#!/usr/bin/env python3
"""
reference.py - 펌웨어 wire 포맷의 Python 레퍼런스.

firmware/common/jsonbody.c 및 sig.c 와 *바이트 단위로 동일*한 출력을 만든다.
이 레퍼런스를 PHP verify_signature_raw 로 교차검증하면(parity_test.py),
동일 알고리즘을 쓰는 펌웨어 C 코드의 wire 계약이 서버와 호환됨을 입증한다.

대응:
  jb_fixed2()        <-> fixed2()
  jb_sht30_event()   <-> sht30_event_body()
  sig_raw_body()     <-> sign_raw()
"""
from __future__ import annotations

import hashlib
import hmac


def fixed2(v: float) -> str:
    """jb_fixed2() 와 동일한 소수 2자리 고정 포맷 (round-half-up, locale 무관)."""
    neg = v < 0
    if neg:
        v = -v
    scaled = int(v * 100.0 + 0.5)          # round half up (C: (long long)(v*100+0.5))
    ip = scaled // 100
    fp = scaled % 100
    sign = "-" if (neg and scaled != 0) else ""
    return f"{sign}{ip}.{fp:02d}"


def _esc(s: str) -> str:
    """jb_estr() 와 동일: '\"','\\\\', 제어문자(<0x20)만 이스케이프. '/'는 그대로."""
    out = []
    for ch in s:
        o = ord(ch)
        if ch == '"':
            out.append('\\"')
        elif ch == '\\':
            out.append('\\\\')
        elif o < 0x20:
            out.append('\\u%04x' % o)
        else:
            out.append(ch)
    return "".join(out)


def sht30_event_body(device_id: str, device_location: str, sensor_id: int,
                     sensor_name: str, event_type: str, timestamp: int,
                     temperature_c: float, humidity_percent: float,
                     metric_status: str, app_version: str) -> str:
    return (
        '{'
        f'"device_id":"{_esc(device_id)}",'
        f'"device_location":"{_esc(device_location)}",'
        f'"sensor_id":{int(sensor_id)},'
        f'"sensor_name":"{_esc(sensor_name)}",'
        f'"event_type":"{_esc(event_type)}",'
        f'"timestamp":{int(timestamp)},'
        f'"metric_type":"sht30",'
        f'"temperature_c":{fixed2(temperature_c)},'
        f'"humidity_percent":{fixed2(humidity_percent)},'
        f'"metric_status":"{_esc(metric_status)}",'
        f'"app_version":"{_esc(app_version)}"'
        '}'
    )


def sign_raw(api_key: str, body: str) -> str:
    """sig_raw_body(): lowercase_hex(HMAC-SHA256(key=api_key, msg=body))."""
    return hmac.new(api_key.encode("utf-8"), body.encode("utf-8"), hashlib.sha256).hexdigest()


# ── SHT3x CRC8 (sht30_convert.c 의 sht30_crc8 과 동일) ───────────────────────
def sht30_crc8(data: bytes) -> int:
    crc = 0xFF
    for b in data:
        crc ^= b
        for _ in range(8):
            crc = ((crc << 1) ^ 0x31) & 0xFF if (crc & 0x80) else (crc << 1) & 0xFF
    return crc


def sht30_parse(frame: bytes):
    """sht30_parse(): (temp_c, rh) 또는 예외."""
    if sht30_crc8(frame[0:2]) != frame[2]:
        raise ValueError("temperature CRC mismatch")
    if sht30_crc8(frame[3:5]) != frame[5]:
        raise ValueError("humidity CRC mismatch")
    raw_t = (frame[0] << 8) | frame[1]
    raw_rh = (frame[3] << 8) | frame[4]
    temp_c = -45.0 + 175.0 * (raw_t / 65535.0)
    rh = 100.0 * (raw_rh / 65535.0)
    return temp_c, rh