mergeist.js

//Changes filter: "conflicts": "function(doc, req) { if(doc._conflicts) { return true; } else { return false; }}"
var dbase = 'focus';
var ddoc = 'app';

var sys = require('sys'),
    couchdb = require('node-couchdb/lib/couchdb'),
    client = couchdb.createClient(5984, 'crate.im'),
    db = client.db(dbase),
    changes = db.changesStream({filter: ddoc + '/conflicts'});

var default_merge = function(conflicts, prevdoc)
{
    if(!prevdoc) {  
        return false; 
    }
    delete prevdoc._rev;
    var newdoc =JSON.parse(JSON.stringify(prevdoc));
    var updated = {};
    for(var i in conflicts)
    {
        sys.puts('  Conflict ' + i + ' ' + JSON.stringify(conflicts[i]));
        for(var k in conflicts[i])
        {
            delete conflicts[i]._rev;
            if(!newdoc[k])
            {
                //Key doesn't exist in previous rev.
                newdoc[k] = conflicts[i][k];
            } else {
                if(!prevdoc[k]) {
                    //Conflicting docs both added the same new field.
                    //not handling this.
                    sys.puts("Both added field " + k);
                    return false;
                } else {
                    //Key is in new doc and previous doc.
                    if(JSON.stringify(conflicts[i][k]) != JSON.stringify(prevdoc[k])) { 
                        //We have a new version of this key.
                        if(!updated[k]) {
                            sys.puts("Field " + k + ": " +  JSON.stringify(prevdoc[k]) + " -> " + JSON.stringify(conflicts[i][k]));
                            //We are the sole updater so far.
                            newdoc[k] = conflicts[i][k];
                            updated[k] = true;
                        } else {
                            //Conflicting docs both updated the same field, not handling this.
                            sys.puts("Both updated field " + k + "\n");
                            return false;
                        }
                    }
                }
            }
        }
    }

    return newdoc;
}

db.getDoc('_design/' + ddoc, function (er, ddoc) {
    if(er) throw new Error("Error fetching design doc");
    var merge = default_merge;
    if(ddoc.merge_func)
    {
        sys.puts("Custom merge function: " + ddoc.merge_func);
        merge = eval(ddoc.merge_func);
    }
    changes.on('data', function (change) {
            sys.print(JSON.stringify(change)+'\n');
            db.request({method: 'get', path: '/' + change.id, query: {conflicts: true, revs: true}}, function(er, doc)
            {
                sys.print('Processing conflict...\n');
                if(doc._conflicts) { 
                    db.request({method: 'get', path: '/'+change.id, query: {
                            rev: (doc._revisions.start - 1) + '-' + doc._revisions.ids[1]
                    }}, function(er, previous) {
                        var conflicts = [];
                        sys.print('  Previous rev: ' + JSON.stringify(previous)+'\n');
                        for(var rev in doc._conflicts) {
                            db.request({method: 'get', path:'/' + change.id, query: {rev: doc._conflicts[rev]}}, function(er, cdoc) {
                                if(er) throw new Error(JSON.stringify(er));
                                conflicts.push(cdoc);
                                if(conflicts.length == doc._conflicts.length) {
                                    var current = JSON.parse(JSON.stringify(doc));
                                    delete current._revisions;
                                    delete current._conflicts;
                                    conflicts.push(current);
                                    var result = merge(conflicts, previous);
                                    if(result)
                                    {
                                        sys.puts('  Merge result: ' + JSON.stringify(result));
                                        result._rev = doc._rev;
                                        db.bulkDocs({docs: [result].concat(doc._conflicts.map(function(x) {
                                                        return {_id: doc._id, _rev: x, _deleted: true};
                                                    }))}, function(er) {
                                                if(er) sys.puts("Commit of merge failed: " + JSON.stringify(er));
                                                sys.puts("Merge successfully saved.");
                                            });
                                    } else { 
                                        sys.puts("Could not resolve conflict automatically.");
                                    }
                                };
                            });
                        }
                    });
                }
            });
    });
});

sys.print('Mergeist - couchdb conflicts automerger\n');