# diffhelper.py - helper routines for patch

#

# Copyright 2009 Olivia Mackall <olivia@selenic.com> and others

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from .i18n import _

from . import (

    error,

)

MISSING_NEWLINE_MARKER = b'\\ No newline at end of file\n'

def addlines(fp, hunk, lena, lenb, a, b):

    """Read lines from fp into the hunk

    The hunk is parsed into two arrays, a and b. a gets the old state of

    the text, b gets the new state. The control char from the hunk is saved

    when inserting into a, but not b (for performance while deleting files.)

    """

    while True:

        todoa = lena - len(a)

        todob = lenb - len(b)

        num = max(todoa, todob)

        if num == 0:

            break

        for i in range(num):

            s = fp.readline()

            if not s:

                raise error.ParseError(_(b'incomplete hunk'))

            if s == MISSING_NEWLINE_MARKER:

                fixnewline(hunk, a, b)

                continue

            if s == b'\n' or s == b'\r\n':

                # Some patches may be missing the control char

                # on empty lines. Supply a leading space.

                s = b' ' + s

            hunk.append(s)

            if s.startswith(b'+'):

                b.append(s[1:])

            elif s.startswith(b'-'):

                a.append(s)

            else:

                b.append(s[1:])

                a.append(s)

def fixnewline(hunk, a, b):

    """Fix up the last lines of a and b when the patch has no newline at EOF"""

    l = hunk[-1]

    # tolerate CRLF in last line

    if l.endswith(b'\r\n'):

        hline = l[:-2]

    else:

        hline = l[:-1]

    if hline.startswith((b' ', b'+')):

        b[-1] = hline[1:]

    if hline.startswith((b' ', b'-')):

        a[-1] = hline

    hunk[-1] = hline

def testhunk(a, b, bstart):

    """Compare the lines in a with the lines in b

    a is assumed to have a control char at the start of each line, this char

    is ignored in the compare.

    """

    alen = len(a)

    blen = len(b)

    if alen > blen - bstart or bstart < 0:

        return False

    for i in range(alen):

        if a[i][1:] != b[i + bstart]:

            return False

    return True