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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * particular file as subject to the "Classpath" exception as provided
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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package jdk.javadoc.internal.doclint;

import java.util.Collections;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import javax.lang.model.element.Name;

import com.sun.tools.javac.util.StringUtils;

import static jdk.javadoc.internal.doclint.HtmlTag.Attr.*;


Enum representing HTML tags.
The intent of this class is to embody the semantics of W3C HTML 4.01
to the extent supported/used by javadoc.
In time, we may wish to transition javadoc and doclint to using HTML 5.
This is derivative of com.sun.tools.doclets.formats.html.markup.HtmlTag.
Eventually, these two should be merged back together, and possibly made
public.

Author:Bhavesh Patel, Jonathan Gibbons (revised)
See Also:
/**
 * Enum representing HTML tags.
 *
 * The intent of this class is to embody the semantics of W3C HTML 4.01
 * to the extent supported/used by javadoc.
 * In time, we may wish to transition javadoc and doclint to using HTML 5.
 *
 * This is derivative of com.sun.tools.doclets.formats.html.markup.HtmlTag.
 * Eventually, these two should be merged back together, and possibly made
 * public.
 *
 * @see <a href="http://www.w3.org/TR/REC-html40/">HTML 4.01 Specification</a>
 * @see <a href="http://www.w3.org/TR/html5/">HTML 5 Specification</a>
 * @see <a href="http://www.w3.org/TR/wai-aria/ ">WAI-ARIA Specification</a>
 * @see <a href="http://www.w3.org/TR/aria-in-html/#recommendations-table">WAI-ARIA Recommendations Table</a>
 * @author Bhavesh Patel
 * @author Jonathan Gibbons (revised)
 */
public enum HtmlTag {
    A(BlockType.INLINE, EndKind.REQUIRED,
            attrs(AttrKind.OK, HREF, TARGET, ID),
            attrs(AttrKind.HTML4, REV, CHARSET, SHAPE, COORDS, NAME)),

    ABBR(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    ACRONYM(ElemKind.HTML4, BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    ADDRESS(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    ARTICLE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    ASIDE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    B(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    BDI(BlockType.INLINE, EndKind.REQUIRED),

    BIG(ElemKind.HTML4, BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT)),

    BLOCKQUOTE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    BODY(BlockType.OTHER, EndKind.REQUIRED),

    BR(BlockType.INLINE, EndKind.NONE,
            attrs(AttrKind.HTML4, CLEAR)),

    CAPTION(BlockType.TABLE_ITEM, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_INLINE, Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, ALIGN)),

    CENTER(ElemKind.HTML4, BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    CITE(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    CODE(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    COL(BlockType.TABLE_ITEM, EndKind.NONE,
            attrs(AttrKind.HTML4, ALIGN, CHAR, CHAROFF, VALIGN, WIDTH)),

    COLGROUP(BlockType.TABLE_ITEM, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN, CHAR, CHAROFF, VALIGN, WIDTH)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == COL);
        }
    },

    DD(BlockType.LIST_ITEM, EndKind.OPTIONAL,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE, Flag.EXPECT_CONTENT)),

    DEL(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST),
            attrs(AttrKind.OK, Attr.CITE, Attr.DATETIME)),

    DFN(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    DIV(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE),
            attrs(AttrKind.HTML4, ALIGN)),

    DL(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, COMPACT)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == DT) || (t == DD);
        }
    },

    DT(BlockType.LIST_ITEM, EndKind.OPTIONAL,
            EnumSet.of(Flag.ACCEPTS_INLINE, Flag.EXPECT_CONTENT)),

    EM(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.NO_NEST)),

    FONT(ElemKind.HTML4, BlockType.INLINE, EndKind.REQUIRED, // tag itself is deprecated
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, SIZE, COLOR, FACE)),

    FOOTER(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)) {
        @Override
        public boolean accepts(HtmlTag t) {
            switch (t) {
                case HEADER: case FOOTER: case MAIN:
                    return false;
                default:
                    return (t.blockType == BlockType.BLOCK) || (t.blockType == BlockType.INLINE);
            }
        }
    },

    FIGURE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    FIGCAPTION(BlockType.BLOCK, EndKind.REQUIRED),

    FRAME(ElemKind.HTML4, BlockType.OTHER, EndKind.NONE),

    FRAMESET(ElemKind.HTML4, BlockType.OTHER, EndKind.REQUIRED),

    H1(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),
    H2(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),
    H3(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),
    H4(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),
    H5(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),
    H6(BlockType.BLOCK, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN)),

    HEAD(BlockType.OTHER, EndKind.REQUIRED),

    HEADER(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)) {
        @Override
        public boolean accepts(HtmlTag t) {
            switch (t) {
                case HEADER: case FOOTER: case MAIN:
                    return false;
                default:
                    return (t.blockType == BlockType.BLOCK) || (t.blockType == BlockType.INLINE);
            }
        }
    },

    HR(BlockType.BLOCK, EndKind.NONE,
            attrs(AttrKind.HTML4, WIDTH, ALIGN, NOSHADE, SIZE)),

    HTML(BlockType.OTHER, EndKind.REQUIRED),

    I(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    IFRAME(BlockType.OTHER, EndKind.REQUIRED),

    IMG(BlockType.INLINE, EndKind.NONE,
            attrs(AttrKind.OK, SRC, ALT, HEIGHT, WIDTH, CROSSORIGIN),
            attrs(AttrKind.HTML4, NAME, ALIGN, HSPACE, VSPACE, BORDER)),

    INS(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST),
            attrs(AttrKind.OK, Attr.CITE, Attr.DATETIME)),

    KBD(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    LI(BlockType.LIST_ITEM, EndKind.OPTIONAL,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE),
            attrs(AttrKind.OK, VALUE),
            attrs(AttrKind.HTML4, TYPE)),

    LINK(BlockType.OTHER, EndKind.NONE),

    MAIN(BlockType.OTHER, EndKind.REQUIRED),

    MARK(BlockType.INLINE, EndKind.REQUIRED),

    MENU(BlockType.BLOCK, EndKind.REQUIRED) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == LI);
        }
    },

    META(BlockType.OTHER, EndKind.NONE),

    NAV(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    NOFRAMES(ElemKind.HTML4, BlockType.OTHER, EndKind.REQUIRED),

    NOSCRIPT(BlockType.BLOCK, EndKind.REQUIRED),

    OL(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.OK, START, TYPE, REVERSED),
            attrs(AttrKind.HTML4, COMPACT)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == LI);
        }
    },

    P(BlockType.BLOCK, EndKind.OPTIONAL,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, ALIGN)),

    PRE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, WIDTH)) {
        @Override
        public boolean accepts(HtmlTag t) {
            switch (t) {
                case IMG: case BIG: case SMALL: case SUB: case SUP:
                    return false;
                default:
                    return (t.blockType == BlockType.INLINE);
            }
        }
    },

    Q(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    S(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    SAMP(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    SCRIPT(BlockType.OTHER, EndKind.REQUIRED,
            attrs(AttrKind.OK, SRC)),

    SECTION(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    SMALL(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT)),

    SPAN(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT)),

    STRIKE(ElemKind.HTML4, BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT)),

    STRONG(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT)),

    STYLE(BlockType.OTHER, EndKind.REQUIRED),

    SUB(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    SUP(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    TABLE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.OK, BORDER),
            attrs(AttrKind.HTML4, SUMMARY, CELLPADDING, CELLSPACING,
                    Attr.FRAME, RULES, WIDTH, ALIGN, BGCOLOR)) {
        @Override
        public boolean accepts(HtmlTag t) {
            switch (t) {
                case CAPTION:
                case COLGROUP:
                case THEAD: case TBODY: case TFOOT:
                case TR: // HTML 3.2
                    return true;
                default:
                    return false;
            }
        }
    },

    TBODY(BlockType.TABLE_ITEM, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, ALIGN, VALIGN, CHAR, CHAROFF)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == TR);
        }
    },

    TD(BlockType.TABLE_ITEM, EndKind.OPTIONAL,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE),
            attrs(AttrKind.OK, COLSPAN, ROWSPAN, HEADERS),
            attrs(AttrKind.HTML4, AXIS, Attr.ABBR, SCOPE, ALIGN, VALIGN, CHAR, CHAROFF,
                    WIDTH, BGCOLOR, HEIGHT, NOWRAP)),

    TEMPLATE(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE)),

    TFOOT(BlockType.TABLE_ITEM, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN, VALIGN, CHAR, CHAROFF)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == TR);
        }
    },

    TH(BlockType.TABLE_ITEM, EndKind.OPTIONAL,
            EnumSet.of(Flag.ACCEPTS_BLOCK, Flag.ACCEPTS_INLINE),
            attrs(AttrKind.OK, COLSPAN, ROWSPAN, HEADERS, SCOPE, Attr.ABBR),
            attrs(AttrKind.HTML4, WIDTH, BGCOLOR, HEIGHT, NOWRAP, AXIS, ALIGN, CHAR, CHAROFF, VALIGN)),

    THEAD(BlockType.TABLE_ITEM, EndKind.REQUIRED,
            attrs(AttrKind.HTML4, ALIGN, VALIGN, CHAR, CHAROFF)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == TR);
        }
    },

    TIME(BlockType.INLINE, EndKind.REQUIRED),

    TITLE(BlockType.OTHER, EndKind.REQUIRED),

    TR(BlockType.TABLE_ITEM, EndKind.OPTIONAL,
            attrs(AttrKind.HTML4, ALIGN, CHAR, CHAROFF, BGCOLOR, VALIGN)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == TH) || (t == TD);
        }
    },

    TT(ElemKind.HTML4, BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    U(BlockType.INLINE, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT, Flag.NO_NEST)),

    UL(BlockType.BLOCK, EndKind.REQUIRED,
            EnumSet.of(Flag.EXPECT_CONTENT),
            attrs(AttrKind.HTML4, COMPACT, TYPE)) {
        @Override
        public boolean accepts(HtmlTag t) {
            return (t == LI);
        }
    },

    WBR(BlockType.INLINE, EndKind.REQUIRED),

    VAR(BlockType.INLINE, EndKind.REQUIRED);

    
Enum representing the supportability of HTML element.

/**
     * Enum representing the supportability of HTML element.
     */
    public static enum ElemKind {
        OK,
        INVALID,
        OBSOLETE,
        HTML4
    }

    
Enum representing the type of HTML element.

/**
     * Enum representing the type of HTML element.
     */
    public static enum BlockType {
        BLOCK,
        INLINE,
        LIST_ITEM,
        TABLE_ITEM,
        OTHER
    }

    
Enum representing HTML end tag requirement.

/**
     * Enum representing HTML end tag requirement.
     */
    public static enum EndKind {
        NONE,
        OPTIONAL,
        REQUIRED
    }

    public static enum Flag {
        ACCEPTS_BLOCK,
        ACCEPTS_INLINE,
        EXPECT_CONTENT,
        NO_NEST
    }

    public static enum Attr {
        ABBR,
        ALIGN,
        ALINK,
        ALT,
        ARIA_ACTIVEDESCENDANT,
        ARIA_CONTROLS,
        ARIA_DESCRIBEDBY,
        ARIA_EXPANDED,
        ARIA_LABEL,
        ARIA_LABELLEDBY,
        ARIA_LEVEL,
        ARIA_MULTISELECTABLE,
        ARIA_OWNS,
        ARIA_POSINSET,
        ARIA_SETSIZE,
        ARIA_READONLY,
        ARIA_REQUIRED,
        ARIA_SELECTED,
        ARIA_SORT,
        AXIS,
        BACKGROUND,
        BGCOLOR,
        BORDER,
        CELLSPACING,
        CELLPADDING,
        CHAR,
        CHAROFF,
        CHARSET,
        CITE,
        CLEAR,
        CLASS,
        COLOR,
        COLSPAN,
        COMPACT,
        COORDS,
        CROSSORIGIN,
        DATETIME,
        FACE,
        FRAME,
        FRAMEBORDER,
        HEADERS,
        HEIGHT,
        HREF,
        HSPACE,
        ID,
        LINK,
        LONGDESC,
        MARGINHEIGHT,
        MARGINWIDTH,
        NAME,
        NOSHADE,
        NOWRAP,
        PROFILE,
        REV,
        REVERSED,
        ROLE,
        ROWSPAN,
        RULES,
        SCHEME,
        SCOPE,
        SCROLLING,
        SHAPE,
        SIZE,
        SPACE,
        SRC,
        START,
        STYLE,
        SUMMARY,
        TARGET,
        TEXT,
        TYPE,
        VALIGN,
        VALUE,
        VERSION,
        VLINK,
        VSPACE,
        WIDTH;

        private final String name;

        Attr() {
            name = StringUtils.toLowerCase(name().replace("_", "-"));
        }

        public String getText() {
            return name;
        }

        static final Map<String,Attr> index = new HashMap<>();
        static {
            for (Attr t: values()) {
                index.put(t.getText(), t);
            }
        }
    }

    public static enum AttrKind {
        OK,
        INVALID,
        OBSOLETE,
        HTML4
    }

    // This class exists to avoid warnings from using parameterized vararg type
    // Map<Attr,AttrKind> in signature of HtmlTag constructor.
    private static class AttrMap extends EnumMap<Attr,AttrKind>  {
        private static final long serialVersionUID = 0;
        AttrMap() {
            super(Attr.class);
        }
    }


    public final ElemKind elemKind;
    public final BlockType blockType;
    public final EndKind endKind;
    public final Set<Flag> flags;
    private final Map<Attr,AttrKind> attrs;

    HtmlTag(BlockType blockType, EndKind endKind, AttrMap... attrMaps) {
        this(ElemKind.OK, blockType, endKind, Collections.emptySet(), attrMaps);
    }

    HtmlTag(ElemKind elemKind, BlockType blockType, EndKind endKind, AttrMap... attrMaps) {
        this(elemKind, blockType, endKind, Collections.emptySet(), attrMaps);
    }

    HtmlTag(BlockType blockType, EndKind endKind, Set<Flag> flags, AttrMap... attrMaps) {
        this(ElemKind.OK, blockType, endKind, flags, attrMaps);
    }

    HtmlTag(ElemKind elemKind, BlockType blockType, EndKind endKind, Set<Flag> flags, AttrMap... attrMaps) {
        this.elemKind = elemKind;
        this.blockType = blockType;
        this.endKind = endKind;
        this.flags = flags;
        this.attrs = new EnumMap<>(Attr.class);
        for (Map<Attr,AttrKind> m: attrMaps)
            this.attrs.putAll(m);
        attrs.put(Attr.CLASS, AttrKind.OK);
        attrs.put(Attr.ID, AttrKind.OK);
        attrs.put(Attr.STYLE, AttrKind.OK);
        attrs.put(Attr.ROLE, AttrKind.OK);
        // for now, assume that all ARIA attributes are allowed on all tags.
        attrs.put(Attr.ARIA_ACTIVEDESCENDANT, AttrKind.OK);
        attrs.put(Attr.ARIA_CONTROLS, AttrKind.OK);
        attrs.put(Attr.ARIA_DESCRIBEDBY, AttrKind.OK);
        attrs.put(Attr.ARIA_EXPANDED, AttrKind.OK);
        attrs.put(Attr.ARIA_LABEL, AttrKind.OK);
        attrs.put(Attr.ARIA_LABELLEDBY, AttrKind.OK);
        attrs.put(Attr.ARIA_LEVEL, AttrKind.OK);
        attrs.put(Attr.ARIA_MULTISELECTABLE, AttrKind.OK);
        attrs.put(Attr.ARIA_OWNS, AttrKind.OK);
        attrs.put(Attr.ARIA_POSINSET, AttrKind.OK);
        attrs.put(Attr.ARIA_READONLY, AttrKind.OK);
        attrs.put(Attr.ARIA_REQUIRED, AttrKind.OK);
        attrs.put(Attr.ARIA_SELECTED, AttrKind.OK);
        attrs.put(Attr.ARIA_SETSIZE, AttrKind.OK);
        attrs.put(Attr.ARIA_SORT, AttrKind.OK);
    }

    public boolean accepts(HtmlTag t) {
        if (flags.contains(Flag.ACCEPTS_BLOCK) && flags.contains(Flag.ACCEPTS_INLINE)) {
            return (t.blockType == BlockType.BLOCK) || (t.blockType == BlockType.INLINE);
        } else if (flags.contains(Flag.ACCEPTS_BLOCK)) {
            return (t.blockType == BlockType.BLOCK);
        } else if (flags.contains(Flag.ACCEPTS_INLINE)) {
            return (t.blockType == BlockType.INLINE);
        } else
            switch (blockType) {
                case BLOCK:
                case INLINE:
                    return (t.blockType == BlockType.INLINE);
                case OTHER:
                    // OTHER tags are invalid in doc comments, and will be
                    // reported separately, so silently accept/ignore any content
                    return true;
                default:
                    // any combination which could otherwise arrive here
                    // ought to have been handled in an overriding method
                    throw new AssertionError(this + ":" + t);
            }
    }

    public boolean acceptsText() {
        // generally, anywhere we can put text we can also put inline tag
        // so check if a typical inline tag is allowed
        return accepts(B);
    }

    public String getText() {
        return StringUtils.toLowerCase(name());
    }

    public Attr getAttr(Name attrName) {
        return Attr.index.get(StringUtils.toLowerCase(attrName.toString()));
    }

    public AttrKind getAttrKind(Name attrName) {
        AttrKind k = attrs.get(getAttr(attrName)); // null-safe
        return (k == null) ? AttrKind.INVALID : k;
    }

    private static AttrMap attrs(AttrKind k, Attr... attrs) {
        AttrMap map = new AttrMap();
        for (Attr a: attrs) map.put(a, k);
        return map;
    }

    private static final Map<String, HtmlTag> index = new HashMap<>();
    static {
        for (HtmlTag t: values()) {
            index.put(t.getText(), t);
        }
    }

    public static HtmlTag get(Name tagName) {
        return index.get(StringUtils.toLowerCase(tagName.toString()));
    }
}