//
//  ComposeAttachmentsViewController.swift
//  Tusker
//
//  Created by Shadowfacts on 3/11/20.
//  Copyright © 2020 Shadowfacts. All rights reserved.
//

import UIKit
import Pachyderm

protocol ComposeAttachmentsViewControllerDelegate: class {
    func composeSelectedAttachmentsDidChange()
    func composeRequiresAttachmentDescriptionsDidChange()
}

class ComposeAttachmentsViewController: UITableViewController {
    
    weak var mastodonController: MastodonController!
    weak var delegate: ComposeAttachmentsViewControllerDelegate?
    
    private var heightConstraint: NSLayoutConstraint!
    
    var attachments: [CompositionAttachment] = [] {
        didSet {
            delegate?.composeSelectedAttachmentsDidChange()
            updateAddAttachmentsButtonEnabled()
        }
    }
    
    var requiresAttachmentDescriptions: Bool {
        if Preferences.shared.requireAttachmentDescriptions {
            return !attachments.allSatisfy { $0.description.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
        } else {
            return false
        }
    }

    init(attachments: [CompositionAttachment], mastodonController: MastodonController) {
        self.attachments = attachments
        self.mastodonController = mastodonController
        super.init(style: .plain)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.rowHeight = UITableView.automaticDimension
        tableView.estimatedRowHeight = 96

        tableView.register(UINib(nibName: "AddAttachmentTableViewCell", bundle: .main), forCellReuseIdentifier: "addAttachment")
        tableView.register(UINib(nibName: "ComposeAttachmentTableViewCell", bundle: .main), forCellReuseIdentifier: "composeAttachment")
        
        heightConstraint = tableView.heightAnchor.constraint(equalToConstant: tableView.contentSize.height)
        heightConstraint.isActive = true
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        updateHeightConstraint()
    }
    
    func setAttachments(_ attachments: [CompositionAttachment]) {
        self.attachments = attachments
        tableView.reloadData()
        updateHeightConstraint()
        delegate?.composeRequiresAttachmentDescriptionsDidChange()
    }
    
    private func updateHeightConstraint() {
        heightConstraint.constant = tableView.contentSize.height
    }
    
    private func isAddAttachmentsButtonEnabled() -> Bool {
        switch mastodonController.instance.instanceType {
        case .pleroma:
            return true
        case .mastodon:
            return !attachments.contains(where: { $0.data.type == .video }) && attachments.count < 4
        }
    }
    
    private func updateAddAttachmentsButtonEnabled() {
        let cell = tableView.cellForRow(at: IndexPath(row: 0, section: 1)) as! AddAttachmentTableViewCell
        cell.setEnabled(isAddAttachmentsButtonEnabled())
    }
    
    func uploadAll(stepProgress: @escaping () -> Void, completion: @escaping (_ success: Bool, _ uploadedAttachments: [Attachment]) -> Void) {
        let group = DispatchGroup()
        
        var anyFailed = false
        var uploadedAttachments: [Result<Attachment, Error>?] = []
        
        for (index, compAttachment) in attachments.enumerated() {
            group.enter()
            
            uploadedAttachments.append(nil)
            
            compAttachment.data.getData { (data, mimeType) in
                stepProgress()
                
                let formAttachment = FormAttachment(mimeType: mimeType, data: data, fileName: "file")
                let request = Client.upload(attachment: formAttachment, description: compAttachment.description)
                self.mastodonController.run(request) { (response) in
                    switch response {
                    case let .failure(error):
                        uploadedAttachments[index] = .failure(error)
                        anyFailed = true
                    case let .success(attachment, _):
                        uploadedAttachments[index] = .success(attachment)
                    }
                    
                    stepProgress()
                    group.leave()
                }
            }
        }
        
        group.notify(queue: .main) {
            if anyFailed {
                let errors: [(Int, Error)] = uploadedAttachments.enumerated().compactMap { (index, result) in
                    switch result {
                    case let .failure(error):
                        return (index, error)
                    default:
                        return nil
                    }
                    
                }
                let title: String
                var message: String
                if errors.count == 1 {
                    title = NSLocalizedString("Could not upload attachment", comment: "single attachment upload failed alert title")
                    message = errors[0].1.localizedDescription
                } else {
                    title = NSLocalizedString("Could not upload the following attachments", comment: "multiple attachment upload failures alert title")
                    message = ""
                    for (index, error) in errors {
                        message.append("Attachment \(index + 1): \(error.localizedDescription)")
                    }
                }
                let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
                alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { (_) in
                    completion(false, [])
                }))
            } else {
                let uploadedAttachments: [Attachment] = uploadedAttachments.compactMap {
                    switch $0 {
                    case let .success(attachment):
                        return attachment
                    default:
                        return nil
                    }
                }
                completion(true, uploadedAttachments)
            }
        }
    }
    
    // MARK: Table view data source
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        return 2
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        switch section {
        case 0:
            return attachments.count
        case 1:
            return 1
        default:
            fatalError("invalid section \(section)")
        }
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        switch indexPath.section {
        case 0:
            let attachment = attachments[indexPath.row]
            let cell = tableView.dequeueReusableCell(withIdentifier: "composeAttachment", for: indexPath) as! ComposeAttachmentTableViewCell
            cell.delegate = self
            cell.updateUI(for: attachment)
            return cell
        case 1:
            let cell = tableView.dequeueReusableCell(withIdentifier: "addAttachment", for: indexPath) as! AddAttachmentTableViewCell
            cell.setEnabled(isAddAttachmentsButtonEnabled())
            return cell
        default:
            fatalError("invalid section \(indexPath.section)")
        }
    }
    
    // MARK: Table view delegate
    
    override func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
        if indexPath.section == 1, isAddAttachmentsButtonEnabled() {
            return indexPath
        }
        return nil
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        
        if indexPath.section == 1 {
            addAttachmentPressed()
        }
    }
    
    func addAttachmentPressed() {
        let sheetContainer = AssetPickerSheetContainerViewController()
        sheetContainer.assetPicker.assetPickerDelegate = self
        present(sheetContainer, animated: true)
    }

}

extension ComposeAttachmentsViewController: AssetPickerViewControllerDelegate {
    func assetPicker(_ assetPicker: AssetPickerViewController, shouldAllowAssetOfType type: CompositionAttachmentData.AttachmentType) -> Bool {
        switch mastodonController.instance.instanceType {
        case .pleroma:
            return true
        case .mastodon:
            if (type == .video && attachments.count > 0) ||
                attachments.contains(where: { $0.data.type == .video }) ||
                assetPicker.currentCollectionSelectedAssets.contains(where: { $0.type == .video }) {
                return false
            }
            return attachments.count + assetPicker.currentCollectionSelectedAssets.count < 4
        }
    }
    
    func assetPicker(_ assetPicker: AssetPickerViewController, didSelectAttachments attachments: [CompositionAttachmentData]) {
        let attachments = attachments.map {
            CompositionAttachment(data: $0)
        }
        let indexPaths = attachments.indices.map { IndexPath(row: $0 + self.attachments.count, section: 0) }
        self.attachments.append(contentsOf: attachments)
        tableView.insertRows(at: indexPaths, with: .automatic)
        updateHeightConstraint()
    }
}

extension ComposeAttachmentsViewController: ComposeAttachmentTableViewCellDelegate {
    func removeAttachment(_ cell: ComposeAttachmentTableViewCell) {
        guard let indexPath = tableView.indexPath(for: cell) else { return }
        attachments.remove(at: indexPath.row)
        tableView.performBatchUpdates({
            tableView.deleteRows(at: [indexPath], with: .automatic)
        }, completion: { (_) in
            // when removing cells, we don't trigger the container height update until after the animation has completed
            // otherwise, during the animation, the height is too short and the last row briefly disappears
            self.updateHeightConstraint()
        })
    }
    
    func attachmentDescriptionChanged(_ cell: ComposeAttachmentTableViewCell) {
        delegate?.composeRequiresAttachmentDescriptionsDidChange()
    }
}