"""revset to select sample of repository

Hopefully this is useful to create interesting discovery cases.

"""

import collections

import random

from mercurial.i18n import _

from mercurial import (

    registrar,

    revset,

    revsetlang,

    smartset,

)

revsetpredicate = registrar.revsetpredicate()

@revsetpredicate(b'subsetspec("<spec>")')

def subsetmarkerspec(repo, subset, x):

    """use a shorthand spec as used by search-discovery-case

    Supported format are:

    - "scratch-count-seed": not scratch(all(), count, "seed")

    - "randomantichain-seed": ::randomantichain(all(), "seed")

    - "rev-REV": "::REV"

    """

    args = revsetlang.getargs(

        x, 0, 1, _(b'subsetspec("spec") required an argument')

    )

    spec = revsetlang.getstring(args[0], _(b"spec should be a string"))

    case = spec.split(b'-')

    t = case[0]

    if t == b'scratch':

        spec_revset = b'not scratch(all(), %s, "%s")' % (case[1], case[2])

    elif t == b'randomantichain':

        spec_revset = b'::randomantichain(all(), "%s")' % case[1]

    elif t == b'rev':

        spec_revset = b'::%d' % case[1]

    else:

        assert False, spec

    selected = repo.revs(spec_revset)

    return selected & subset

@revsetpredicate(b'scratch(REVS, <count>, [seed])')

def scratch(repo, subset, x):

    """randomly remove <count> revision from the repository top

    This subset is created by recursively picking changeset starting from the

    heads. It can be summarized using the following algorithm::

        selected = set()

        for i in range(<count>):

            unselected = repo.revs("not <selected>")

            candidates = repo.revs("heads(<unselected>)")

            pick = random.choice(candidates)

            selected.add(pick)

    """

    m = _(b"scratch expects revisions, count argument and an optional seed")

    args = revsetlang.getargs(x, 2, 3, m)

    if len(args) == 2:

        x, n = args

        rand = random

    elif len(args) == 3:

        x, n, seed = args

        seed = revsetlang.getinteger(seed, _(b"seed should be a number"))

        rand = random.Random(seed)

    else:

        assert False

    n = revsetlang.getinteger(n, _(b"scratch expects a number"))

    selected = set()

    heads = set()

    children_count = collections.defaultdict(lambda: 0)

    parents = repo.changelog._uncheckedparentrevs

    baseset = revset.getset(repo, smartset.fullreposet(repo), x)

    baseset.sort()

    for r in baseset:

        heads.add(r)

        p1, p2 = parents(r)

        if p1 >= 0:

            heads.discard(p1)

            children_count[p1] += 1

        if p2 >= 0:

            heads.discard(p2)

            children_count[p2] += 1

    for h in heads:

        assert children_count[h] == 0

    selected = set()

    for x in range(n):

        if not heads:

            break

        pick = rand.choice(list(heads))

        heads.remove(pick)

        assert pick not in selected

        selected.add(pick)

        p1, p2 = parents(pick)

        if p1 in children_count:

            assert p1 in children_count

            children_count[p1] -= 1

            assert children_count[p1] >= 0

            if children_count[p1] == 0:

                assert p1 not in selected, (r, p1)

                heads.add(p1)

        if p2 in children_count:

            assert p2 in children_count

            children_count[p2] -= 1

            assert children_count[p2] >= 0

            if children_count[p2] == 0:

                assert p2 not in selected, (r, p2)

                heads.add(p2)

    return smartset.baseset(selected) & subset

@revsetpredicate(b'randomantichain(REVS, [seed])')

def antichain(repo, subset, x):

    """Pick a random anti-chain in the repository

    A antichain is a set of changeset where there isn't any element that is

    either a descendant or ancestors of any other element in the set. In other

    word, all the elements are independant. It can be summarized with the

    following algorithm::

    selected = set()

    unselected = repo.revs('all()')

    while unselected:

        pick = random.choice(unselected)

        selected.add(pick)

        unselected -= repo.revs('::<pick> + <pick>::')

    """

    args = revsetlang.getargs(

        x, 1, 2, _(b"randomantichain expects revisions and an optional seed")

    )

    if len(args) == 1:

        (x,) = args

        rand = random

    elif len(args) == 2:

        x, seed = args

        seed = revsetlang.getinteger(seed, _(b"seed should be a number"))

        rand = random.Random(seed)

    else:

        assert False

    selected = set()

    baseset = revset.getset(repo, smartset.fullreposet(repo), x)

    undecided = baseset

    while undecided:

        pick = rand.choice(list(undecided))

        selected.add(pick)

        undecided = repo.revs(

            '%ld and not (::%ld or %ld::head())', baseset, selected, selected

        )

    return smartset.baseset(selected) & subset