"""Package with general repository related functions"""
import os
from string import digits

from gitdb.exc import BadObject
from git.refs import SymbolicReference
from git.objects import Object
from gitdb.util import (
    join,
    isdir,
    isfile,
    dirname,
    hex_to_bin,
    bin_to_hex
)
from git.compat import xrange


__all__ = ('rev_parse', 'is_git_dir', 'touch', 'read_gitfile', 'find_git_dir', 'name_to_object',
           'short_to_long', 'deref_tag', 'to_commit')


def touch(filename):
    fp = open(filename, "a")
    fp.close()


def is_git_dir(d):
    """ This is taken from the git setup.c:is_git_directory
    function."""
    if isdir(d) and \
            isdir(join(d, 'objects')) and \
            isdir(join(d, 'refs')):
        headref = join(d, 'HEAD')
        return isfile(headref) or \
            (os.path.islink(headref) and
             os.readlink(headref).startswith('refs'))
    return False


def find_git_dir(d):
    if is_git_dir(d):
        return d
    elif isfile(d):
        with open(d) as fp:
            content = fp.read().rstrip()
        if content.startswith('gitdir: '):
            d = join(dirname(d), content[8:])
            return find_git_dir(d)
    return None


def read_gitfile(f):
    """ This is taken from the git setup.c:read_gitfile function.
    :return gitdir path or None if gitfile is invalid."""
    if f is None:
        return None
    try:
        line = open(f, 'r').readline().rstrip()
    except (OSError, IOError):
        # File might not exist or is unreadable - ignore
        return None
    # end handle file access
    if line[0:8] != 'gitdir: ':
        return None
    path = os.path.realpath(line[8:])
    return path if is_git_dir(path) else None


def short_to_long(odb, hexsha):
    """:return: long hexadecimal sha1 from the given less-than-40 byte hexsha
        or None if no candidate could be found.
    :param hexsha: hexsha with less than 40 byte"""
    try:
        return bin_to_hex(odb.partial_to_complete_sha_hex(hexsha))
    except BadObject:
        return None
    # END exception handling


def name_to_object(repo, name, return_ref=False):
    """
    :return: object specified by the given name, hexshas ( short and long )
        as well as references are supported
    :param return_ref: if name specifies a reference, we will return the reference
        instead of the object. Otherwise it will raise BadObject
    """
    hexsha = None

    # is it a hexsha ? Try the most common ones, which is 7 to 40
    if repo.re_hexsha_shortened.match(name):
        if len(name) != 40:
            # find long sha for short sha
            hexsha = short_to_long(repo.odb, name)
        else:
            hexsha = name
        # END handle short shas
    # END find sha if it matches

    # if we couldn't find an object for what seemed to be a short hexsha
    # try to find it as reference anyway, it could be named 'aaa' for instance
    if hexsha is None:
        for base in ('%s', 'refs/%s', 'refs/tags/%s', 'refs/heads/%s', 'refs/remotes/%s', 'refs/remotes/%s/HEAD'):
            try:
                hexsha = SymbolicReference.dereference_recursive(repo, base % name)
                if return_ref:
                    return SymbolicReference(repo, base % name)
                # END handle symbolic ref
                break
            except ValueError:
                pass
        # END for each base
    # END handle hexsha

    # didn't find any ref, this is an error
    if return_ref:
        raise BadObject("Couldn't find reference named %r" % name)
    # END handle return ref

    # tried everything ? fail
    if hexsha is None:
        raise BadObject(name)
    # END assert hexsha was found

    return Object.new_from_sha(repo, hex_to_bin(hexsha))


def deref_tag(tag):
    """Recursively dereerence a tag and return the resulting object"""
    while True:
        try:
            tag = tag.object
        except AttributeError:
            break
    # END dereference tag
    return tag


def to_commit(obj):
    """Convert the given object to a commit if possible and return it"""
    if obj.type == 'tag':
        obj = deref_tag(obj)

    if obj.type != "commit":
        raise ValueError("Cannot convert object %r to type commit" % obj)
    # END verify type
    return obj


def rev_parse(repo, rev):
    """
    :return: Object at the given revision, either Commit, Tag, Tree or Blob
    :param rev: git-rev-parse compatible revision specification, please see
        http://www.kernel.org/pub/software/scm/git/docs/git-rev-parse.html
        for details
    :note: Currently there is no access to the rev-log, rev-specs may only contain
        topological tokens such ~ and ^.
    :raise BadObject: if the given revision could not be found
    :raise ValueError: If rev couldn't be parsed
    :raise IndexError: If invalid reflog index is specified"""

    # colon search mode ?
    if rev.startswith(':/'):
        # colon search mode
        raise NotImplementedError("commit by message search ( regex )")
    # END handle search

    obj = None
    ref = None
    output_type = "commit"
    start = 0
    parsed_to = 0
    lr = len(rev)
    while start < lr:
        if rev[start] not in "^~:@":
            start += 1
            continue
        # END handle start

        token = rev[start]

        if obj is None:
            # token is a rev name
            if start == 0:
                ref = repo.head.ref
            else:
                if token == '@':
                    ref = name_to_object(repo, rev[:start], return_ref=True)
                else:
                    obj = name_to_object(repo, rev[:start])
                # END handle token
            # END handle refname

            if ref is not None:
                obj = ref.commit
            # END handle ref
        # END initialize obj on first token

        start += 1

        # try to parse {type}
        if start < lr and rev[start] == '{':
            end = rev.find('}', start)
            if end == -1:
                raise ValueError("Missing closing brace to define type in %s" % rev)
            output_type = rev[start + 1:end]  # exclude brace

            # handle type
            if output_type == 'commit':
                pass  # default
            elif output_type == 'tree':
                try:
                    obj = to_commit(obj).tree
                except (AttributeError, ValueError):
                    pass    # error raised later
                # END exception handling
            elif output_type in ('', 'blob'):
                if obj.type == 'tag':
                    obj = deref_tag(obj)
                else:
                    # cannot do anything for non-tags
                    pass
                # END handle tag
            elif token == '@':
                # try single int
                assert ref is not None, "Requre Reference to access reflog"
                revlog_index = None
                try:
                    # transform reversed index into the format of our revlog
                    revlog_index = -(int(output_type) + 1)
                except ValueError:
                    # TODO: Try to parse the other date options, using parse_date
                    # maybe
                    raise NotImplementedError("Support for additional @{...} modes not implemented")
                # END handle revlog index

                try:
                    entry = ref.log_entry(revlog_index)
                except IndexError:
                    raise IndexError("Invalid revlog index: %i" % revlog_index)
                # END handle index out of bound

                obj = Object.new_from_sha(repo, hex_to_bin(entry.newhexsha))

                # make it pass the following checks
                output_type = None
            else:
                raise ValueError("Invalid output type: %s ( in %s )" % (output_type, rev))
            # END handle output type

            # empty output types don't require any specific type, its just about dereferencing tags
            if output_type and obj.type != output_type:
                raise ValueError("Could not accomodate requested object type %r, got %s" % (output_type, obj.type))
            # END verify ouput type

            start = end + 1                   # skip brace
            parsed_to = start
            continue
        # END parse type

        # try to parse a number
        num = 0
        if token != ":":
            found_digit = False
            while start < lr:
                if rev[start] in digits:
                    num = num * 10 + int(rev[start])
                    start += 1
                    found_digit = True
                else:
                    break
                # END handle number
            # END number parse loop

            # no explicit number given, 1 is the default
            # It could be 0 though
            if not found_digit:
                num = 1
            # END set default num
        # END number parsing only if non-blob mode

        parsed_to = start
        # handle hiererarchy walk
        try:
            if token == "~":
                obj = to_commit(obj)
                for item in xrange(num):
                    obj = obj.parents[0]
                # END for each history item to walk
            elif token == "^":
                obj = to_commit(obj)
                # must be n'th parent
                if num:
                    obj = obj.parents[num - 1]
            elif token == ":":
                if obj.type != "tree":
                    obj = obj.tree
                # END get tree type
                obj = obj[rev[start:]]
                parsed_to = lr
            else:
                raise ValueError("Invalid token: %r" % token)
            # END end handle tag
        except (IndexError, AttributeError):
            raise BadObject("Invalid Revision in %s" % rev)
        # END exception handling
    # END parse loop

    # still no obj ? Its probably a simple name
    if obj is None:
        obj = name_to_object(repo, rev)
        parsed_to = lr
    # END handle simple name

    if obj is None:
        raise ValueError("Revision specifier could not be parsed: %s" % rev)

    if parsed_to != lr:
        raise ValueError("Didn't consume complete rev spec %s, consumed part: %s" % (rev, rev[:parsed_to]))

    return obj