css.h

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Copyright (c) 2021, Jan Koester jan.koester@gmx.net
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#pragma once
 
#include <string>
#include <vector>
#include <map>
#include <set>
#include <memory>
#include <array>
 
namespace libhtmlpp {
 
    class CSSProperty {
    public:
        CSSProperty();
        CSSProperty(const std::string &name, const std::string &value);
        CSSProperty(const CSSProperty &prop);
        ~CSSProperty();
 
        CSSProperty& operator=(const CSSProperty &prop);
 
        const std::string& getName() const;
        void                setName(const std::string &name);
 
        const std::string& getValue() const;
        void                setValue(const std::string &value);
 
    private:
        std::string _Name;
        std::string _Value;
    };
 
    class CSSDeclaration {
    public:
        CSSDeclaration();
        CSSDeclaration(const CSSDeclaration &decl);
        ~CSSDeclaration();
 
        CSSDeclaration& operator=(const CSSDeclaration &decl);
 
        void addProperty(const std::string &name, const std::string &value);
        void removeProperty(const std::string &name);
 
        const CSSProperty* getProperty(const std::string &name) const;
 
        const std::vector<CSSProperty>& getProperties() const;
 
        std::string serialize() const;
 
        void parse(const std::string &input);
        void clear();
 
    private:
        std::vector<CSSProperty> _Properties;
    };
 
    class CSSRule {
    public:
        CSSRule();
        CSSRule(const std::string &selector);
        CSSRule(const CSSRule &rule);
        ~CSSRule();
 
        CSSRule& operator=(const CSSRule &rule);
 
        const std::string& getSelector() const;
        void                setSelector(const std::string &selector);
 
        CSSDeclaration&       getDeclaration();
        const CSSDeclaration& getDeclaration() const;
 
        std::string serialize(bool formatted = false) const;
 
    private:
        std::string     _Selector;
        CSSDeclaration  _Declaration;
    };
 
    struct AncestorFrame {
        std::string tag;
        std::vector<std::string> classes;
        std::string id;
        std::map<std::string,std::string> attributes;
    };
 
    struct AttributeCondition {
        std::string name;
        std::string op;
        std::string value;
    };
 
    class CSSStyleSheet {
    public:
        CSSStyleSheet();
        CSSStyleSheet(const CSSStyleSheet &sheet);
        ~CSSStyleSheet();
 
        CSSStyleSheet& operator=(const CSSStyleSheet &sheet);
 
        void parse(const std::string &input);
 
        void addRule(const CSSRule &rule);
        void removeRule(size_t index);
 
        const CSSRule* getRule(size_t index) const;
        size_t         getRuleCount() const;
 
        const std::vector<CSSRule>& getRules() const;
 
        std::string serialize(bool formatted = false) const;
        void clear();
 
        static CSSDeclaration parseInlineStyle(const std::string &style);
 
        static bool approximateSelectorMatch(const std::string &selector,
                                              const std::string &tag,
                                              const std::vector<std::string> &classes,
                                              const std::string &id,
                                              const std::vector<AncestorFrame> *ancestors = nullptr);
 
        void collectApproximateMatches(const std::string &tag,
                                        const std::string &cssClass,
                                        const std::string &id,
                                        std::map<std::string,std::string> &props,
                                        std::string &mediaRules,
                                        std::set<std::string> &seenMediaBlocks,
                                        const std::vector<AncestorFrame> *ancestors = nullptr,
                                        const std::map<std::string,std::string> *targetAttributes = nullptr) const;
 
    private:
        void _skipWhitespace(const std::string &input, size_t &pos) const;
        void _skipComment(const std::string &input, size_t &pos) const;
        std::vector<CSSRule> _Rules;
 
        // collectApproximateMatches is called once per imported HTML element
        // (see htmlimport.cpp), and re-parsing every rule's selector list
        // (comma-split, trim, strip combinator, reject unsupported syntax)
        // fresh on every single one of those calls is pure waste: none of
        // that depends on the element being matched, only on _Rules, which
        // doesn't change between them. On a real page-builder site (~2500
        // rules from ~115 <style> blocks, ~2000 importable elements) that
        // redundant re-parsing was confirmed to cost over half the total
        // import time. This caches each rule's already-split/filtered
        // selector branches the first time collectApproximateMatches runs
        // after a mutation, so the expensive parsing happens O(rules) times
        // total instead of O(rules * elements).
        struct _CompoundCacheBranch {
            bool skip;            // true if this branch's syntax can't be safely evaluated
            bool isAtRule;
            std::string atWrapper;      // e.g. "@media (max-width: 600px)" -- only set if isAtRule
            std::string trimmedSelector; // the (possibly per-branch) selector text, for at-rule block reconstruction
            std::string tag;
            std::vector<std::string> classes;
            std::string id;
            // Attribute-selector conditions found on the TARGET compound
            // itself (e.g. the "[data-fit=fill]" in ".fade-box[data-fit=
            // fill]"), verified against collectApproximateMatches's
            // @p targetAttributes when given -- see AttributeCondition.
            std::vector<AttributeCondition> attrConditions;
            bool hadCombinator;
            // Every compound left of the target one above, left-to-right/
            // outermost-first (e.g. for ".a .b .c", this holds ".a" and ".b"
            // -- "c" is the tag/classes/id/hadCombinator fields already
            // above). Empty tag/classes/id/attrConditions within one entry
            // means that compound's syntax couldn't be safely evaluated at
            // all (an unsupported pseudo-class was present -- see
            // hasUnsupportedSelectorSyntax) -- ancestorChainSatisfies treats
            // that as vacuously satisfied rather than an unmet requirement.
            // A compound with ONLY attrConditions (no tag/class/id, e.g.
            // "[data-fit=fill]") is a real, checkable requirement now that
            // AncestorFrame can carry an ancestor's own attributes -- see
            // ancestorChainSatisfies.
            struct AncestorCompound {
                std::string tag;
                std::vector<std::string> classes;
                std::string id;
                std::vector<AttributeCondition> attrConditions;
            };
            std::vector<AncestorCompound> ancestorCompounds;
            // Approximate CSS specificity of this branch's full selector
            // text (trimmedSelector), as the standard (id-count,
            // class/attribute/pseudo-class-count, type/pseudo-element-count)
            // triple -- see computeSpecificity in css.cpp. Used by
            // collectApproximateMatches to let a more specific matching rule
            // win regardless of source order, instead of the plain
            // last-rule-wins approximation this file used everywhere else.
            std::array<int,3> specificity{0,0,0};
        };
        mutable std::vector<std::vector<_CompoundCacheBranch>> _compoundCache;
        mutable bool _compoundCacheValid = false;
        void _rebuildCompoundCache() const;
    };
 
    std::string resolveCSSVariables(const std::string &value,
                                     const std::map<std::string,std::string> &customProperties,
                                     bool *unresolved = nullptr);
 
}