# -*- coding: utf-8 -*-
import struct
import sys
import time
from typing import Callable, Collection, Optional

from libscrc import modbus  # type: ignore

from .constants import ACTION_READ, ACTION_WRITE, POSSIBLE_MARKER
from .interfaces import BaseInterface
from .solar_types import (
    DATA_BATTERY_STATE,
    HISTORICAL_DATA,
    ChargerState,
    DataItem,
    HistoricalData,
    HistoricalExtraInfo,
)
from .util import log


def write(fh, data):
    bdata = bytes(data)
    crc = modbus(bdata)
    bcrc = bytes([crc & 0xFF, (crc & 0xFF00) >> 8])
    fh.write(data + bcrc)


def construct_read_request(address, words=1, marker=0xFF):
    assert marker in POSSIBLE_MARKER, f"marker should be one of {POSSIBLE_MARKER}"
    return struct.pack("!BBHH", marker, ACTION_READ, address, words)


def construct_write_request(address, marker=0xFF):
    assert marker in POSSIBLE_MARKER, f"marker should be one of {POSSIBLE_MARKER}"
    return struct.pack("!BBH", marker, ACTION_WRITE, address)


def parse(data: bytes, items: Collection[DataItem], offset: int = 0) -> dict:
    pos = offset
    res = {}

    for i in items:
        res[i.name] = i.transform(struct.unpack_from(i.st_format, data, offset=pos)[0])
        pos += i.st_size

    return res


# GET_BATTERY_STATE
def parse_battery_state(data: bytes) -> dict:
    return parse(data, DATA_BATTERY_STATE)


def parse_historical_entry(data: bytes) -> dict:
    res = parse(data, HISTORICAL_DATA[:10])

    res_datalen = sum([x.st_size for x in HISTORICAL_DATA[:10]])

    if len(data) > res_datalen:
        res.update(parse(data, HISTORICAL_DATA[10:], offset=res_datalen))

    return res


def parse_packet(data):
    tag, operation, size = struct.unpack_from("BBB", data)
    _unpacked = struct.unpack_from(f"<{size}BH", data, offset=3)
    crc = _unpacked[-1]
    payload = _unpacked[:-1]
    calculated_crc = modbus(bytes([tag, operation, size, *payload]))

    if crc != calculated_crc:
        e = ValueError(f"CRC missmatch: expected {crc:04X}, got {calculated_crc:04X}.")
        # e.tag = tag
        # e.operation = operation
        # e.size = size
        # e.payload = payload
        # e.crc = crc
        # e.calculated_crc = calculated_crc
        raise e

    return payload


def discardUntil(fh: BaseInterface, byte: int, timeout=10) -> Optional[int]:
    assert byte >= 0 and byte < 256, f"byte: Expected 8bit unsigned int, got {byte}"

    def expand(b: Optional[bytes]):
        if not b:
            return None
        return b[0]

    start = time.time()
    discarded = 0
    read_byte = expand(fh.read(1))
    while read_byte != byte:
        if read_byte is not None:
            if not discarded:
                log("Discarding", end="")
            discarded += 1
            print(f" {read_byte:02X}", end="")
            sys.stdout.flush()

        if time.time() - start > timeout:
            read_byte = None
            break

        read_byte = expand(fh.read(1))

    if discarded:
        print()
        sys.stdout.flush()

    return read_byte


def readMemory(fh: BaseInterface, address: int, words: int = 1) -> Optional[bytes]:
    # log(f"Reading {words} words from 0x{address:04X}")
    request = construct_read_request(address, words=words)
    # log("Request:", request)
    write(fh, request)

    tag = discardUntil(fh, 0xFF)
    if tag is None:
        return None

    header = fh.read(2)
    if header and len(header) == 2:
        operation, size = header
        data = fh.read(size)
        _crc = fh.read(2)
        if data and _crc:
            try:
                crc = struct.unpack_from("<H", _crc)[0]
            except struct.error:
                log(f"readMemory: CRC error; read {len(_crc)} bytes (2 expected)")
                return None
            calculated_crc = modbus(bytes([tag, operation, size, *data]))
            if crc == calculated_crc:
                return data
            else:
                log(f"readMemory: CRC error; {crc:04X} != {calculated_crc:04X}")
        log("data or crc is falsely", header, data, _crc)
    return None


# set(255, 266, 1 or 0)
# ff 06 01 0a 00 01
# CMD_ENABLE_LOAD = b"\xff\x06\x01\x0a\x00\x01"
# CMD_DISABLE_LOAD = b"\xff\x06\x01\x0a\x00\x00"
# REG_LOAD_ENABLE = 0x010A


def writeMemory(fh: BaseInterface, address: int, data: bytes):
    if len(data) != 2:
        raise ValueError(f"Data must consist of a two-byte word, got {len(data)} bytes")

    header = construct_write_request(address)
    write(fh, header + data)

    tag = discardUntil(fh, 0xFF)
    if tag is None:
        return None

    header = fh.read(3)
    if header and len(header) == 3:
        operation, size, address = header
        log(header)
        # size field is zero when writing device name for whatever reason
        # write command seems to only accept a single word, so this is fine;
        # we just hardcode the number of bytes read to two here.
        rdata = fh.read(2)
        _crc = fh.read(2)
        if rdata and _crc:
            try:
                crc = struct.unpack_from("<H", _crc)[0]
            except struct.error:
                log(f"writeMemory: CRC error; read {len(_crc)} bytes (2 expected)")
                return None
            calculated_crc = modbus(bytes([tag, operation, size, address, *rdata]))
            if crc == calculated_crc:
                return rdata
            else:
                log(f"writeMemory: CRC error; {crc:04X} != {calculated_crc:04X}")
        log("data or crc is falsely", header, rdata, _crc)
    return None


def writeMemoryMultiple(fh: BaseInterface, address: int, data: bytes):
    if len(data) % 2:
        raise ValueError(f"Data must consist of two-byte words, got {len(data)} bytes")
    res = bytearray()
    for i in range(len(data) // 2):
        d = data[i * 2 : (i + 1) * 2]
        log(address + i, d)
        r = writeMemory(fh, address + i, d)
        if r:
            res.extend(r)
    return res


def try_read_parse(
    dev: BaseInterface,
    address: int,
    words: int = 1,
    parser: Optional[Callable] = None,
    attempts=5,
) -> Optional[dict]:
    while attempts:
        attempts -= 1
        res = readMemory(dev, address, words)
        if res:
            try:
                if parser:
                    return parser(res)
            except struct.error as e:
                log(e)
                log("0x0100 Unpack error:", len(res), res)
                _timeout = dev.timeout
                dev.timeout = 0.5
                log("Flushed from read buffer; ", dev.read())
                dev.timeout = _timeout
        else:
            log(f"No data read, expected {words*2} bytes (attempts left: {attempts})")
    return None


class ChargeController:
    device: BaseInterface

    def __init__(self, device: BaseInterface):
        self.device = device

    @property
    def serial(self) -> str:
        data = readMemory(self.device, 0x18, 3)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        p1 = data[0]
        p2 = data[1]
        p3 = (data[2] << 8) + data[3]
        return f"{p1}-{p2}-{p3}"

    @property
    def model(self) -> str:
        data = readMemory(self.device, 0x0C, 8)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return data.decode("utf-8").strip()

    @property
    def version(self) -> str:
        data = readMemory(self.device, 0x14, 4)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        major = (data[0] << 8) + data[1]
        minor = data[2]
        patch = data[3]

        return f"{major}.{minor}.{patch}"

    @property
    def load_enabled(self) -> bool:
        data = readMemory(self.device, 0x010A, 1)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return struct.unpack("x?", data)[0]

    @load_enabled.setter
    def load_enabled(self, value: bool):
        data = writeMemory(self.device, 0x010A, struct.pack("x?", value))
        if data is not None:
            res = struct.unpack("x?", data)[0]
            if res != value:
                log(f"setting load_enabled failed; {res!r} != {value!r}")
        else:
            log("setting load_enabled failed; communications error")

    @property
    def state(self) -> ChargerState:
        data = readMemory(self.device, 0x0100, 11)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return ChargerState(data)

    def get_historical(self, day) -> HistoricalData:
        data = readMemory(self.device, 0xF000 + day, 10)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return HistoricalData(data)

    @property
    def today(self) -> HistoricalData:
        data = readMemory(self.device, 0x010B, 10)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return HistoricalData(data)

    @property
    def extra(self) -> HistoricalExtraInfo:
        data = readMemory(self.device, 0x0115, 11)
        if data is None:
            raise IOError  # FIXME: Raise specific error in readMemory

        return HistoricalExtraInfo(data)