//
//  YHExplorerViewController.m
//  YohoExplorerDemo
//
//  Created by gaoqiang xu on 2/27/15.
//  Copyright (c) 2015 gaoqiang xu. All rights reserved.
//

static float kprogressViewHeight = 2.0f;
static float kprogressViewRadius = 2.0f;

#import "YHExplorerViewController.h"
#import "YHWebViewProgress.h"
#import "YHWebViewProgressView.h"
#import "CDVUIWebViewEngine.h"
#import "CDVWKWebViewEngine.h"
#import <objc/message.h>
#import "YHInjectJsCordovaManager.h"

@interface YHExplorerViewController ()<UIWebViewDelegate, WKNavigationDelegate, WKUIDelegate>
{
    BOOL _scalesPageToFit;
}

@property (strong, nonatomic) NSURLRequest *originRequest;

@property (strong, nonatomic) YHWebViewProgress *progressBar;
@property (strong, nonatomic) YHWebViewProgressView *progressView;

@property (nonatomic) BOOL isAppeared;
@property (strong, nonatomic) NSMutableArray *linkParsers;

@property (strong, nonatomic) NSValue *pointerValue;

@end

@implementation YHExplorerViewController


- (void)dealloc
{
    [self stopLoading];
    
    self.progressBar = nil;
    [self removeProgress];
    self.progressView = nil;
    
    if ([self.webViewEngine isKindOfClass:NSClassFromString(@"CDVWKWebViewEngine").class]) {
        [self.webView removeObserver:self forKeyPath:@"title"];
    }
}

- (void)initializeExplorer
{
    _commandDelegate = [[YHExplorerCommandDelegate alloc] initWithViewController:self];
    _commandQueue = [[YHExplorerCommandQueue alloc] initWithViewController:self];
    _progressBarEnabled = NO;
    _automaticallySchemeHandle = YES;
}

- (instancetype)initWithNibName:(NSString*)nibNameOrNil bundle:(NSBundle*)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        [self initializeExplorer];
    }
    return self;
}

- (instancetype)initWithCurrentNaviBar:(UINavigationBar *)currentNaviBar
{
    self = [self init];
    if (self) {
        self.currentNaviBar = currentNaviBar;
    }
    return self;
}


- (void)viewDidLoad
{
    [super viewDidLoad];
    self.isAppeared = NO;
    
    YHLinkDefaultParser *parser = [[YHLinkDefaultParser alloc] init];
    [self registerLinkParser:parser];
    
    if (self.progressBar && !self.progressBar.progressView.superview) {
        [self.currentNaviBar addSubview:self.progressBar.progressView];
    }
    
    if ([self.webViewEngine isKindOfClass:NSClassFromString(@"CDVWKWebViewEngine")]) {
        [self.progressView useWkWebView:(WKWebView *)self.webView];
        [self.webView addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:nil];
    }
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return [super shouldAutorotateToInterfaceOrientation:interfaceOrientation];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    self.isAppeared = YES;
    if (self.progressBar) {
        if (!self.progressBar.progressView.superview) {
            [self.currentNaviBar addSubview:self.progressBar.progressView];
        } else {
            [self.currentNaviBar bringSubviewToFront:self.progressBar.progressView];
        }
    }
}

/**
 *  移除滚动条
 */
- (void)removeProgress
{
    if (self.progressView) {
        [self.progressView removeFromSuperview];
    }
}

#pragma mark - Override Setter & Getter
- (NSMutableArray *)linkParsers
{
    if (!_linkParsers) {
        _linkParsers = [[NSMutableArray alloc] initWithCapacity:1];
    }
    return _linkParsers;
}

- (void)setProgressBarEnabled:(BOOL)progressBarEnabled
{
    if (_progressBarEnabled == progressBarEnabled) {
        return;
    }
    
    _progressBarEnabled = progressBarEnabled;
    
    if (progressBarEnabled) {
        self.progressView.layer.cornerRadius = kprogressViewRadius;
        
        [self.progressView setFrame:CGRectMake(0, 41 , CGRectGetWidth(self.view.frame), kprogressViewHeight)];
        self.progressView.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleBottomMargin;
        if (self.isAppeared) {
            [_currentNaviBar addSubview:self.progressView];
        }
        _progressBar.progressView = self.progressView;
        
        _progressBar = [[YHWebViewProgress alloc] init];
        _progressBar.progressView = self.progressView;
        
    } else {
        if (self.progressBar) {
            [self.progressBar.progressView removeFromSuperview];
            self.progressBar = nil;
        }
    }
}

- (YHWebViewProgressView *)progressView
{
    static YHWebViewProgressView *sharedProgressViewInstance = nil;
    static dispatch_once_t predicate;
    dispatch_once(&predicate, ^{
        sharedProgressViewInstance = [[YHWebViewProgressView alloc] init];
    });
    return sharedProgressViewInstance;
}

- (NSMutableArray *)autoSchemes
{
    if (!_autoSchemes) {
        _autoSchemes = [[NSMutableArray alloc] initWithObjects:
                        @"itms-apps",
                        @"itms-appss",
                        @"itmss",
                        @"tel",
                        @"sms",
                        @"mailto",
                        @"yohoefashion4in1",
                        @"yohomars", nil];
    }
    return _autoSchemes;
}

- (NSMutableArray *)autoHosts
{
    if (!_autoHosts) {
        _autoHosts = @[@"itunes.apple.com"].mutableCopy;
    }
    return _autoHosts;
}

- (NSValue *)pointerValue
{
    if (!_pointerValue) {
        _pointerValue = [NSValue valueWithPointer:(__bridge const void *)(self)];
    }
    return _pointerValue;
}

- (NSString*)userAgent
{
    _userAgent = [super userAgent];
    if ([self.delegate respondsToSelector:@selector(extraUserAgent)]) {
        NSString *ua = [self.delegate extraUserAgent];
        if (ua.length) {
            return [NSString stringWithFormat:@"%@ %@", _userAgent, ua];
        }
    }
    return _userAgent;
}

#pragma mark - Public
- (instancetype)initWithUrl:(NSString *)url
{
    self = [self init];
    if (self) {
        self.startPage = url;
    }
    
    return self;
}

- (void)loadWebUrl:(NSString *)urlStr
{
    NSURL *URL = nil;
    if (urlStr.length > 0) {
        URL = [NSURL URLWithString:urlStr];
        if (URL == nil) {
            // 如果url里面含有需要转码的字符，则这里进行一次编码
            urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
            URL = [NSURL URLWithString:urlStr];
        }
    }
    [self loadURL:URL];
}

- (void)loadURL:(NSURL *)URL
{
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
    self.originRequest = request;

    if ([self.delegate respondsToSelector:@selector(explorerWillLoadRequest:)]) {
        [self.delegate explorerWillLoadRequest:request];
    }
    self.startPage = request.URL.absoluteString;
    [self.webViewEngine loadRequest:request];
}

- (void)loadHTMLString:(NSString *)html
{
    [self.webViewEngine loadHTMLString:html baseURL:[[NSBundle mainBundle] bundleURL]];
}

- (void)loadHTMLString:(NSString *)html baseURL:(nullable NSURL *)baseURL
{
    [self.webViewEngine loadHTMLString:html baseURL:baseURL];
}

- (void)setProgressBarColor:(UIColor *)color
{
    if (self.progressBar) {
        YHWebViewProgressView *view = (YHWebViewProgressView *)self.progressBar.progressView;
        view.progressBarColor = color;
    }
}

- (void)registerLinkParser:(id <YHLinkParserDelegate>)parser
{
    if ([self.linkParsers containsObject:parser]) {
        return;
    }
    
    __weak typeof(self)weakSelf = self;
    parser.completion = ^(NSDictionary *result) {
        [weakSelf parseFinishedWithResult:result];
    };
    
    [self.linkParsers addObject:parser];
}

- (void)unRegisterLinkParser:(id <YHLinkParserDelegate>)parser
{
    [self.linkParsers removeObject:parser];
}

#pragma mark - Private
- (void)parseFinishedWithResult:(NSDictionary *)result
{
    if ([self.delegate respondsToSelector:@selector(explorerDidDetectParameters:)])
    {
        [self.delegate explorerDidDetectParameters:result];
    }
    
    if ([self.delegate respondsToSelector:@selector(explorer:didDetectParameters:)]) {
        [self.delegate explorer:self didDetectParameters:result];
    }
}

#pragma mark - UIWebDelegate

- (void)webViewDidStartLoad:(UIWebView*)theWebView
{
    if (self.progressBar) {
        [self.progressBar webViewDidStartLoad:theWebView];
    }
    [self callback_webViewDidStartLoad];
}

- (void)webViewDidFinishLoad:(UIWebView*)theWebView
{
    [[YHInjectJsCordovaManager sharedInstance] cycleInject:theWebView];
    
    if (self.originRequest == nil) {
        self.originRequest = theWebView.request;
    }
    
    NSString *title = [theWebView stringByEvaluatingJavaScriptFromString: @"document.title"];
    _pageTitle = title;
    
    if (self.delegate && [self.delegate respondsToSelector:@selector(pageTitleUpdated:)]) {
        [self.delegate pageTitleUpdated:title];
    }
    
    if (self.progressBar) {
        [self.progressBar webViewDidFinishLoad:theWebView];
    }
    
    [self callback_webViewDidFinishLoad];
    
    NSString *key = [[NSString alloc] initWithFormat:@"WebKit%@%@", @"CacheModel", @"PreferenceKey"];//WebKitCacheModelPreferenceKey
    [[NSUserDefaults standardUserDefaults] setInteger:0 forKey:key];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

- (void)webView:(UIWebView*)theWebView didFailLoadWithError:(NSError*)error
{
    if (self.progressBar) {
        [self.progressBar webView:theWebView didFailLoadWithError:error];
    }
    [self callback_webViewDidFailLoadWithError:error];
}

- (BOOL)webView:(UIWebView*)theWebView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType
{
    if (self.progressBar && [self.progressBar checkIfRPCURL:request]) {
        return NO;
    }
    
    BOOL currentShouldStartLoadWithRequest = [self callback_webViewShouldStartLoadWithRequest:request navigationType:navigationType];
    
    if (self.progressBar && currentShouldStartLoadWithRequest) {
        currentShouldStartLoadWithRequest = [self.progressBar webView:theWebView shouldStartLoadWithRequest:request navigationType:navigationType];
    }
    
    return currentShouldStartLoadWithRequest;
}


#pragma mark WKNavigationDelegate implementation
//页面开始加载时调用 1
- (void)webView:(WKWebView*)webView didStartProvisionalNavigation:(WKNavigation*)navigation
{
    [self callback_webViewDidStartLoad];
}

// 页面加载完成之后调用 2
- (void)webView:(WKWebView*)webView didFinishNavigation:(WKNavigation*)navigation
{
    [self callback_webViewDidFinishLoad];
}
// 页面加载失败时调用
- (void)webView:(WKWebView*)theWebView didFailProvisionalNavigation:(WKNavigation*)navigation withError:(NSError*)error
{
    [self callback_webViewDidFailLoadWithError:error];
}
// 数据加载发生错误时调用
- (void)webView:(WKWebView*)theWebView didFailNavigation:(WKNavigation*)navigation withError:(NSError*)error
{
    [self callback_webViewDidFailLoadWithError:error];
}
// 进程被终止时调用
- (void)webViewWebContentProcessDidTerminate:(WKWebView *)webView
{
    [webView reload];
}

//在发送请求之前，决定是否跳转
- (void)webView: (WKWebView *) webView decidePolicyForNavigationAction: (WKNavigationAction*) navigationAction decisionHandler: (void (^)(WKNavigationActionPolicy)) decisionHandler
{
    NSURLRequest *request = navigationAction.request;
    BOOL result = [self callback_webViewShouldStartLoadWithRequest:request navigationType:navigationAction.navigationType];
    if (result) {
        decisionHandler(WKNavigationActionPolicyAllow);
    } else {
        decisionHandler(WKNavigationActionPolicyCancel);
    }
}

#pragma mark - WKUIDelegate
- (WKWebView *)webView:(WKWebView *)webView createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration forNavigationAction:(WKNavigationAction *)navigationAction windowFeatures:(WKWindowFeatures *)windowFeatures
{
    if (!navigationAction.targetFrame.isMainFrame) {
        [webView loadRequest:navigationAction.request];
    }
    return nil;
}

#pragma mark - WebViewDelegate Callback
- (void)callback_webViewDidStartLoad
{
    [self.commandQueue resetRequestId];
    if ([self.delegate respondsToSelector:@selector(yhExplorer_webViewDidStartLoad:)])
    {
        [self.delegate yhExplorer_webViewDidStartLoad:self];
    }
}

- (void)callback_webViewDidFinishLoad
{
    [CDVUserAgentUtil releaseLock:self.userAgentLockToken];
    if ([self.delegate respondsToSelector:@selector(yhExplorer_webViewDidFinishLoad:)])
    {
        [self.delegate yhExplorer_webViewDidFinishLoad:self];
    }
}

- (void)callback_webViewDidFailLoadWithError:(NSError *)error
{
    [CDVUserAgentUtil releaseLock:self.userAgentLockToken];
    if ([self.delegate respondsToSelector:@selector(yhExplorer_webView:didFailLoadWithError:)])
    {
        [self.delegate yhExplorer_webView:self didFailLoadWithError:error];
    }
}

- (BOOL)callback_webViewShouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(NSInteger)navigationType
{
    if ([self.delegate respondsToSelector:@selector(yhExplorer_webView:shouldStartLoadWithRequest:navigationType:)])
    {
        if (![self.delegate yhExplorer_webView:self shouldStartLoadWithRequest:request navigationType:navigationType]) {
            return NO;
        }
    }
    
    NSURL *url = [request URL];
    
    /*
     * Execute any commands queued with cordova.exec() on the JS side.
     * The part of the URL after gap:// is irrelevant.
     */
    if ([[url scheme] isEqualToString:@"gap"]) {
        [self.commandQueue fetchCommandsFromJs];
        // The delegate is called asynchronously in this case, so we don't have to use
        // flushCommandQueueWithDelayedJs (setTimeout(0)) as we do with hash changes.
        [self.commandQueue executePending];
        return NO;
    }
    
    if (self.automaticallySchemeHandle) {
        if ([[UIApplication sharedApplication] canOpenURL:url]) {
            NSArray *array = [self.autoSchemes filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF = %@", url.scheme]];
            if (array.count > 0) {
                [[UIApplication sharedApplication] openURL:url];
                return NO;
            }
            array = [self.autoHosts filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF = %@", url.host]];
            if (array.count > 0) {
                [[UIApplication sharedApplication] openURL:url];
                return NO;
            }
        }
    }
    
    /*
     * Give plugins the chance to handle the url
     */
    
    if (navigationType == -1/*WKNavigationTypeOther*/)
    {
        navigationType = UIWebViewNavigationTypeOther;
    }
    
    BOOL anyPluginsResponded = NO;
    BOOL shouldAllowRequest = NO;
    
    for (NSString* pluginName in self.pluginObjects) {
        CDVPlugin* plugin = [self.pluginObjects objectForKey:pluginName];
        SEL selector = NSSelectorFromString(@"shouldOverrideLoadWithRequest:navigationType:");
        if ([plugin respondsToSelector:selector]) {
            anyPluginsResponded = YES;
            shouldAllowRequest = (((BOOL (*)(id, SEL, id, int))objc_msgSend)(plugin, selector, request, (UIWebViewNavigationType)navigationType));
            if (!shouldAllowRequest) {
                break;
            }
        }
    }

    if (anyPluginsResponded) {
        return shouldAllowRequest;
    }
    return YES;
}

#pragma mark - WebViewProtocol

- (UIScrollView *)scrollView
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        return [(UIWebView *)self.webView scrollView];
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView scrollView];
    }
    return nil;
}

- (NSURL *)requestURL
{
    return [self.webViewEngine URL];
}

- (BOOL)canGoBack
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        return [(UIWebView *)self.webView canGoBack];
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView canGoBack];
    }
    return NO;
}

- (BOOL)canGoForward
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        return [(UIWebView *)self.webView canGoForward];
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView canGoForward];
    }
    return NO;
}

- (id)goBack
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        [(UIWebView *)self.webView goBack];
        return nil;
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView goBack];
    }
    return nil;
}

- (id)goForward
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        [(UIWebView *)self.webView goForward];
        return nil;
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView goForward];
    }
    return nil;
}

- (id)reload
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        [(UIWebView *)self.webView reload];
        return nil;
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView reload];
    }
    return nil;
}

- (id)reloadFromOrigin
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        [(UIWebView *)self.webView reload];
        if (self.originRequest) {
            [self evaluateJavaScript:[NSString stringWithFormat:@"window.location.replace('%@')", self.originRequest.URL.absoluteString] completionHandler:nil];
        }
        return nil;
    } else if ([self.webView isKindOfClass:[WKWebView class]]) {
        return [(WKWebView *)self.webView reloadFromOrigin];
    }
    return nil;
}

- (void)stopLoading
{
    if ([self.webView isKindOfClass:UIWebView.class]) {
        [(UIWebView *)self.webView stopLoading];
    } else if ([self.webView isKindOfClass:WKWebView.class]) {
        [(WKWebView *)self.webView stopLoading];
    }
}

- (BOOL)scalesPageToFit
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        _scalesPageToFit = [(UIWebView *)self.webView scalesPageToFit];
    }
    return _scalesPageToFit;
}

- (void)setScalesPageToFit:(BOOL)scalesPageToFit
{
    if ([self.webView isKindOfClass:[UIWebView class]]) {
        [(UIWebView *)self.webView setScalesPageToFit:scalesPageToFit];
    }
    _scalesPageToFit = scalesPageToFit;
}

- (void)evaluateJavaScript:(NSString *)javaScriptString completionHandler:(void (^)(id, NSError *))completionHandler
{
    if ([self.webView isKindOfClass:UIWebView.class]) {
        [self.webViewEngine evaluateJavaScript:javaScriptString completionHandler:completionHandler];
    } else if ([self.webView isKindOfClass:WKWebView.class]) {
        [((WKWebView *)self.webView) evaluateJavaScript:javaScriptString completionHandler:completionHandler];
    }
}

- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)javaScriptString
{
    if ([self.webView isKindOfClass:UIWebView.class]) {
        NSString *result = [(UIWebView *)self.webView stringByEvaluatingJavaScriptFromString:javaScriptString];
        return result;
    } else if ([self.webView isKindOfClass:WKWebView.class]) {
        __block NSString *result = nil;
        __block BOOL isExecuted = NO;
        [(WKWebView*)self.webView evaluateJavaScript:javaScriptString completionHandler:^(id obj, NSError* error) {
            result = obj;
            isExecuted = YES;
        }];
        
        while (isExecuted == NO) {
            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        }
        return result;
    }
    return nil;
}

- (void)yh_setScrollEnabled:(BOOL)enabled
{
    UIView *view = self.webView;
    UIScrollView *scrollView = view.scrollView;
    
    scrollView.scrollEnabled = enabled;
    scrollView.panGestureRecognizer.enabled = enabled;
    
    // There is one subview as of iOS 8.1 of class WKScrollView
    for (UIView* subview in view.subviews) {
        if ([subview respondsToSelector:@selector(setScrollEnabled:)]) {
            [(id)subview setScrollEnabled:enabled];
        }
        
        if ([subview respondsToSelector:@selector(panGestureRecognizer)]) {
            [[(id)subview panGestureRecognizer] setEnabled:enabled];
        }
        
        // here comes the tricky part, desabling
        for (UIView* subScrollView in subview.subviews) {
            if ([subScrollView isKindOfClass:NSClassFromString(@"UIWebBrowserView")]) {
                for (UIGestureRecognizer *gesture in [subScrollView gestureRecognizers]) {
                    if ([gesture isKindOfClass:NSClassFromString(@"UIWebTouchEventsGestureRecognizer")])
                        [gesture setEnabled:enabled];
                }
            }
        }
    }
}

#pragma mark - KVO
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if([keyPath isEqualToString:@"title"])
    {
        NSString *title = change[NSKeyValueChangeNewKey];
        _pageTitle = title;
        if (self.delegate && [self.delegate respondsToSelector:@selector(pageTitleUpdated:)]) {
            [self.delegate pageTitleUpdated:title];
        }
    }
}

#pragma mark - CDVYHInterfaceDelegate
- (BOOL)parseLink:(NSString *)linkUrl
{
    for (id <YHLinkParserDelegate> parser in self.linkParsers) {
        if ([parser parseString:linkUrl]) {
            return YES;
        }
    }
    
    return NO;
}

- (void)nativeActionDidTriggerEventWithUserInfo:(NSDictionary *)userInfo completion:(void (^)(id, BOOL))completion {
    
    dispatch_async(dispatch_get_main_queue(), ^{
        if ([self.delegate respondsToSelector:@selector(didGetMessageFromWeb:completion:)]) {
            [self.delegate didGetMessageFromWeb:userInfo completion:completion];
        }
    });
}

#pragma mark - Method Forwarding
- (BOOL)respondsToSelector:(SEL)aSelector
{
    if ([super respondsToSelector:aSelector]) {
        return YES;
    }
    
    if ([self.webView respondsToSelector:aSelector]) {
        return YES;
    }
    
    return NO;
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
    NSMethodSignature *signature = [super methodSignatureForSelector:aSelector];
    if (!signature) {
        if (self.webView && [self.webView respondsToSelector:aSelector]) {
            return [(NSObject *)self.webView methodSignatureForSelector:aSelector];
        }
    }
    
    return signature;
}

- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    if (self.webView && [self.webView respondsToSelector:[anInvocation selector]]) {
        [anInvocation invokeWithTarget:self.webView];
    }
}

@end


@implementation YHExplorerCommandDelegate

#pragma mark CDVCommandDelegate implementation

- (id)getCommandInstance:(NSString*)className
{
    return [super getCommandInstance:className];
}

- (NSString*)pathForResource:(NSString*)resourcepath
{
    return [super pathForResource:resourcepath];
}

@end

@implementation YHExplorerCommandQueue

- (BOOL)execute:(CDVInvokedUrlCommand*)command
{
    return [super execute:command];
}

@end