/**
* @file 合成reducer
* @author Leon(leon@outlook.com)
* @requires underscore
*/
var u = require('underscore');
/**
* 合成reducer
*
* @public
* @method module:ei.composeReducer
* @param {...(Function | Object)} reducers 一个reducer，或多个reducer的map
* @return {Function}
*/
function composeReducer(reducers) {
if (u.isFunction(reducers)) {
return reducers;
}
reducers = u.reduce(
u.toArray(arguments),
function (finalReducer, reducer) {
return u.extendOwn(finalReducer, reducer);
},
{}
);
return function (state, action) {
var isChanged = false;
var nextState = {};
for (var name in state) {
if (!u.has(state, name)) {
continue;
}
if (u.has(reducers, name)) {
var value = state[name];
var nextValue = nextState[name] = reducers[name](value, action);
if (nextValue !== value) {
isChanged = true;
}
}
else {
nextState[name] = state[name];
}
}
return isChanged ? nextState : state;
};
}
module.exports = composeReducer;