letro-ios/ElementX/Sources/Screens/FilePreviewScreen/TimelineMediaPreviewModels.swift

//
// Copyright 2024 New Vector Ltd.
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
// Please see LICENSE files in the repository root for full details.
//

import Combine
import QuickLook
import SwiftUI

enum TimelineMediaPreviewViewModelAction: Equatable {
    case viewInRoomTimeline(TimelineItemIdentifier)
    case dismiss
}

struct TimelineMediaPreviewViewState: BindableState {
    /// All of the items in the timeline that can be previewed.
    var previewItems: [TimelineMediaPreviewItem]
    /// The index of the initial item inside of `previewItems` that is to be shown.
    let initialItemIndex: Int
    
    /// The media item that is currently being previewed.
    var currentItem: TimelineMediaPreviewItem
    /// All of the available actions for the current item.
    var currentItemActions: TimelineItemMenuActions?
    
    /// The namespace used for the zoom transition.
    let transitionNamespace: Namespace.ID
    /// A publisher that the view model uses to signal to the QLPreviewController when the current item has been loaded.
    let fileLoadedPublisher = PassthroughSubject<TimelineItemIdentifier, Never>()
    
    var bindings = TimelineMediaPreviewViewStateBindings()
}

struct TimelineMediaPreviewViewStateBindings {
    /// A binding that will present the Details view for the specified item.
    var mediaDetailsItem: TimelineMediaPreviewItem?
    /// A binding that will present a confirmation to redact the specified item.
    var redactConfirmationItem: TimelineMediaPreviewItem?
    /// A binding that will present a document picker to export the specified file.
    var fileToExport: TimelineMediaPreviewFileExportPicker.File?
    
    var alertInfo: AlertInfo<TimelineMediaPreviewAlertType>?
}

enum TimelineMediaPreviewAlertType {
    case authorizationRequired
}

/// Wraps a media file and title to be previewed with QuickLook.
class TimelineMediaPreviewItem: NSObject, QLPreviewItem, Identifiable {
    let timelineItem: EventBasedMessageTimelineItemProtocol
    var fileHandle: MediaFileHandleProxy?
    var downloadError: Error?
    
    init(timelineItem: EventBasedMessageTimelineItemProtocol) {
        self.timelineItem = timelineItem
    }
    
    init?(roomTimelineItemViewState: RoomTimelineItemViewState) {
        switch roomTimelineItemViewState.type {
        case .audio(let audioRoomTimelineItem):
            timelineItem = audioRoomTimelineItem
        case .file(let fileRoomTimelineItem):
            timelineItem = fileRoomTimelineItem
        case .image(let imageRoomTimelineItem):
            timelineItem = imageRoomTimelineItem
        case .video(let videoRoomTimelineItem):
            timelineItem = videoRoomTimelineItem
        default:
            return nil
        }
    }
    
    // MARK: Identifiable
    
    var id: TimelineItemIdentifier { timelineItem.id }
    
    // MARK: QLPreviewItem
    
    var previewItemURL: URL? {
        // Falling back to a clear image allows the presentation animation to work when
        // the item is in the event cache and just needs to be loaded from the store.
        fileHandle?.url ?? Bundle.main.url(forResource: "clear", withExtension: "png")
    }
    
    var previewItemTitle: String? {
        filename
    }
    
    // MARK: Event details
    
    var sender: TimelineItemSender {
        timelineItem.sender
    }
    
    var timestamp: Date {
        timelineItem.timestamp
    }
    
    // MARK: Media details
    
    var mediaSource: MediaSourceProxy? {
        switch timelineItem {
        case let audioItem as AudioRoomTimelineItem:
            audioItem.content.source
        case let fileItem as FileRoomTimelineItem:
            fileItem.content.source
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.imageInfo.source
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.videoInfo.source
        default:
            nil
        }
    }
    
    var thumbnailMediaSource: MediaSourceProxy? {
        switch timelineItem {
        case let fileItem as FileRoomTimelineItem:
            fileItem.content.thumbnailSource
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.thumbnailInfo?.source
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.thumbnailInfo?.source
        default:
            nil
        }
    }
    
    var filename: String? {
        switch timelineItem {
        case let audioItem as AudioRoomTimelineItem:
            audioItem.content.filename
        case let fileItem as FileRoomTimelineItem:
            fileItem.content.filename
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.filename
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.filename
        default:
            nil
        }
    }
    
    var fileSize: Double? {
        previewItemURL.flatMap { try? FileManager.default.sizeForItem(at: $0) } ?? expectedFileSize
    }
    
    private var expectedFileSize: Double? {
        let fileSize: UInt? = switch timelineItem {
        case let audioItem as AudioRoomTimelineItem:
            audioItem.content.fileSize
        case let fileItem as FileRoomTimelineItem:
            fileItem.content.fileSize
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.imageInfo.fileSize
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.videoInfo.fileSize
        default:
            nil
        }
        
        return fileSize.map(Double.init)
    }
    
    var caption: String? {
        timelineItem.mediaCaption
    }
    
    var contentType: String? {
        switch timelineItem {
        case let audioItem as AudioRoomTimelineItem:
            audioItem.content.contentType?.localizedDescription
        case let fileItem as FileRoomTimelineItem:
            fileItem.content.contentType?.localizedDescription
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.contentType?.localizedDescription
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.contentType?.localizedDescription
        default:
            nil
        }
    }
    
    var blurhash: String? {
        switch timelineItem {
        case let imageItem as ImageRoomTimelineItem:
            imageItem.content.blurhash
        case let videoItem as VideoRoomTimelineItem:
            videoItem.content.blurhash
        default:
            nil
        }
    }
}

enum TimelineMediaPreviewViewAction {
    case updateCurrentItem(TimelineMediaPreviewItem)
    case saveCurrentItem
    case showCurrentItemDetails
    case menuAction(TimelineItemMenuAction, item: TimelineMediaPreviewItem)
    case redactConfirmation(item: TimelineMediaPreviewItem)
    case dismiss
}