#!/usr/bin/python
#
# Automatic patch dependency checker and Makefile/README.md generator.
#
# Copyright (C) 2014 Sebastian Lackner
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
#

from multiprocessing import Pool
from xml.dom import minidom
import contextlib
import hashlib
import itertools
import os
import patchutils
import pickle
import re
import subprocess
import sys
import textwrap
import urllib

# Cached information to speed up patch dependency checks
latest_wine_commit  = None
cached_patch_result = {}
cached_original_src = {}

class PatchUpdaterError(RuntimeError):
    """Failed to update patches."""
    pass

class AuthorInfo(object):
    def __init__(self):
        self.author         = ""
        self.subject        = ""
        self.revision       = ""

class PatchSet(object):
    def __init__(self, name):
        self.name           = name
        self.authors        = []
        self.fixes          = []
        self.changes        = []

        self.files          = []
        self.patches        = []
        self.modified_files = set()
        self.depends        = set()

        self.verify_depends = set()
        self.verify_time    = None

def _pairs(a):
    """Iterate over all pairs of elements contained in the list a."""
    for i, j in enumerate(a):
        for k in a[i+1:]:
            yield (j, k)

def _load_dict(filename):
    """Load a Python dictionary object from a file."""
    try:
        with open(filename) as fp:
            return pickle.load(fp)
    except IOError:
        return {}

def _save_dict(filename, value):
    """Save a Python dictionary object to a file."""
    with open(filename, "wb") as fp:
        pickle.dump(value, fp, pickle.HIGHEST_PROTOCOL)

def _download(url):
    """Open a specific URL and return the content."""
    with contextlib.closing(urllib.urlopen(url)) as fp:
        return fp.read()

def read_patchsets(directory):
    """Read information about all patchsets in a given directory."""

    def _iter_kv_from_file(filename):
        """Iterate through all key/value pairs in a file."""
        with open(filename) as fp:
            for line in fp:
                if line.startswith("#"):
                    continue
                tmp = line.split(":", 1)
                if len(tmp) != 2:
                    yield None, None
                else:
                    yield tmp[0].lower(), tmp[1].strip()

    unique_id   = itertools.count()
    all_patches = {}
    name_to_id  = {}
    all_bugs    = []

    # Read in sorted order (to ensure created Makefile doesn't change too much)
    for name in sorted(os.listdir(directory)):
        if name in [".", ".."]: continue
        subdirectory = os.path.join(directory, name)
        if not os.path.isdir(subdirectory): continue

        patch = PatchSet(name)

        # Enumerate .patch files in the given directory, enumerate individual patches and affected files
        for f in sorted(os.listdir(subdirectory)):
            if not f.endswith(".patch") or not os.path.isfile(os.path.join(subdirectory, f)):
                continue
            patch.files.append(f)
            for p in patchutils.read_patch(os.path.join(subdirectory, f)):
                patch.patches.append(p)
                patch.modified_files.add(p.modified_file)

        # No single patch within this directory, ignore it
        if len(patch.patches) == 0:
            del patch
            continue

        i = next(unique_id)
        all_patches[i]   = patch
        name_to_id[name] = i

    # Now read the definition files in a second step
    for i, patch in all_patches.iteritems():
        deffile = os.path.join(os.path.join(directory, patch.name), "definition")

        if not os.path.isfile(deffile):
            raise PatchUpdaterError("Missing definition file %s" % deffile)

        info = AuthorInfo()

        for key, val in _iter_kv_from_file(deffile):
            if key is None:
                if len(info.author) and len(info.subject) and len(info.revision):
                    patch.authors.append(info)
                    info = AuthorInfo()
                continue

            if key == "author":
                if len(info.author): info.author += ", "
                info.author += val

            elif key == "subject" or key == "title":
                if len(info.subject): info.subject += " "
                info.subject += val

            elif key == "revision":
                if len(info.revision): info.revision += ", "
                info.revision += val

            elif key == "fixes":
                r = re.match("^[0-9]+$", val)
                if r:
                    bugid = int(val)
                    patch.fixes.append((bugid, None, None))
                    all_bugs.append(bugid)
                    continue

                r = re.match("^\\[ *([0-9]+) *\\](.*)$", val)
                if r:
                    bugid, description = int(r.group(1)), r.group(2).strip()
                    patch.fixes.append((bugid, None, description))   
                    all_bugs.append(bugid)
                    continue

                patch.fixes.append((None, None, val))

            elif key == "depends":
                if not name_to_id.has_key(val):
                    raise PatchUpdaterError("Definition file %s references unknown dependency %s" % (deffile, val))
                patch.depends.add(name_to_id[val])

            else:
                print "WARNING: Ignoring unknown command in definition file %s: %s" % (deffile, line)

        if len(info.author) and len(info.subject) and len(info.revision):
            patch.authors.append(info)

    # In a third step query information for the patches from Wine bugzilla
    pool = Pool(8)

    bug_short_desc = {None:None}
    for bugid, data in zip(all_bugs, pool.map(_download, ["http://bugs.winehq.org/show_bug.cgi?id=%d&ctype=xml&field=short_desc" % bugid for bugid in all_bugs])):
        bug_short_desc[bugid] = minidom.parseString(data).getElementsByTagName('short_desc')[0].firstChild.data

    # The following command triggers a (harmless) python bug, which would confuse the user:
    # > Exception RuntimeError: RuntimeError('cannot join current thread',) in <Finalize object, dead> ignored
    # To avoid that just keep the pool until it destroyed by the garbage collector.
    # pool.close()

    for i, patch in all_patches.iteritems():
        patch.fixes = [(bugid, bug_short_desc[bugid], description) for bugid, dummy, description in patch.fixes]

    return all_patches

def causal_time_combine(a, b):
    """Combines two timestamps into a new one."""
    return [max(a, b) for a, b in zip(a, b)]

def causal_time_smaller(a, b):
    """Checks if timestamp a is smaller than timestamp b."""
    return all([i <= j for i, j in zip(a,b)]) and any([i < j for i, j in zip(a,b)])

def causal_time_relation(all_patches, indices):
    """Checks if the dependencies of patches are compatible with a specific apply order."""
    for i, j in _pairs(indices):
        if causal_time_smaller(all_patches[j].verify_time, all_patches[i].verify_time):
            return False
    return True

def causal_time_relation_any(all_patches, indices):
    """Similar to causal_time_relation(), but also check all possible permutations of indices."""
    for i, j in _pairs(indices):
        if not (causal_time_smaller(all_patches[i].verify_time, all_patches[j].verify_time) or \
                causal_time_smaller(all_patches[j].verify_time, all_patches[i].verify_time)):
            return False
    return True

def causal_time_permutations(all_patches, indices, filename):
    """Iterate over all possible permutations of patches affecting
       a specific file, which are compatible with dependencies."""
    for permutation in itertools.permutations(indices):
        if causal_time_relation(all_patches, permutation):
            selected_patches = []
            for i in permutation:
                selected_patches += [patch for patch in all_patches[i].patches if patch.modified_file == filename]
            yield selected_patches

def contains_binary_patch(all_patches, indices, filename):
    """Checks if any patch with given indices affecting filename is a binary patch."""
    for i in indices:
        for patch in all_patches[i].patches:
            if patch.modified_file == filename and patch.is_binary():
                return True
    return False

def get_wine_file(filename, force=False):
    """Return the hash and optionally the content of a file."""

    # If we're not forced, we try to save time and only lookup the cached checksum
    entry = "%s:%s" % (latest_wine_commit, filename)
    if not force and cached_original_src.has_key(entry):
        return (cached_original_src[entry], None)

    # Grab original file from the wine git repository
    try:
        with open(os.devnull, 'w') as devnull:
            content = subprocess.check_output(["git", "show", entry], cwd="./debian/tools/wine",
                                                                      stderr=devnull)
    except subprocess.CalledProcessError as e:
        if e.returncode != 128: raise # not found
        content = ""

    content_hash = hashlib.sha256(content).digest()
    cached_original_src[entry] = content_hash
    return (content_hash, content)

def verify_patch_order(all_patches, indices, filename):
    """Checks if the dependencies are defined correctly by applying on the patches on a copy from the git tree."""
    global cached_patch_result

    # If one of patches is a binary patch, then we cannot / won't verify it - require dependencies in this case
    if contains_binary_patch(all_patches, indices, filename):
        if not causal_time_relation_any(all_patches, indices):
            raise PatchUpdaterError("Because of binary patch modifying file %s the following patches need explicit dependencies: %s" %
                                    (filename, ", ".join([all_patches[i].name for i in indices])))
        return

    # Get at least the checksum of the original file
    original_content_hash, original_content = get_wine_file(filename)

    # Check for possible ways to apply the patch
    failed_to_apply   = False
    last_result_hash  = None
    for patches in causal_time_permutations(all_patches, indices, filename):

        # Calculate unique hash based on the original content and the order in which the patches are applied
        m = hashlib.sha256()
        m.update(original_content_hash)
        for patch in patches:
            m.update(patch.hash())
        unique_hash = m.digest()

        # Fast path -> we know that it applies properly
        if cached_patch_result.has_key(unique_hash):
            result_hash = cached_patch_result[unique_hash]

        else:
            # Now really get the file, if we don't have it yet
            if original_content is None:
                original_content_hash, original_content = get_wine_file(filename, force=True)

            # Apply the patches (without fuzz)
            try:
                content = patchutils.apply_patch(original_content, patches, fuzz=0)
            except patchutils.PatchApplyError:
                if last_result_hash is not None: break
                failed_to_apply = True
                continue

            # Get hash of resulting file and add to cache
            result_hash = hashlib.sha256(content).digest()
            cached_patch_result[unique_hash] = result_hash

        if last_result_hash is None:
            last_result_hash = result_hash
            if failed_to_apply: break
        elif last_result_hash != result_hash:
            last_result_hash = None
            break

    # If something failed, then show the appropriate error message.
    if failed_to_apply and last_result_hash is None:
        raise PatchUpdaterError("Changes to file %s don't apply on git source tree: %s" %
                                (filename, ", ".join([all_patches[i].name for i in indices])))

    elif failed_to_apply or last_result_hash is None:
        raise PatchUpdaterError("Depending on the order some changes to file %s dont't apply / lead to different results: %s" %
                                (filename, ", ".join([all_patches[i].name for i in indices])))

    else:
        assert len(last_result_hash) == 32

def verify_dependencies(all_patches):
    """Resolve dependencies, and afterwards run verify_patch_order() to check if everything applies properly."""

    def _load_patch_cache():
        """Load dictionary for cached patch dependency tests into cached_patch_result."""
        global cached_patch_result
        global cached_original_src
        cached_patch_result = _load_dict("./.depcache")
        cached_original_src = _load_dict("./.srccache")

    def _save_patch_cache():
        """Save dictionary for cached patch depdency tests."""
        _save_dict("./.depcache", cached_patch_result)
        _save_dict("./.srccache", cached_original_src)

    max_patches = max(all_patches.keys()) + 1

    for i, patch in all_patches.iteritems():
        patch.verify_depends = set(patch.depends)
        patch.verify_time    = [0]*max_patches

    # Check for circular dependencies and perform modified vector clock algorithm
    patches = dict(all_patches)
    while len(patches):

        to_delete = []
        for i, patch in patches.iteritems():
            if len(patch.verify_depends) == 0:
                patch.verify_time[i] += 1
                to_delete.append(i)

        if len(to_delete) == 0:
            raise PatchUpdaterError("Circular dependency in set of patches: %s" %
                                    ", ".join([patch.name for i, patch in patches.iteritems()]))

        for j in to_delete:
            for i, patch in patches.iteritems():
                if i != j and j in patch.verify_depends:
                    patch.verify_time = causal_time_combine(patch.verify_time, patches[j].verify_time)
                    patch.verify_depends.remove(j)
            del patches[j]

    # Find out which files are modified by multiple patches
    modified_files = {}
    for i, patch in all_patches.iteritems():
        for f in patch.modified_files:
            if f not in modified_files:
                modified_files[f] = []
            modified_files[f].append(i)

    # Check if patches always apply correctly
    _load_patch_cache()
    try:
        for f, indices in modified_files.iteritems():
            verify_patch_order(all_patches, indices, f)
    finally:
        _save_patch_cache()

def generate_makefile(all_patches, fp):
    """Generate Makefile for a specific set of patches."""

    with open("./debian/tools/Makefile.in") as template_fp:
        template = template_fp.read()
    fp.write(template.format(patchlist=" \\\n\t\t".join(["%s.ok" % patch.name for i, patch in all_patches.iteritems()])))

    for i, patch in all_patches.iteritems():
        fp.write("# Patchset %s\n" % patch.name)
        fp.write("# |\n")
        fp.write("# | Included patches:\n")

        # List all patches and their corresponding authors
        for info in patch.authors:
            if not info.subject: continue
            s = []
            if info.revision and info.revision != "1": s.append("rev %s" % info.revision)
            if info.author: s.append("by %s" % info.author)
            if len(s): s = " [%s]" % ", ".join(s)
            fp.write("# |   *\t%s\n" % "\n# | \t".join(textwrap.wrap(info.subject + s, 120)))
        fp.write("# |\n")

        # List all bugs fixed by this patchset
        if any([bugid is not None for bugid, bugname, description in patch.fixes]):
            fp.write("# | This patchset fixes the following Wine bugs:\n")
            for bugid, bugname, description in patch.fixes:
                if bugid is not None:
                    fp.write("# |   *\t%s\n" % "\n# | \t".join(textwrap.wrap("[#%d] %s" % (bugid, bugname), 120)))
            fp.write("# |\n")

        # List all modified files
        fp.write("# | Modified files: \n")
        fp.write("# |   *\t%s\n" % "\n# | \t".join(textwrap.wrap(", ".join(sorted(patch.modified_files)), 120)))
        fp.write("# |\n")

        # Generate dependencies and code to apply patches
        fp.write(".INTERMEDIATE: %s.ok\n" % patch.name)
        depends = " ".join([""] + ["%s.ok" % all_patches[d].name for d in patch.depends]) if len(patch.depends) else ""
        fp.write("%s.ok:%s\n" % (patch.name, depends))
        for f in patch.files:
            fp.write("\t$(PATCH) < %s\n" % os.path.join(patch.name, f))

        # Create *.ok file (used to generate patchlist)
        if len(patch.authors):
            fp.write("\t@( \\\n")
            for info in patch.authors:
                if not info.subject: continue
                s = info.subject.replace("\\", "\\\\\\\\").replace("\"", "\\\\\"")
                if info.revision and info.revision != "1": s += " [rev %s]" % info.revision
                fp.write("\t\techo '+    { \"%s\", \"%s\", \"%s\" },'; \\\n" % (patch.name, info.author, s))
            fp.write("\t) > %s.ok\n" % patch.name)
        else:
            fp.write("\ttouch %s.ok\n" % patch.name)
        fp.write("\n");

def generate_readme(all_patches, fp):
    """Generate README.md including information about specific patches and bugfixes."""

    # Get list of all bugs
    def _all_bugs():
        all_bugs = []
        for i, patch in all_patches.iteritems():
            for (bugid, bugname, description) in patch.fixes:
                if bugid is not None:
                    if description is None: description = bugname
                    all_bugs.append((bugid, bugname, description))
        for (bugid, bugname, description) in sorted(all_bugs, key=lambda x: x[2]):
            yield "%s ([Wine Bug #%d](http://bugs.winehq.org/show_bug.cgi?id=%d \"%s\"))" % \
                  (description, bugid, bugid, bugname.replace("\\", "\\\\").replace("\"", "\\\""))

    # Get list of all fixes
    def _all_fixes():
        all_fixes = []
        for i, patch in all_patches.iteritems():
            for (bugid, bugname, description) in patch.fixes:
                if bugid is None: all_fixes.append(description)
        for description in sorted(all_fixes):
            yield description

    # Create enumeration from list
    def _enum(x):
        return "* " + "\n* ".join(x)

    # Read information from changelog
    def _read_changelog():
        with open("debian/changelog") as fp:
            for line in fp:
                r = re.match("^([a-zA-Z0-9][^(]*)\((.*)\) ([^;]*)", line)
                if r: yield (r.group(1).strip(), r.group(2).strip(), r.group(3).strip())

    # Get version number of the latest stable release
    def _latest_stable_version():
        for package, version, distro in _read_changelog():
            if distro.lower() != "unreleased":
                return version

    with open("./debian/tools/README.md.in") as template_fp:
        template = template_fp.read()
    fp.write(template.format(bugs=_enum(_all_bugs()), fixes=_enum(_all_fixes()), version=_latest_stable_version()))

if __name__ == "__main__":
    if not os.path.isdir("./debian/tools/wine"):
        raise RuntimeError("Please create a symlink to the wine repository in ./debian/tools/wine")

    # Get the latest wine commit (sha1)
    latest_wine_commit = subprocess.check_output(["git", "rev-parse", "origin/master"],
                                                 cwd="./debian/tools/wine").strip()
    assert len(latest_wine_commit) == 40

    try:
        all_patches = read_patchsets("./patches")
        verify_dependencies(all_patches)
    except PatchUpdaterError as e:
        print ""
        print "ERROR: %s" % e
        print ""
        exit(1)

    with open("./patches/Makefile", "w") as fp:
        generate_makefile(all_patches, fp)

    with open("./README.md", "w") as fp:
        generate_readme(all_patches, fp)