"""
test_ota.py — OTA firmware update utilities (Issue #124)

Tests:
  - CRC-32/ISO-HDLC  (crc32_file / binascii.crc32)
<<<<<<< HEAD
  - CRC-32/MPEG-2    (stm32_crc32 — matches ESP32 hardware CRC unit)
=======
  - CRC-32/MPEG-2    (stm32_crc32 — matches ESP32-S3 hardware CRC unit)
>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
  - CRC-16/XMODEM    (_crc16_xmodem — JLink frame integrity)
  - DFU_ENTER frame  (JLINK_CMD_DFU_ENTER = 0x06, no payload)
  - Safety constants (BKP index, flash region, magic value)
"""

import binascii
import os
import struct
import sys
import tempfile

import pytest

# Add scripts directory to path so we can import flash_firmware.py
sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', 'scripts'))
from flash_firmware import (
    crc32_file,
    stm32_crc32,
    _crc16_xmodem,
    _build_jlink_frame,
    FLASH_BASE,
    FLASH_SIZE,
    DFU_VID,
    DFU_PID,
)


# ── CRC-32/ISO-HDLC (crc32_file) ──────────────────────────────────────────

class TestCrc32File:
    def test_known_empty(self, tmp_path):
        """binascii.crc32 of empty file = 0x00000000."""
        p = tmp_path / "empty.bin"
        p.write_bytes(b'')
        assert crc32_file(str(p)) == 0x00000000

    def test_known_sequence(self, tmp_path):
        """CRC-32/ISO-HDLC of b'123456789' = 0xCBF43926 (well-known vector)."""
        p = tmp_path / "seq.bin"
        p.write_bytes(b'123456789')
        assert crc32_file(str(p)) == 0xCBF43926

    def test_deterministic(self, tmp_path):
        """Same file produces same result on repeated calls."""
        p = tmp_path / "data.bin"
        p.write_bytes(b'\xDE\xAD\xBE\xEF' * 256)
        assert crc32_file(str(p)) == crc32_file(str(p))

    def test_single_bit_flip(self, tmp_path):
        """Flipping one bit changes the CRC."""
        p0 = tmp_path / "d0.bin"
        p1 = tmp_path / "d1.bin"
        p0.write_bytes(b'\x00' * 64)
        p1.write_bytes(b'\x01' + b'\x00' * 63)
        assert crc32_file(str(p0)) != crc32_file(str(p1))

    def test_result_is_uint32(self, tmp_path):
        """Result fits in 32 bits."""
        p = tmp_path / "rnd.bin"
        p.write_bytes(bytes(range(256)))
        result = crc32_file(str(p))
        assert 0 <= result <= 0xFFFFFFFF


# ── CRC-32/MPEG-2 (stm32_crc32) ───────────────────────────────────────────

class TestStm32Crc32:
    def test_result_is_uint32(self):
        assert 0 <= stm32_crc32(b'\x00\x00\x00\x00') <= 0xFFFFFFFF

    def test_deterministic(self):
        data = b'\xDE\xAD\xBE\xEF' * 256
        assert stm32_crc32(data) == stm32_crc32(data)

    def test_avalanche(self):
        d0 = b'\x00' * 256
        d1 = b'\x01' + b'\x00' * 255
        assert stm32_crc32(d0) != stm32_crc32(d1)

    def test_differs_from_iso_hdlc(self):
        """MPEG-2 and ISO-HDLC produce different results for non-trivial input."""
        data = b'\x01\x02\x03\x04' * 64
        iso  = binascii.crc32(data) & 0xFFFFFFFF
        mpeg = stm32_crc32(data)
        assert iso != mpeg, "CRC algorithms should differ"

    def test_pads_to_4bytes(self):
        """Odd-length input padded to 4-byte boundary with 0xFF."""
        assert stm32_crc32(b'\xAA\xBB\xCC') == stm32_crc32(b'\xAA\xBB\xCC\xFF')

    def test_full_flash_consistent(self):
        """All-0xFF 512 KB (erased flash) produces a consistent result."""
        data = b'\xFF' * FLASH_SIZE
        r1   = stm32_crc32(data)
        r2   = stm32_crc32(data)
        assert r1 == r2
        assert 0 <= r1 <= 0xFFFFFFFF

    def test_512kb_multiple_of_4(self):
        """Flash size is a multiple of 4 (no padding needed for full image)."""
        assert FLASH_SIZE % 4 == 0

    def test_different_data_different_crc(self):
        """Two distinct 4-byte words produce different CRC."""
        a = stm32_crc32(b'\x00\x00\x00\x00')
        b = stm32_crc32(b'\xFF\xFF\xFF\xFF')
        assert a != b

    def test_word_endian_sensitivity(self):
        """Byte ordering within a 32-bit word affects the result."""
        le_word = struct.pack('<I', 0xDEADBEEF)  # EF BE AD DE in memory
        be_word = struct.pack('>I', 0xDEADBEEF)  # DE AD BE EF in memory
        assert stm32_crc32(le_word) != stm32_crc32(be_word)


# ── CRC-16/XMODEM (_crc16_xmodem) ─────────────────────────────────────────

class TestCrc16Xmodem:
    def test_empty(self):
        """CRC16 of empty input = 0x0000."""
        assert _crc16_xmodem(b'') == 0x0000

    def test_known_vector(self):
        """CRC-16/XMODEM of b'123456789' = 0x31C3 (well-known vector)."""
        assert _crc16_xmodem(b'123456789') == 0x31C3

    def test_single_heartbeat_byte(self):
        """CRC of HEARTBEAT command byte (0x01) is deterministic and non-zero."""
        r = _crc16_xmodem(bytes([0x01]))
        assert isinstance(r, int)
        assert 0 <= r <= 0xFFFF
        assert r != 0

    def test_dfu_cmd_byte(self):
        """CRC of DFU_ENTER command byte (0x06) is within 16-bit range."""
        r = _crc16_xmodem(bytes([0x06]))
        assert 0 <= r <= 0xFFFF

    def test_deterministic(self):
        data = b'\xCA\xFE\xBA\xBE'
        assert _crc16_xmodem(data) == _crc16_xmodem(data)

    def test_avalanche(self):
        assert _crc16_xmodem(b'\x00') != _crc16_xmodem(b'\x01')

    def test_two_byte_differs_from_one_byte(self):
        """CRC of two-byte input differs from single-byte input."""
        assert _crc16_xmodem(bytes([0x06, 0x00])) != _crc16_xmodem(bytes([0x06]))


# ── DFU_ENTER frame structure ──────────────────────────────────────────────

JLINK_CMD_DFU_ENTER  = 0x06
JLINK_CMD_HEARTBEAT  = 0x01
JLINK_CMD_ESTOP      = 0x07

class TestDfuEnterFrame:
    def test_cmd_id(self):
        """JLINK_CMD_DFU_ENTER is 0x06 (between PID_SET=0x05 and ESTOP=0x07)."""
        assert JLINK_CMD_DFU_ENTER == 0x06

    def test_cmd_id_between_pid_and_estop(self):
        assert JLINK_CMD_DFU_ENTER > 0x05   # > PID_SET
        assert JLINK_CMD_DFU_ENTER < JLINK_CMD_ESTOP

    def test_frame_length(self):
        """DFU_ENTER frame = 6 bytes: STX LEN CMD CRC_hi CRC_lo ETX."""
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        assert len(frame) == 6

    def test_frame_stx(self):
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        assert frame[0] == 0x02

    def test_frame_etx(self):
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        assert frame[-1] == 0x03

    def test_frame_len_byte(self):
        """LEN byte = 1 (CMD only, no payload)."""
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        assert frame[1] == 1

    def test_frame_cmd_byte(self):
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        assert frame[2] == JLINK_CMD_DFU_ENTER

    def test_frame_crc_valid(self):
        """Embedded CRC validates against CMD byte."""
        frame     = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        cmd_byte  = frame[2]
        crc_hi    = frame[3]
        crc_lo    = frame[4]
        expected  = _crc16_xmodem(bytes([cmd_byte]))
        assert (crc_hi << 8 | crc_lo) == expected

    def test_frame_differs_from_heartbeat(self):
        """DFU_ENTER frame is distinct from HEARTBEAT frame."""
        assert (_build_jlink_frame(JLINK_CMD_DFU_ENTER) !=
                _build_jlink_frame(JLINK_CMD_HEARTBEAT))

    def test_frame_differs_from_estop(self):
        assert (_build_jlink_frame(JLINK_CMD_DFU_ENTER) !=
                _build_jlink_frame(JLINK_CMD_ESTOP))

    def test_no_payload(self):
        """DFU_ENTER frame has no payload bytes between CMD and CRC."""
        frame = _build_jlink_frame(JLINK_CMD_DFU_ENTER)
        # Layout: STX LEN CMD [no payload here] CRC_hi CRC_lo ETX
        assert len(frame) == 6   # STX(1)+LEN(1)+CMD(1)+CRC(2)+ETX(1)


# ── Safety / constants ─────────────────────────────────────────────────────

class TestOtaConstants:
    def test_dfu_magic(self):
        """DFU magic = 0xDEADBEEF (Betaflight-proven pattern)."""
        OTA_DFU_MAGIC = 0xDEADBEEF
        assert OTA_DFU_MAGIC == 0xDEADBEEF

    def test_dfu_magic_fits_uint32(self):
        assert 0 <= 0xDEADBEEF <= 0xFFFFFFFF

    def test_bkp_idx_avoids_bno055(self):
        """BKP15 does not overlap BNO055 range BKP0–BKP6 (PR #150)."""
        OTA_DFU_BKP_IDX   = 15
        BNO055_BKP_RANGE  = range(0, 7)
        assert OTA_DFU_BKP_IDX not in BNO055_BKP_RANGE

<<<<<<< HEAD
    def test_bkp_idx_valid_esp32(self):
        """ESP32 has 32 backup registers (BKP0R–BKP31R)."""
=======
    def test_bkp_idx_valid_esp32s3(self):
        """ESP32-S3 has 32 backup registers (BKP0R–BKP31R)."""
>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
        OTA_DFU_BKP_IDX = 15
        assert 0 <= OTA_DFU_BKP_IDX <= 31

    def test_flash_base(self):
        assert FLASH_BASE == 0x08000000

    def test_flash_size_512k(self):
        assert FLASH_SIZE == 512 * 1024

    def test_flash_size_word_aligned(self):
        assert FLASH_SIZE % 4 == 0

    def test_dfu_vid_stmicro(self):
        """Default VID = 0x0483 (STMicroelectronics)."""
        assert DFU_VID == 0x0483

    def test_dfu_pid_dfu_mode(self):
<<<<<<< HEAD
        """Default PID = 0xDF11 (ESP32 DFU mode)."""
=======
        """Default PID = 0xDF11 (ESP32-S3 DFU mode)."""
>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
        assert DFU_PID == 0xDF11

    def test_bkp_idx_not_zero(self):
        """BKP15 ≠ 0 — the old request_bootloader() used BKP0R."""
        assert 15 != 0