#!/usr/bin/env python

# Copyright (c) 2007 Rocco Rutte <pdmef@gmx.net>
# License: GPLv2

"""hg2git.py - A mercurial-to-git filter for git-fast-import(1)
Usage: hg2git.py <hg repo url> <marks file> <heads file> <tip file>
"""

from mercurial import repo,hg,cmdutil,util,ui,revlog,node
from tempfile import mkstemp
from optparse import OptionParser
import re
import sys
import os

# silly regex to catch Signed-off-by lines in log message
sob_re=re.compile('^Signed-[Oo]ff-[Bb]y: (.+)$')
# silly regex to see if user field has email address
user_re=re.compile('([^<]+) (<[^>]+>)$')
# silly regex to clean out user names
user_clean_re=re.compile('^["]([^"]+)["]$')
# git branch for hg's default 'HEAD' branch
cfg_master='master'
# insert 'checkpoint' command after this many commits or none at all if 0
cfg_checkpoint_count=0
# write some progress message every this many file contents written
cfg_export_boundary=1000

def usage(ret):
  sys.stderr.write(__doc__)
  return ret

def setup_repo(url):
  myui=ui.ui()
  return myui,hg.repository(myui,url)

def fixup_user(user,authors):
  if authors!=None:
    # if we have an authors table, try to get mapping
    # by defaulting to the current value of 'user'
    user=authors.get(user,user)
  name,mail,m='','',user_re.match(user)
  if m==None:
    # if we don't have 'Name <mail>' syntax, use 'user
    # <devnull@localhost>' if use contains no at and
    # 'user <user>' otherwise
    name=user
    if '@' not in user:
      mail='<devnull@localhost>'
    else:
      mail='<%s>' % user
  else:
    # if we have 'Name <mail>' syntax, everything is fine :)
    name,mail=m.group(1),m.group(2)

  # remove any silly quoting from username
  m2=user_clean_re.match(name)
  if m2!=None:
    name=m2.group(1)
  return '%s %s' % (name,mail)

def get_branch(name):
  if name=='HEAD':
    name=cfg_master
  return name

def get_changeset(ui,repo,revision,authors):
  node=repo.lookup(revision)
  (manifest,user,(time,timezone),files,desc,extra)=repo.changelog.read(node)
  tz="%+03d%02d" % (-timezone / 3600, ((-timezone % 3600) / 60))
  branch=get_branch(extra.get('branch','master'))
  return (manifest,fixup_user(user,authors),(time,tz),files,desc,branch,extra)

def gitmode(x):
  return x and '100755' or '100644'

def wr(msg=''):
  print msg
  map(lambda x: sys.stderr.write('\t[%s]\n' % x),msg.split('\n'))

def checkpoint(count):
  count=count+1
  if cfg_checkpoint_count>0 and count%cfg_checkpoint_count==0:
    sys.stderr.write("Checkpoint after %d commits\n" % count)
    wr('checkpoint')
    wr()
  return count

def get_parent_mark(parent,marks):
  """Get the mark for some parent.
  If we saw it in the current session, return :%d syntax and
  otherwise the SHA1 from the cache."""
  return marks.get(str(parent+1),':%d' % (parent+1))

def mismatch(f1,f2):
  """See if two revisions of a file are not equal."""
  return node.hex(f1)!=node.hex(f2)

def outer_set(dleft,dright,l,c,r):
  """Loop over our repository and find all changed and missing files."""
  for left in dleft.keys():
    right=dright.get(left,None)
    if right==None:
      # we have the file but our parent hasn't: add to left set
      l.append(left)
    elif mismatch(dleft[left],right):
      # we have it but checksums mismatch: add to center set
      c.append(left)
  for right in dright.keys():
    left=dleft.get(right,None)
    if left==None:
      # if parent has file but we don't: add to right set
      r.append(right)
    # change is already handled when comparing child against parent
  return l,c,r

def get_filechanges(repo,revision,parents,mleft):
  """Given some repository and revision, find all changed/deleted files."""
  l,c,r=[],[],[]
  for p in parents:
    if p<0: continue
    mright=repo.changectx(p).manifest()
    dleft=mleft.keys()
    dleft.sort()
    dright=mright.keys()
    dright.sort()
    l,c,r=outer_set(mleft,mright,l,c,r)
  return l,c,r

def get_author(logmessage,committer,authors):
  """As git distincts between author and committer of a patch, try to
  extract author by detecting Signed-off-by lines.

  This walks from the end of the log message towards the top skipping
  empty lines. Upon the first non-empty line, it walks all Signed-off-by
  lines upwards to find the first one. For that (if found), it extracts
  authorship information the usual way (authors table, cleaning, etc.)

  If no Signed-off-by line is found, this defaults to the committer.

  This may sound stupid (and it somehow is), but in log messages we
  accidentially may have lines in the middle starting with
  "Signed-off-by: foo" and thus matching our detection regex. Prevent
  that."""

  loglines=logmessage.split('\n')
  i=len(loglines)
  # from tail walk to top skipping empty lines
  while i>=0:
    i-=1
    if len(loglines[i].strip())==0: continue
    break
  if i>=0:
    # walk further upwards to find first sob line, store in 'first'
    first=None
    while i>=0:
      m=sob_re.match(loglines[i])
      if m==None: break
      first=m
      i-=1
    # if the last non-empty line matches our Signed-Off-by regex: extract username
    if first!=None:
      r=fixup_user(first.group(1),authors)
      return r
  return committer

def export_file_contents(ctx,manifest,files):
  count=0
  max=len(files)
  for file in files:
    fctx=ctx.filectx(file)
    d=fctx.data()
    wr('M %s inline %s' % (gitmode(manifest.execf(file)),file))
    wr('data %d' % len(d)) # had some trouble with size()
    wr(d)
    count+=1
    if count%cfg_export_boundary==0:
      sys.stderr.write('Exported %d/%d files\n' % (count,max))
  if max>cfg_export_boundary:
    sys.stderr.write('Exported %d/%d files\n' % (count,max))

def export_commit(ui,repo,revision,marks,heads,last,max,count,authors,sob):
  (_,user,(time,timezone),files,desc,branch,_)=get_changeset(ui,repo,revision,authors)
  parents=repo.changelog.parentrevs(revision)

  wr('commit refs/heads/%s' % branch)
  wr('mark :%d' % (revision+1))
  if sob:
    wr('author %s %d %s' % (get_author(desc,user,authors),time,timezone))
  wr('committer %s %d %s' % (user,time,timezone))
  wr('data %d' % (len(desc)+1)) # wtf?
  wr(desc)
  wr()

  src=heads.get(branch,'')
  link=''
  if src!='':
    # if we have a cached head, this is an incremental import: initialize it
    # and kill reference so we won't init it again
    wr('from %s' % src)
    heads[branch]=''
    sys.stderr.write('Initializing branch [%s] to parent [%s]\n' %
        (branch,src))
    link=src # avoid making a merge commit for incremental import
  elif link=='' and not heads.has_key(branch) and revision>0:
    # newly created branch and not the first one: connect to parent
    tmp=get_parent_mark(parents[0],marks)
    wr('from %s' % tmp)
    sys.stderr.write('Link new branch [%s] to parent [%s]\n' %
        (branch,tmp))
    link=tmp # avoid making a merge commit for branch fork

  if parents:
    l=last.get(branch,revision)
    for p in parents:
      # 1) as this commit implicitely is the child of the most recent
      #    commit of this branch, ignore this parent
      # 2) ignore nonexistent parents
      # 3) merge otherwise
      if p==l or p==revision or p<0:
        continue
      tmp=get_parent_mark(p,marks)
      # if we fork off a branch, don't merge with our parent via 'merge'
      # as we have 'from' already above
      if tmp==link:
        continue
      sys.stderr.write('Merging branch [%s] with parent [%s] from [r%d]\n' %
          (branch,tmp,p))
      wr('merge %s' % tmp)

  last[branch]=revision
  heads[branch]=''
  # we need this later to write out tags
  marks[str(revision)]=':%d'%(revision+1)

  ctx=repo.changectx(str(revision))
  man=ctx.manifest()

  if revision==0:
    # first revision: feed in full manifest
    sys.stderr.write('Exporting full revision %d/%d with %d added files\n' %
        (revision,max,len(man.keys())))
    export_file_contents(ctx,man,man.keys())
  else:
    # later revision: feed in changed manifest
    added,changed,removed=get_filechanges(repo,revision,parents,man)
    sys.stderr.write('Exporting delta revision %d/%d with %d/%d/%d added/changed/removed files\n' %
        (revision,max,len(added),len(changed),len(removed)))
    export_file_contents(ctx,man,added+changed)
    for r in removed:
      wr('D %s' % r)

  wr()
  return checkpoint(count)

def export_tags(ui,repo,marks_cache,start,end,count,authors):
  l=repo.tagslist()
  for tag,node in l:
    # ignore latest revision
    if tag=='tip': continue
    rev=repo.changelog.rev(node)
    # ignore those tags not in our import range
    if rev<start or rev>=end: continue

    ref=marks_cache.get(str(rev),None)
    if ref==None:
      sys.stderr.write('Failed to find reference for creating tag'
          ' %s at r%d\n' % (tag,rev))
      continue
    (_,user,(time,timezone),_,desc,branch,_)=get_changeset(ui,repo,rev,authors)
    sys.stderr.write('Exporting tag [%s] at [hg r%d] [git %s]\n' % (tag,rev,ref))
    wr('tag %s' % tag)
    wr('from %s' % ref)
    wr('tagger %s %d %s' % (user,time,timezone))
    msg='hg2git created tag %s for hg revision %d on branch %s on (summary):\n\t%s' % (tag,
        rev,branch,desc.split('\n')[0])
    wr('data %d' % (len(msg)+1))
    wr(msg)
    wr()
    count=checkpoint(count)
  return count

def load_authors(filename):
  cache={}
  if not os.path.exists(filename):
    return cache
  f=open(filename,'r')
  l=0
  lre=re.compile('^([^=]+)[ ]*=[ ]*(.+)$')
  for line in f.readlines():
    l+=1
    m=lre.match(line)
    if m==None:
      sys.stderr.write('Invalid file format in [%s], line %d\n' % (filename,l))
      continue
    # put key:value in cache, key without ^:
    cache[m.group(1).strip()]=m.group(2).strip()
  f.close()
  sys.stderr.write('Loaded %d authors\n' % l)
  return cache

def load_cache(filename):
  cache={}
  if not os.path.exists(filename):
    return cache
  f=open(filename,'r')
  l=0
  for line in f.readlines():
    l+=1
    fields=line.split(' ')
    if fields==None or not len(fields)==2 or fields[0][0]!=':':
      sys.stderr.write('Invalid file format in [%s], line %d\n' % (filename,l))
      continue
    # put key:value in cache, key without ^:
    cache[fields[0][1:]]=fields[1].split('\n')[0]
  f.close()
  return cache

def save_cache(filename,cache):
  f=open(filename,'w+')
  map(lambda x: f.write(':%s %s\n' % (str(x),str(cache.get(x)))),cache.keys())
  f.close()

def verify_heads(ui,repo,cache):
  def getsha1(branch):
    try:
      f=open(os.getenv('GIT_DIR','/dev/null')+'/refs/heads/'+branch)
      sha1=f.readlines()[0].split('\n')[0]
      f.close()
      return sha1
    except IOError:
      return None

  # get list of hg's branches to verify, don't take all git has
  branches=repo.branchtags()
  l=[(-repo.changelog.rev(n), n, t) for t, n in branches.items()]
  l.sort()

  for _,_,b in l:
    b=get_branch(b)
    sys.stderr.write('Verifying branch [%s]\n' % b)
    sha1=getsha1(b)
    c=cache.get(b)
    if sha1!=c:
      sys.stderr.write('Warning: Branch [%s] modified outside hg2git:'
        '\n%s (repo) != %s (cache)\n' % (b,sha1,c))
  return True

def hg2git(repourl,m,marksfile,headsfile,tipfile,authors={},sob=False):
  _max=int(m)

  marks_cache=load_cache(marksfile)
  heads_cache=load_cache(headsfile)
  state_cache=load_cache(tipfile)

  ui,repo=setup_repo(repourl)

  if not verify_heads(ui,repo,heads_cache):
    return 1

  tip=repo.changelog.count()

  min=int(state_cache.get('tip',0))
  max=_max
  if _max<0:
    max=tip

  c=0
  last={}
  for rev in range(min,max):
    c=export_commit(ui,repo,rev,marks_cache,heads_cache,last,max,c,authors,sob)

  c=export_tags(ui,repo,marks_cache,min,max,c,authors)

  sys.stderr.write('Issued %d commands\n' % c)

  state_cache['tip']=max
  state_cache['repo']=repourl
  save_cache(tipfile,state_cache)

  return 0

if __name__=='__main__':
  def bail(parser,opt):
    sys.stderr.write('Error: No %s option given\n' % opt)
    parser.print_help()
    sys.exit(2)

  parser=OptionParser()

  parser.add_option("-m","--max",type="int",dest="max",
      help="Maximum hg revision to import")
  parser.add_option("--marks",dest="marksfile",
      help="File to read git-fast-import's marks from")
  parser.add_option("--heads",dest="headsfile",
      help="File to read last run's git heads from")
  parser.add_option("--status",dest="statusfile",
      help="File to read status from")
  parser.add_option("-r","--repo",dest="repourl",
      help="URL of repo to import")
  parser.add_option("-s",action="store_true",dest="sob",
      default=False,help="Enable parsing Signed-off-by lines")
  parser.add_option("-A","--authors",dest="authorfile",
      help="Read authormap from AUTHORFILE")

  (options,args)=parser.parse_args()

  m=-1
  if options.max!=None: m=options.max

  if options.marksfile==None: bail(parser,'--marks')
  if options.marksfile==None: bail(parser,'--heads')
  if options.marksfile==None: bail(parser,'--status')
  if options.marksfile==None: bail(parser,'--repo')

  a={}
  if options.authorfile!=None:
    a=load_authors(options.authorfile)

  sys.exit(hg2git(options.repourl,m,options.marksfile,options.headsfile,
    options.statusfile,authors=a,sob=options.sob))