var Q = require('q')
  , _ = require('underscore')
  , CouchDB = require('../util/couch').CouchDB
  ;

var schema = require('./couchdb-schema');

module.exports = function(couchServerURL,dbName,upgrade) {
    var server = new CouchDB(couchServerURL,dbName);
    var designRe = /^_design\//;
    return server.get('/_all_docs')
    .then(function(allDocs){
        return _.chain(allDocs.rows)
        .filter(function(doc){
            return doc.id.match(designRe) === null;
        })
        .reduce(function(memo, doc){
            return memo.then(function(result){
                return server.get(doc.id)
                .then(function(doc){
                    Q.when(upgrade(doc))
                    .then(function(newDoc){
                        return server.put(doc._id,newDoc)
                        .then(function(){
                            result[doc._id] = true;
                            return result;
                        });
                    },function(){
                        result[doc._id] = false;
                    });
                    return result;
                });
            });
        }, Q.resolve({}))
        .value();
    }).all();
};