#!/usr/bin/python3

"""Binary grepper."""

import os
import re
import sys
import getopt


def usage(retval):
    """Output a usage message."""
    if retval:
        write = sys.stderr.write
    else:
        write = sys.stdout.write

    write('usage: bgrep [-e] [-b] [-A after_bytes] [-B before_bytes] [-o] pattern filelist\n')
    write('\n')
    write('\t-h\t\toutput this help message\n')
    write('\t-e\t\techo pattern to stderr - for troubleshooting shell quoting issues\n')
    write('\t-i\t\tignore case\n')
    write('\t-f\t\tflush frequently\n')
    write('\t-b buffer_len\tdefines the buffer length\n')
    write('\t-o overlap_size\tdefines the amount of overlap between two buffers\n')
    write('\t-l\t\tlist filenames along with the offsets\n')
    write('\t-A num_bytes\tnumber of bytes to display after the match.  Must include the match itself\n')
    write('\t-B num_bytes\tnumber of bytes to display before the match\n')
    write('\t-x\t\tTreat pattern as a hexadecimal string.  Note that it is still compiled as a regex\n')
    write('\tpattern\t\tis an emacs-style regular expression (or hex with -x)\n')
    write('\tfilelist\tis a list of filenames\n')
    write('\n')
    sys.exit(retval)


LIST_FILENAMES = False
LAST_HIT = -1


def to_bytes(string):
    """Convert string to bytes."""
    return string.encode(encoding='ASCII')


def show(string):
    """Output a string, with octal escapes for unprintable characters."""
    for i in range(len(string)):
        character = string[i:i + 1]
        if not character:
            break
        if character in b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789/.,<>?";:\'|\\][{}=+-_`~!@#$%^&*()\n \t':
            os.write(1, character)
        else:
            os.write(1, b'\\' + to_bytes(oct(ord(character))))
    os.write(1, b'\n')


def show_occurences(flush_frequently, stuff, reg, offset, before, after, filename):
    # pylint: disable=too-many-arguments,global-statement
    """Show occurences of pattern 'reg' within 'filename'."""
    global LAST_HIT
    start = 0
    while True:
        result = reg.search(stuff, start)
        if result is None:
            break
        pos = result.span()[0]
        left = pos
        right = pos + len(result.group()) + 1
        left -= before
        right += after
        if LAST_HIT == -1:
            # these are zero based
            LAST_HIT = pos + 1 + offset
            if LIST_FILENAMES:
                sys.stdout.write(filename+':')
            if after:
                show(stuff[left:right])
            else:
                print(LAST_HIT)
        elif LAST_HIT != pos + 1 + offset:
            LAST_HIT = pos + 1 + offset
            if LIST_FILENAMES:
                sys.stdout.write(filename+':')
            if after:
                show(stuff[pos:pos+after])
            else:
                print(LAST_HIT)
        if flush_frequently:
            sys.stdout.flush()
        start = pos + 1


def main():
    # pylint: disable=too-many-locals,too-many-branches,too-many-statements,global-statement
    # buffer -does- have file-like methods
    # pylint: disable=no-member
    """Search in binary data."""
    # \( is grouping
    # \| is "or"
    # \+ and \? are operators
    # newlines are normal characters
    global LIST_FILENAMES
    buffer_size = 256 * 1024
    overlap_size = 4 * 1024
    after = 0
    before = 0
    ignore_case = False
    echo = False
    flush_frequently = False
    treat_pattern_as_hex = False
    try:
        (optlist, args) = getopt.getopt(sys.argv[1:], 'fb:o:lA:B:ex')
    except getopt.GetoptError:
        usage(1)
    for opt in optlist:
        if opt[0] == '-b':
            try:
                buffer_size = int(opt[1])
            except ValueError:
                usage(1)
        elif opt[0] == '-f':
            flush_frequently = True
        elif opt[0] == '-l':
            LIST_FILENAMES = True
        elif opt[0] == '-e':
            echo = True
        elif opt[0] == '-B':
            before = int(opt[1])
        elif opt[0] == '-A':
            after = int(opt[1])
        elif opt[0] == '-i':
            ignore_case = True
        elif opt[0] == '-x':
            treat_pattern_as_hex = True
        elif opt[0] == '-o':
            try:
                overlap_size = int(opt[1])
            except ValueError:
                usage(1)
    if len(args) < 1:
        usage(1)
    if len(args) == 1:
        args.append('-')
    if treat_pattern_as_hex:
        pattern = bytes.fromhex(args[0])
    else:
        pattern = os.fsencode(args[0])
    del args[0]
    filenames = args
    if ignore_case:
        reg = re.compile(pattern, re.IGNORECASE | re.MULTILINE)
    else:
        reg = re.compile(pattern, re.MULTILINE)
    if echo:
        sys.stderr.write('pattern is %s\n' % pattern)
    for filename in filenames:
        skip = False
        if filename == '-':
            file_ = sys.stdin.buffer
        else:
            try:
                file_ = open(filename, 'rb')
            except IOError:
                tuple_ = sys.exc_info()
                sys.stderr.write("Could not open {}: {}\n".format(filename, tuple_[1]))
                skip = True
        if not skip:
            try:
                stuff = file_.read(buffer_size+overlap_size)
            except (OSError, IOError):
                sys.stderr.write('Got I/O Error reading file %s\n' % filename)
                if filename != '-':
                    file_.close()
                continue
            offset = 0
            if stuff:
                show_occurences(flush_frequently, stuff, reg, offset, before, after, filename)
                while True:
                    new = file_.read(buffer_size)
                    stuff = stuff[buffer_size:] + new
                    if not new:
                        if filename != '-':
                            file_.close()
                        break
                    # print 'looking in',len(stuff)
                    offset = offset + buffer_size
                    show_occurences(flush_frequently, stuff, reg, offset, before, after, filename)
            if filename != '-':
                file_.close()
    if LAST_HIT == -1:
        sys.exit(1)
    else:
        sys.exit(0)


main()