# extorder.py - dependencies for extensions
#
# Copyright 2015 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""
loading order for extensions.

In the extorder section of your hgrc you can define order of extension loading.
For example:
  [extorder]
  extension1 = extension3, extension4
  extension2 = extension1

This will cause the extension1 to be loaded after 3 and 4. Also extension2 will
be loaded after extension1.

Also there are two special configs in this section: 'preferlast' and
'preferfirst'. Those are lists of extensions which prefer to be loaded first or
last. But these are not guaranteed -- normal dependencies have higher priority.

Please not that this extension modifies only order of loading extensions. It
will not load them for you
"""

from mercurial import (
    extensions,
    registrar,
)

try:
    from mercurial import chgserver
except ImportError:
    from hgext import chgserver
chgserver._configsections.append('extorder')

testedwith = 'ships-with-fb-hgext'

configtable = {}
configitem = registrar.configitem(configtable)

class MercurialExtOrderException(BaseException):
    '''Special exception to bypass upstream exception catching

    Upstream mercurial catches all Exception from uisetup or extsetup - see
    ea1c2eb7abd341c84422f489af75bccb02622671. We need to throw something that is
    subclass of BaseException to actually abort the program if extension order
    is incorrect. That's why this class exists.
    '''
    pass

def uisetup(ui):

    deps = {}
    preferlast = []
    preferfirst = []

    # The configs being read here are user defined, so we need to suppress
    # warnings telling us to register them.
    with ui.configoverride({("devel", "all-warnings"): False}):
        for item, _v in ui.configitems('extorder'):
            val = ui.configlist('extorder', item)
            if item == 'preferlast':
                preferlast.extend(val)
            elif item == 'preferfirst':
                preferfirst.extend(val)
            else:
                deps[item] = val

    exts = list(extensions._order)
    for e in preferfirst + preferlast:
        exts.remove(e)
    unvisited = preferfirst + exts + preferlast

    temp = set()
    order = list()

    def visit(n):
        if n in temp:
            raise MercurialExtOrderException(
                "extorder: conflicting extension order")
        elif n in unvisited:
            temp.add(n)
            for m in deps.get(n, []):
                visit(m)
            unvisited.remove(n)
            temp.remove(n)
            order.append(n)
    while len(unvisited) > 0:
        visit(unvisited[0])

    extensions._order = order