my-files-sample/Modules/Sources/Browse/UI/Views/DocumentView.swift

//
//  DocumentView.swift
//  Browse
//
//  Created by Javier Cicchelli on 16/12/2022.
//  Copyright © 2022 Röck+Cöde. All rights reserved.
//

import DataModels
import KeychainStorage
import SwiftUI

struct DocumentView: View {
    
    // MARK: Environments
    
    @Environment(\.dismiss) private var dismiss
    
    // MARK: Storages
    
    @KeychainStorage(key: .KeychainStorage.account) private var account: Account?
    
    // MARK: States
    
    @State private var status: ViewStatus = .loading
    @State private var loadedData: Data?
    @State private var showDownloadFile: Bool = false
    
    private let getData = GetDataUseCase()
    
    // MARK: Properties
    
    let document: Document
    let login: ActionClosure

    // MARK: Body
    
    var body: some View {
        content
            .navigationTitle(document.name)
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                DocumentToolbar(disabled: isToolbarDisabled) {
                    showDownloadFile = true
                }
            }
            .sheet(isPresented: $showDownloadFile) {
                DownloadView(
                    id: document.id,
                    name: document.name,
                    data: loadedData
                ) {
                    // downloaded closure.
                }
            }
            .task {
                await loadDataIfPossible()
            }
    }

}

// MARK: - UI

private extension DocumentView {
    var isToolbarDisabled: Bool { loadedData == nil }
    
    @ViewBuilder var content: some View {
        switch status {
        case .noCredentials:
            MessageView(
                type: .noCredentials,
                action: login
            )
        case .notSupported:
            MessageView(type: .notSupported) {
                dismiss()
            }
        case .loading:
            LoadingView()
        case .loaded:
            Image(uiImage: imageFromData)
                .resizable()
                .scaledToFit()
        case .empty:
            EmptyView()
        case .error:
            MessageView(type: .error) {
                Task {
                    await loadDataIfPossible()
                }
            }
        }
    }
}

// MARK: - Helpers

private extension DocumentView {
    
    // MARK: Computed
    
    var supportedContentTypes: [String] {
        [.ContentType.jpeg, .ContentType.png]
    }
    
    var imageFromData: UIImage {
        guard
            let loadedData,
            let image = UIImage(data: loadedData)
        else {
            return .init()
        }
        
        return image
    }
    
    // MARK: Functions
    
    func loadDataIfPossible() async {
        guard supportedContentTypes.contains(document.contentType) else {
            status = .notSupported
            return
        }
        guard let account else {
            status = .noCredentials
            return
        }
        
        do {
            status = .loading
            
            let data = try await getData(
                id: document.id,
                username: account.username,
                password: account.password
            )
            
            if data.isEmpty {
                status = .error
            } else {
                loadedData = data
                status = .loaded
            }
        } catch {
            status = .error
        }
    }
}

// MARK: - String+Constants

private extension String {
    enum ContentType {
        static let jpeg = "image/jpeg"
        static let png = "image/png"
    }
}

// MARK: - Previews

struct DocumentView_Previews: PreviewProvider {
    static var previews: some View {
        DocumentView(document: .init(
            id: "1234567890",
            name: "Some document name goes in here...",
            contentType: "some content type",
            size: .random(in: 1 ... 100),
            lastModifiedAt: .now
        )) {
            // login closure.
        }
    }
}