//
//  SearchController.swift
//  TagTunes
//
//  Created by Kim Wittenburg on 06.03.16.
//  Copyright © 2016 Kim Wittenburg. All rights reserved.
//

import SearchAPI
import AppKitPlus

/// A search delegate is notified when a `SearchController` selects an item.
protocol SearchDelegate: class {

    /// The view controller displaying the content.
    var contentViewController: ContentViewController! { get }

    /// Invoked when the `searchController` selected a item. In the
    /// implementation the selected `searchResult` should be added to the
    /// `contentViewController`.
    func searchController(searchController: SearchController, didSelectSearchResult searchResult: TagTunesItem)

}

/// Manages the user interface for search results.
public class SearchController: NSObject, PopUpSearchFieldDelegate {

    /// This struct contains *magic numbers* like references to storyboard
    /// identifiers.
    private struct Constants {

        /// The identifier used for the rows in the search results pop up.
        static let AlbumTableCellViewIdentifier = "AlbumTableCellViewIdentifier"

        /// The identifier used for the `No Results` row in the search results
        /// pop up.
        static let NoResultsTableCellViewIdentifier = "NoResultsTableCellViewIdentifier"

    }

    weak var delegate: SearchDelegate?

    /// The search field. This should be set by the view controller containing
    /// the user interface for searching.
    public weak var searchField: PopUpSearchField! {
        willSet {
            searchField?.popUpDelegate = nil
        }
        didSet {
            searchField?.popUpDelegate = self
        }
    }

    /// Used for searching and loading search results
    private let urlSession = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration(), delegate: nil, delegateQueue: NSOperationQueue.mainQueue())

    /// The URL task currently loading the search results.
    private var searchTask: NSURLSessionTask? {
        didSet {
            searching = searchTask != nil
        }
    }

    public private(set) dynamic var searching: Bool = false

    /// The search results for the current search term.
    private var searchResults = [Album]() {
        didSet {
            searchField.updatePopUp()
        }
    }

    /// The error that occured during searching, if any.
    private var searchError: NSError?

    /// Begins searching for the `searchField`'s `stringValue`.
    public func beginSearch() {
        let searchString = searchField.stringValue
        cancelSearch()
        if searchString == "" {
            searchResults = []
        } else {
            var request = SearchAPIRequest(searchRequestWithTerm: searchString)
            request.mediaType = .Music
            request.entity = .Album
            request.maximumNumberOfResults = UInt(Preferences.sharedPreferences.numberOfSearchResults)
            if Preferences.sharedPreferences.useEnglishTags {
                request.language = .English
            }
            request.country = Preferences.sharedPreferences.iTunesStore
            searchTask = urlSession.dataTaskWithURL(request.URL, completionHandler: processSearchResults)
            searchTask!.resume()
        }
    }

    /// Cancels the current search (if there is one) and removes the search
    /// results.
    private func cancelSearch() {
        searchTask?.cancel()
    }

    /// Processes the data returned from a network request into the
    /// `searchResults` array.
    private func processSearchResults(data: NSData?, response: NSURLResponse?, error: NSError?) {
        searchTask = nil
        var newResults = [Album]()
        if let theData = data where error == nil {
            do {
                let result = try SearchAPIResult(data: theData)
                newResults = result.resultEntities.flatMap{ $0 as? Album }
            } catch let error as NSError {
                searchError = error
            }
        } else if let theError = error {
            searchError = theError
        }
        searchResults = newResults
    }

    public func popUpSearchFieldWillHidePopUp(searchField: PopUpSearchField) {
        cancelSearch()
    }

    public func popUpSearchFieldShouldShowPopUp(searchField: PopUpSearchField) -> Bool {
        return !searchField.stringValue.isEmpty
    }

    public func popUpSearchField(searchField: PopUpSearchField, didSelectPopUpEntryAtRow row: Int) {
        let searchResult = searchResults[row]
        let albumItem = AlbumItem(entity: searchResult)
        albumItem.beginLoadingChildren()
        delegate?.searchController(self, didSelectSearchResult: albumItem)
        searchField.reloadPopUpRow(row)
    }

    private var shouldDisplayNoResults: Bool {
        return searchResults.isEmpty && !searchField.stringValue.isEmpty && searchTask == nil
    }

    public func numberOfRowsInTableView(tableView: NSTableView) -> Int {
        if shouldDisplayNoResults {
            return 1
        }
        return searchResults.count
    }

    public func tableView(tableView: NSTableView, heightOfRow row: Int) -> CGFloat {
        return 39
    }

    public func tableView(tableView: NSTableView, viewForTableColumn tableColumn: NSTableColumn?, row: Int) -> NSView? {
        if shouldDisplayNoResults {
            var view = tableView.makeViewWithIdentifier(Constants.NoResultsTableCellViewIdentifier, owner: nil) as? CenteredTableCellView
            if view == nil {
                view = CenteredTableCellView()
                view?.identifier = Constants.NoResultsTableCellViewIdentifier
            }
            view?.setupForNoResults()
            return view
        } else {
            var view = tableView.makeViewWithIdentifier(Constants.AlbumTableCellViewIdentifier, owner: nil) as? AlbumTableCellView
            if view == nil {
                view = AlbumTableCellView()
                view?.identifier = Constants.AlbumTableCellViewIdentifier
            }
            let searchResult = searchResults[row]
            let height = self.tableView(tableView, heightOfRow: row)
            let albumEnabled = delegate?.contentViewController.itemForEntity(searchResult) == nil
            view?.setupForAlbum(searchResult, enabled: albumEnabled, height: height)
            return view
        }
    }

    public func tableView(tableView: NSTableView, shouldSelectRow row: Int) -> Bool {
        if shouldDisplayNoResults {
            return false
        } else {
            return delegate?.contentViewController?.itemForEntity(searchResults[row]) == nil
        }
    }

}