[ErrorProcessing]: Make toast show underlying errors (if there are any)

SideStore/Utils/dignostics/errors/ErrorProcessing.swift

@@ -0,0 +1,81 @@
+//
+//  ErrorProcessing.swift
+//  AltStore
+//
+//  Created by Magesh K on 20/01/25.
+//  Copyright © 2025 SideStore. All rights reserved.
+//
+
+class ErrorProcessing {
+    
+    enum InfoMode: String {
+        case fullError
+        case localizedDescription
+    }
+    
+    let info: InfoMode
+    let unique: Bool
+    let recur: Bool
+    
+    
+    var errors: Set<String> = []
+    
+    // by default we will process only the localDesc on first level errors
+    init(_ mode: InfoMode = .localizedDescription, unique: Bool = false, recur: Bool = false){
+        self.info = mode
+        self.unique = unique
+        self.recur = recur
+    }
+    
+    private func processError(_ error: NSError, getMoreErrors: (_ error: NSError)->String) -> String{
+        // if unique was requested and if this error is duplicate, ignore processing it
+        let serializedError = "\(error)"
+        if unique && errors.contains(serializedError) {
+            return ""
+        }
+        errors.insert(serializedError)    // mark this as processed
+        
+        var title = ""
+        var desc = ""
+        switch (info){
+            case .localizedDescription:
+                title = (error.localizedTitle.map{$0+"\n"} ?? "")
+                desc = error.localizedDescription
+            case .fullError:
+                desc = serializedError
+        }
+        var moreErrors = getMoreErrors(error)
+        moreErrors = moreErrors == "" ? "" : "\n" + moreErrors
+        return title + desc + moreErrors
+    }
+
+    func getDescription(error: NSError) -> String{
+        errors = []  // reinit for each request
+        return getDescriptionText(error: error)
+    }
+    
+    private lazy var recurseErrors = { error in
+        self.getDescriptionText(error: error)        // recursively process underlying error(s) if any
+    }
+    
+    func getDescriptionText(error: NSError) -> String{
+        var description = ""
+
+        // process current error only if recur was not requested
+        let processMoreErrors = recur ? recurseErrors : {_ in ""}
+        
+        let underlyingErrors = error.underlyingErrors
+        if !underlyingErrors.isEmpty {
+            description += underlyingErrors.map{ error in
+                let error = error as NSError
+                return processError(error, getMoreErrors: processMoreErrors)
+            }.joined(separator: "\n")
+        } else if let underlyingError = error.underlyingError as? NSError {
+            let error = underlyingError as NSError
+            description += processError(error, getMoreErrors: processMoreErrors)
+        } else {
+            description += processError(error, getMoreErrors: processMoreErrors)
+        }
+        return description
+    }
+}