// Sources/iMessageMax/Utilities/MessageTextExtractor.swift
import Foundation
enum MessageTextExtractor {
/// Extract displayable text from a message, trying plain text first,
/// then falling back to attributedBody binary parsing.
/// Replaces \u{FFFC} (object replacement character) with [Photo].
static func extract(text: String?, attributedBody: Data?) -> String? {
if let text = text, !text.isEmpty {
return text.replacingOccurrences(of: "\u{FFFC}", with: "[Photo]")
}
guard let blob = attributedBody else { return nil }
guard let parsed = extractFromTypedstream(blob) else { return nil }
return parsed.replacingOccurrences(of: "\u{FFFC}", with: "[Photo]")
}
/// Parse Apple typedstream format to extract plain text.
/// Searches for "NSString" / "NSMutableString" marker, skips 5 bytes,
/// reads length byte (0x81 = 2-byte, 0x82 = 3-byte, else single byte),
/// then reads UTF-8 text of that length.
static func extractFromTypedstream(_ data: Data) -> String? {
// Look for NSString or NSMutableString marker in the typedstream
guard let nsStringRange = data.range(of: Data("NSString".utf8)) ??
data.range(of: Data("NSMutableString".utf8)) else {
return nil
}
// Skip past the class name marker to the length field
// The format is: marker + some bytes + length + data
let idx = nsStringRange.upperBound + 5
guard idx < data.count else { return nil }
let lengthByte = data[idx]
let length: Int
let dataStart: Int
// Parse length based on prefix byte
if lengthByte == 0x81 {
// 2-byte length (little endian)
guard idx + 3 <= data.count else { return nil }
length = Int(data[idx + 1]) | (Int(data[idx + 2]) << 8)
dataStart = idx + 3
} else if lengthByte == 0x82 {
// 3-byte length (little endian)
guard idx + 4 <= data.count else { return nil }
length = Int(data[idx + 1]) | (Int(data[idx + 2]) << 8) | (Int(data[idx + 3]) << 16)
dataStart = idx + 4
} else {
// Single byte length
length = Int(lengthByte)
dataStart = idx + 1
}
guard length > 0 && dataStart + length <= data.count else { return nil }
let textData = data[dataStart..<(dataStart + length)]
return String(data: textData, encoding: .utf8)
}
}
