tagtunes/TagTunes/LookupOperation.swift

//
//  LookupOperation.swift
//  TagTunes
//
//  Created by Kim Wittenburg on 08.04.16.
//  Copyright © 2016 Kim Wittenburg. All rights reserved.
//

import SearchAPI
import AppKitPlus


class LookupOperation: Operation {

    /// The `NSURLSession` used to perform lookup tasks.
    private let urlSession = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration(), delegate: nil, delegateQueue: NSOperationQueue.mainQueue())

    let tracks: [TagTunesTrack]

    private var lookupTask: NSURLSessionTask!
    private var lookupData: NSData?
    private var lookupError: ErrorType?

    init<S: SequenceType where S.Generator.Element == TagTunesTrack>(tracks: S) {
        self.tracks = Array(tracks)
        var request = SearchAPIRequest(lookupRequestWithIDs: tracks.flatMap { $0.id })
        request.entity = .Album
        request.country = Preferences.sharedPreferences.iTunesStore
        if Preferences.sharedPreferences.useEnglishTags {
            request.language = .English
        }
        super.init()
        self.lookupTask = urlSession.dataTaskWithURL(request.URL, completionHandler: downloadFinishedWithData)
        addCondition(MutuallyExclusive<LookupOperation>())
    }

    private func downloadFinishedWithData(data: NSData?, response: NSURLResponse?, error: NSError?) {
        lookupData = data
        lookupError = error
    }

    override func willEnqueue() {
        let operation = URLSessionTaskOperation(task: lookupTask)
        addDependency(operation)
        produceOperation(operation)
        super.willEnqueue()
    }

    override func execute() {
        // TODO: This must be executed after the url data task finished. Is that the case?
        do {
            if let data = lookupData {
                let result = try SearchAPIResult(data: data)
                for track in tracks where track.id != nil {
                    if let resultTrack = result.entityForID(track.id!) as? Track {
                        track.lookupState = .Found(resultTrack)
                    } else {
                        track.lookupState = .NotFound
                    }
                }
                finish()
            } else {
                throw lookupError!
            }
        } catch {
            for track in tracks {
                track.lookupState = .Error(error)
            }
            finishWithError(error as NSError?)
        }
    }

}