# -*- coding: iso-8859-1 -*-
#
# Copyright (C) 2006,2008 Herbert Valerio Riedel <hvr@gnu.org>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

from __future__ import with_statement

import os, re, sys, time, weakref
from collections import deque
from functools import partial
from threading import Lock
from subprocess import Popen, PIPE
import cStringIO
import string

__all__ = ["git_version", "GitError", "GitErrorSha", "Storage", "StorageFactory"]

class GitError(Exception):
    pass

class GitErrorSha(GitError):
    pass

class GitCore:
    def __init__(self, git_dir=None, git_bin="git"):
        self.__git_bin = git_bin
        self.__git_dir = git_dir

    def __build_git_cmd(self, gitcmd, *args):
        "construct command tuple for git call suitable for Popen()"

        cmd = [self.__git_bin]
        if self.__git_dir:
            cmd.append('--git-dir=%s' % self.__git_dir)
        cmd.append(gitcmd)
        cmd.extend(args)

        return cmd

    def __execute(self, git_cmd, *cmd_args):
        "execute git command and return file-like object of stdout"

        #print >>sys.stderr, "DEBUG:", git_cmd, cmd_args

        if sys.platform == "win32":
            p = Popen(self.__build_git_cmd(git_cmd, *cmd_args),
                      stdin=None, stdout=PIPE, stderr=PIPE)
        else:
            p = Popen(self.__build_git_cmd(git_cmd, *cmd_args),
                      stdin=None, stdout=PIPE, stderr=PIPE, close_fds=True)

        stdout_data, stderr_data = p.communicate()
        #TODO, do something with p.returncode, e.g. raise exception

        return stdout_data

    def __getattr__(self, name):
        return partial(self.__execute, name.replace('_','-'))

    __is_sha_pat = re.compile(r'[0-9A-Fa-f]*$')

    @classmethod
    def is_sha(cls,sha):
        """returns whether sha is a potential sha id
        (i.e. proper hexstring between 4 and 40 characters"""
        if not (4 <= len(sha) <= 40):
            return False

        return bool(cls.__is_sha_pat.match(sha))

# helper class for caching...
class SizedDict(dict):
    def __init__(self, max_size=0):
        dict.__init__(self)
        self.__max_size = max_size
        self.__key_fifo = deque()
        self.__lock = Lock()

    def __setitem__(self, name, value):
        with self.__lock:
            assert len(self) == len(self.__key_fifo) # invariant

            if not self.__contains__(name):
                self.__key_fifo.append(name)

            rc = dict.__setitem__(self, name, value)

            while len(self.__key_fifo) > self.__max_size:
                self.__delitem__(self.__key_fifo.popleft())

            assert len(self) == len(self.__key_fifo) # invariant

            return rc

    def setdefault(k,d=None):
        # TODO
        raise AttributeError("SizedDict has no setdefault() method")

class StorageFactory:
    __dict = weakref.WeakValueDictionary()
    __dict_nonweak = dict()
    __dict_lock = Lock()

    def __init__(self, repo, log, weak=True, git_bin='git'):
        self.logger = log

        with StorageFactory.__dict_lock:
            try:
                i = StorageFactory.__dict[repo]
            except KeyError:
                i = Storage(repo, log, git_bin)
                StorageFactory.__dict[repo] = i

                # create or remove additional reference depending on 'weak' argument
                if weak:
                    try:
                        del StorageFactory.__dict_nonweak[repo]
                    except KeyError:
                        pass
                else:
                    StorageFactory.__dict_nonweak[repo] = i

        self.__inst = i
        self.__repo = repo

    def getInstance(self):
        is_weak = self.__repo not in StorageFactory.__dict_nonweak
        self.logger.debug("requested %sPyGIT.Storage instance %d for '%s'"
                          % (("","weak ")[is_weak], id(self.__inst), self.__repo))
        return self.__inst

class Storage:
    __SREV_MIN = 4 # minimum short-rev length

    @staticmethod
    def __rev_key(rev):
        assert len(rev) >= 4
        #assert GitCore.is_sha(rev)
        srev_key = int(rev[:4], 16)
        assert srev_key >= 0 and srev_key <= 0xffff
        return srev_key

    @staticmethod
    def git_version(git_bin="git"):
        GIT_VERSION_MIN_REQUIRED = (1,5,6)
        try:
            g = GitCore(git_bin=git_bin)
            [v] = g.version().splitlines()
            _,_,version = v.strip().split()
            # 'version' has usually at least 3 numeric version components, e.g.::
            #  1.5.4.2
            #  1.5.4.3.230.g2db511
            #  1.5.4.GIT

            def try_int(s):
                try:
                    return int(s)
                except ValueError:
                    return s

            split_version = tuple(map(try_int, version.split('.')))

            result = {}
            result['v_str'] = version
            result['v_tuple'] = split_version
            result['v_min_tuple'] = GIT_VERSION_MIN_REQUIRED
            result['v_min_str'] = ".".join(map(str, GIT_VERSION_MIN_REQUIRED))
            result['v_compatible'] = split_version >= GIT_VERSION_MIN_REQUIRED
            return result
        except:
            raise GitError("Could not retrieve GIT version")

    def __init__(self, git_dir, log, git_bin='git'):
        self.logger = log

        # simple sanity checking
        __git_file_path = partial(os.path.join, git_dir)
        if not all(map(os.path.exists,
                       map(__git_file_path,
                           ['HEAD','objects','refs']))):
            self.logger.error("GIT control files missing in '%s'" % git_dir)
            if os.path.exists(__git_file_path('.git')):
                self.logger.error("entry '.git' found in '%s'"
                                  " -- maybe use that folder instead..." % git_dir)
            raise GitError("GIT control files not found, maybe wrong directory?")

        self.logger.debug("PyGIT.Storage instance %d constructed" % id(self))

        self.repo = GitCore(git_dir, git_bin=git_bin)

        self.commit_encoding = None

        # caches
        self.__rev_cache = None
        self.__rev_cache_lock = Lock()

        # cache the last 200 commit messages
        self.__commit_msg_cache = SizedDict(200)
        self.__commit_msg_lock = Lock()



    def __del__(self):
        self.logger.debug("PyGIT.Storage instance %d destructed" % id(self))

    #
    # cache handling
    #

    # called by Storage.sync()
    def __rev_cache_sync(self, youngest_rev=None):
        "invalidates revision db cache if necessary"
        with self.__rev_cache_lock:
            need_update = False
            if self.__rev_cache:
                last_youngest_rev = self.__rev_cache[0]
                if last_youngest_rev != youngest_rev:
                    self.logger.debug("invalidated caches (%s != %s)" % (last_youngest_rev, youngest_rev))
                    need_update = True
            else:
                need_update = True # almost NOOP

            if need_update:
                self.__rev_cache = None

            return need_update

    def get_rev_cache(self):
        with self.__rev_cache_lock:
            if self.__rev_cache is None: # can be cleared by Storage.__rev_cache_sync()
                self.logger.debug("triggered rebuild of commit tree db for %d" % id(self))
                new_db = {}
                new_sdb = {}
                new_tags = set([])
                youngest = None
                oldest = None
                for revs in self.repo.rev_parse("--tags").splitlines():
                    new_tags.add(revs.strip())

                # helper for reusing strings
                __rev_seen = {}
                def __rev_reuse(rev):
                    rev = str(rev)
                    return __rev_seen.setdefault(rev, rev)

                rev = ord_rev = 0
                for revs in self.repo.rev_list("--parents", "--all").splitlines():
                    revs = revs.strip().split()

                    revs = map(__rev_reuse, revs)

                    rev = revs[0]

                    # shortrev "hash" map
                    srev_key = self.__rev_key(rev)
                    new_sdb.setdefault(srev_key, []).append(rev)

                    parents = tuple(revs[1:])

                    ord_rev += 1

                    # first rev seen is assumed to be the youngest one (and has ord_rev=1)
                    if not youngest:
                        youngest = rev

                    # new_db[rev] = (children(rev), parents(rev), ordinal_id(rev))
                    if new_db.has_key(rev):
                        _children,_parents,_ord_rev = new_db[rev]
                        assert _children
                        assert not _parents
                        assert _ord_rev == 0
                    else:
                        _children = []

                    # create/update entry
                    new_db[rev] = _children, parents, ord_rev

                    # update all parents(rev)'s children
                    for parent in parents:
                        # by default, a dummy ordinal_id is used for the mean-time
                        _children, _parents, _ord_rev = new_db.setdefault(parent, ([], [], 0))
                        if rev not in _children:
                            _children.append(rev)

                # last rev seen is assumed to be the oldest one (with highest ord_rev)
                oldest = rev

                __rev_seen = None

                assert len(new_db) == ord_rev

                # convert children lists to tuples
                tmp = {}
                try:
                    while True:
                        k,v = new_db.popitem()
                        assert v[2] > 0
                        tmp[k] = tuple(v[0]),v[1],v[2]
                except KeyError:
                    pass

                assert len(new_db) == 0
                new_db = tmp

                # convert sdb either to dict or array depending on size
                tmp = [()]*(max(new_sdb.keys())+1) if len(new_sdb) > 5000 else {}

                try:
                    while True:
                        k,v = new_sdb.popitem()
                        tmp[k] = tuple(v)
                except KeyError:
                    pass

                assert len(new_sdb) == 0
                new_sdb = tmp

                # atomically update self.__rev_cache
                self.__rev_cache = youngest, oldest, new_db, new_tags, new_sdb
                self.logger.debug("rebuilt commit tree db for %d with %d entries" % (id(self),len(new_db)))

            assert all(e is not None for e in self.__rev_cache) or not any(self.__rev_cache)

            return self.__rev_cache
        # with self.__rev_cache_lock

    # tuple: youngest_rev, oldest_rev, rev_dict, tag_dict, short_rev_dict
    rev_cache = property(get_rev_cache)

    def get_commits(self):
        return self.rev_cache[2]

    def oldest_rev(self):
        return self.rev_cache[1]

    def youngest_rev(self):
        return self.rev_cache[0]

    def history_relative_rev(self, sha, rel_pos):
        db = self.get_commits()

        if sha not in db:
            raise GitErrorSha

        if rel_pos == 0:
            return sha

        lin_rev = db[sha][2] + rel_pos

        if lin_rev < 1 or lin_rev > len(db):
            return None

        for k,v in db.iteritems():
            if v[2] == lin_rev:
                return k

        # should never be reached if db is consistent
        raise GitError("internal inconsistency detected")

    def hist_next_revision(self, sha):
        return self.history_relative_rev(sha, -1)

    def hist_prev_revision(self, sha):
        return self.history_relative_rev(sha, +1)

    def get_commit_encoding(self):
        if self.commit_encoding is None:
            self.commit_encoding = \
                self.repo.repo_config("--get", "i18n.commitEncoding").strip() or 'utf-8'

        return self.commit_encoding

    def head(self):
        "get current HEAD commit id"
        return self.verifyrev("HEAD")

    def verifyrev(self, rev):
        "verify/lookup given revision object and return a sha id or None if lookup failed"
        rev = str(rev)

        db, tag_db = self.rev_cache[2:4]

        if GitCore.is_sha(rev):
            # maybe it's a short or full rev
            fullrev = self.fullrev(rev)
            if fullrev:
                return fullrev

        # fall back to external git calls
        rc = self.repo.rev_parse("--verify", rev).strip()
        if not rc:
            return None

        if db.has_key(rc):
            return rc

        if rc in tag_db:
            sha=self.repo.cat_file("tag", rc).split(None, 2)[:2]
            if sha[0] != 'object':
                self.logger.debug("unexpected result from 'git-cat-file tag %s'" % rc)
                return None
            return sha[1]

        return None

    def shortrev(self, rev, min_len=7):
        "try to shorten sha id"
        #try to emulate the following:
        #return self.repo.rev_parse("--short", str(rev)).strip()
        rev = str(rev)

        if min_len < self.__SREV_MIN:
            min_len = self.__SREV_MIN

        db, tag_db, sdb = self.rev_cache[2:5]

        if rev not in db:
            return None

        srev = rev[:min_len]
        srevs = set(sdb[self.__rev_key(rev)])

        if len(srevs) == 1:
            return srev # we already got a unique id

        # find a shortened id for which rev doesn't conflict with
        # the other ones from srevs
        crevs = srevs - set([rev])

        for l in range(min_len+1, 40):
            srev = rev[:l]
            if srev not in [ r[:l] for r in crevs ]:
                return srev

        return rev # worst-case, all except the last character match

    def fullrev(self, srev):
        "try to reverse shortrev()"
        srev = str(srev)
        db, tag_db, sdb = self.rev_cache[2:5]

        # short-cut
        if len(srev) == 40 and srev in db:
            return srev

        if not GitCore.is_sha(srev):
            return None

        try:
            srevs = sdb[self.__rev_key(srev)]
        except KeyError:
            return None

        srevs = filter(lambda s: s.startswith(srev), srevs)
        if len(srevs) == 1:
            return srevs[0]

        return None

    def get_branches(self):
        "returns list of (local) branches, with active (= HEAD) one being the first item"
        result=[]
        for e in self.repo.branch("-v", "--no-abbrev").splitlines():
            (bname,bsha)=e[1:].strip().split()[:2]
            if e.startswith('*'):
                result.insert(0,(bname,bsha))
            else:
                result.append((bname,bsha))
        return result

    def get_tags(self):
        return [e.strip() for e in self.repo.tag("-l").splitlines()]

    def ls_tree(self, rev, path=""):
        rev = rev and str(rev) or 'HEAD' # paranoia
        if path.startswith('/'):
            path = path[1:]

        tree = self.repo.ls_tree("-z", "-l", rev, "--", path).split('\0')

        def split_ls_tree_line(l):
            "split according to '<mode> <type> <sha> <size>\t<fname>'"
            meta,fname = l.split('\t')
            _mode,_type,_sha,_size = meta.split()

            if _size == '-':
                _size = None
            else:
                _size = int(_size)

            return _mode,_type,_sha,_size,fname

        return [ split_ls_tree_line(e) for e in tree if e ]

    def read_commit(self, commit_id):
        if not commit_id:
            raise GitError("read_commit called with empty commit_id")

        commit_id, commit_id_orig = self.fullrev(commit_id), commit_id

        db = self.get_commits()
        if commit_id not in db:
            self.logger.info("read_commit failed for '%s' ('%s')" %
                             (commit_id, commit_id_orig))
            raise GitErrorSha

        with self.__commit_msg_lock:
            if self.__commit_msg_cache.has_key(commit_id):
                # cache hit
                result = self.__commit_msg_cache[commit_id]
                return result[0], dict(result[1])

            # cache miss
            raw = self.repo.cat_file("commit", commit_id)
            raw = unicode(raw, self.get_commit_encoding(), 'replace')
            lines = raw.splitlines()

            if not lines:
                raise GitErrorSha

            line = lines.pop(0)
            props = {}
            while line:
                (key,value) = line.split(None, 1)
                props.setdefault(key,[]).append(value.strip())
                line = lines.pop(0)

            result = ("\n".join(lines), props)

            self.__commit_msg_cache[commit_id] = result

            return result[0], dict(result[1])

    def get_file(self, sha):
        return cStringIO.StringIO(self.repo.cat_file("blob", str(sha)))

    def get_obj_size(self, sha):
        sha = str(sha)

        try:
            obj_size = int(self.repo.cat_file("-s", sha).strip())
        except ValueError:
            raise GitErrorSha("object '%s' not found" % sha)

        return obj_size

    def children(self, sha):
        db = self.get_commits()

        try:
            return list(db[sha][0])
        except KeyError:
            return []

    def children_recursive(self, sha):
        db = self.get_commits()

        work_list = deque()
        seen = set()

        seen.update(db[sha][0])
        work_list.extend(db[sha][0])

        while work_list:
            p = work_list.popleft()
            yield p

            _children = set(db[p][0]) - seen

            seen.update(_children)
            work_list.extend(_children)

        assert len(work_list) == 0

    def parents(self, sha):
        db = self.get_commits()

        try:
            return list(db[sha][1])
        except KeyError:
            return []

    def all_revs(self):
        return self.get_commits().iterkeys()

    def sync(self):
        rev = self.repo.rev_list("--max-count=1", "--all").strip()
        return self.__rev_cache_sync(rev)

    def last_change(self, sha, path):
        return self.repo.rev_list("--max-count=1",
                                  sha, "--", path).strip() or None

    def history(self, sha, path, limit=None):
        if limit is None:
            limit = -1

        tmp = self.repo.rev_list("--max-count=%d" % limit, str(sha), "--", path)
        return [ rev.strip() for rev in tmp.splitlines() ]

    def history_timerange(self, start, stop):
        return [ rev.strip() for rev in \
                     self.repo.rev_list("--reverse",
                                        "--max-age=%d" % start,
                                        "--min-age=%d" % stop,
                                        "--all").splitlines() ]

    def rev_is_anchestor_of(self, rev1, rev2):
        """return True if rev2 is successor of rev1"""
        rev1 = rev1.strip()
        rev2 = rev2.strip()
        return rev2 in self.children_recursive(rev1)

    def blame(self, commit_sha, path):
        in_metadata = False

        for line in self.repo.blame("-p", "--", path, str(commit_sha)).splitlines():
            assert line
            if in_metadata:
                in_metadata = not line.startswith('\t')
            else:
                split_line = line.split()
                if len(split_line) == 4:
                    (sha, orig_lineno, lineno, group_size) = split_line
                else:
                    (sha, orig_lineno, lineno) = split_line

                assert len(sha) == 40
                yield (sha, lineno)
                in_metadata = True

        assert not in_metadata

    def diff_tree(self, tree1, tree2, path="", find_renames=False):
        """calls `git diff-tree` and returns tuples of the kind
        (mode1,mode2,obj1,obj2,action,path1,path2)"""

        # diff-tree returns records with the following structure:
        # :<old-mode> <new-mode> <old-sha> <new-sha> <change> NUL <old-path> NUL [ <new-path> NUL ]

        path = path.strip("/")
        diff_tree_args = ["-z", "-r"]
        if find_renames:
            diff_tree_args.append("-M")
        diff_tree_args.extend([str(tree1) if tree1 else "--root",
                               str(tree2),
                               "--", path])

        lines = self.repo.diff_tree(*diff_tree_args).split('\0')

        assert lines[-1] == ""
        del lines[-1]

        if tree1 is None and lines:
            # if only one tree-sha is given on commandline,
            # the first line is just the redundant tree-sha itself...
            assert not lines[0].startswith(':')
            del lines[0]

        chg = None

        def __chg_tuple():
            if len(chg) == 6:
                chg.append(None)
            assert len(chg) == 7
            return tuple(chg)

        for line in lines:
            if line.startswith(':'):
                if chg:
                    yield __chg_tuple()

                chg = line[1:].split()
                assert len(chg) == 5
            else:
                chg.append(line)

        if chg:
            yield __chg_tuple()

############################################################################
############################################################################
############################################################################

if __name__ == '__main__':
    import sys, logging, timeit

    assert not GitCore.is_sha("123")
    assert GitCore.is_sha("1a3f")
    assert GitCore.is_sha("f"*40)
    assert not GitCore.is_sha("x"+"f"*39)
    assert not GitCore.is_sha("f"*41)

    print "git version [%s]" % str(Storage.git_version())

    # custom linux hack reading `/proc/<PID>/statm`
    if sys.platform == "linux2":
        __pagesize = os.sysconf('SC_PAGESIZE')

        def proc_statm(pid = os.getpid()):
            __proc_statm = '/proc/%d/statm' % pid
            try:
                t = open(__proc_statm)
                result = t.read().split()
                t.close()
                assert len(result) == 7
                return tuple([ __pagesize*int(p) for p in result ])
            except:
                raise RuntimeError("failed to get memory stats")

    else: # not linux2
        print "WARNING - meminfo.proc_statm() not available"
        def proc_statm():
            return (0,)*7

    print "statm =", proc_statm()
    __data_size = proc_statm()[5]
    __data_size_last = __data_size

    def print_data_usage():
        global __data_size_last
        __tmp = proc_statm()[5]
        print "DATA: %6d %+6d" % (__tmp - __data_size, __tmp - __data_size_last)
        __data_size_last = __tmp

    print_data_usage()

    g = Storage(sys.argv[1], logging)

    print_data_usage()

    print "[%s]" % g.head()
    print g.ls_tree(g.head())
    print "--------------"
    print_data_usage()
    print g.read_commit(g.head())
    print "--------------"
    print_data_usage()
    p = g.parents(g.head())
    print list(p)
    print "--------------"
    print list(g.children(list(p)[0]))
    print list(g.children(list(p)[0]))
    print "--------------"
    print g.get_commit_encoding()
    print "--------------"
    print g.get_branches()
    print "--------------"
    print g.hist_prev_revision(g.oldest_rev()), g.oldest_rev(), g.hist_next_revision(g.oldest_rev())
    print_data_usage()
    print "--------------"
    p = g.youngest_rev()
    print g.hist_prev_revision(p), p, g.hist_next_revision(p)
    print "--------------"

    p = g.head()
    for i in range(-5,5):
        print i, g.history_relative_rev(p, i)

    # check for loops
    def check4loops(head):
        print "check4loops", head
        seen = set([head])
        for sha in g.children_recursive(head):
            if sha in seen:
                print "dupe detected :-/", sha, len(seen)
            seen.add(sha)
        return seen

    print len(check4loops(g.parents(g.head())[0]))

    #p = g.head()
    #revs = [ g.history_relative_rev(p, i) for i in range(0,10) ]
    print_data_usage()
    revs = g.get_commits().keys()
    print_data_usage()

    def shortrev_test():
        for i in revs:
            i = str(i)
            s = g.shortrev(i, min_len=4)
            assert i.startswith(s)
            assert g.fullrev(s) == i

    iters = 1
    print "timing %d*shortrev_test()..." % len(revs)
    t = timeit.Timer("shortrev_test()", "from __main__ import shortrev_test")
    print "%.2f usec/rev" % (1000000 * t.timeit(number=iters)/len(revs))

    #print len(check4loops(g.oldest_rev()))
    #print len(list(g.children_recursive(g.oldest_rev())))

    print_data_usage()

    # perform typical trac operations:

    if 1:
        print "--------------"
        rev = g.head()
        for mode,type,sha,_size,name in g.ls_tree(rev):
            [last_rev] = g.history(rev, name, limit=1)
            s = g.get_obj_size(sha) if type == "blob" else 0
            msg = g.read_commit(last_rev)

            print "%s %s %10d [%s]" % (type, last_rev, s, name)

    print "allocating 2nd instance"
    print_data_usage()
    g2 = Storage(sys.argv[1], logging)
    g2.head()
    print_data_usage()
    print "allocating 3rd instance"
    g3 = Storage(sys.argv[1], logging)
    g3.head()
    print_data_usage()