# Revision graph generator for Mercurial

#

# Copyright 2008 Dirkjan Ochtman <dirkjan@ochtman.nl>

# Copyright 2007 Joel Rosdahl <joel@rosdahl.net>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2, incorporated herein by reference.

from node import nullrev

def graph(repo, start_rev, stop_rev):

    """incremental revision grapher

    This generator function walks through the revision history from

    revision start_rev to revision stop_rev (which must be less than

    or equal to start_rev) and for each revision emits tuples with the

    following elements:

      - Edges; a list of (col, next_col, color) indicating the edges between

        the current node and its parents.

    """

    if start_rev == nullrev and not stop_rev:

        return

    assert start_rev >= stop_rev

    assert stop_rev >= 0

    curr_rev = start_rev

    revs = []

    cl = repo.changelog

    colors = {}

    new_color = 1

    while curr_rev >= stop_rev:

        # Compute revs and next_revs

        if curr_rev not in revs:

            revs.append(curr_rev) # new head

            colors[curr_rev] = new_color

            new_color += 1

        idx = revs.index(curr_rev)

        color = colors.pop(curr_rev)

        next = revs[:]

        # Add parents to next_revs

        parents = [x for x in cl.parentrevs(curr_rev) if x != nullrev]

        addparents = [p for p in parents if p not in next]

        next[idx:idx + 1] = addparents

        # Set colors for the parents

        for i, p in enumerate(addparents):

            if not i:

                colors[p] = color

            else:

                colors[p] = new_color

                new_color += 1

        # Add edges to the graph

        edges = []

        for col, r in enumerate(revs):

            if r in next:

                edges.append((col, next.index(r), colors[r]))

            elif r == curr_rev:

                for p in parents:

                    edges.append((col, next.index(p), colors[p]))

        # Yield and move on

        yield (repo[curr_rev], (idx, color), edges)

        revs = next

        curr_rev -= 1