"""
PlatformIO post-build script: generates a Nordic DFU package (.zip) from the
built firmware .hex using adafruit-nrfutil.

The resulting firmware_dfu.zip can be uploaded to the device via:
  - nRF Connect mobile app (iOS / Android) after triggering OTA mode
  - nRF Connect for Desktop
  - adafruit-nrfutil over BLE (advanced)

Trigger OTA mode on the device:
  - Send BLE command 0x02 to cfgCommand (0x1236), OR
  - Type 'o' in the serial monitor

Usage: referenced from platformio.ini as:
    extra_scripts = pre:scripts/git_hash.py, post:scripts/generate_dfu.py
"""
import subprocess, os

Import("env")  # noqa: F821 - PlatformIO injects this

def generate_dfu_package(source, target, env):
    build_dir   = env.subst("$BUILD_DIR")
    project_dir = env.subst("$PROJECT_DIR")
    hex_path    = os.path.join(build_dir, "firmware.hex")

    if not os.path.exists(hex_path):
        print(f"[generate_dfu] firmware.hex not found at {hex_path}, skipping")
        return

    out_path = os.path.join(project_dir, "firmware_dfu.zip")

    try:
        result = subprocess.run(
            [
                "adafruit-nrfutil", "dfu", "genpkg",
                "--dev-type", "0x0052",   # nRF52840
                "--application", hex_path,
                out_path,
            ],
            capture_output=True,
            text=True,
        )
        if result.returncode == 0:
            size_kb = os.path.getsize(out_path) / 1024
            print(f"[generate_dfu] DFU package ready: firmware_dfu.zip ({size_kb:.1f} KB)")
            print(f"[generate_dfu] Upload with nRF Connect after sending OTA command (0x02) via BLE")
        else:
            print(f"[generate_dfu] adafruit-nrfutil error: {result.stderr.strip()}")
    except FileNotFoundError:
        print("[generate_dfu] adafruit-nrfutil not found - skipping DFU package generation")
        print("[generate_dfu] Install with: pip install adafruit-nrfutil")

env.AddPostAction("$BUILD_DIR/firmware.hex", generate_dfu_package)  # noqa: F821