'use strict';var _extends=Object.assign||function(target){for(var i=1;i<arguments.length;i++){var source=arguments[i];for(var key in source){if(Object.prototype.hasOwnProperty.call(source,key)){target[key]=source[key];}}}return target;};

var invariant=require('fbjs/lib/invariant');
var shallowEqual=require('fbjs/lib/shallowEqual');







var SCENE_KEY_PREFIX='scene_';




function compareKey(one,two){
var delta=one.length-two.length;
if(delta>0){
return 1;
}
if(delta<0){
return-1;
}
return one>two?1:-1;
}




function compareScenes(
one,
two)
{
if(one.index>two.index){
return 1;
}
if(one.index<two.index){
return-1;
}

return compareKey(
one.key,
two.key);

}




function areScenesShallowEqual(
one,
two)
{
return(
one.key===two.key&&
one.index===two.index&&
one.isStale===two.isStale&&
one.isActive===two.isActive&&
areRoutesShallowEqual(one.route,two.route));

}




function areRoutesShallowEqual(
one,
two)
{
if(!one||!two){
return one===two;
}

if(one.key!==two.key){
return false;
}

return shallowEqual(one,two);
}

function NavigationScenesReducer(
scenes,
nextState,
prevState)
{
if(prevState===nextState){
return scenes;
}

var prevScenes=new Map();
var freshScenes=new Map();
var staleScenes=new Map();


scenes.forEach(function(scene){var
key=scene.key;
if(scene.isStale){
staleScenes.set(key,scene);
}
prevScenes.set(key,scene);
});

var nextKeys=new Set();
nextState.routes.forEach(function(route,index){
var key=SCENE_KEY_PREFIX+route.key;
var scene={
index:index,
isActive:false,
isStale:false,
key:key,
route:route};

invariant(
!nextKeys.has(key),
'navigationState.routes['+index+'].key "'+key+'" conflicts with '+
'another route!');

nextKeys.add(key);

if(staleScenes.has(key)){


staleScenes.delete(key);
}
freshScenes.set(key,scene);
});

if(prevState){

prevState.routes.forEach(function(route,index){
var key=SCENE_KEY_PREFIX+route.key;
if(freshScenes.has(key)){
return;
}
staleScenes.set(key,{
index:index,
isActive:false,
isStale:true,
key:key,
route:route});

});
}

var nextScenes=[];

var mergeScene=function mergeScene(nextScene){var
key=nextScene.key;
var prevScene=prevScenes.has(key)?prevScenes.get(key):null;
if(prevScene&&areScenesShallowEqual(prevScene,nextScene)){


nextScenes.push(prevScene);
}else{
nextScenes.push(nextScene);
}
};

staleScenes.forEach(mergeScene);
freshScenes.forEach(mergeScene);

nextScenes.sort(compareScenes);

var activeScenesCount=0;
nextScenes.forEach(function(scene,ii){
var isActive=!scene.isStale&&scene.index===nextState.index;
if(isActive!==scene.isActive){
nextScenes[ii]=_extends({},
scene,{
isActive:isActive});

}
if(isActive){
activeScenesCount++;
}
});

invariant(
activeScenesCount===1,
'there should always be only one scene active, not %s.',
activeScenesCount);


if(nextScenes.length!==scenes.length){
return nextScenes;
}

if(nextScenes.some(
function(scene,index){return!areScenesShallowEqual(scenes[index],scene);}))
{
return nextScenes;
}


return scenes;
}

module.exports=NavigationScenesReducer;