//
//  WRPageView.m
//  WeRead (微信读书)
//
//  Detailed pseudo-code reconstruction of the page rendering view.
//  This view draws text directly via CoreText into CGContext — no UILabel
//  or UITextView is used for the reading content.
//

#import "WRPageView.h"
#import "WRChapterData.h"
#import "WRCoreTextLayoutFrame.h"
#import "WRActivityIndicator.h"
#import "WRLoadingProgressView.h"
#import "WRFriendReviewsButton.h"

// ============================================================================
#pragma mark - Private Helpers
// ============================================================================

/// Extracts a plain-text NSString from a given range of the chapter's
/// attributed string, stripping any attachment characters.
static NSString *WRPlainStringFromRange(NSAttributedString *attrStr, NSRange range) {
    if (!attrStr || range.location == NSNotFound) return @"";
    NSString *raw = [[attrStr string] substringWithRange:range];
    // Remove object replacement characters used for image attachments.
    return [raw stringByReplacingOccurrencesOfString:@"" withString:@""];
}

/// Converts a UITouch point from view coordinates to the flipped coordinate
/// system expected by CoreText (origin at bottom-left).
static CGPoint WRSFlipPointForCoreText(CGPoint viewPoint, CGFloat viewHeight) {
    return CGPointMake(viewPoint.x, viewHeight - viewPoint.y);
}

// ============================================================================
#pragma mark - WRPageView ()
// ============================================================================

@interface WRPageView ()

// ---- Private selection tracking ----
@property (nonatomic, assign) NSInteger selectionStartIndex;
@property (nonatomic, assign) NSInteger selectionEndIndex;
@property (nonatomic, assign) BOOL isSelecting;

// ---- Gesture recognizers ----
@property (nonatomic, strong) UITapGestureRecognizer *singleTapGR;
@property (nonatomic, strong) UILongPressGestureRecognizer *longPressGR;
@property (nonatomic, strong) UIPanGestureRecognizer *panGR;

// ---- Highlight/underline drawing cache ----
@property (nonatomic, strong) NSMutableArray<NSDictionary *> *highlightRects;

@end

// ============================================================================
#pragma mark - WRPageView Implementation
// ============================================================================

@implementation WRPageView

// ---- Synthesize properties backed by ivars from the binary ----
// The binary shows these ivar types:
//   NSArray          -> imageAttachments
//   NSMutableArray   -> visibleHighlights
//   NSTimer          -> autoReadTimer
//   NSTimer          -> loadingTimeoutTimer
//   NSString         -> chapterId
//   UILabel          -> headerLabel
//   UIImageView      -> backgroundImageView
//   WRActivityIndicator -> activityIndicator
//   UILabel          -> statusLabel
//   QMUIButton       -> retryButton
//   QMUIButton       -> shareButton
//   WRLoadingProgressView -> loadingProgressView
//   QMUIButton       -> bookmarkButton
//   QMUIButton       -> fontSizeUpButton
//   QMUIButton       -> fontSizeDownButton
//   WRFriendReviewsButton -> friendReviewsButton

// ============================================================================
#pragma mark - Lifecycle
// ============================================================================

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // CoreText views must be opaque and have a cleared background for
        // the CGContext to render correctly.
        self.opaque = YES;
        self.backgroundColor = [UIColor whiteColor];
        self.clearsContextBeforeDrawing = YES;

        // Enable multiple touches for selection handles.
        self.multipleTouchEnabled = YES;

        _selectionStartIndex = NSNotFound;
        _selectionEndIndex   = NSNotFound;
        _isSelecting         = NO;

        [self _setupSubviews];
        [self _setupGestureRecognizers];
    }
    return self;
}

- (void)dealloc {
    [_autoReadTimer invalidate];
    [_loadingTimeoutTimer invalidate];
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

// ============================================================================
#pragma mark - Subview Setup
// ============================================================================

/// Creates the non-text overlay UI elements. The reading text itself is
/// rendered entirely in -drawRect: via CoreText, so these are all floating
/// controls layered on top.
- (void)_setupSubviews {
    // ---- Background image (e.g., paper texture) ----
    _backgroundImageView = [[UIImageView alloc] initWithFrame:self.bounds];
    _backgroundImageView.autoresizingMask = UIViewAutoresizingFlexibleWidth |
                                            UIViewAutoresizingFlexibleHeight;
    _backgroundImageView.contentMode = UIViewContentModeScaleAspectFill;
    [self addSubview:_backgroundImageView];

    // ---- Header label (chapter title, page indicator) ----
    _headerLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    _headerLabel.font = [UIFont systemFontOfSize:12.0];
    _headerLabel.textColor = [UIColor grayColor];
    _headerLabel.textAlignment = NSTextAlignmentCenter;
    [self addSubview:_headerLabel];

    // ---- Activity indicator (shown during chapter load) ----
    _activityIndicator = [[WRActivityIndicator alloc] initWithFrame:CGRectZero];
    _activityIndicator.hidden = YES;
    [self addSubview:_activityIndicator];

    // ---- Status label (error / empty state) ----
    _statusLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    _statusLabel.font = [UIFont systemFontOfSize:15.0];
    _statusLabel.textColor = [UIColor darkGrayColor];
    _statusLabel.textAlignment = NSTextAlignmentCenter;
    _statusLabel.numberOfLines = 0;
    _statusLabel.hidden = YES;
    [self addSubview:_statusLabel];

    // ---- Retry button ----
    _retryButton = [QMUIButton buttonWithType:UIButtonTypeSystem];
    [_retryButton setTitle:@"重试" forState:UIControlStateNormal]; // "Retry"
    [_retryButton addTarget:self
                     action:@selector(_retryButtonTapped:)
           forControlEvents:UIControlEventTouchUpInside];
    _retryButton.hidden = YES;
    [self addSubview:_retryButton];

    // ---- Share button ----
    _shareButton = [QMUIButton buttonWithType:UIButtonTypeSystem];
    [_shareButton setImage:[UIImage imageNamed:@"icon_share"]
                  forState:UIControlStateNormal];
    [_shareButton addTarget:self
                     action:@selector(_shareButtonTapped:)
           forControlEvents:UIControlEventTouchUpInside];
    _shareButton.hidden = YES;
    [self addSubview:_shareButton];

    // ---- Loading progress view ----
    _loadingProgressView = [[WRLoadingProgressView alloc] initWithFrame:CGRectZero];
    _loadingProgressView.hidden = YES;
    [self addSubview:_loadingProgressView];

    // ---- Bookmark button ----
    _bookmarkButton = [QMUIButton buttonWithType:UIButtonTypeSystem];
    [_bookmarkButton addTarget:self
                        action:@selector(_bookmarkButtonTapped:)
              forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:_bookmarkButton];

    // ---- Font size buttons ----
    _fontSizeUpButton = [QMUIButton buttonWithType:UIButtonTypeSystem];
    [_fontSizeUpButton setTitle:@"A+" forState:UIControlStateNormal];
    [_fontSizeUpButton addTarget:self
                          action:@selector(_fontSizeUpTapped:)
                forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:_fontSizeUpButton];

    _fontSizeDownButton = [QMUIButton buttonWithType:UIButtonTypeSystem];
    [_fontSizeDownButton setTitle:@"A-" forState:UIControlStateNormal];
    [_fontSizeDownButton addTarget:self
                            action:@selector(_fontSizeDownTapped:)
                  forControlEvents:UIControlEventTouchUpInside];
    [self addSubview:_fontSizeDownButton];

    // ---- Friend reviews button ----
    _friendReviewsButton = [[WRFriendReviewsButton alloc] initWithFrame:CGRectZero];
    [_friendReviewsButton addTarget:self
                             action:@selector(_friendReviewsTapped:)
                   forControlEvents:UIControlEventTouchUpInside];
    _friendReviewsButton.hidden = YES;
    [self addSubview:_friendReviewsButton];
}

// ============================================================================
#pragma mark - Gesture Recognizers
// ============================================================================

- (void)_setupGestureRecognizers {
    // Single tap: link detection, selection dismissal, toolbar toggle.
    _singleTapGR = [[UITapGestureRecognizer alloc]
        initWithTarget:self action:@selector(_handleSingleTap:)];
    _singleTapGR.numberOfTapsRequired = 1;
    [self addGestureRecognizer:_singleTapGR];

    // Long press: initiate text selection.
    _longPressGR = [[UILongPressGestureRecognizer alloc]
        initWithTarget:self action:@selector(_handleLongPress:)];
    _longPressGR.minimumPressDuration = 0.5;
    [self addGestureRecognizer:_longPressGR];

    // Pan: extend selection after long press.
    _panGR = [[UIPanGestureRecognizer alloc]
        initWithTarget:self action:@selector(_handlePan:)];
    _panGR.enabled = NO; // Enabled only when selecting.
    [self addGestureRecognizer:_panGR];

    // Long press should fail before single tap fires.
    [_singleTapGR requireGestureRecognizerToFail:_longPressGR];
}

// ============================================================================
#pragma mark - Layout
// ============================================================================

- (void)layoutSubviews {
    [super layoutSubviews];
    // Position the header label at the top edge with padding.
    CGFloat headerHeight = 20.0;
    _headerLabel.frame = CGRectMake(16.0, 8.0,
                                    CGRectGetWidth(self.bounds) - 32.0,
                                    headerHeight);

    // Center the activity indicator.
    _activityIndicator.center = CGPointMake(CGRectGetMidX(self.bounds),
                                            CGRectGetMidY(self.bounds));

    // Position the friend reviews button at bottom-right.
    CGSize reviewSize = CGSizeMake(60.0, 30.0);
    _friendReviewsButton.frame =
        CGRectMake(CGRectGetWidth(self.bounds) - reviewSize.width - 16.0,
                   CGRectGetHeight(self.bounds) - reviewSize.height - 40.0,
                   reviewSize.width, reviewSize.height);
}

// ============================================================================
#pragma mark - CoreText Drawing (drawRect:)
// ============================================================================

///
/// This is the heart of the page view. It draws the chapter text directly
/// into the CGContext using CoreText. No UILabel or UITextView is involved.
///
/// The flow is:
///   1. Get the current graphics context.
///   2. Flip the coordinate system for CoreText (origin at bottom-left).
///   3. Call WRCoreTextLayoutFrame to draw the attributed string runs.
///   4. Draw inline images at their attachment positions.
///   5. Draw highlight/underline overlays.
///
- (void)drawRect:(CGRect)rect {
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    if (!ctx) return;

    // If there is no chapter data or layout frame, just clear and return.
    if (!self.chapterData || !self.layoutFrame) {
        CGContextClearRect(ctx, rect);
        return;
    }

    // ---- Step 1: Fill background ----
    UIColor *bgColor = self.backgroundColor ?: [UIColor whiteColor];
    CGContextSetFillColorWithColor(ctx, bgColor.CGColor);
    CGContextFillRect(ctx, rect);

    // ---- Step 2: Flip coordinate system for CoreText ----
    // CoreText uses a bottom-left origin; UIKit uses top-left.
    CGContextSetTextMatrix(ctx, CGAffineTransformIdentity);
    CGContextTranslateCTM(ctx, 0.0, CGRectGetHeight(self.bounds));
    CGContextScaleCTM(ctx, 1.0, -1.0);

    // ---- Step 3: Draw the layout frame ----
    // This calls WRCoreTextLayoutFrame -drawInContext:image:size:inRect:position:
    // which iterates over CTLine objects, draws glyphs, and positions images.
    CGSize pageSize = self.bounds.size;
    CGPoint drawOrigin = CGPointMake(0.0, 0.0); // Could include margins.
    CGRect drawRect = UIEdgeInsetsInsetRect(self.bounds,
                                            self.chapterData.contentInsets);

    [self.layoutFrame drawInContext:ctx
                             image:self.backgroundImageView.image
                              size:pageSize
                            inRect:drawRect
                          position:drawOrigin];

    // ---- Step 4: Draw highlights and underlines ----
    [self _drawHighlightsInContext:ctx];

    // ---- Step 5: Draw selection handles if selecting ----
    if (self.isSelecting) {
        [self _drawSelectionInContext:ctx];
    }
}

/// Draws highlight rectangles and underline paths for annotations,
/// bookmarks, and the current selection.
- (void)_drawHighlightsInContext:(CGContextRef)ctx {
    for (NSDictionary *entry in self.highlightRects) {
        CGRect hlRect = [entry[@"rect"] CGRectValue];
        UIColor *color = entry[@"color"] ?: [UIColor yellowColor];
        BOOL isUnderline = [entry[@"underline"] boolValue];

        CGContextSetFillColorWithColor(ctx,
            [color colorWithAlphaComponent:0.3].CGColor);
        CGContextFillRect(ctx, hlRect);

        if (isUnderline) {
            CGFloat y = CGRectGetMaxY(hlRect);
            CGContextSetStrokeColorWithColor(ctx, color.CGColor);
            CGContextSetLineWidth(ctx, 1.0);
            CGContextMoveToPoint(ctx, CGRectGetMinX(hlRect), y);
            CGContextAddLineToPoint(ctx, CGRectGetMaxX(hlRect), y);
            CGContextStrokePath(ctx);
        }
    }
}

/// Draws the selection highlight between selectionStartIndex and
/// selectionEndIndex using CTLineGetOffsetForStringIndex.
- (void)_drawSelectionInContext:(CGContextRef)ctx {
    if (_selectionStartIndex == NSNotFound || _selectionEndIndex == NSNotFound) {
        return;
    }

    // Clamp range.
    NSInteger lo = MIN(_selectionStartIndex, _selectionEndIndex);
    NSInteger hi = MAX(_selectionStartIndex, _selectionEndIndex);
    NSRange selRange = NSMakeRange((NSUInteger)lo, (NSUInteger)(hi - lo));

    // Ask the layout frame for the rects covering this range.
    NSArray<NSValue *> *rects = [self.layoutFrame rectsWithinRange:selRange];
    UIColor *selColor = [UIColor colorWithRed:0.2 green:0.5 blue:1.0 alpha:0.3];

    for (NSValue *val in rects) {
        CGRect r = [val CGRectValue];
        CGContextSetFillColorWithColor(ctx, selColor.CGColor);
        CGContextFillRect(ctx, r);
    }
}

// ============================================================================
#pragma mark - Drawing API (called externally)
// ============================================================================

/// External entry point for drawing. Delegates to the layout frame.
- (void)drawInContext:(CGContextRef)context
            withData:(WRChapterData *)chapterData
                size:(CGSize)size
              inRect:(CGRect)rect
            position:(CGPoint)position {
    // Store references so -drawRect: can use them.
    self.chapterData = chapterData;

    // Trigger a redraw.
    [self setNeedsDisplay];
}

// ============================================================================
#pragma mark - Text Selection via CoreText Hit Testing
// ============================================================================

/// Converts a view-coordinate point to a string index in the attributed string
/// using CTLineGetStringIndexForPosition.
- (NSInteger)stringIndexForPoint:(CGPoint)point {
    if (!self.layoutFrame) return NSNotFound;

    // Flip Y for CoreText.
    CGPoint ctPoint = WRSFlipPointForCoreText(point, CGRectGetHeight(self.bounds));

    // Walk the CTLine objects in the layout frame to find the line at this Y,
    // then use CTLineGetStringIndexForPosition to get the character index.
    NSInteger index = [self.layoutFrame stringIndexForPoint:ctPoint];
    return index;
}

/// Returns the range of the line containing the given string index,
/// using CTLineGetOffsetForStringIndex to find line boundaries.
- (NSRange)lineRangeForStringIndex:(NSInteger)index {
    if (!self.layoutFrame || index == NSNotFound) {
        return NSMakeRange(NSNotFound, 0);
    }
    return [self.layoutFrame lineRangeForStringIndex:index];
}

/// Clears the current text selection and disables the pan gesture.
- (void)clearSelection {
    _selectionStartIndex = NSNotFound;
    _selectionEndIndex   = NSNotFound;
    _isSelecting         = NO;
    _panGR.enabled       = NO;
    [self setNeedsDisplay];
}

// ============================================================================
#pragma mark - Gesture Handlers
// ============================================================================

- (void)_handleSingleTap:(UITapGestureRecognizer *)gr {
    CGPoint pt = [gr locationInView:self];

    // If currently selecting, dismiss selection.
    if (self.isSelecting) {
        [self clearSelection];
        return;
    }

    // Check if the tap hits a link in the layout frame.
    NSInteger idx = [self stringIndexForPoint:pt];
    if (idx != NSNotFound) {
        NSURL *linkURL = [self.layoutFrame linkURLAtIndex:idx];
        if (linkURL) {
            if ([self.delegate respondsToSelector:@selector(pageView:didTapLinkWithURL:)]) {
                [self.delegate pageView:self didTapLinkWithURL:linkURL];
            }
            return;
        }
    }

    // Otherwise, toggle toolbar / delegate the tap.
    // (In the real app, this toggles the reader chrome.)
}

- (void)_handleLongPress:(UILongPressGestureRecognizer *)gr {
    if (gr.state == UIGestureRecognizerStateBegan) {
        CGPoint pt = [gr locationInView:self];
        NSInteger idx = [self stringIndexForPoint:pt];

        if (idx != NSNotFound) {
            _selectionStartIndex = idx;
            _selectionEndIndex   = idx;
            _isSelecting         = YES;
            _panGR.enabled       = YES;
            [self setNeedsDisplay];

            if ([self.delegate respondsToSelector:@selector(pageView:didBeginSelectionAtPoint:)]) {
                [self.delegate pageView:self didBeginSelectionAtPoint:pt];
            }
        }
    }
}

- (void)_handlePan:(UIPanGestureRecognizer *)gr {
    if (!self.isSelecting) return;

    CGPoint pt = [gr locationInView:self];
    NSInteger idx = [self stringIndexForPoint:pt];

    if (idx != NSNotFound && idx != _selectionEndIndex) {
        _selectionEndIndex = idx;
        [self setNeedsDisplay];

        // Notify delegate of selection range change.
        NSInteger lo = MIN(_selectionStartIndex, _selectionEndIndex);
        NSInteger hi = MAX(_selectionStartIndex, _selectionEndIndex);
        NSRange selRange = NSMakeRange((NSUInteger)lo, (NSUInteger)(hi - lo));

        if ([self.delegate respondsToSelector:@selector(pageView:selectionDidChangeWithRange:)]) {
            [self.delegate pageView:self selectionDidChangeWithRange:selRange];
        }
    }
}

// ============================================================================
#pragma mark - Accessibility
// ============================================================================

/// Provides a plain-text representation of the page for VoiceOver.
- (nullable NSString *)accessibilityValue {
    if (!self.chapterData) return nil;
    NSAttributedString *attrStr = self.chapterData.typesetAttributedString;
    if (!attrStr) return nil;

    // Return the plain text for the current page range.
    NSRange pageRange = [self.chapterData rangeOfPage:self.pageIndex];
    return WRPlainStringFromRange(attrStr, pageRange);
}

/// Supports VoiceOver scroll gestures to flip pages.
- (BOOL)accessibilityScroll:(UIAccessibilityScrollDirection)direction {
    // Post a page-change notification for the WRPageViewController to handle.
    NSString *dirStr = nil;
    switch (direction) {
        case UIAccessibilityScrollDirectionLeft:
            dirStr = @"next";
            break;
        case UIAccessibilityScrollDirectionRight:
            dirStr = @"previous";
            break;
        default:
            return NO;
    }

    [[NSNotificationCenter defaultCenter]
        postNotificationName:@"WRPageViewAccessibilityScroll"
                      object:self
                    userInfo:@{@"direction": dirStr}];
    return YES;
}

// ============================================================================
#pragma mark - Friend Reviews
// ============================================================================

- (void)friendReviewsCount:(NSUInteger)count {
    self.friendReviewsButton.hidden = (count == 0);
    [self.friendReviewsButton setReviewCount:count];
}

// ============================================================================
#pragma mark - Loading / Error States
// ============================================================================

- (void)showLoadingWithProgress:(float)progress {
    self.activityIndicator.hidden = NO;
    [self.activityIndicator startAnimating];

    if (progress > 0.0 && progress < 1.0) {
        self.loadingProgressView.hidden = NO;
        self.loadingProgressView.progress = progress;
    } else {
        self.loadingProgressView.hidden = YES;
    }

    // Start a timeout timer — if loading takes too long, show an error.
    [_loadingTimeoutTimer invalidate];
    _loadingTimeoutTimer =
        [NSTimer scheduledTimerWithTimeInterval:15.0
                                         target:self
                                       selector:@selector(_loadingDidTimeout)
                                       userInfo:nil
                                        repeats:NO];
}

- (void)hideLoading {
    [_loadingTimeoutTimer invalidate];
    _loadingTimeoutTimer = nil;

    [self.activityIndicator stopAnimating];
    self.activityIndicator.hidden = YES;
    self.loadingProgressView.hidden = YES;
}

- (void)showErrorWithMessage:(NSString *)message {
    [self hideLoading];
    self.statusLabel.text = message;
    self.statusLabel.hidden = NO;
    self.retryButton.hidden = NO;
}

- (void)_loadingDidTimeout {
    [self showErrorWithMessage:@"加载超时，请重试"]; // "Loading timed out, please retry"
}

// ============================================================================
#pragma mark - Button Actions
// ============================================================================

- (void)_retryButtonTapped:(QMUIButton *)sender {
    self.statusLabel.hidden = YES;
    self.retryButton.hidden = YES;
    if ([self.delegate respondsToSelector:@selector(pageViewNeedsReload:)]) {
        [self.delegate pageViewNeedsReload:self];
    }
}

- (void)_shareButtonTapped:(QMUIButton *)sender {
    // Share current page content.
    // Handled by delegate or responder chain.
}

- (void)_bookmarkButtonTapped:(QMUIButton *)sender {
    // Toggle bookmark for current page.
    sender.selected = !sender.selected;
}

- (void)_fontSizeUpTapped:(QMUIButton *)sender {
    // Increase font size — triggers re-typeset.
    [[NSNotificationCenter defaultCenter]
        postNotificationName:@"WRPageViewFontSizeChange"
                      object:self
                    userInfo:@{@"delta": @(1)}];
}

- (void)_fontSizeDownTapped:(QMUIButton *)sender {
    [[NSNotificationCenter defaultCenter]
        postNotificationName:@"WRPageViewFontSizeChange"
                      object:self
                    userInfo:@{@"delta": @(-1)}];
}

- (void)_friendReviewsTapped:(QMUIButton *)sender {
    if ([self.delegate respondsToSelector:@selector(pageView:didTapFriendReviewsWithCount:)]) {
        [self.delegate pageView:self
            didTapFriendReviewsWithCount:sender.tag];
    }
}

// ============================================================================
#pragma mark - Auto-Read Timer
// ============================================================================

/// Starts the auto-read timer that periodically advances the page.
- (void)startAutoReadWithInterval:(NSTimeInterval)interval {
    [_autoReadTimer invalidate];
    _autoReadTimer =
        [NSTimer scheduledTimerWithTimeInterval:interval
                                         target:self
                                       selector:@selector(_autoReadTick)
                                       userInfo:nil
                                        repeats:YES];
}

- (void)stopAutoRead {
    [_autoReadTimer invalidate];
    _autoReadTimer = nil;
}

- (void)_autoReadTick {
    // Post notification for the page view controller to advance.
    [[NSNotificationCenter defaultCenter]
        postNotificationName:@"WRPageViewAutoReadAdvance"
                      object:self];
}

@end