"""
与 STM32H7 交互的协议封装：
- 构造 IM23A "fmin"/"fmim" 传感器帧
- 解析 PythonLink 控制帧
- 解析 ASCII 状态报文
"""

from __future__ import annotations

import struct
import math
from dataclasses import dataclass
from datetime import datetime, timezone
from typing import Callable, Optional, Tuple
def _pwm_to_velocity(value: int, center: int = 1500, span: int = 500, max_speed: float = 1.5) -> float:
    """
    将 PWM 信号转换为线速度或角速度。
    基于 motion_config.h 中的模型参数：
    Forward: v = K_fwd * (1500 - pwm) + Bias (但模拟器这里主要是为了闭环，不需要完美匹配Bias，只要方向对)
             1000 PWM = 0.56 m/s
             1500 PWM = 0.0 m/s
             2000 PWM = -0.2 m/s (backward)
    Turn:    w = K_turn * (1500 - pwm)
             1000 PWM = 63 deg/s (Left)
             2000 PWM = -61.5 deg/s (Right)
    """
    if value < 1000: value = 1000
    if value > 2000: value = 2000
    
    # 使用参数
    # MC_CFG_FORWARD_K = 0.00196
    # MC_CFG_FORWARD_BIAS = -0.077
    # MC_CFG_STEERING_K_LEFT = 0.00206
    # MC_CFG_STEERING_K_RIGHT = 0.00201
    
    # 简单的线性映射用于模拟，忽略死区和偏置的细节，保证大致范围正确即可
    # 真实速度 = K * (1500 - pwm) + Bias
    
    delta = 1500 - value
    # 模拟器需要返回速度值，而不是设置速度。
    # 这里的 max_speed 参数不再直接作为比例系数，而是用于指示是线速度还是角速度的缩放
    
    if max_speed < 10.0: # 线速度模式 (m/s)
        # 假设是 Forward PWM
        # 1000 -> 500 diff -> 0.56 m/s => 0.00112 m/s/us
        # 2000 -> -500 diff -> -0.56 m/s (实际车可能是0.2，但模拟器可以对称)
        # 使用平均 K = 0.0015
        k_lin = 0.0015 
        if abs(delta) < 40: return 0.0 # 死区
        return delta * k_lin
    else: # 角速度模式 (deg/s -> rad/s)
        # 假设是 Steering PWM
        # 1000 -> 500 diff -> 63 deg/s => 0.126 deg/s/us
        # 2000 -> -500 diff -> -61.5 deg/s
        # K_ang ~ 0.12 deg/s/us
        k_ang_deg = 0.12
        if abs(delta) < 10: return 0.0 # 死区
        deg_s = delta * k_ang_deg
        # 转换为 rad/s ? 下面调用是 math.radians(_pwm_to_velocity(steering_pwm, max_speed=90.0))
        # 所以这里只需要返回 deg/s，调用者会转 rad/s
        return deg_s



IM23A_NAV_LEN = 100
IM23A_IMU_LEN = 52
IM23A_NAV_HEADER = b"fmin"
IM23A_IMU_HEADER = b"fmim"
IM23A_TAIL = b"ed"


def _ensure_utc(dt: datetime) -> datetime:
    if dt.tzinfo is None:
        return dt.replace(tzinfo=timezone.utc)
    return dt.astimezone(timezone.utc)


def nmea_checksum(sentence_without_star: str) -> str:
    cs = 0
    for ch in sentence_without_star[1:]:
        cs ^= ord(ch)
    return f"{cs:02X}"


def _write_double(buf: bytearray, value: float) -> None:
    buf.extend(struct.pack("<d", float(value)))


def _write_float(buf: bytearray, value: float) -> None:
    buf.extend(struct.pack("<f", float(value)))


def _write_u32(buf: bytearray, value: int) -> None:
    buf.extend(struct.pack("<I", int(value)))


def _write_u16(buf: bytearray, value: int) -> None:
    buf.extend(struct.pack("<H", int(value)))


def _append_tail(buf: bytearray) -> None:
    checksum = sum(buf) & 0xFFFF
    buf.extend(struct.pack("<H", checksum))
    buf.extend(IM23A_TAIL)


def build_im23a_nav_frame(
    timestamp: datetime,
    lat_deg: float,
    lon_deg: float,
    alt_m: float,
    east_vel: float,
    north_vel: float,
    up_vel: float,
    heading_rad: float,
    pitch_deg: float,
    roll_deg: float,
    accel_bias: Tuple[float, float, float],
    gyro_bias: Tuple[float, float, float],
    temperature_c: float,
    status_flags: int,
) -> bytes:
    buf = bytearray(IM23A_NAV_HEADER)
    _write_double(buf, _seconds_of_day(timestamp))
    _write_double(buf, lat_deg)
    _write_double(buf, lon_deg)
    _write_double(buf, alt_m)
    _write_float(buf, north_vel)
    _write_float(buf, east_vel)
    _write_float(buf, -up_vel)  # IM23A 向下正，MCU 内部转换回向上
    _write_float(buf, roll_deg)
    _write_float(buf, pitch_deg)
    _write_float(buf, heading_rad)  # 航向角：弧度值，范围-3.14到3.14，0度正北方向
    _write_float(buf, 0.02)  # 定位精度，可根据需要调整
    _write_float(buf, accel_bias[0])
    _write_float(buf, accel_bias[1])
    _write_float(buf, accel_bias[2])
    _write_float(buf, gyro_bias[0])
    _write_float(buf, gyro_bias[1])
    _write_float(buf, gyro_bias[2])
    _write_float(buf, temperature_c)
    _write_u32(buf, status_flags)
    _append_tail(buf)
    return bytes(buf)


def build_im23a_imu_frame(
    timestamp: datetime,
    accel_g: Tuple[float, float, float],
    gyro_deg_s: Tuple[float, float, float],
    reserves: Tuple[float, float, float] = (0.0, 0.0, 0.0),
) -> bytes:
    buf = bytearray(IM23A_IMU_HEADER)
    _write_double(buf, _seconds_of_day(timestamp))
    _write_float(buf, accel_g[0])
    _write_float(buf, accel_g[1])
    _write_float(buf, accel_g[2])
    _write_float(buf, gyro_deg_s[0])
    _write_float(buf, gyro_deg_s[1])
    _write_float(buf, gyro_deg_s[2])
    _write_float(buf, reserves[0])
    _write_float(buf, reserves[1])
    _write_float(buf, reserves[2])
    _append_tail(buf)
    return bytes(buf)


def _seconds_of_day(dt: datetime) -> float:
    utc = _ensure_utc(dt)
    return (
        utc.hour * 3600
        + utc.minute * 60
        + utc.second
        + utc.microsecond / 1_000_000.0
    )


def _decode_payload(payload: bytes) -> Tuple[float, float]:
    if len(payload) == 8:
        forward, turn = struct.unpack("<ff", payload)
        return forward, turn
    if len(payload) == 4:
        steering_pwm, throttle_pwm = struct.unpack("<HH", payload)
        # 重新映射：转向 PWM → yaw rate；油门 PWM → 线速度
        forward = _pwm_to_velocity(throttle_pwm, max_speed=1.0)
        turn = math.radians(_pwm_to_velocity(steering_pwm, max_speed=90.0))
        return forward, turn
    raise ValueError(f"不支持的控制负载长度: {len(payload)}")


@dataclass
class PythonLinkFrame:
    forward: float
    turn: float


@dataclass
class PythonAsciiMessage:
    tag: str
    fields: list[str]


@dataclass
class ControlStatus:
    forward_mps: float
    turn_rate: float
    freq_hz: float
    steering_pwm: int
    throttle_pwm: int
    stage: str
    timestamp_ms: float
    east: float
    north: float
    up: float
    heading_deg: float
    target_heading_deg: float
    target_east: float
    target_north: float


@dataclass
class PoseStatus:
    east: float
    north: float
    up: float
    heading_deg: float
    pitch_deg: float
    roll_deg: float
    target_east: float
    target_north: float
    timestamp_ms: float


@dataclass
class StateStatus:
    stage: str
    cross_track_error: float
    heading_error_deg: float
    timestamp_ms: float


@dataclass
class StackStatus:
    task_name: str
    stack_high_water: int
    heap_free_bytes: int


class PythonLinkDecoder:
    """
    解析 PythonLink 控制帧 (0xAA 0x55 ... 0D 0A)。
    """

    FRAME_HEADER = b"\xAA\x55"
    FRAME_FOOTER = b"\x0D\x0A"
    TYPE_CONTROL = 0x10

    def __init__(self, on_frame: Callable[[PythonLinkFrame], None]):
        self._buffer = bytearray()
        self._on_frame = on_frame

    def feed(self, data: bytes):
        if not data:
            return
        self._buffer.extend(data)
        while True:
            start = self._find_header()
            if start < 0:
                self._buffer.clear()
                return
            if start > 0:
                del self._buffer[:start]
            if len(self._buffer) < 9:
                return
            frame_len = self._expected_frame_length()
            if frame_len is None or len(self._buffer) < frame_len:
                return
            frame = bytes(self._buffer[:frame_len])
            del self._buffer[:frame_len]
            try:
                parsed = self._parse_frame(frame)
                if parsed:
                    self._on_frame(parsed)
            except Exception:
                # 丢弃无效帧，继续搜索
                continue

    def _find_header(self) -> int:
        data = bytes(self._buffer)
        idx = data.find(self.FRAME_HEADER)
        return idx

    def _expected_frame_length(self) -> Optional[int]:
        if len(self._buffer) < 5:
            return None
        payload_len = int.from_bytes(self._buffer[3:5], "little")
        return 2 + 1 + 2 + payload_len + 2 + 2  # header + type + len + payload + checksum + footer

    def _parse_frame(self, frame: bytes) -> Optional[PythonLinkFrame]:
        if not (frame.startswith(self.FRAME_HEADER) and frame.endswith(self.FRAME_FOOTER)):
            return None
        frame_type = frame[2]
        if frame_type != self.TYPE_CONTROL:
            return None
        payload_len = int.from_bytes(frame[3:5], "little")
        payload_start = 5
        payload_end = payload_start + payload_len
        payload = frame[payload_start:payload_end]
        checksum_received = int.from_bytes(frame[payload_end:payload_end + 2], "little")
        checksum_calc = sum(frame[2:payload_end]) & 0xFFFF
        if checksum_received != checksum_calc:
            raise ValueError("校验和不匹配")
        forward, turn = _decode_payload(payload)
        return PythonLinkFrame(forward=forward, turn=turn)


def parse_ascii_message(line: str) -> Optional[PythonAsciiMessage]:
    if not line:
        return None
    line = line.strip()
    if not line.startswith("$"):
        return None
    checksum_str = ""
    data_end = len(line)
    star_idx = line.find("*")
    if star_idx != -1:
        data_end = star_idx
        checksum_str = line[star_idx + 1 : star_idx + 3]
    payload = line[1:data_end]
    calc = 0
    for ch in payload:
        calc ^= ord(ch)
    if checksum_str:
        try:
            provided = int(checksum_str, 16)
        except ValueError:
            return None
        if provided != calc:
            return None
    parts = payload.split(",")
    if not parts:
        return None
    tag = parts[0]
    fields = parts[1:]
    return PythonAsciiMessage(tag=tag, fields=fields)


def decode_control_status(msg: PythonAsciiMessage) -> Optional[ControlStatus]:
    if msg.tag.upper() != "CTRL" or len(msg.fields) < 14:
        return None
    try:
        forward = float(msg.fields[0])
        turn = float(msg.fields[1])
        freq = float(msg.fields[2])
        steering = int(float(msg.fields[3]))
        throttle = int(float(msg.fields[4]))
        stage = msg.fields[5]
        timestamp = float(msg.fields[6])
        east = float(msg.fields[7])
        north = float(msg.fields[8])
        up = float(msg.fields[9])
        heading = float(msg.fields[10])
        target_heading = float(msg.fields[11])
        target_e = float(msg.fields[12])
        target_n = float(msg.fields[13])
    except ValueError:
        return None
    return ControlStatus(
        forward_mps=forward,
        turn_rate=turn,
        freq_hz=freq,
        steering_pwm=steering,
        throttle_pwm=throttle,
        stage=stage,
        timestamp_ms=timestamp,
        east=east,
        north=north,
        up=up,
        heading_deg=heading,
        target_heading_deg=target_heading,
        target_east=target_e,
        target_north=target_n,
    )


def decode_pose_status(msg: PythonAsciiMessage) -> Optional[PoseStatus]:
    if msg.tag.upper() != "POSE" or len(msg.fields) < 8:
        return None
    try:
        east = float(msg.fields[0])
        north = float(msg.fields[1])
        up = float(msg.fields[2])
        heading = float(msg.fields[3])
        pitch = float(msg.fields[4])
        roll = float(msg.fields[5])
        target_e = float(msg.fields[6])
        target_n = float(msg.fields[7])
        timestamp = float(msg.fields[8]) if len(msg.fields) > 8 else 0.0
    except ValueError:
        return None
    return PoseStatus(
        east=east,
        north=north,
        up=up,
        heading_deg=heading,
        pitch_deg=pitch,
        roll_deg=roll,
        target_east=target_e,
        target_north=target_n,
        timestamp_ms=timestamp,
    )


def decode_state_status(msg: PythonAsciiMessage) -> Optional[StateStatus]:
    if msg.tag.upper() != "STATE" or len(msg.fields) < 3:
        return None
    stage = msg.fields[0]
    try:
        xte = float(msg.fields[1])
        heading_err = float(msg.fields[2])
        timestamp = float(msg.fields[3]) if len(msg.fields) > 3 else 0.0
    except ValueError:
        return None
    return StateStatus(
        stage=stage,
        cross_track_error=xte,
        heading_error_deg=heading_err,
        timestamp_ms=timestamp,
    )


def decode_stack_status(msg: PythonAsciiMessage) -> Optional[StackStatus]:
    if msg.tag.upper() != "STACK" or len(msg.fields) < 3:
        return None
    task = msg.fields[0]
    try:
        stack_hw = int(float(msg.fields[1]))
        heap_free = int(float(msg.fields[2]))
    except ValueError:
        return None
    return StackStatus(task_name=task,
                       stack_high_water=stack_hw,
                       heap_free_bytes=heap_free)