# Contains standalone functions to accompany the index implementation and make it
# more versatile
# NOTE: Autodoc hates it if this is a docstring
from stat import (
    S_IFDIR,
    S_IFLNK,
    S_ISLNK,
    S_ISDIR,
    S_IFMT,
    S_IFREG,
)

from io import BytesIO
import os
import subprocess

from git.util import IndexFileSHA1Writer
from git.exc import (
    UnmergedEntriesError,
    HookExecutionError
)
from git.objects.fun import (
    tree_to_stream,
    traverse_tree_recursive,
    traverse_trees_recursive
)

from .typ import (
    BaseIndexEntry,
    IndexEntry,
    CE_NAMEMASK,
    CE_STAGESHIFT
)

from .util import (
    pack,
    unpack
)

from gitdb.base import IStream
from gitdb.typ import str_tree_type
from git.compat import (
    defenc,
    force_text,
    force_bytes
)

S_IFGITLINK = S_IFLNK | S_IFDIR     # a submodule
CE_NAMEMASK_INV = ~CE_NAMEMASK

__all__ = ('write_cache', 'read_cache', 'write_tree_from_cache', 'entry_key',
           'stat_mode_to_index_mode', 'S_IFGITLINK', 'run_commit_hook', 'hook_path')


def hook_path(name, git_dir):
    """:return: path to the given named hook in the given git repository directory"""
    return os.path.join(git_dir, 'hooks', name)


def run_commit_hook(name, index):
    """Run the commit hook of the given name. Silently ignores hooks that do not exist.
    :param name: name of hook, like 'pre-commit'
    :param index: IndexFile instance
    :raises HookExecutionError: """
    hp = hook_path(name, index.repo.git_dir)
    if not os.access(hp, os.X_OK):
        return

    env = os.environ.copy()
    env['GIT_INDEX_FILE'] = index.path
    env['GIT_EDITOR'] = ':'
    cmd = subprocess.Popen(hp,
                           env=env,
                           stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE,
                           cwd=index.repo.working_dir,
                           close_fds=(os.name == 'posix'))
    stdout, stderr = cmd.communicate()
    cmd.stdout.close()
    cmd.stderr.close()

    if cmd.returncode != 0:
        stdout = force_text(stdout, defenc)
        stderr = force_text(stderr, defenc)
        raise HookExecutionError(hp, cmd.returncode, stdout, stderr)
    # end handle return code


def stat_mode_to_index_mode(mode):
    """Convert the given mode from a stat call to the corresponding index mode
    and return it"""
    if S_ISLNK(mode):   # symlinks
        return S_IFLNK
    if S_ISDIR(mode) or S_IFMT(mode) == S_IFGITLINK:    # submodules
        return S_IFGITLINK
    return S_IFREG | 0o644 | (mode & 0o100)       # blobs with or without executable bit


def write_cache(entries, stream, extension_data=None, ShaStreamCls=IndexFileSHA1Writer):
    """Write the cache represented by entries to a stream

    :param entries: **sorted** list of entries
    :param stream: stream to wrap into the AdapterStreamCls - it is used for
        final output.

    :param ShaStreamCls: Type to use when writing to the stream. It produces a sha
        while writing to it, before the data is passed on to the wrapped stream

    :param extension_data: any kind of data to write as a trailer, it must begin
        a 4 byte identifier, followed by its size ( 4 bytes )"""
    # wrap the stream into a compatible writer
    stream = ShaStreamCls(stream)

    tell = stream.tell
    write = stream.write

    # header
    version = 2
    write(b"DIRC")
    write(pack(">LL", version, len(entries)))

    # body
    for entry in entries:
        beginoffset = tell()
        write(entry[4])         # ctime
        write(entry[5])         # mtime
        path = entry[3]
        path = force_bytes(path, encoding=defenc)
        plen = len(path) & CE_NAMEMASK      # path length
        assert plen == len(path), "Path %s too long to fit into index" % entry[3]
        flags = plen | (entry[2] & CE_NAMEMASK_INV)     # clear possible previous values
        write(pack(">LLLLLL20sH", entry[6], entry[7], entry[0],
                   entry[8], entry[9], entry[10], entry[1], flags))
        write(path)
        real_size = ((tell() - beginoffset + 8) & ~7)
        write(b"\0" * ((beginoffset + real_size) - tell()))
    # END for each entry

    # write previously cached extensions data
    if extension_data is not None:
        stream.write(extension_data)

    # write the sha over the content
    stream.write_sha()


def read_header(stream):
    """Return tuple(version_long, num_entries) from the given stream"""
    type_id = stream.read(4)
    if type_id != b"DIRC":
        raise AssertionError("Invalid index file header: %r" % type_id)
    version, num_entries = unpack(">LL", stream.read(4 * 2))

    # TODO: handle version 3: extended data, see read-cache.c
    assert version in (1, 2)
    return version, num_entries


def entry_key(*entry):
    """:return: Key suitable to be used for the index.entries dictionary
    :param entry: One instance of type BaseIndexEntry or the path and the stage"""
    if len(entry) == 1:
        return (entry[0].path, entry[0].stage)
    else:
        return tuple(entry)
    # END handle entry


def read_cache(stream):
    """Read a cache file from the given stream
    :return: tuple(version, entries_dict, extension_data, content_sha)
    * version is the integer version number
    * entries dict is a dictionary which maps IndexEntry instances to a path at a stage
    * extension_data is '' or 4 bytes of type + 4 bytes of size + size bytes
    * content_sha is a 20 byte sha on all cache file contents"""
    version, num_entries = read_header(stream)
    count = 0
    entries = dict()

    read = stream.read
    tell = stream.tell
    while count < num_entries:
        beginoffset = tell()
        ctime = unpack(">8s", read(8))[0]
        mtime = unpack(">8s", read(8))[0]
        (dev, ino, mode, uid, gid, size, sha, flags) = \
            unpack(">LLLLLL20sH", read(20 + 4 * 6 + 2))
        path_size = flags & CE_NAMEMASK
        path = read(path_size).decode(defenc)

        real_size = ((tell() - beginoffset + 8) & ~7)
        read((beginoffset + real_size) - tell())
        entry = IndexEntry((mode, sha, flags, path, ctime, mtime, dev, ino, uid, gid, size))
        # entry_key would be the method to use, but we safe the effort
        entries[(path, entry.stage)] = entry
        count += 1
    # END for each entry

    # the footer contains extension data and a sha on the content so far
    # Keep the extension footer,and verify we have a sha in the end
    # Extension data format is:
    # 4 bytes ID
    # 4 bytes length of chunk
    # repeated 0 - N times
    extension_data = stream.read(~0)
    assert len(extension_data) > 19, "Index Footer was not at least a sha on content as it was only %i bytes in size"\
                                     % len(extension_data)

    content_sha = extension_data[-20:]

    # truncate the sha in the end as we will dynamically create it anyway
    extension_data = extension_data[:-20]

    return (version, entries, extension_data, content_sha)


def write_tree_from_cache(entries, odb, sl, si=0):
    """Create a tree from the given sorted list of entries and put the respective
    trees into the given object database

    :param entries: **sorted** list of IndexEntries
    :param odb: object database to store the trees in
    :param si: start index at which we should start creating subtrees
    :param sl: slice indicating the range we should process on the entries list
    :return: tuple(binsha, list(tree_entry, ...)) a tuple of a sha and a list of
        tree entries being a tuple of hexsha, mode, name"""
    tree_items = list()
    tree_items_append = tree_items.append
    ci = sl.start
    end = sl.stop
    while ci < end:
        entry = entries[ci]
        if entry.stage != 0:
            raise UnmergedEntriesError(entry)
        # END abort on unmerged
        ci += 1
        rbound = entry.path.find('/', si)
        if rbound == -1:
            # its not a tree
            tree_items_append((entry.binsha, entry.mode, entry.path[si:]))
        else:
            # find common base range
            base = entry.path[si:rbound]
            xi = ci
            while xi < end:
                oentry = entries[xi]
                orbound = oentry.path.find('/', si)
                if orbound == -1 or oentry.path[si:orbound] != base:
                    break
                # END abort on base mismatch
                xi += 1
            # END find common base

            # enter recursion
            # ci - 1 as we want to count our current item as well
            sha, tree_entry_list = write_tree_from_cache(entries, odb, slice(ci - 1, xi), rbound + 1)
            tree_items_append((sha, S_IFDIR, base))

            # skip ahead
            ci = xi
        # END handle bounds
    # END for each entry

    # finally create the tree
    sio = BytesIO()
    tree_to_stream(tree_items, sio.write)
    sio.seek(0)

    istream = odb.store(IStream(str_tree_type, len(sio.getvalue()), sio))
    return (istream.binsha, tree_items)


def _tree_entry_to_baseindexentry(tree_entry, stage):
    return BaseIndexEntry((tree_entry[1], tree_entry[0], stage << CE_STAGESHIFT, tree_entry[2]))


def aggressive_tree_merge(odb, tree_shas):
    """
    :return: list of BaseIndexEntries representing the aggressive merge of the given
        trees. All valid entries are on stage 0, whereas the conflicting ones are left
        on stage 1, 2 or 3, whereas stage 1 corresponds to the common ancestor tree,
        2 to our tree and 3 to 'their' tree.
    :param tree_shas: 1, 2 or 3 trees as identified by their binary 20 byte shas
        If 1 or two, the entries will effectively correspond to the last given tree
        If 3 are given, a 3 way merge is performed"""
    out = list()
    out_append = out.append

    # one and two way is the same for us, as we don't have to handle an existing
    # index, instrea
    if len(tree_shas) in (1, 2):
        for entry in traverse_tree_recursive(odb, tree_shas[-1], ''):
            out_append(_tree_entry_to_baseindexentry(entry, 0))
        # END for each entry
        return out
    # END handle single tree

    if len(tree_shas) > 3:
        raise ValueError("Cannot handle %i trees at once" % len(tree_shas))

    # three trees
    for base, ours, theirs in traverse_trees_recursive(odb, tree_shas, ''):
        if base is not None:
            # base version exists
            if ours is not None:
                # ours exists
                if theirs is not None:
                    # it exists in all branches, if it was changed in both
                    # its a conflict, otherwise we take the changed version
                    # This should be the most common branch, so it comes first
                    if(base[0] != ours[0] and base[0] != theirs[0] and ours[0] != theirs[0]) or \
                            (base[1] != ours[1] and base[1] != theirs[1] and ours[1] != theirs[1]):
                        # changed by both
                        out_append(_tree_entry_to_baseindexentry(base, 1))
                        out_append(_tree_entry_to_baseindexentry(ours, 2))
                        out_append(_tree_entry_to_baseindexentry(theirs, 3))
                    elif base[0] != ours[0] or base[1] != ours[1]:
                        # only we changed it
                        out_append(_tree_entry_to_baseindexentry(ours, 0))
                    else:
                        # either nobody changed it, or they did. In either
                        # case, use theirs
                        out_append(_tree_entry_to_baseindexentry(theirs, 0))
                    # END handle modification
                else:

                    if ours[0] != base[0] or ours[1] != base[1]:
                        # they deleted it, we changed it, conflict
                        out_append(_tree_entry_to_baseindexentry(base, 1))
                        out_append(_tree_entry_to_baseindexentry(ours, 2))
                    # else:
                    #   we didn't change it, ignore
                    #   pass
                    # END handle our change
                # END handle theirs
            else:
                if theirs is None:
                    # deleted in both, its fine - its out
                    pass
                else:
                    if theirs[0] != base[0] or theirs[1] != base[1]:
                        # deleted in ours, changed theirs, conflict
                        out_append(_tree_entry_to_baseindexentry(base, 1))
                        out_append(_tree_entry_to_baseindexentry(theirs, 3))
                    # END theirs changed
                    # else:
                    #   theirs didnt change
                    #   pass
                # END handle theirs
            # END handle ours
        else:
            # all three can't be None
            if ours is None:
                # added in their branch
                out_append(_tree_entry_to_baseindexentry(theirs, 0))
            elif theirs is None:
                # added in our branch
                out_append(_tree_entry_to_baseindexentry(ours, 0))
            else:
                # both have it, except for the base, see whether it changed
                if ours[0] != theirs[0] or ours[1] != theirs[1]:
                    out_append(_tree_entry_to_baseindexentry(ours, 2))
                    out_append(_tree_entry_to_baseindexentry(theirs, 3))
                else:
                    # it was added the same in both
                    out_append(_tree_entry_to_baseindexentry(ours, 0))
                # END handle two items
            # END handle heads
        # END handle base exists
    # END for each entries tuple

    return out
