interface IReducerState{
    someNumber: number;
};

const rootReducer = {
    getInitialState: function():IReducerState{
        return {
            someNumber: 42,
        };
    }
};

const addReducer = {
    addOne: function(prevState:IReducerState):IReducerState{
        prevState.someNumber += 1;
        return prevState;
    }
};

const Reducer = debug(
    extend(rootReducer,addReducer)
);

export default Reducer;

/////////////////////////////////////////////////
///                  Helpers
/////////////////////////////////////////////////

// Takes two typed variables and returns a combined type
function extend<T,U>(first: T,second:U):T & U{
    let result = {};

    for(let id in first){
        (result as any)[id] = (first as any)[id];
    }

    for(let id in second){
        if(!result.hasOwnProperty(id)){
            (result as any)[id] = (second as any)[id];
        }
    }

    return result as T & U;
}


// Takes a reducer object and returns a copy that logs actions
function debug<T>(reducer:T):T{
    Object.keys(reducer).forEach(function(key){
        if(key == 'getInitialState'){
            const initialFunction = reducer['getInitialState'];

            reducer[key] = function(){
                const result = initialFunction();
                console.log('State initialized',result);
                return result;
            }
        }
        else{
            const originalFunc = reducer[key];

            reducer[key] = function(){
                const funcResult = originalFunc.apply(this,arguments);

                return function(prevState){
                    const actualResult = funcResult(prevState);

                    console.log('State changed ('+key+')',actualResult);
                }
            }
        }
    });

    return reducer;
}