# (c) Copyright 2018 by Coinkite Inc. This file is covered by license found in COPYING-CC.
#
# utils.py - Misc utils. My favourite kind of source file.
#
import gc, sys, ustruct, ngu
from ubinascii import unhexlify as a2b_hex
from ubinascii import hexlify as b2a_hex
from ubinascii import a2b_base64, b2a_base64
from uhashlib import sha256

B2A = lambda x: str(b2a_hex(x), 'ascii')

class imported:
    # Context manager that temporarily imports
    # a list of modules.
    # LATER: doubtful this saves any memory when all the code is frozen.

    def __init__(self, *modules):
        self.modules = modules

    def __enter__(self):
        # import everything required
        rv = tuple(__import__(n) for n in self.modules)

        return rv[0] if len(self.modules) == 1 else rv

    def __exit__(self, exc_type, exc_value, traceback):

        for n in self.modules:
            if n in sys.modules:
                del sys.modules[n]

        # recovery that tasty memory.
        gc.collect()

# class min_dramatic_pause:
#     # insure that something takes at least N ms
#     def __init__(self, min_time):
#         import utime
# 
#         self.min_time = min_time
#         self.start_time = utime.ticks_ms()
#     
#     def __enter__(self):
#         pass
# 
#     def __exit__(self, exc_type, exc_value, traceback):
#         import utime
# 
#         if exc_type is not None: return
# 
#         actual = utime.ticks_ms() - self.start_time
#         if actual < self.min_time:
#             utime.sleep_ms(self.min_time - actual)
# 

def pretty_delay(n):
    # decode # of seconds into various ranges, need not be precise.
    if n < 120:
        return '%d seconds' % n
    n /= 60
    if n < 60:
        return '%d minutes' % n
    n /= 60
    if n < 48:
        return '%.1f hours' % n
    n /= 24
    return 'about %d days' % n

def pretty_short_delay(sec):
    # precise, shorter on screen display
    if sec >= 3600:
        return '%2dh %2dm %2ds' % (sec //3600, (sec//60) % 60, sec % 60)
    else:
        return '%2dm %2ds' % ((sec//60) % 60, sec % 60)

def pop_count(i):
    # 32-bit population count for integers
    # from <https://stackoverflow.com/questions/9829578>
    i = i - ((i >> 1) & 0x55555555)
    i = (i & 0x33333333) + ((i >> 2) & 0x33333333)

    return (((i + (i >> 4) & 0xF0F0F0F) * 0x1010101) & 0xffffffff) >> 24

def get_filesize(fn):
    # like os.path.getsize()
    import uos
    try:
        return uos.stat(fn)[6]
    except OSError:
        return 0

class HexWriter:
    # Emulate a file/stream but convert binary to hex as they write
    def __init__(self, fd):
        self.fd = fd
        self.pos = 0
        self.checksum = sha256()

    def __enter__(self):
        self.fd.__enter__()
        return self

    def __exit__(self, *a, **k):
        self.fd.seek(0, 3)          # go to end
        self.fd.write(b'\r\n')
        return self.fd.__exit__(*a, **k)

    def tell(self):
        return self.pos

    def write(self, b):
        self.checksum.update(b)
        self.pos += len(b)

        self.fd.write(b2a_hex(b))

    def seek(self, offset, whence=0):
        assert whence == 0          # limited support
        self.pos = offset
        self.fd.seek((2*offset), 0)

    def read(self, ll):
        b = self.fd.read(ll*2)
        if not b:
            return b
        assert len(b)%2 == 0
        self.pos += len(b)//2
        return a2b_hex(b)

    def read_into(self, buf):
        b = self.read(len(buf))
        buf[0:len(b)] = b
        return len(b)

class Base64Writer:
    # Emulate a file/stream but convert binary to Base64 as they write
    def __init__(self, fd):
        self.fd = fd
        self.runt = b''

    def __enter__(self):
        self.fd.__enter__()
        return self

    def __exit__(self, *a, **k):
        if self.runt:
            self.fd.write(b2a_base64(self.runt))
        self.fd.write(b'\r\n')
        return self.fd.__exit__(*a, **k)

    def write(self, buf):
        if self.runt:
            buf = self.runt + buf
        rl = len(buf) % 3
        self.runt = buf[-rl:] if rl else b''
        if rl < len(buf):
            tmp = b2a_base64(buf[:(-rl if rl else None)])
            # library puts in newlines!?
            assert tmp[-1:] == b'\n', tmp
            assert tmp[-2:-1] != b'=', tmp
            self.fd.write(tmp[:-1])

def swab32(n):
    # endian swap: 32 bits
    return ustruct.unpack('>I', ustruct.pack('<I', n))[0]

def xfp2str(xfp):
    # Standardized way to show an xpub's fingerprint... it's a 4-byte string
    # and not really an integer. Used to show as '0x%08x' but that's wrong endian.
    return b2a_hex(ustruct.pack('<I', xfp)).decode().upper()

def str2xfp(txt):
    # Inverse of xfp2str
    return ustruct.unpack('<I', a2b_hex(txt))[0]

def problem_file_line(exc):
    # return a string of just the filename.py and line number where
    # an exception occured. Best used on AssertionError.
    import uio, sys, ure

    tmp = uio.StringIO()
    sys.print_exception(exc, tmp)
    lines = tmp.getvalue().split('\n')[-3:]
    del tmp

    # convert: 
    #   File "main.py", line 63, in interact
    #    into just:
    #   main.py:63
    #
    # on simulator, huge path is included, remove that too

    rv = None
    for ln in lines:
        mat = ure.match(r'.*"(/.*/|)(.*)", line (.*), ', ln)
        if mat:
            try:
                rv = mat.group(2) + ':' + mat.group(3)
            except: pass

    return rv or str(exc) or 'Exception'

def cleanup_deriv_path(bin_path, allow_star=False):
    # Clean-up path notation as string.
    # - raise exceptions on junk
    # - standardize on 'prime' notation (34' not 34p, or 34h)
    # - assume 'm' prefix, so '34' becomes 'm/34', etc
    # - do not assume /// is m/0/0/0
    # - if allow_star, then final position can be * or *' (wildcard)
    import ure
    from public_constants import MAX_PATH_DEPTH
    try:
        s = str(bin_path, 'ascii').lower()
    except UnicodeError:
        raise AssertionError('must be ascii')

    # empty string is valid
    if s == '': return 'm'

    s = s.replace('p', "'").replace('h', "'")
    mat = ure.match(r"(m|m/|)[0-9/']*" + ('' if not allow_star else r"(\*'|\*|)"), s)
    assert mat.group(0) == s, "invalid characters"

    parts = s.split('/')

    # the m/ prefix is optional
    if parts and parts[0] == 'm':
        parts = parts[1:]

    if not parts:
        # rather than: m/
        return 'm'

    assert len(parts) <= MAX_PATH_DEPTH, "too deep"

    for p in parts:
        assert p != '' and p != "'", "empty path component"
        if allow_star and '*' in p:
            # - star or star' can be last only (checked by regex above)
            assert p == '*' or p == "*'", "bad wildcard"
            continue
        if p[-1] == "'":
            p = p[0:-1]
        try:
            ip = int(p, 10)
        except:
            ip = -1 
        assert 0 <= ip < 0x80000000 and p == str(ip), "bad component: "+p
            
    return 'm/' + '/'.join(parts)

def keypath_to_str(bin_path, prefix='m/', skip=1):
    # take binary path, like from a PSBT and convert into text notation
    rv = prefix + '/'.join(str(i & 0x7fffffff) + ("'" if i & 0x80000000 else "")
                            for i in bin_path[skip:])
    return 'm' if rv == 'm/' else rv

def str_to_keypath(xfp, path):
    # Take a numeric xfp, and string derivation, and make a list of numbers,
    # like occurs in a PSBT.
    # - no error checking here

    rv = [xfp]
    for i in path.split('/'):
        if i == 'm': continue
        if not i: continue      # trailing or duplicated slashes

        if i[-1] == "'":
            here = int(i[:-1]) | 0x80000000
        else:
            here = int(i)

        rv.append(here)

    return rv

def match_deriv_path(patterns, path):
    # check for exact string match, or wildcard match (star in last position)
    # - both args must be cleaned by cleanup_deriv_path() already
    # - will accept any path, if 'any' in patterns
    if 'any' in patterns:
        return True

    for pat in patterns:
        if pat == path:
            return True

        if pat.endswith("/*") or pat.endswith("/*'"):
            if pat[-1] == "'" and path[-1] != "'": continue
            if pat[-1] == "*" and path[-1] == "'": continue

            # same hardness so check up to last component of path
            if pat.split('/')[:-1] == path.split('/')[:-1]:
                return True

    return False

class DecodeStreamer:
    def __init__(self):
        self.runt = bytearray()

    def more(self, buf):
        # Generator:
        # - accumulate into mod-N groups
        # - strip whitespace
        for ch in buf:
            if chr(ch).isspace(): continue
            self.runt.append(ch)
            if len(self.runt) == 128*self.mod:
                yield self.a2b(self.runt)
                self.runt = bytearray()

        here = len(self.runt) - (len(self.runt) % self.mod)
        if here:
            yield self.a2b(self.runt[0:here])
            self.runt = self.runt[here:]

class HexStreamer(DecodeStreamer):
    # be a generator that converts hex digits into binary
    # NOTE: mpy a2b_hex doesn't care about unicode vs bytes
    mod = 2
    def a2b(self, x):
        return a2b_hex(x)

class Base64Streamer(DecodeStreamer):
    # be a generator that converts Base64 into binary
    mod = 4
    def a2b(self, x):
        return a2b_base64(x)


def check_firmware_hdr(hdr, binary_size):
    # Check basics of new firmware being loaded. Return text of error msg if any.
    # - basic checks only: for confused customers, not attackers.
    # - hdr must be a bytearray(FW_HEADER_SIZE+more)

    from sigheader import FW_HEADER_SIZE, FW_HEADER_MAGIC, FWH_PY_FORMAT
    from sigheader import MK_1_OK, MK_2_OK, MK_3_OK
    from ustruct import unpack_from
    from version import hw_label
    import callgate

    try:
        assert len(hdr) >= FW_HEADER_SIZE

        magic_value, timestamp, version_string, pk, fw_size, install_flags, hw_compat = \
                        unpack_from(FWH_PY_FORMAT, hdr)[0:7]

        assert magic_value == FW_HEADER_MAGIC, 'bad magic'
        assert fw_size == binary_size or fw_size == (binary_size-128), 'size problem'

    except Exception as exc:
        return "That does not look like a firmware " \
                    "file we would want to use: %s" % exc

    if hw_compat != 0:
        # check this hardware is compatible
        ok = False
        if hw_label == 'mk1':
            ok = (hw_compat & MK_1_OK)
        elif hw_label == 'mk2':
            ok = (hw_compat & MK_2_OK)
        elif hw_label == 'mk3':
            ok = (hw_compat & MK_3_OK)
        
        if not ok:
            return "New firmware doesn't support this version of Coldcard hardware (%s)."%hw_label

    water = callgate.get_highwater()
    if water[0] and timestamp < water:
        return "That downgrade is not supported."

    return None


def clean_shutdown(style=0):
    # wipe SPI flash and shutdown (wiping main memory)
    import callgate
    from sflash import SF

    try:
        SF.wipe_most()
    except: pass

    callgate.show_logout(style)

def call_later_ms(delay, cb, *args):
    import uasyncio

    async def doit():
        await uasyncio.sleep_ms(delay)
        await cb(*args)
        
    uasyncio.create_task(doit())

def word_wrap(ln, w):
    while ln:
        sp = ln.rfind(' ', 0, w)

        if sp == -1:
            # bad-break the line
            sp = min(len(ln), w)
            nsp = sp
            if ln[nsp:nsp+1] == ' ':
                nsp += 1
        else:
            nsp = sp+1

        left = ln[0:sp]
        ln = ln[nsp:]

        if len(left) + 1 + len(ln) <= w:
            left = left + ' ' + ln
            ln = ''

        yield left

# EOF