#!/usr/bin/env python

#

# This is a generalized framework for converting between SCM

# repository formats.

#

# In its current form, it's hardcoded to convert incrementally between

# git and Mercurial.

#

# To use, you must first import the first git version into Mercurial,

# and establish a mapping between the git commit hash and the hash in

# Mercurial for that version. This mapping is kept in a simple text

# file with lines like so:

#

# <git hash> <mercurial hash>

#

# To convert the rest of the repo, run:

#

# convert-repo <git-dir> <hg-dir> <mapfile>

#

# This updates the mapfile on each commit copied, so it can be

# interrupted and can be run repeatedly to copy new commits.

import sys, os, zlib, sha

from mercurial import hg, ui, util

class convert_git:

    def __init__(self, path):

        self.path = path

    def getheads(self):

        h = file(self.path + "/.git/HEAD").read()[:-1]

        return [h]

    def getfile(self, name, rev):

        a = file(self.path + ("/.git/objects/%s/%s"

                              % (rev[:2], rev[2:]))).read()

        b = zlib.decompress(a)

        if sha.sha(b).hexdigest() != rev: raise "bad hash"

        head, text = b.split('\0', 1)

        return text

    def getchanges(self, version):

        path = os.getcwd()

        os.chdir(self.path)

        fh = os.popen("git-diff-tree -m -r %s" % (version))

        os.chdir(path)

        changes = []

        for l in fh:

            if "\t" not in l: continue

            m, f = l[:-1].split("\t")

            m = m.split()

            h = m[3]

            p = (m[1] == "100755")

            changes.append((f, h, p))

        return changes

    def getcommit(self, version):

        c = self.getfile("", version) # read the commit hash

        end = c.find("\n\n")

        message = c[end+2:]

        l = c[:end].splitlines()

        manifest = l[0].split()[1]

        parents = []

        for e in l[1:]:

            n,v = e.split(" ", 1)

            if n == "author":

                p = v.split()

                date = " ".join(p[-2:])

                author = " ".join(p[:-2])

                if author[0] == "<": author = author[1:-1]

            if n == "committer": 

                p = v.split()

                date = " ".join(p[-2:])

                committer = " ".join(p[:-2])

                if committer[0] == "<": committer = committer[1:-1]

                message += "\ncommitter: %s %s\n" % (committer, date)

            if n == "parent": parents.append(v)

        return (parents, author, date, message)

class convert_mercurial:

    def __init__(self, path):

        self.path = path

        u = ui.ui()

        self.repo = hg.repository(u, path)

    def getheads(self):

        h = self.repo.changelog.heads()

        h = [ hg.hex(x) for x in h ]

        return h

    def putfile(self, f, e, data):

        self.repo.wfile(f, "w").write(data)

        util.set_exec(self.repo.wjoin(f), e)

    def delfile(self, f):

        try:

            os.unlink(self.repo.wjoin(f))

            self.repo.remove([f])

        except:

            pass

    def putcommit(self, files, parents, author, dest, text):

        if not parents: parents = ["0" * 40]

        if len(parents) < 2: parents.append("0" * 40)

        seen = {}

        pl = []

        for p in parents:

            if p not in seen:

                pl.append(p)

                seen[p] = 1

        parents = pl

        p2 = parents.pop(0)

        c = self.repo.changelog.count()

        while parents:

            p1 = p2

            p2 = parents.pop(0)

            self.repo.rawcommit(files, text, author, dest, 

                                hg.bin(p1), hg.bin(p2))

            text = "(octopus merge fixup)\n"

        return hg.hex(self.repo.changelog.node(c))

class convert:

    def __init__(self, source, dest, mapfile):

        self.source = source

        self.dest = dest

        self.mapfile = mapfile

        self.commitcache = {}

        self.map = {}

        for l in file(self.mapfile):

            sv, dv = l[:-1].split()

            self.map[sv] = dv

    def walktree(self, heads):

        visit = heads

        known = {}

        parents = {}

        while visit:

            n = visit.pop(0)

            if n in known or n in self.map: continue

            known[n] = 1

            self.commitcache[n] = self.source.getcommit(n)

            cp = self.commitcache[n][0]

            for p in cp:

                parents.setdefault(n, []).append(p)

                visit.append(p)

        return parents

    def toposort(self, parents):

        visit = parents.keys()

        seen = {}

        children = {}

        while visit:

            n = visit.pop(0)

            if n in seen: continue

            seen[n] = 1

            pc = 0

            if n in parents:

                for p in parents[n]:

                    if p not in self.map: pc += 1

                    visit.append(p)

                    children.setdefault(p, []).append(n)

            if not pc: root = n

        s = []

        removed = {}

        visit = parents.keys()

        while visit:

            n = visit.pop(0)

            if n in removed: continue

            dep = 0

            if n in parents:

                for p in parents[n]:

                    if p in self.map: continue

                    if p not in removed:

                        # we're still dependent

                        visit.append(n)

                        dep = 1

                        break

            if not dep:

                # all n's parents are in the list

                removed[n] = 1

                s.append(n)

                if n in children:

                    for c in children[n]:

                        visit.insert(0, c)

        return s

    def copy(self, rev):

        p, a, d, t = self.commitcache[rev]

        files = self.source.getchanges(rev)

        for f,v,e in files:

            try:

                data = self.source.getfile(f, v)

            except IOError, inst:

                self.dest.delfile(f)

            else:

                self.dest.putfile(f, e, data)

        r = [self.map[v] for v in p]

        f = [f for f,v,e in files]

        self.map[rev] = self.dest.putcommit(f, r, a, d, t)

        file(self.mapfile, "a").write("%s %s\n" % (rev, self.map[rev]))

    def convert(self):

        heads = self.source.getheads()

        parents = self.walktree(heads)

        t = self.toposort(parents)

        num = len(t)

        for c in t:

            num -= 1

            if c in self.map: continue

            desc = self.commitcache[c][3].splitlines()[0]

            print num, desc

            self.copy(c)

gitpath, hgpath, mapfile = sys.argv[1:]

c = convert(convert_git(gitpath), convert_mercurial(hgpath), mapfile)

c.convert()