change->canPublish($member)) {
				return false;
			}
		}

		// Default permission
		return $this->can(__FUNCTION__, $member);
	}

	/**
	 * Check if this changeset (if published) can be reverted
	 *
	 * @param Member $member
	 * @return bool
	 */
	public function canRevert($member = null) {
		// All changes must be publishable
		foreach($this->Changes() as $change) {
			/** @var ChangeSetItem $change */
			if(!$change->canRevert($member)) {
				return false;
			}
		}

		// Default permission
		return $this->can(__FUNCTION__, $member);
	}

	/**
	 * Default permissions for this changeset
	 *
	 * @param string $perm
	 * @param Member $member
	 * @param array $context
	 * @return bool
	 */
	public function can($perm, $member = null, $context = array()) {
		if(!$member) {
			$member = Member::currentUser();
		}

		// Allow extensions to bypass default permissions, but only if
		// each change can be individually published.
		$extended = $this->extendedCan($perm, $member, $context);
		if($extended !== null) {
			return $extended;
		}

		// Default permissions
		return (bool)Permission::checkMember($member, $this->config()->required_permission);
	}

	public function getCMSFields() {
		$fields = new FieldList();
		$fields->push(TextField::create('Name', $this->fieldLabel('Name')));
		if($this->isInDB()) {
			$state = ReadonlyField::create('State', $this->fieldLabel('State'))
				->setDontEscape(true);
			$fields->push($state); // Escape is done in react
		}
		$this->extend('updateCMSFields', $fields);
		return $fields;
	}

	/**
	 * Gets summary of items in changeset
	 *
	 * @return string
	 */
	public function getDescription() {
		// Initialise list of items to count
		$counted = [];
		$countedOther = 0;
		foreach($this->config()->important_classes as $type) {
			if(class_exists($type)) {
				$counted[$type] = 0;
			}
		}

		// Check each change item
		/** @var ChangeSetItem $change */
		foreach($this->Changes() as $change) {
			$found = false;
			foreach($counted as $class => $num) {
				if(is_a($change->ObjectClass, $class, true)) {
					$counted[$class]++;
					$found = true;
					break;
				}
			}
			if(!$found) {
				$countedOther++;
			}
		}

		// Describe set based on this output
		$counted = array_filter($counted);

		// Empty state
		if(empty($counted) && empty($countedOther)) {
			return '';
		}

		// Put all parts together
		$parts = [];
		foreach($counted as $class => $count) {
			$parts[] = DataObject::singleton($class)->i18n_pluralise($count);
		}

		// Describe non-important items
		if($countedOther) {
			if ($counted) {
				$parts[] = i18n::pluralise(
					_t('ChangeSet.DESCRIPTION_OTHER_ITEM', 'other item'),
					_t('ChangeSet.DESCRIPTION_OTHER_ITEMS', 'other items'),
					$countedOther
				);
			} else {
				$parts[] = i18n::pluralise(
					_t('ChangeSet.DESCRIPTION_ITEM', 'item'),
					_t('ChangeSet.DESCRIPTION_ITEMS', 'items'),
					$countedOther
				);
			}
		}

		// Figure out how to join everything together
		if(empty($parts)) {
			return '';
		}
		if(count($parts) === 1) {
			return $parts[0];
		}

		// Non-comma list
		if(count($parts) === 2) {
			return _t(
				'ChangeSet.DESCRIPTION_AND',
				'{first} and {second}',
				[
					'first' => $parts[0],
					'second' => $parts[1],
				]
			);
		}

		// First item
		$string = _t(
			'ChangeSet.DESCRIPTION_LIST_FIRST',
			'{item}',
			['item' => $parts[0]]
		);

		// Middle items
		for($i = 1; $i < count($parts) - 1; $i++) {
			$string = _t(
				'ChangeSet.DESCRIPTION_LIST_MID',
				'{list}, {item}',
				[
					'list' => $string,
					'item' => $parts[$i]
				]
			);
		}

		// Oxford comma
		$string = _t(
			'ChangeSet.DESCRIPTION_LIST_LAST',
			'{list}, and {item}',
			[
				'list' => $string,
				'item' => end($parts)
			]
		);
		return $string;
	}

	public function fieldLabels($includerelations = true) {
		$labels = parent::fieldLabels($includerelations);
		$labels['Name'] = _t('ChangeSet.NAME', 'Name');
		$labels['State'] = _t('ChangeSet.STATE', 'State');

		return $labels;
	}
}