//
//  WRChapterData.m
//  WeRead (读书)
//
//  Detailed pseudo-code reconstruction of the chapter data model.
//  Stores the typeset NSAttributedString, manages highlights, underlines,
//  reviews, page ranges, and outline generation.
//

#import "WRChapterData.h"
#import "WRCoreTextLayouter.h"

// ============================================================================
#pragma mark - Constants
// ============================================================================

static NSString *const kHighlightRangeKey   = @"range";
static NSString *const kHighlightKeyKey     = @"key";
static NSString *const kHighlightItemIdKey  = @"itemId";
static NSString *const kHighlightColorKey   = @"color";
static NSString *const kUnderlineStyleKey   = @"style";
static NSString *const kUnderlineTypeKey    = @"type";

// Custom attribute name used in the attributed string to mark underlines.
static NSString *const kWRUnderlineAttributeName =
    @"com.weread.underline";

// Custom attribute name for highlight color.
static NSString *const kWRHighlightAttributeName =
    @"com.weread.highlight";

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

@interface WRChapterData ()

/// Internal mutable copy of highlights for mutation.
@property (nonatomic, strong) NSMutableArray<NSDictionary *> *mutableHighlights;

/// Internal mutable copy of underlines.
@property (nonatomic, strong) NSMutableArray<NSDictionary *> *mutableUnderlines;

/// Internal mutable copy of temp review highlights.
@property (nonatomic, strong) NSMutableArray<NSDictionary *> *mutableTempReviewHighlights;

@end

// ============================================================================
#pragma mark - WRChapterData Implementation
// ============================================================================

@implementation WRChapterData

// ============================================================================
#pragma mark - Initialization
// ============================================================================

- (instancetype)init {
    self = [super init];
    if (self) {
        _mutableHighlights           = [NSMutableArray array];
        _mutableUnderlines           = [NSMutableArray array];
        _mutableTempReviewHighlights = [NSMutableArray array];
        _bookmarkedPages             = [NSSet set];
        _freeTrialCutOffLocation     = NSNotFound;
        _contentInsets               = UIEdgeInsetsMake(20.0, 16.0, 20.0, 16.0);
    }
    return self;
}

// ============================================================================
#pragma mark - Class Methods
// ============================================================================

///
/// Adds an underline decoration to an NSMutableAttributedString at the
/// specified range. The underline is stored as a custom attribute so the
/// drawing code can render it with the correct style and color.
///
/// @param attributedString The mutable attributed string to modify.
/// @param range            The character range to underline.
/// @param itemId           Identifier for the item (e.g., bookmark or review ID).
/// @param style            The underline style (solid, dashed, wavy).
/// @param color            The underline color.
///
+ (void)addUnderLineToAttributedString:(NSMutableAttributedString *)attributedString
                                 range:(NSRange)range
                                itemId:(NSString *)itemId
                                 style:(WRUnderlineStyle)style
                                 color:(UIColor *)color {
    if (!attributedString || range.location == NSNotFound) return;
    if (NSMaxRange(range) > attributedString.length) return;

    // Build the underline descriptor dictionary.
    NSDictionary *underlineInfo = @{
        kHighlightItemIdKey : itemId ?: @"",
        kUnderlineStyleKey  : @(style),
        kHighlightColorKey  : color ?: [UIColor blackColor],
    };

    // Apply as a custom attribute. The rendering code in WRCoreTextLayoutFrame
    // will read this attribute and draw the underline during -drawInContext:.
    [attributedString addAttribute:kWRUnderlineAttributeName
                             value:underlineInfo
                             range:range];
}

///
/// Calculates the free trial cutoff location within the attributed string.
/// The book object provides trial chapter limits; this method finds the
/// corresponding character position in the typeset string.
///
/// @param attributedString The typeset attributed string.
/// @param book             The book model object (provides trial info).
/// @return The character index at which to cut off, or NSNotFound if fully accessible.
///
+ (NSUInteger)freeTrialChapterCutOffStringLocaionWithAttributedString:(NSAttributedString *)attributedString
                                                                 book:(id)book {
    if (!attributedString || !book) return NSNotFound;

    // In the real implementation, this queries the book model for:
    //   - The number of free trial characters / chapters allowed.
    //   - Whether this specific chapter falls within the trial range.
    // It then maps that to a character index in the attributed string.
    //
    // Typical logic:
    //   1. Ask `book` for the trial character count or chapter index limit.
    //   2. If this chapter is entirely within the trial, return NSNotFound (no cutoff).
    //   3. If this chapter is entirely beyond the trial, return 0 (show nothing).
    //   4. If the cutoff falls within this chapter, calculate the offset.

    // Placeholder: assume the book responds to -freeTrialCharacterLimit.
    if ([book respondsToSelector:NSSelectorFromString(@"freeTrialCharacterLimit")]) {
        NSUInteger limit = [[book valueForKey:@"freeTrialCharacterLimit"] unsignedIntegerValue];
        NSUInteger totalLength = attributedString.length;

        if (limit >= totalLength) {
            // Entire chapter is accessible.
            return NSNotFound;
        } else if (limit == 0) {
            // No access.
            return 0;
        } else {
            return limit;
        }
    }

    return NSNotFound;
}

// ============================================================================
#pragma mark - Highlight & Underline Management
// ============================================================================

/// Adds an auto-read underline. This is a visual indicator showing which
/// text is being auto-scrolled through.
- (void)addAutoReadUnderLineInRange:(NSRange)range
                               style:(WRUnderlineStyle)style
                                color:(UIColor *)color {
    if (range.location == NSNotFound) return;

    // Apply the underline attribute to the typeset string.
    [WRChapterData addUnderLineToAttributedString:self.typesetAttributedString
                                            range:range
                                           itemId:@"autoRead"
                                            style:style
                                            color:color];
}

/// Adds a persistent highlight annotation.
- (void)addHighlightInRange:(NSRange)range
                        key:(NSString *)key
                     itemId:(NSString *)itemId
                      color:(UIColor *)color {
    if (range.location == NSNotFound) return;

    NSDictionary *entry = @{
        kHighlightRangeKey  : [NSValue valueWithRange:range],
        kHighlightKeyKey    : key ?: @"",
        kHighlightItemIdKey : itemId ?: @"",
        kHighlightColorKey  : color ?: [UIColor yellowColor],
    };

    [_mutableHighlights addObject:entry];
    _highlights = [_mutableHighlights copy];

    // Also apply the highlight as a custom attribute on the attributed string
    // so the CoreText drawing code can render the background color.
    [self.typesetAttributedString addAttribute:kWRHighlightAttributeName
                                        value:@{kHighlightColorKey: (color ?: [UIColor yellowColor])}
                                        range:range];
}

/// Adds a review underline (from a friend's annotation or review).
- (void)addReviewUnderlineInRange:(NSRange)range
                           itemId:(NSString *)itemId
                             type:(WRReviewType)type {
    if (range.location == NSNotFound) return;

    NSDictionary *entry = @{
        kHighlightRangeKey  : [NSValue valueWithRange:range],
        kHighlightItemIdKey : itemId ?: @"",
        kUnderlineTypeKey   : @(type),
    };

    [_mutableUnderlines addObject:entry];
    _underlines = [_mutableUnderlines copy];

    // Apply underline attribute for rendering.
    WRUnderlineStyle style = (type == WRReviewTypeHighlight)
                                 ? WRUnderlineStyleNone
                                 : WRUnderlineStyleSolid;
    UIColor *color = (type == WRReviewTypeHighlight)
                         ? [UIColor colorWithRed:0.2 green:0.6 blue:1.0 alpha:0.3]
                         : [UIColor colorWithRed:1.0 green:0.4 blue:0.4 alpha:0.8];

    if (style != WRUnderlineStyleNone) {
        [WRChapterData addUnderLineToAttributedString:self.typesetAttributedString
                                                range:range
                                               itemId:itemId
                                                style:style
                                                color:color];
    }
}

/// Adds a temporary review highlight (used during the review creation flow
/// before the user confirms and persists it).
- (void)addTempReviewHighlightInRange:(NSRange)range
                               itemId:(NSString *)itemId {
    [self addTempReviewHighlightInRange:range
                                 itemId:itemId
                                  color:[UIColor colorWithRed:0.2
                                                        green:0.6
                                                         blue:1.0
                                                        alpha:0.3]];
}

/// Adds a temporary review highlight with a custom color.
- (void)addTempReviewHighlightInRange:(NSRange)range
                               itemId:(NSString *)itemId
                                color:(UIColor *)color {
    if (range.location == NSNotFound) return;

    NSDictionary *entry = @{
        kHighlightRangeKey  : [NSValue valueWithRange:range],
        kHighlightItemIdKey : itemId ?: @"",
        kHighlightColorKey  : color ?: [UIColor yellowColor],
    };

    [_mutableTempReviewHighlights addObject:entry];
    _tempReviewHighlights = [_mutableTempReviewHighlights copy];

    // Apply as a temporary attribute (not persisted).
    [self.typesetAttributedString addAttribute:kWRHighlightAttributeName
                                        value:@{kHighlightColorKey: (color ?: [UIColor yellowColor]),
                                                @"temporary": @YES}
                                        range:range];
}

/// Removes a review underline from both the internal array and the
/// attributed string attributes.
- (void)deleteReviewUnderlineInRange:(NSRange)range
                                type:(WRReviewType)type {
    if (range.location == NSNotFound) return;

    // Remove matching entries from the mutable array.
    NSMutableArray *toRemove = [NSMutableArray array];
    for (NSDictionary *entry in _mutableUnderlines) {
        NSRange entryRange = [entry[kHighlightRangeKey] rangeValue];
        WRReviewType entryType = [entry[kUnderlineTypeKey] integerValue];
        if (NSEqualRanges(entryRange, range) && entryType == type) {
            [toRemove addObject:entry];
        }
    }
    [_mutableUnderlines removeObjectsInArray:toRemove];
    _underlines = [_mutableUnderlines copy];

    // Remove the custom underline/highlight attributes from the string.
    [self.typesetAttributedString removeAttribute:kWRUnderlineAttributeName range:range];
    [self.typesetAttributedString removeAttribute:kWRHighlightAttributeName range:range];
}

// ============================================================================
#pragma mark - Page Range Queries
// ============================================================================

/// Returns the character range for the given page index.
/// The pageRanges array is computed during layout by WRCoreTextLayouter
/// and stored as an array of NSValue-wrapped NSRange objects.
- (NSRange)rangeOfPage:(NSUInteger)pageIndex {
    if (pageIndex >= self.pageRanges.count) {
        return NSMakeRange(NSNotFound, 0);
    }
    return [self.pageRanges[pageIndex] rangeValue];
}

// ============================================================================
#pragma mark - Outline Generation
// ============================================================================

/// Scans the typeset attributed string for heading-level paragraph styles
/// and builds an array of outline entries. Each entry is a dictionary with:
///   @"title" : NSString (the heading text)
///   @"level" : NSNumber (1 for H1, 2 for H2, etc.)
///   @"range" : NSValue wrapping the NSRange in the attributed string.
- (void)generateOutlineContents {
    NSMutableArray<NSDictionary *> *outline = [NSMutableArray array];
    NSAttributedString *str = self.typesetAttributedString;
    if (!str || str.length == 0) {
        self.outlineContents = @[];
        return;
    }

    // Walk the attributed string by paragraph.
    NSString *plainText = [str string];
    NSUInteger length = plainText.length;
    NSUInteger searchLoc = 0;

    while (searchLoc < length) {
        // Find the paragraph range.
        NSRange paraRange = [plainText rangeOfString:@"\n"
                                             options:0
                                               range:NSMakeRange(searchLoc, length - searchLoc)];
        if (paraRange.location == NSNotFound) {
            paraRange = NSMakeRange(searchLoc, length - searchLoc);
        } else {
            paraRange = NSMakeRange(searchLoc, paraRange.location - searchLoc + 1);
        }

        // Check if this paragraph has a heading font attribute.
        if (paraRange.length > 0) {
            NSDictionary *attrs = [str attributesAtIndex:paraRange.location
                                   effectiveRange:NULL];
            UIFont *font = attrs[NSFontAttributeName];

            // Heuristic: heading fonts are typically larger than body text.
            // In WeRead, headings may use a custom attribute or a specific
            // font descriptor. We check for font size > bodySize + 4.
            CGFloat bodySize = 16.0; // Typical body font size.
            if (font && font.pointSize > bodySize + 4.0) {
                NSString *title = [plainText substringWithRange:
                    NSMakeRange(paraRange.location,
                                paraRange.length > 1 ? paraRange.length - 1 : paraRange.length)];
                title = [title stringByTrimmingCharactersInSet:
                    [NSCharacterSet whitespaceAndNewlineCharacterSet]];

                if (title.length > 0) {
                    NSInteger level = 1;
                    if (font.pointSize < bodySize + 8.0) level = 2;
                    if (font.pointSize < bodySize + 6.0) level = 3;

                    [outline addObject:@{
                        @"title": title,
                        @"level": @(level),
                        @"range": [NSValue valueWithRange:paraRange],
                    }];
                }
            }
        }

        searchLoc = NSMaxRange(paraRange);
        if (searchLoc >= length) break;
    }

    self.outlineContents = [outline copy];
}

// ============================================================================
#pragma mark - Free Trial Cutoff
// ============================================================================

/// Returns the real string location accounting for typesetting differences.
/// The raw cutoff location from the server may differ from the position in
/// the typeset attributed string due to inserted image attachments, etc.
- (NSUInteger)freeTrialChapterCutOffRealStringLocation {
    if (self.freeTrialCutOffLocation == NSNotFound) {
        return NSNotFound;
    }

    // In the real implementation, this maps from the source string index
    // to the typeset string index, accounting for:
    //   - Image attachment characters () inserted during typesetting.
    //   - Font substitution changes in string length (rare).
    //
    // Simple approach: walk both strings in parallel, counting the offset.

    NSUInteger sourceLoc = self.freeTrialCutOffLocation;
    NSAttributedString *source = self.sourceAttributedString;
    NSMutableAttributedString *typeset = self.typesetAttributedString;

    if (!source || !typeset) return sourceLoc;

    // If the source and typeset strings have the same length, no mapping needed.
    if (source.length == typeset.length) return sourceLoc;

    // Otherwise, use a character-by-character mapping.
    // This is a simplified version; the real code may use a precomputed map.
    NSUInteger typesetLoc = 0;
    NSUInteger sourceIdx = 0;
    NSString *sourcePlain = [source string];
    NSString *typesetPlain = [typeset string];

    while (sourceIdx < sourceLoc && typesetLoc < typesetPlain.length) {
        // Skip image attachment characters in the typeset string.
        unichar tc = [typesetPlain characterAtIndex:typesetLoc];
        if (tc == 0xFFFC) { // NSAttachmentCharacter
            typesetLoc++;
            continue;
        }
        sourceIdx++;
        typesetLoc++;
    }

    return typesetLoc;
}

/// Sets the free trial cutoff location from the source string index.
- (void)markFreeTrialChapterCutOffStringLocation:(NSUInteger)location {
    self.freeTrialCutOffLocation = location;
}

// ============================================================================
#pragma mark - Property Accessors (Ivar-backed from binary)
// ============================================================================

// The binary shows these ivar types:
//   NSMutableAttributedString -> _typesetAttributedString
//   NSArray -> _pageRanges
//   NSArray -> _highlights
//   NSArray -> _underlines
//   NSArray -> _tempReviewHighlights
//   NSArray -> _outlineContents
//   NSArray -> _imageAttachments (used by layout for inline images)
//   WRCoreTextLayouter -> _layouter
//   NSSet -> _bookmarkedPages
//   NSAttributedString -> _sourceAttributedString

// These are standard @property synthesized accessors; the binary confirms
// the backing ivar names and types match.

@end