# patch.py -- For dealing with packed-style patches.
# Copyright (C) 2009-2013 Jelmer Vernooij <jelmer@jelmer.uk>
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#

"""Classes for dealing with git am-style patches.

These patches are basically unified diffs with some extra metadata tacked
on.
"""

import email.parser
import time
from difflib import SequenceMatcher
from typing import BinaryIO, Optional, TextIO, Union

from .objects import S_ISGITLINK, Blob, Commit
from .pack import ObjectContainer

FIRST_FEW_BYTES = 8000


def write_commit_patch(f, commit, contents, progress, version=None, encoding=None):
    """Write a individual file patch.

    Args:
      commit: Commit object
      progress: Tuple with current patch number and total.

    Returns:
      tuple with filename and contents
    """
    encoding = encoding or getattr(f, "encoding", "ascii")
    if isinstance(contents, str):
        contents = contents.encode(encoding)
    (num, total) = progress
    f.write(
        b"From "
        + commit.id
        + b" "
        + time.ctime(commit.commit_time).encode(encoding)
        + b"\n"
    )
    f.write(b"From: " + commit.author + b"\n")
    f.write(
        b"Date: " + time.strftime("%a, %d %b %Y %H:%M:%S %Z").encode(encoding) + b"\n"
    )
    f.write(
        ("Subject: [PATCH %d/%d] " % (num, total)).encode(encoding)
        + commit.message
        + b"\n"
    )
    f.write(b"\n")
    f.write(b"---\n")
    try:
        import subprocess

        p = subprocess.Popen(
            ["diffstat"], stdout=subprocess.PIPE, stdin=subprocess.PIPE
        )
    except (ImportError, OSError):
        pass  # diffstat not available?
    else:
        (diffstat, _) = p.communicate(contents)
        f.write(diffstat)
        f.write(b"\n")
    f.write(contents)
    f.write(b"-- \n")
    if version is None:
        from dulwich import __version__ as dulwich_version

        f.write(b"Dulwich %d.%d.%d\n" % dulwich_version)
    else:
        f.write(version.encode(encoding) + b"\n")


def get_summary(commit):
    """Determine the summary line for use in a filename.

    Args:
      commit: Commit
    Returns: Summary string
    """
    decoded = commit.message.decode(errors="replace")
    return decoded.splitlines()[0].replace(" ", "-")


#  Unified Diff
def _format_range_unified(start, stop):
    """Convert range to the "ed" format."""
    # Per the diff spec at http://www.unix.org/single_unix_specification/
    beginning = start + 1  # lines start numbering with one
    length = stop - start
    if length == 1:
        return f"{beginning}"
    if not length:
        beginning -= 1  # empty ranges begin at line just before the range
    return f"{beginning},{length}"


def unified_diff(
    a,
    b,
    fromfile="",
    tofile="",
    fromfiledate="",
    tofiledate="",
    n=3,
    lineterm="\n",
    tree_encoding="utf-8",
    output_encoding="utf-8",
):
    """difflib.unified_diff that can detect "No newline at end of file" as
    original "git diff" does.

    Based on the same function in Python2.7 difflib.py
    """
    started = False
    for group in SequenceMatcher(None, a, b).get_grouped_opcodes(n):
        if not started:
            started = True
            fromdate = f"\t{fromfiledate}" if fromfiledate else ""
            todate = f"\t{tofiledate}" if tofiledate else ""
            yield f"--- {fromfile.decode(tree_encoding)}{fromdate}{lineterm}".encode(
                output_encoding
            )
            yield f"+++ {tofile.decode(tree_encoding)}{todate}{lineterm}".encode(
                output_encoding
            )

        first, last = group[0], group[-1]
        file1_range = _format_range_unified(first[1], last[2])
        file2_range = _format_range_unified(first[3], last[4])
        yield f"@@ -{file1_range} +{file2_range} @@{lineterm}".encode(output_encoding)

        for tag, i1, i2, j1, j2 in group:
            if tag == "equal":
                for line in a[i1:i2]:
                    yield b" " + line
                continue
            if tag in ("replace", "delete"):
                for line in a[i1:i2]:
                    if not line[-1:] == b"\n":
                        line += b"\n\\ No newline at end of file\n"
                    yield b"-" + line
            if tag in ("replace", "insert"):
                for line in b[j1:j2]:
                    if not line[-1:] == b"\n":
                        line += b"\n\\ No newline at end of file\n"
                    yield b"+" + line


def is_binary(content):
    """See if the first few bytes contain any null characters.

    Args:
      content: Bytestring to check for binary content
    """
    return b"\0" in content[:FIRST_FEW_BYTES]


def shortid(hexsha):
    if hexsha is None:
        return b"0" * 7
    else:
        return hexsha[:7]


def patch_filename(p, root):
    if p is None:
        return b"/dev/null"
    else:
        return root + b"/" + p


def write_object_diff(f, store: ObjectContainer, old_file, new_file, diff_binary=False):
    """Write the diff for an object.

    Args:
      f: File-like object to write to
      store: Store to retrieve objects from, if necessary
      old_file: (path, mode, hexsha) tuple
      new_file: (path, mode, hexsha) tuple
      diff_binary: Whether to diff files even if they
        are considered binary files by is_binary().

    Note: the tuple elements should be None for nonexistent files
    """
    (old_path, old_mode, old_id) = old_file
    (new_path, new_mode, new_id) = new_file
    patched_old_path = patch_filename(old_path, b"a")
    patched_new_path = patch_filename(new_path, b"b")

    def content(mode, hexsha):
        if hexsha is None:
            return Blob.from_string(b"")
        elif S_ISGITLINK(mode):
            return Blob.from_string(b"Subproject commit " + hexsha + b"\n")
        else:
            return store[hexsha]

    def lines(content):
        if not content:
            return []
        else:
            return content.splitlines()

    f.writelines(
        gen_diff_header((old_path, new_path), (old_mode, new_mode), (old_id, new_id))
    )
    old_content = content(old_mode, old_id)
    new_content = content(new_mode, new_id)
    if not diff_binary and (is_binary(old_content.data) or is_binary(new_content.data)):
        binary_diff = (
            b"Binary files "
            + patched_old_path
            + b" and "
            + patched_new_path
            + b" differ\n"
        )
        f.write(binary_diff)
    else:
        f.writelines(
            unified_diff(
                lines(old_content),
                lines(new_content),
                patched_old_path,
                patched_new_path,
            )
        )


# TODO(jelmer): Support writing unicode, rather than bytes.
def gen_diff_header(paths, modes, shas):
    """Write a blob diff header.

    Args:
      paths: Tuple with old and new path
      modes: Tuple with old and new modes
      shas: Tuple with old and new shas
    """
    (old_path, new_path) = paths
    (old_mode, new_mode) = modes
    (old_sha, new_sha) = shas
    if old_path is None and new_path is not None:
        old_path = new_path
    if new_path is None and old_path is not None:
        new_path = old_path
    old_path = patch_filename(old_path, b"a")
    new_path = patch_filename(new_path, b"b")
    yield b"diff --git " + old_path + b" " + new_path + b"\n"

    if old_mode != new_mode:
        if new_mode is not None:
            if old_mode is not None:
                yield (f"old file mode {old_mode:o}\n").encode("ascii")
            yield (f"new file mode {new_mode:o}\n").encode("ascii")
        else:
            yield (f"deleted file mode {old_mode:o}\n").encode("ascii")
    yield b"index " + shortid(old_sha) + b".." + shortid(new_sha)
    if new_mode is not None and old_mode is not None:
        yield (f" {new_mode:o}").encode("ascii")
    yield b"\n"


# TODO(jelmer): Support writing unicode, rather than bytes.
def write_blob_diff(f, old_file, new_file):
    """Write blob diff.

    Args:
      f: File-like object to write to
      old_file: (path, mode, hexsha) tuple (None if nonexisting)
      new_file: (path, mode, hexsha) tuple (None if nonexisting)

    Note: The use of write_object_diff is recommended over this function.
    """
    (old_path, old_mode, old_blob) = old_file
    (new_path, new_mode, new_blob) = new_file
    patched_old_path = patch_filename(old_path, b"a")
    patched_new_path = patch_filename(new_path, b"b")

    def lines(blob):
        if blob is not None:
            return blob.splitlines()
        else:
            return []

    f.writelines(
        gen_diff_header(
            (old_path, new_path),
            (old_mode, new_mode),
            (getattr(old_blob, "id", None), getattr(new_blob, "id", None)),
        )
    )
    old_contents = lines(old_blob)
    new_contents = lines(new_blob)
    f.writelines(
        unified_diff(old_contents, new_contents, patched_old_path, patched_new_path)
    )


def write_tree_diff(f, store, old_tree, new_tree, diff_binary=False):
    """Write tree diff.

    Args:
      f: File-like object to write to.
      old_tree: Old tree id
      new_tree: New tree id
      diff_binary: Whether to diff files even if they
        are considered binary files by is_binary().
    """
    changes = store.tree_changes(old_tree, new_tree)
    for (oldpath, newpath), (oldmode, newmode), (oldsha, newsha) in changes:
        write_object_diff(
            f,
            store,
            (oldpath, oldmode, oldsha),
            (newpath, newmode, newsha),
            diff_binary=diff_binary,
        )


def git_am_patch_split(f: Union[TextIO, BinaryIO], encoding: Optional[str] = None):
    """Parse a git-am-style patch and split it up into bits.

    Args:
      f: File-like object to parse
      encoding: Encoding to use when creating Git objects
    Returns: Tuple with commit object, diff contents and git version
    """
    encoding = encoding or getattr(f, "encoding", "ascii")
    encoding = encoding or "ascii"
    contents = f.read()
    if isinstance(contents, bytes):
        bparser = email.parser.BytesParser()
        msg = bparser.parsebytes(contents)
    else:
        uparser = email.parser.Parser()
        msg = uparser.parsestr(contents)
    return parse_patch_message(msg, encoding)


def parse_patch_message(msg, encoding=None):
    """Extract a Commit object and patch from an e-mail message.

    Args:
      msg: An email message (email.message.Message)
      encoding: Encoding to use to encode Git commits
    Returns: Tuple with commit object, diff contents and git version
    """
    c = Commit()
    c.author = msg["from"].encode(encoding)
    c.committer = msg["from"].encode(encoding)
    try:
        patch_tag_start = msg["subject"].index("[PATCH")
    except ValueError:
        subject = msg["subject"]
    else:
        close = msg["subject"].index("] ", patch_tag_start)
        subject = msg["subject"][close + 2 :]
    c.message = (subject.replace("\n", "") + "\n").encode(encoding)
    first = True

    body = msg.get_payload(decode=True)
    lines = body.splitlines(True)
    line_iter = iter(lines)

    for line in line_iter:
        if line == b"---\n":
            break
        if first:
            if line.startswith(b"From: "):
                c.author = line[len(b"From: ") :].rstrip()
            else:
                c.message += b"\n" + line
            first = False
        else:
            c.message += line
    diff = b""
    for line in line_iter:
        if line == b"-- \n":
            break
        diff += line
    try:
        version = next(line_iter).rstrip(b"\n")
    except StopIteration:
        version = None
    return c, diff, version
