export const HISTORY_PREFIX = 'HOMEBREWERY-HISTORY';
export const HISTORY_SLOTS = 5;
// const HISTORY_SAVE_DELAYS = {
//  0: 0,           // 0 minutes (if not specified)
// 	1: 2,			// 2 minutes
// 	2: 10,			// 10 minutes
// 	3: 60,			// 60 minutes
// 	4: 12 * 60,     // 12 hours
// 	5: 2 * 24 * 60  // 2 days
// };
//
// const GARBAGE_COLLECT_DELAY = 28 * 24 * 60; // 28 days


// <=================== TEST VALUES STARTS ===================>

// Test values
const HISTORY_SAVE_DELAYS = {
	0 : 0,           // 0 minutes (if not specified)
	1 : 1,			// 1 minutes
	2 : 2,			// 2 minutes
	3 : 3,			// 3 minutes
	4 : 4,           // 4 minutes
	5 : 5            // 5 minutes
};
const GARBAGE_COLLECT_DELAY = 10; // 10 minutes

// <==================== TEST VALUES ENDS ====================>



const DEFAULT_STORED_BREW = {
	shareId  : 'default_brew',
	expireAt : '2000-01-01T00:00:00.000Z'
};

function getKeyBySlot(brew, slot){
	return `${HISTORY_PREFIX}-${brew.shareId}-${slot}`;
};

function getVersionBySlot(brew, slot){
	// Read stored brew data
	// - If it exists, parse data to object
	// - If it doesn't exist, pass default object
	const key = getKeyBySlot(brew, slot);
	const storedVersion = localStorage.getItem(key);
	const output = storedVersion ? JSON.parse(storedVersion) : { ...DEFAULT_STORED_BREW, ...brew };
	return output;
};

function updateStoredBrew(brew, slot=0){
	const archiveBrew = {};

	// Data from brew to be stored
	archiveBrew.title = brew.title;
	archiveBrew.text = brew.text;
	archiveBrew.style = brew.style;
	archiveBrew.version = brew.version;
	archiveBrew.shareId = brew.shareId;

	// Calculated values
	archiveBrew.savedAt = brew?.savedAt || new Date();
	archiveBrew.expireAt = new Date();
	archiveBrew.expireAt.setMinutes(archiveBrew.expireAt.getMinutes() + HISTORY_SAVE_DELAYS[slot]);

	// Store data
	const key = getKeyBySlot(brew, slot);
	localStorage.setItem(key, JSON.stringify(archiveBrew));
	return;
};

export function historyExists(brew){
	return Object.keys(localStorage)
        .some((key)=>{
        	return key.startsWith(`${HISTORY_PREFIX}-${brew.shareId}`);
        });
}

export function loadHistory(brew){
	const history = {};

	// Load data from local storage to History object
	for (let i = 1; i <= HISTORY_SLOTS; i++){
		history[i] = getVersionBySlot(brew, i);
	};

	return history;
}

export function updateHistory(brew) {
	const history = loadHistory(brew);

	// Walk each version position
	for (let slot = HISTORY_SLOTS; slot > 0; slot--){
		const storedVersion = history[slot];

		// If slot has expired, update all lower slots and break
		if(new Date() >= new Date(storedVersion.expireAt)){
			for (let updateSlot = slot - 1; updateSlot>0; updateSlot--){
				// Move data from updateSlot to updateSlot + 1
				updateStoredBrew({ ...history[updateSlot], shareId: brew.shareId }, updateSlot + 1);
			};

			// Update the most recent brew
			updateStoredBrew(brew, 1);

			// Break out of data checks because we found an expired value
			break;
		}
	};
};

export function getHistoryItems(brew){
	const historyArray = [];

	for (let i = 1; i <= HISTORY_SLOTS; i++){
		historyArray.push(getVersionBySlot(brew, i));
	}

	return historyArray;
};

export function versionHistoryGarbageCollection(){
	Object.keys(localStorage)
        .filter((key)=>{
        	return key.startsWith(HISTORY_PREFIX);
        })
        .forEach((key)=>{
        	const collectAt = new Date(JSON.parse(localStorage.getItem(key)).expireAt);
        	collectAt.setMinutes(collectAt.getMinutes() + GARBAGE_COLLECT_DELAY);
        	if(new Date() > collectAt){
        		localStorage.removeItem(key);
        	}
        });
};