import os
import struct
import binascii

DATA = 0
EOF = 1
EXTLINADR = 4

class HexFileException(Exception):
    pass

def parseHexLine(line):
    """ Parses a hexfile line into three parts """
    line = line[1:] # Remove ':'
    nums = bytes.fromhex(line)
    bytecount = nums[0]
    if len(nums) != bytecount + 5:
        raise HexFileException('byte count field incorrect')
    crc = sum(nums)
    if (crc & 0xFF) != 0:
        raise HexFileException('crc incorrect')
    address = struct.unpack('>H', nums[1:3])[0]
    typ = nums[3]
    data = nums[4:-1]
    return (address, typ, data)

def makeHexLine(address, typ, data=bytes()):
    bytecount = len(data)
    nums = bytearray()
    nums.append(bytecount)
    nums.extend(struct.pack('>H', address))
    nums.append(typ)
    nums.extend(data)
    crc = sum(nums)
    crc = ((~crc) + 1) & 0xFF
    nums.append(crc)
    line = ':' + binascii.hexlify(nums).decode('ascii')
    return line

def chunks(data, csize=16):
    idx = 0
    while idx < len(data):
        s = min(len(data) - idx, csize)
        yield data[idx:idx+s]
        idx += s

def hexfields(f):
    for line in f:
        line = line.strip() # Strip spaces and newlines
        if not line:
            continue # Skip empty lines
        if line[0] != ':':
            continue # Skip lines that do not start with a ':'
        yield parseHexLine(line)


class HexFile:
    """ Represents an intel hexfile """
    def __init__(self):
        self.regions = []
        self.startAddress = 0

    def load(self, f):
        endOfFile = False
        ext = 0
        for address, typ, data in hexfields(f):
            if endOfFile:
                raise HexFileException('hexfile line after end of file record')
            if typ == 0x0: # Data record
                self.addRegion(address + ext, data)
            elif typ == EXTLINADR: # Extended linear address record
                ext = (struct.unpack('>H', data[0:2])[0]) << 16
            elif typ == EOF: # End of file record
                if len(data) != 0:
                    raise HexFileException('end of file not empty')
                endOfFile = True
            elif typ == 0x5: # Start address record (where IP goes after loading)
                self.startAddress = struct.unpack('>I', data[0:4])[0]
            else:
                raise HexFileException('record type {0} not implemented'.format(typ))

    def __repr__(self):
        size = sum(len(r.data) for r in self.regions)
        return 'Hexfile containing {} bytes'.format(size)

    def dump(self):
        print(self)
        for r in self.regions:
            print(r)

    def __eq__(self, other):
        regions = self.regions
        oregions = other.regions
        if len(regions) != len(oregions):
            return False
        return all(rs == ro for rs, ro in zip(regions, oregions))

    def addRegion(self, address, data):
        r = HexFileRegion(address, data)
        self.regions.append(r)
        self.check()

    def check(self):
        self.regions.sort(key=lambda r: r.address)
        change = True
        while change and len(self.regions) > 1:
            change = False
            for r1, r2 in zip(self.regions[:-1], self.regions[1:]):
                if r1.EndAddress == r2.address:
                    r1.addData(r2.data)
                    self.regions.remove(r2)
                    change = True
                elif r1.EndAddress > r2.address:
                    raise HexFileException('Overlapping regions')

    def merge(self, other):
        for r in other.regions:
            self.addRegion(r.address, r.data)

    def save(self, f):
        def emit(address, typ, data=bytes()):
            print(makeHexLine(address, typ, data), file=f)
        for r in self.regions:
            ext = r.address & 0xFFFF0000
            emit(0, EXTLINADR, struct.pack('>H', ext >> 16))
            address = r.address - ext
            for chunk in chunks(r.data):
                if address >= 0x10000:
                    ext += 0x10000
                    emit(0, EXTLINADR, struct.pack('>H', ext >> 16))
                    address -= 0x10000
                emit(address, DATA, chunk)
                address += len(chunk)
        emit(0, EOF)

class HexFileRegion:
    def __init__(self, address, data = bytes()):
        self.address = address
        self.data = data

    def __repr__(self):
        return 'Region at 0x{:08X} of {} bytes'.format(self.address, len(self.data))

    def __eq__(self, other):
        return (self.address, self.data) == (other.address, other.data)

    def addData(self, d):
        self.data = self.data + d

    @property
    def EndAddress(self):
        return self.address + len(self.data)