import Foundation

/// Splits a byte stream into newline-terminated lines, dropping CR and
/// enforcing the 64 KB line cap — the same framing the C++ and Kotlin
/// receivers use. Extracted so the logic is testable in isolation.
final class LineAssembler {
    private var pending: [UInt8] = []
    private let maxLine = SignalingMessage.maxMessageBytes

    /// Feed a chunk of received bytes; returns the complete lines it contained.
    func feed(_ chunk: [UInt8]) -> [String] {
        var lines: [String] = []
        for b in chunk {
            if b == 0x0A { // \n
                let text = String(bytes: pending, encoding: .utf8) ?? ""
                pending.removeAll(keepingCapacity: true)
                if !text.isEmpty { lines.append(text) }
            } else if b != 0x0D { // \r
                if pending.count < maxLine {
                    pending.append(b)
                } else {
                    // Hostile or broken peer: drop the oversized line.
                    pending.removeAll(keepingCapacity: true)
                }
            }
        }
        return lines
    }

    func reset() {
        pending.removeAll(keepingCapacity: true)
    }
}