<?php namespace BookStack\Services;

use BookStack\Book;
use BookStack\Chapter;
use BookStack\Entity;
use BookStack\Page;
use BookStack\SearchTerm;
use Illuminate\Database\Connection;
use Illuminate\Database\Query\Builder;
use Illuminate\Database\Query\JoinClause;
use Illuminate\Support\Collection;

class SearchService
{
    protected $searchTerm;
    protected $book;
    protected $chapter;
    protected $page;
    protected $db;
    protected $permissionService;
    protected $entities;

    /**
     * Acceptable operators to be used in a query
     * @var array
     */
    protected $queryOperators = ['<=', '>=', '=', '<', '>', 'like', '!='];

    /**
     * SearchService constructor.
     * @param SearchTerm $searchTerm
     * @param Book $book
     * @param Chapter $chapter
     * @param Page $page
     * @param Connection $db
     * @param PermissionService $permissionService
     */
    public function __construct(SearchTerm $searchTerm, Book $book, Chapter $chapter, Page $page, Connection $db, PermissionService $permissionService)
    {
        $this->searchTerm = $searchTerm;
        $this->book = $book;
        $this->chapter = $chapter;
        $this->page = $page;
        $this->db = $db;
        $this->entities = [
            'page' => $this->page,
            'chapter' => $this->chapter,
            'book' => $this->book
        ];
        $this->permissionService = $permissionService;
    }

    /**
     * Search all entities in the system.
     * @param string $searchString
     * @param string $entityType
     * @param int $page
     * @param int $count
     * @return Collection
     */
    public function searchEntities($searchString, $entityType = 'all', $page = 0, $count = 20)
    {
        $terms = $this->parseSearchString($searchString);
        $entityTypes = array_keys($this->entities);
        $entityTypesToSearch = $entityTypes;
        $results = collect();

        if ($entityType !== 'all') {
            $entityTypesToSearch = $entityType;
        } else if (isset($terms['filters']['type'])) {
            $entityTypesToSearch = explode('|', $terms['filters']['type']);
        }

        // TODO - Check drafts don't show up in results
        foreach ($entityTypesToSearch as $entityType) {
            if (!in_array($entityType, $entityTypes)) continue;
            $search = $this->searchEntityTable($terms, $entityType, $page, $count);
            $results = $results->merge($search);
        }

        return $results->sortByDesc('score');
    }

    /**
     * Search across a particular entity type.
     * @param array $terms
     * @param string $entityType
     * @param int $page
     * @param int $count
     * @return \Illuminate\Database\Eloquent\Collection|static[]
     */
    public function searchEntityTable($terms, $entityType = 'page', $page = 0, $count = 20)
    {
        $entity = $this->getEntity($entityType);
        $entitySelect = $entity->newQuery();

        // Handle normal search terms
        if (count($terms['search']) > 0) {
            $subQuery = $this->db->table('search_terms')->select('entity_id', 'entity_type', \DB::raw('SUM(score) as score'));
            $subQuery->where(function(Builder $query) use ($terms) {
                foreach ($terms['search'] as $inputTerm) {
                    $query->orWhere('term', 'like', $inputTerm .'%');
                }
            })->groupBy('entity_type', 'entity_id');
            $entitySelect->join(\DB::raw('(' . $subQuery->toSql() . ') as s'), function(JoinClause $join) {
                $join->on('id', '=', 'entity_id');
            })->selectRaw($entity->getTable().'.*, s.score')->orderBy('score', 'desc');
            $entitySelect->mergeBindings($subQuery);
        }

        // Handle exact term matching
        if (count($terms['exact']) > 0) {
            $entitySelect->where(function(\Illuminate\Database\Eloquent\Builder $query) use ($terms, $entity) {
                foreach ($terms['exact'] as $inputTerm) {
                    $query->where(function (\Illuminate\Database\Eloquent\Builder $query) use ($inputTerm, $entity) {
                        $query->where('name', 'like', '%'.$inputTerm .'%')
                            ->orWhere($entity->textField, 'like', '%'.$inputTerm .'%');
                    });
                }
            });
        }

        // Handle tag searches
        foreach ($terms['tags'] as $inputTerm) {
            $this->applyTagSearch($entitySelect, $inputTerm);
        }

        // Handle filters
        foreach ($terms['filters'] as $filterTerm => $filterValue) {
            $functionName = camel_case('filter_' . $filterTerm);
            if (method_exists($this, $functionName)) $this->$functionName($entitySelect, $entity, $filterValue);
        }

        $entitySelect->skip($page * $count)->take($count);
        $query = $this->permissionService->enforceEntityRestrictions($entityType, $entitySelect, 'view');
        return $query->get();
    }


    /**
     * Parse a search string into components.
     * @param $searchString
     * @return array
     */
    protected function parseSearchString($searchString)
    {
        $terms = [
            'search' => [],
            'exact' => [],
            'tags' => [],
            'filters' => []
        ];

        $patterns = [
            'exact' => '/"(.*?)"/',
            'tags' => '/\[(.*?)\]/',
            'filters' => '/\{(.*?)\}/'
        ];

        // Parse special terms
        foreach ($patterns as $termType => $pattern) {
            $matches = [];
            preg_match_all($pattern, $searchString, $matches);
            if (count($matches) > 0) {
                $terms[$termType] = $matches[1];
                $searchString = preg_replace($pattern, '', $searchString);
            }
        }

        // Parse standard terms
        foreach (explode(' ', trim($searchString)) as $searchTerm) {
            if ($searchTerm !== '') $terms['search'][] = $searchTerm;
        }

        // Split filter values out
        $splitFilters = [];
        foreach ($terms['filters'] as $filter) {
            $explodedFilter = explode(':', $filter, 1);
            $splitFilters[$explodedFilter[0]] = (count($explodedFilter) > 1) ? $explodedFilter[1] : '';
        }
        $terms['filters'] = $splitFilters;

        return $terms;
    }

    /**
     * Get the available query operators as a regex escaped list.
     * @return mixed
     */
    protected function getRegexEscapedOperators()
    {
        $escapedOperators = [];
        foreach ($this->queryOperators as $operator) {
            $escapedOperators[] = preg_quote($operator);
        }
        return join('|', $escapedOperators);
    }

    /**
     * Apply a tag search term onto a entity query.
     * @param \Illuminate\Database\Eloquent\Builder $query
     * @param string $tagTerm
     * @return mixed
     */
    protected function applyTagSearch(\Illuminate\Database\Eloquent\Builder $query, $tagTerm) {
        preg_match("/^(.*?)((".$this->getRegexEscapedOperators().")(.*?))?$/", $tagTerm, $tagSplit);
        $query->whereHas('tags', function(\Illuminate\Database\Eloquent\Builder $query) use ($tagSplit) {
            $tagName = $tagSplit[1];
            $tagOperator = count($tagSplit) > 2 ? $tagSplit[3] : '';
            $tagValue = count($tagSplit) > 3 ? $tagSplit[4] : '';
            $validOperator = in_array($tagOperator, $this->queryOperators);
            if (!empty($tagOperator) && !empty($tagValue) && $validOperator) {
                if (!empty($tagName)) $query->where('name', '=', $tagName);
                if (is_numeric($tagValue) && $tagOperator !== 'like') {
                    // We have to do a raw sql query for this since otherwise PDO will quote the value and MySQL will
                    // search the value as a string which prevents being able to do number-based operations
                    // on the tag values. We ensure it has a numeric value and then cast it just to be sure.
                    $tagValue = (float) trim($query->getConnection()->getPdo()->quote($tagValue), "'");
                    $query->whereRaw("value ${tagOperator} ${tagValue}");
                } else {
                    $query->where('value', $tagOperator, $tagValue);
                }
            } else {
                $query->where('name', '=', $tagName);
            }
        });
        return $query;
    }

    /**
     * Get an entity instance via type.
     * @param $type
     * @return Entity
     */
    protected function getEntity($type)
    {
        return $this->entities[strtolower($type)];
    }

    /**
     * Index the given entity.
     * @param Entity $entity
     */
    public function indexEntity(Entity $entity)
    {
        $this->deleteEntityTerms($entity);
        $nameTerms = $this->generateTermArrayFromText($entity->name, 5);
        $bodyTerms = $this->generateTermArrayFromText($entity->getText(), 1);
        $terms = array_merge($nameTerms, $bodyTerms);
        foreach ($terms as $index => $term) {
            $terms[$index]['entity_type'] = $entity->getMorphClass();
            $terms[$index]['entity_id'] = $entity->id;
        }
        $this->searchTerm->newQuery()->insert($terms);
    }

    /**
     * Index multiple Entities at once
     * @param Entity[] $entities
     */
    protected function indexEntities($entities) {
        $terms = [];
        foreach ($entities as $entity) {
            $nameTerms = $this->generateTermArrayFromText($entity->name, 5);
            $bodyTerms = $this->generateTermArrayFromText($entity->getText(), 1);
            foreach (array_merge($nameTerms, $bodyTerms) as $term) {
                $term['entity_id'] = $entity->id;
                $term['entity_type'] = $entity->getMorphClass();
                $terms[] = $term;
            }
        }

        $chunkedTerms = array_chunk($terms, 500);
        foreach ($chunkedTerms as $termChunk) {
            $this->searchTerm->newQuery()->insert($termChunk);
        }
    }

    /**
     * Delete and re-index the terms for all entities in the system.
     */
    public function indexAllEntities()
    {
        $this->searchTerm->truncate();

        // Chunk through all books
        $this->book->chunk(1000, function ($books) {
            $this->indexEntities($books);
        });

        // Chunk through all chapters
        $this->chapter->chunk(1000, function ($chapters) {
            $this->indexEntities($chapters);
        });

        // Chunk through all pages
        $this->page->chunk(1000, function ($pages) {
            $this->indexEntities($pages);
        });
    }

    /**
     * Delete related Entity search terms.
     * @param Entity $entity
     */
    public function deleteEntityTerms(Entity $entity)
    {
        $entity->searchTerms()->delete();
    }

    /**
     * Create a scored term array from the given text.
     * @param $text
     * @param float|int $scoreAdjustment
     * @return array
     */
    protected function generateTermArrayFromText($text, $scoreAdjustment = 1)
    {
        $tokenMap = []; // {TextToken => OccurrenceCount}
        $splitText = explode(' ', $text);
        foreach ($splitText as $token) {
            if ($token === '') continue;
            if (!isset($tokenMap[$token])) $tokenMap[$token] = 0;
            $tokenMap[$token]++;
        }

        $terms = [];
        foreach ($tokenMap as $token => $count) {
            $terms[] = [
                'term' => $token,
                'score' => $count * $scoreAdjustment
            ];
        }
        return $terms;
    }


    /**
     * Custom entity search filters
     */

    protected function filterUpdatedAfter(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        try { $date = date_create($input);
        } catch (\Exception $e) {return;}
        $query->where('updated_at', '>=', $date);
    }

    protected function filterUpdatedBefore(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        try { $date = date_create($input);
        } catch (\Exception $e) {return;}
        $query->where('updated_at', '<', $date);
    }

    protected function filterCreatedAfter(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        try { $date = date_create($input);
        } catch (\Exception $e) {return;}
        $query->where('created_at', '>=', $date);
    }

    protected function filterCreatedBefore(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        try { $date = date_create($input);
        } catch (\Exception $e) {return;}
        $query->where('created_at', '<', $date);
    }

    protected function filterCreatedBy(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        if (!is_numeric($input)) return;
        $query->where('created_by', '=', $input);
    }

    protected function filterUpdatedBy(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        if (!is_numeric($input)) return;
        $query->where('updated_by', '=', $input);
    }

    protected function filterInName(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        $query->where('name', 'like', '%' .$input. '%');
    }

    protected function filterInTitle(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input) {$this->filterInName($query, $model, $input);}

    protected function filterInBody(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        $query->where($model->textField, 'like', '%' .$input. '%');
    }

    protected function filterIsRestricted(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        $query->where('restricted', '=', true);
    }

    protected function filterViewedByMe(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        $query->whereHas('views', function($query) {
            $query->where('user_id', '=', user()->id);
        });
    }

    protected function filterNotViewedByMe(\Illuminate\Database\Eloquent\Builder $query, Entity $model, $input)
    {
        $query->whereDoesntHave('views', function($query) {
            $query->where('user_id', '=', user()->id);
        });
    }

}