import os
import time
import sys


def _estimate_fw_timeout_seconds(conn, total_size: int) -> float:
    base = float(getattr(conn, "timeout", 5.0))
    erase_budget = 8.0
    stream_and_write_budget = total_size / (25.0 * 1024.0)
    return max(base, erase_budget + stream_and_write_budget)


def execute(conn, source: str):
    if not os.path.isfile(source):
        raise FileNotFoundError(f"Firmware-Datei nicht gefunden: {source}")

    with open(source, "rb") as f:
        data = f.read()

    total_size = len(data)
    if total_size == 0:
        raise ValueError("Firmware-Datei ist leer.")

    print(f"Sende 🧩 Firmware ({total_size / 1024:.1f} KB) -> secondary slot")
    fw_timeout = _estimate_fw_timeout_seconds(conn, total_size)
    print(f"  Timeout fw_put: {fw_timeout:.1f}s")
    print("  Phase 1/3: Lösche secondary slot und initialisiere Flash...")

    start_time = time.monotonic()
    last_ui_update = start_time
    transfer_started = False

    def progress_handler(chunk_len, sent_file, total_file):
        nonlocal last_ui_update, transfer_started
        if not transfer_started:
            transfer_started = True
            print("  Phase 2/3: Übertrage Firmware...")
        now = time.monotonic()
        if now - last_ui_update < 0.2 and sent_file < total_file:
            return
        last_ui_update = now

        elapsed = now - start_time
        speed = (sent_file / 1024.0) / elapsed if elapsed > 0 else 0.0
        perc = (sent_file / total_file) * 100.0 if total_file > 0 else 100.0
        eta_sec = ((total_file - sent_file) / (sent_file / elapsed)) if sent_file > 0 and elapsed > 0 else 0.0
        eta_str = f"{int(eta_sec // 60):02d}:{int(eta_sec % 60):02d}"

        sys.stdout.write(
            f"\r  \033[90mProg: {perc:3.0f}% | {speed:6.1f} KB/s | ETA: {eta_str}\033[0m"
        )
        sys.stdout.flush()

    crc32 = conn.fw_put_data(data, timeout=fw_timeout, progress_callback=progress_handler)
    print("\n  Phase 3/3: Finalisiere und warte auf Geräte-ACK...")
    print(f"\r  \033[32mFertig: Firmware übertragen (CRC32: 0x{crc32:08x}).{' ' * 16}\033[0m")
    print("ℹ️  Nächste Schritte: reboot -> testen -> confirm")