feat: Update message body loading logic (#1542)

Mail/Views/Thread/Message/BodyImageProcessor.swift

@@ -0,0 +1,130 @@
+/*
+ Infomaniak Mail - iOS App
+ Copyright (C) 2024 Infomaniak Network SA
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import Foundation
+import MailCore
+import OSLog
+import UIKit
+
+struct BodyImageProcessor {
+    private let bodyImageMutator = BodyImageMutator()
+
+    /// Download and encode all images for the current chunk in parallel.
+    public func fetchBase64Images(
+        _ attachments: ArraySlice<Attachment>,
+        mailboxManager: MailboxManager
+    ) async -> [ImageBase64AndMime?] {
+        // Force a fixed max concurrency to be a nice citizen to the network.
+        let base64Images: [ImageBase64AndMime?] = await attachments
+            .concurrentMap(customConcurrency: Constants.concurrentNetworkCalls) { attachment in
+                do {
+                    let attachmentData = try await mailboxManager.attachmentData(attachment)
+
+                    // Skip compression on non static images types or already heic sources
+                    guard attachment.mimeType.contains("jpg")
+                        || attachment.mimeType.contains("jpeg")
+                        || attachment.mimeType.contains("png") else {
+                        let base64String = attachmentData.base64EncodedString()
+                        return ImageBase64AndMime(base64String, attachment.mimeType)
+                    }
+
+                    // Skip compression with lockdown mode enables as images can glitch
+                    let isLockdownModeEnabled = (UserDefaults.standard.object(forKey: "LDMGlobalEnabled") as? Bool) ?? false
+                    guard !isLockdownModeEnabled else {
+                        let base64String = attachmentData.base64EncodedString()
+                        return ImageBase64AndMime(base64String, attachment.mimeType)
+                    }
+
+                    let compressedImage = compressedBase64ImageAndMime(
+                        attachmentData: attachmentData,
+                        attachmentMime: attachment.mimeType
+                    )
+                    return compressedImage
+                } catch {
+                    Logger.general.error("Error \(error) : Failed to fetch data  for attachment: \(attachment)")
+                    return nil
+                }
+            }
+
+        assert(base64Images.count == attachments.count, "Arrays count should match")
+        return base64Images
+    }
+
+    /// Try to compress the attachment with the best matched algorithm. Trade CPU cycles to reduce render time and memory usage.
+    private func compressedBase64ImageAndMime(attachmentData: Data, attachmentMime: String) -> ImageBase64AndMime {
+        guard #available(iOS 17.0, *) else {
+            let base64String = attachmentData.base64EncodedString()
+            return ImageBase64AndMime(base64String, attachmentMime)
+        }
+
+        // On iOS17 Safari and iOS has support for heic. Quality is unchanged. Size is halved.
+        let image = UIImage(data: attachmentData)
+        guard let imageCompressed = image?.heicData(), imageCompressed.count < attachmentData.count else {
+            let base64String = attachmentData.base64EncodedString()
+            return ImageBase64AndMime(base64String, attachmentMime)
+        }
+
+        let base64String = imageCompressed.base64EncodedString()
+        return ImageBase64AndMime(base64String, "image/heic")
+    }
+
+    /// Inject base64 images in a body
+    public func injectImagesInBody(
+        body: String?,
+        attachments: ArraySlice<Attachment>,
+        base64Images: [ImageBase64AndMime?]
+    ) async -> String? {
+        guard let body, !body.isEmpty else {
+            return nil
+        }
+
+        var workingBody = body
+        for (index, attachment) in attachments.enumerated() {
+            guard !Task.isCancelled else {
+                break
+            }
+
+            guard let contentId = attachment.contentId,
+                  let base64Image = base64Images[safe: index] as? ImageBase64AndMime else {
+                continue
+            }
+
+            bodyImageMutator.replaceContentIdForBase64Image(
+                in: &workingBody,
+                contentId: contentId,
+                mimeType: base64Image.mimeType,
+                contentBase64Encoded: base64Image.imageEncoded
+            )
+        }
+        return workingBody
+    }
+}
+
+struct BodyImageMutator {
+    func replaceContentIdForBase64Image(
+        in body: inout String,
+        contentId: String,
+        mimeType: String,
+        contentBase64Encoded: String
+    ) {
+        body = body.replacingOccurrences(
+            of: "cid:\(contentId)",
+            with: "data:\(mimeType);base64,\(contentBase64Encoded)"
+        )
+    }
+}