Indexer.swift

import Foundation
import os.log

final class Searcher {

    struct Result: Equatable {
        let count: Int
        let hasMore: Bool
    }

    let indexer: Indexer

    init(index: Indexer) {
        self.indexer = index
    }

    func search(query: String)  -> Result {
        let flushed = indexer.flush()
        print("Flushed = \(flushed ? "yes": "no")")

        let options = SKSearchOptions(kSKSearchOptionDefault)
        let skSearch = SKSearchCreate(indexer.index, query as NSString, options).takeRetainedValue()

        var documentIDs =  [SKDocumentID]()
        var scores = [Float]()
        var foundCount = 0

        let hasMore = SKSearchFindMatches(skSearch, 100, &documentIDs, &scores, 0, &foundCount)

        return Result(count: foundCount, hasMore: hasMore)
    }
}

final class Indexer {
    enum IndexerError: Error {
        case unableToCreate
    }

    let index: SKIndex

    init(url: URL, name: String) throws {
        guard let index = SKIndexCreateWithURL(url as NSURL, name as NSString, SKIndexType(kSKIndexInverted.rawValue), nil)?.takeRetainedValue() else {
            throw IndexerError.unableToCreate
        }

        self.index = index
    }

    func flush() -> Bool {
        return SKIndexFlush(index)
    }

    func index(_ source: Searchable) {
        let objectURL = source.URIRepresentation as NSURL
        let document = SKDocumentCreateWithURL(objectURL).takeRetainedValue()
        let indexed = SKIndexAddDocumentWithText(index, document, source.summary as NSString, true)
        os_log("Indexed to disk: %@", indexed ? "true" : "false")

        let flushed = self.flush()
        os_log("Flushed index to disk: %@", flushed ? "true" : "false")
    }

    func createSearch() -> Searcher {
        return Searcher(index: self)
    }

    func search(query: String)  -> Searcher.Result {
        return createSearch().search(query: query)
    }
    
}