import re
import os
import urllib

from mercurial import hg
from mercurial import node
from mercurial import util as hgutil


b_re = re.compile(r'^\+\+\+ b\/([^\n]*)', re.MULTILINE)
a_re = re.compile(r'^--- a\/([^\n]*)', re.MULTILINE)
devnull_re = re.compile(r'^([-+]{3}) /dev/null', re.MULTILINE)
header_re = re.compile(r'^diff --git .* b\/(.*)', re.MULTILINE)
newfile_devnull_re = re.compile(r'^--- /dev/null\n\+\+\+ b/([^\n]*)',
                                re.MULTILINE)


def formatrev(rev):
    if rev == -1:
        return '\t(working copy)'
    return '\t(revision %d)' % rev


def filterdiff(diff, oldrev, newrev):
    diff = newfile_devnull_re.sub(r'--- \1\t(revision 0)' '\n'
                                  r'+++ \1\t(working copy)',
                                  diff)
    oldrev = formatrev(oldrev)
    newrev = formatrev(newrev)
    diff = a_re.sub(r'--- \1'+ oldrev, diff)
    diff = b_re.sub(r'+++ \1' + newrev, diff)
    diff = devnull_re.sub(r'\1 /dev/null\t(working copy)', diff)
    diff = header_re.sub(r'Index: \1' + '\n' + ('=' * 67), diff)
    return diff


def parentrev(ui, repo, meta, hashes):
    """Find the svn parent revision of the repo's dirstate.
    """
    workingctx = repo.parents()[0]
    outrev = outgoing_revisions(repo, hashes, workingctx.node())
    if outrev:
        workingctx = repo[outrev[-1]].parents()[0]
    return workingctx


def islocalrepo(url):
    if not url.startswith('file:///'):
        return False
    if '#' in url.split('/')[-1]: # strip off #anchor
        url = url[:url.rfind('#')]
    path = url[len('file://'):]
    path = urllib.url2pathname(path).replace(os.sep, '/')
    while '/' in path:
        if reduce(lambda x,y: x and y,
                  map(lambda p: os.path.exists(os.path.join(path, p)),
                      ('hooks', 'format', 'db', ))):
            return True
        path = path.rsplit('/', 1)[0]
    return False


def version(ui):
    """Return version information if available."""
    try:
        import __version__
        return __version__.version
    except ImportError:
        try:
            dn = os.path.dirname
            repo = hg.repository(ui, dn(dn(__file__)))
            ver = repo.dirstate.parents()[0]
            return node.hex(ver)[:12]
        except:
            return 'unknown'


def normalize_url(url):
    if url.startswith('svn+http://') or url.startswith('svn+https://'):
        url = url[4:]
    url, revs, checkout = hg.parseurl(url)
    url = url.rstrip('/')
    if checkout:
        url = '%s#%s' % (url, checkout)
    return url


class PrefixMatch(object):
    def __init__(self, prefix):
        self.p = prefix

    def files(self):
        return []

    def __call__(self, fn):
        return fn.startswith(self.p)

def outgoing_revisions(repo, reverse_map, sourcerev):
    """Given a repo and an hg_editor, determines outgoing revisions for the
    current working copy state.
    """
    outgoing_rev_hashes = []
    if sourcerev in reverse_map:
        return
    sourcerev = repo[sourcerev]
    while (not sourcerev.node() in reverse_map
           and sourcerev.node() != node.nullid):
        outgoing_rev_hashes.append(sourcerev.node())
        sourcerev = sourcerev.parents()
        if len(sourcerev) != 1:
            raise hgutil.Abort("Sorry, can't find svn parent of a merge revision.")
        sourcerev = sourcerev[0]
    if sourcerev.node() != node.nullid:
        return outgoing_rev_hashes

default_commit_msg = '*** empty log message ***'

def describe_commit(ui, h, b):
    ui.note(' committed to "%s" as %s\n' % ((b or 'default'), node.short(h)))


def swap_out_encoding(new_encoding="UTF-8"):
    from mercurial import encoding
    old = encoding.encoding
    encoding.encoding = new_encoding
    return old


def issamefile(parentctx, childctx, f):
    """Assuming f exists and is the same in childctx and parentctx, return True."""
    if parentctx == childctx:
        return True
    if parentctx.rev() > childctx.rev():
        parentctx, childctx = childctx, parentctx

    def selfandancestors(selfctx):
        yield selfctx
        for ctx in selfctx.ancestors():
            yield ctx

    for pctx in selfandancestors(childctx):
        if pctx.rev() <= parentctx.rev():
            return True
        if f in pctx.files():
            return False
    # parentctx is not an ancestor of childctx, files are unrelated
    return False