# -*- coding: utf-8  -*-
#
# Copyright (C) 2011-2018 Ben Kurtovic <ben.kurtovic@gmail.com>
# Released under the terms of the MIT License. See LICENSE for details.
import logging
from glob import glob
import os
import re
import shlex

from colorama import Fore, Style
from git import RemoteReference as RemoteRef, Repo, exc
from git.util import RemoteProgress

logger = logging.getLogger(__name__)

__all__ = ["update_bookmarks", "update_directories", "run_command"]

BOLD = Style.BRIGHT
BLUE = Fore.BLUE + BOLD
GREEN = Fore.GREEN + BOLD
RED = Fore.RED + BOLD
CYAN = Fore.CYAN + BOLD
YELLOW = Fore.YELLOW + BOLD
RESET = Style.RESET_ALL

INDENT1 = " " * 3
INDENT2 = " " * 7
ERROR = RED + "Error:" + RESET


class _ProgressMonitor(RemoteProgress):
    """Displays relevant output during the fetching process."""

    def __init__(self):
        super(_ProgressMonitor, self).__init__()
        self._started = False

    def update(self, op_code, cur_count, max_count=None, message=""):
        """Called whenever progress changes. Overrides default behavior."""
        if op_code & (self.COMPRESSING | self.RECEIVING):
            cur_count = str(int(cur_count))
            if max_count:
                max_count = str(int(max_count))
            if op_code & self.BEGIN:
                print("\b, " if self._started else " (", end="")
                if not self._started:
                    self._started = True
            if op_code & self.END:
                end = ")"
            elif max_count:
                end = "\b" * (1 + len(cur_count) + len(max_count))
            else:
                end = "\b" * len(cur_count)
            if max_count:
                print("{0}/{1}".format(cur_count, max_count), end=end)
            else:
                print(str(cur_count), end=end)


def _fetch_remotes(remotes, prune):
    """Fetch a list of remotes, displaying progress info along the way."""

    def _get_name(ref):
        """Return the local name of a remote or tag reference."""
        return ref.remote_head if isinstance(ref, RemoteRef) else ref.name

    # TODO: missing branch deleted (via --prune):
    info = [
        ("NEW_HEAD", "new branch", "new branches"),
        ("NEW_TAG", "new tag", "new tags"),
        ("FAST_FORWARD", "branch update", "branch updates"),
    ]
    up_to_date = BLUE + "up to date" + RESET

    for remote in remotes:
        print(INDENT2, "Fetching", BOLD + remote.name, end="")

        if not remote.config_reader.has_option("fetch"):
            print(":", YELLOW + "skipped:", "no configured refspec.")
            continue

        try:
            results = remote.fetch(progress=_ProgressMonitor(), prune=prune)
        except exc.GitCommandError as err:
            # We should have to do this ourselves, but GitPython doesn't give
            # us a sensible way to get the raw stderr...
            msg = _git_error_text(err)
            if not msg:
                command = " ".join(shlex.quote(arg) for arg in err.command)
                msg = "{0} failed with status {1}.".format(command, err.status)
            elif not msg.endswith("."):
                msg += "."
            print(":", RED + "error:", msg)
            return
        except AssertionError:  # Seems to be the result of a bug in GitPython
            # This happens when git initiates an auto-gc during fetch:
            print(
                ":",
                RED + "error:",
                "something went wrong in GitPython,",
                "but the fetch might have been successful.",
            )
            return
        rlist = []
        for attr, singular, plural in info:
            names = [
                _get_name(res.ref) for res in results if res.flags & getattr(res, attr)
            ]
            if names:
                desc = singular if len(names) == 1 else plural
                colored = GREEN + desc + RESET
                rlist.append("{0} ({1})".format(colored, ", ".join(names)))
        print(":", (", ".join(rlist) if rlist else up_to_date) + ".")


def _git_error_text(err):
    """Return a concise message from a GitPython command error."""
    raw = err.stderr or ""
    if isinstance(raw, bytes):
        raw = raw.decode("utf8", errors="replace")
    msg = re.sub(r"\s+", " ", raw).strip()
    msg = re.sub(r"^stderr: *'(fatal: *)?", "", msg).strip("'")
    return msg


def _same_path(left, right):
    """Return whether two filesystem paths refer to the same location."""
    if not left or not right:
        return False
    try:
        return os.path.samefile(left, right)
    except OSError:
        return os.path.normcase(os.path.realpath(left)) == os.path.normcase(
            os.path.realpath(right)
        )


def _parse_worktree_porcelain(output):
    """Map local branch names to the worktree path where they are checked out."""

    def attrs_from_entry(entry):
        attrs = {}
        for line in entry.splitlines():
            if not line:
                continue
            if " " in line:
                key, value = line.split(" ", 1)
                attrs[key] = value
            else:
                attrs[line] = True
        return attrs

    def branch_and_path(attrs):
        path = attrs.get("worktree")
        ref = attrs.get("branch")
        if not path or not isinstance(ref, str):
            return None
        name = (
            ref[len("refs/heads/") :] if ref.startswith("refs/heads/") else ref
        )
        return name, path

    normalized = output.replace("\r\n", "\n")
    pairs = [
        branch_and_path(attrs_from_entry(entry))
        for entry in normalized.split("\n\n")
    ]
    return dict(pair for pair in pairs if pair)


def _branch_worktrees(repo):
    """Return {branch_name: worktree_path} for checkouts with a branch."""
    try:
        # GitPython puts kwargs before subcommands (`worktree --porcelain list`),
        # which git rejects. Pass --porcelain as a positional argument.
        output = repo.git.worktree("list", "--porcelain")
    except exc.GitCommandError:
        return {}
    return _parse_worktree_porcelain(output or "")


def _repo_for_workdir(repo, worktree_path):
    """Return a Repo for *worktree_path*, reusing *repo* when it is the same tree."""
    if repo.working_dir and _same_path(repo.working_dir, worktree_path):
        return repo
    return Repo(worktree_path)


def _merge_ff_only(repo, upstream_name):
    """Fast-forward *repo*'s current checkout; print done or skipped."""
    try:
        repo.git.merge(upstream_name, ff_only=True)
        print(GREEN + "done", end=".\n")
    except exc.GitCommandError as err:
        msg = _git_error_text(err)
        if "local changes" in msg and "would be overwritten" in msg:
            print(YELLOW + "skipped:", "uncommitted changes.")
        else:
            print(YELLOW + "skipped:", "not possible to fast-forward.")


def _update_branch(repo, branch, is_active=False, worktrees=None):
    """Update a single branch.

    Branches checked out in this repo or another worktree are fast-forwarded
    with ``merge --ff-only`` in that checkout. Other tracking branches are
    moved with ``git branch --force`` when the update is a fast-forward.
    """
    print(INDENT2, "Updating", BOLD + branch.name, end=": ")
    try:
        _update_branch_body(repo, branch, is_active, worktrees)
    except exc.GitCommandError as err:
        msg = _git_error_text(err) or "git command failed"
        if not msg.endswith("."):
            msg += "."
        print(YELLOW + "skipped:", msg)


def _update_branch_body(repo, branch, is_active, worktrees):
    """Perform the update for a single branch, printing the result."""
    upstream = branch.tracking_branch()
    if not upstream:
        print(YELLOW + "skipped:", "no upstream is tracked.")
        return
    try:
        branch.commit
    except ValueError:
        print(YELLOW + "skipped:", "branch has no revisions.")
        return
    try:
        upstream.commit
    except ValueError:
        print(YELLOW + "skipped:", "upstream does not exist.")
        return

    try:
        base = repo.git.merge_base(branch.commit, upstream.commit)
    except exc.GitCommandError as err:
        logger.debug(err)
        print(YELLOW + "skipped:", "can't find merge base with upstream.")
        return

    if repo.commit(base) == upstream.commit:
        print(BLUE + "up to date", end=".\n")
        return

    if worktrees is None:
        worktrees = _branch_worktrees(repo)
    checkout = worktrees.get(branch.name)

    if is_active or checkout:
        try:
            target = _repo_for_workdir(repo, checkout) if checkout else repo
        except (exc.NoSuchPathError, exc.InvalidGitRepositoryError):
            print(YELLOW + "skipped:", "worktree path does not exist.")
            return
        _merge_ff_only(target, upstream.name)
        return

    status = repo.git.merge_base(
        branch.commit,
        upstream.commit,
        is_ancestor=True,
        with_extended_output=True,
        with_exceptions=False,
    )[0]
    if status != 0:
        print(YELLOW + "skipped:", "not possible to fast-forward.")
        return
    repo.git.branch(branch.name, upstream.name, force=True)
    print(GREEN + "done", end=".\n")


def _update_repository(repo, repo_name, args):
    """Update a single git repository by fetching remotes and rebasing/merging.

    The specific actions depend on the arguments given. We will fetch all
    remotes if *args.current_only* is ``False``, or only the remote tracked by
    the current branch if ``True``. If *args.fetch_only* is ``False``, we will
    also update all fast-forwardable branches that are tracking valid
    upstreams. If *args.prune* is ``True``, remote-tracking branches that no
    longer exist on their remote after fetching will be deleted.
    """
    print(INDENT1, BOLD + repo_name + ":")

    try:
        active = repo.active_branch
    except TypeError:  # Happens when HEAD is detached
        active = None
    if args.current_only:
        if not active:
            print(
                INDENT2,
                ERROR,
                "--current-only doesn't make sense with a detached HEAD.",
            )
            return
        ref = active.tracking_branch()
        if not ref:
            print(INDENT2, ERROR, "no remote tracked by current branch.")
            return
        remotes = [repo.remotes[ref.remote_name]]
    else:
        remotes = repo.remotes

    if not remotes:
        print(INDENT2, ERROR, "no remotes configured to fetch.")
        return
    _fetch_remotes(remotes, args.prune)

    if not args.fetch_only:
        worktrees = _branch_worktrees(repo)
        for branch in sorted(repo.heads, key=lambda b: b.name):
            _update_branch(repo, branch, branch == active, worktrees)


def _run_command(repo, repo_name, args):
    """Run an arbitrary shell command on the given repository."""
    print(INDENT1, BOLD + repo_name + ":")

    cmd = shlex.split(args.command)
    try:
        out = repo.git.execute(cmd, with_extended_output=True, with_exceptions=False)
    except exc.GitCommandNotFound as err:
        print(INDENT2, ERROR, err)
        return

    for line in out[1].splitlines() + out[2].splitlines():
        print(INDENT2, line)


def _dispatch(base_path, callback, args):
    """Apply a callback function on each valid repo in the given path.

    Determine whether the directory is a git repo on its own, a directory of
    git repositories, a shell glob pattern, or something invalid. If the first,
    apply the callback on it; if the second or third, apply the callback on all
    repositories contained within; if the last, print an error.

    The given args are passed directly to the callback function after the repo.
    """

    def _collect(paths, max_depth):
        """Return all valid repo paths in the given paths, recursively."""
        if max_depth == 0:
            return []

        valid = []
        for path in paths:
            try:
                Repo(path)
                valid.append(path)
            except exc.InvalidGitRepositoryError:
                if not os.path.isdir(path):
                    continue
                children = [os.path.join(path, it) for it in os.listdir(path)]
                valid += _collect(children, max_depth - 1)
            except exc.NoSuchPathError:
                continue
        return valid

    def _get_basename(base, path):
        """Return a reasonable name for a repo path in the given base."""
        if path.startswith(base + os.path.sep):
            return path.split(base + os.path.sep, 1)[1]
        prefix = os.path.commonprefix([base, path])
        while not base.startswith(prefix + os.path.sep):
            old = prefix
            prefix = os.path.split(prefix)[0]
            if prefix == old:
                break  # Prevent infinite loop, but should be almost impossible
        return path.split(prefix + os.path.sep, 1)[1]

    base = os.path.expanduser(base_path)
    max_depth = args.max_depth
    if max_depth >= 0:
        max_depth += 1

    try:
        Repo(base)
        valid = [base]
    except exc.NoSuchPathError:
        if is_comment(base):
            comment = get_comment(base)
            if comment:
                print(CYAN + BOLD + comment)
            return
        paths = glob(base)
        if not paths:
            print(ERROR, BOLD + base, "doesn't exist!")
            return
        valid = _collect(paths, max_depth)
    except exc.InvalidGitRepositoryError:
        if not os.path.isdir(base) or args.max_depth == 0:
            print(ERROR, BOLD + base, "isn't a repository!")
            return
        valid = _collect([base], max_depth)

    base = os.path.abspath(base)
    suffix = "" if len(valid) == 1 else "s"
    print(BOLD + base, "({0} repo{1}):".format(len(valid), suffix))

    valid = [os.path.abspath(path) for path in valid]
    paths = [(_get_basename(base, path), path) for path in valid]
    for name, path in sorted(paths):
        callback(Repo(path), name, args)


def is_comment(path):
    """Does the line start with a # symbol?"""
    return path.lstrip().startswith("#")


def get_comment(path):
    """Return the string minus the comment symbol."""
    return path.lstrip().lstrip("#").strip()


def update_bookmarks(bookmarks, args):
    """Loop through and update all bookmarks."""
    if not bookmarks:
        print("You don't have any bookmarks configured! Get help with 'gitup -h'.")
        return

    for path in bookmarks:
        _dispatch(path, _update_repository, args)


def update_directories(paths, args):
    """Update a list of directories supplied by command arguments."""
    for path in paths:
        _dispatch(path, _update_repository, args)


def run_command(paths, args):
    """Run an arbitrary shell command on all repos."""
    for path in paths:
        _dispatch(path, _run_command, args)