361 lines
8.6 KiB
Go
361 lines
8.6 KiB
Go
package blackfriday
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import (
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"bytes"
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"fmt"
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)
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// NodeType specifies a type of a single node of a syntax tree. Usually one
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// node (and its type) corresponds to a single markdown feature, e.g. emphasis
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// or code block.
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type NodeType int
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// Constants for identifying different types of nodes. See NodeType.
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const (
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Document NodeType = iota
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BlockQuote
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List
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Item
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Paragraph
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Heading
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HorizontalRule
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Emph
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Strong
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Del
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Link
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Image
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Text
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HTMLBlock
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CodeBlock
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Softbreak
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Hardbreak
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Code
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HTMLSpan
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Table
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TableCell
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TableHead
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TableBody
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TableRow
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)
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var nodeTypeNames = []string{
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Document: "Document",
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BlockQuote: "BlockQuote",
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List: "List",
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Item: "Item",
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Paragraph: "Paragraph",
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Heading: "Heading",
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HorizontalRule: "HorizontalRule",
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Emph: "Emph",
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Strong: "Strong",
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Del: "Del",
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Link: "Link",
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Image: "Image",
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Text: "Text",
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HTMLBlock: "HTMLBlock",
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CodeBlock: "CodeBlock",
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Softbreak: "Softbreak",
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Hardbreak: "Hardbreak",
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Code: "Code",
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HTMLSpan: "HTMLSpan",
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Table: "Table",
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TableCell: "TableCell",
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TableHead: "TableHead",
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TableBody: "TableBody",
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TableRow: "TableRow",
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}
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func (t NodeType) String() string {
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return nodeTypeNames[t]
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}
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// ListData contains fields relevant to a List and Item node type.
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type ListData struct {
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ListFlags ListType
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Tight bool // Skip <p>s around list item data if true
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BulletChar byte // '*', '+' or '-' in bullet lists
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Delimiter byte // '.' or ')' after the number in ordered lists
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RefLink []byte // If not nil, turns this list item into a footnote item and triggers different rendering
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IsFootnotesList bool // This is a list of footnotes
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}
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// LinkData contains fields relevant to a Link node type.
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type LinkData struct {
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Destination []byte // Destination is what goes into a href
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Title []byte // Title is the tooltip thing that goes in a title attribute
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NoteID int // NoteID contains a serial number of a footnote, zero if it's not a footnote
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Footnote *Node // If it's a footnote, this is a direct link to the footnote Node. Otherwise nil.
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}
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// CodeBlockData contains fields relevant to a CodeBlock node type.
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type CodeBlockData struct {
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IsFenced bool // Specifies whether it's a fenced code block or an indented one
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Info []byte // This holds the info string
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FenceChar byte
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FenceLength int
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FenceOffset int
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}
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// TableCellData contains fields relevant to a TableCell node type.
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type TableCellData struct {
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IsHeader bool // This tells if it's under the header row
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Align CellAlignFlags // This holds the value for align attribute
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}
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// HeadingData contains fields relevant to a Heading node type.
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type HeadingData struct {
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Level int // This holds the heading level number
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HeadingID string // This might hold heading ID, if present
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IsTitleblock bool // Specifies whether it's a title block
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}
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// Node is a single element in the abstract syntax tree of the parsed document.
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// It holds connections to the structurally neighboring nodes and, for certain
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// types of nodes, additional information that might be needed when rendering.
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type Node struct {
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Type NodeType // Determines the type of the node
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Parent *Node // Points to the parent
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FirstChild *Node // Points to the first child, if any
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LastChild *Node // Points to the last child, if any
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Prev *Node // Previous sibling; nil if it's the first child
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Next *Node // Next sibling; nil if it's the last child
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Literal []byte // Text contents of the leaf nodes
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HeadingData // Populated if Type is Heading
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ListData // Populated if Type is List
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CodeBlockData // Populated if Type is CodeBlock
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LinkData // Populated if Type is Link
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TableCellData // Populated if Type is TableCell
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content []byte // Markdown content of the block nodes
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open bool // Specifies an open block node that has not been finished to process yet
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}
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// NewNode allocates a node of a specified type.
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func NewNode(typ NodeType) *Node {
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return &Node{
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Type: typ,
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open: true,
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}
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}
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func (n *Node) String() string {
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ellipsis := ""
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snippet := n.Literal
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if len(snippet) > 16 {
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snippet = snippet[:16]
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ellipsis = "..."
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}
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return fmt.Sprintf("%s: '%s%s'", n.Type, snippet, ellipsis)
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}
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// Unlink removes node 'n' from the tree.
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// It panics if the node is nil.
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func (n *Node) Unlink() {
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if n.Prev != nil {
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n.Prev.Next = n.Next
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} else if n.Parent != nil {
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n.Parent.FirstChild = n.Next
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}
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if n.Next != nil {
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n.Next.Prev = n.Prev
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} else if n.Parent != nil {
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n.Parent.LastChild = n.Prev
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}
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n.Parent = nil
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n.Next = nil
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n.Prev = nil
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}
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// AppendChild adds a node 'child' as a child of 'n'.
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// It panics if either node is nil.
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func (n *Node) AppendChild(child *Node) {
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child.Unlink()
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child.Parent = n
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if n.LastChild != nil {
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n.LastChild.Next = child
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child.Prev = n.LastChild
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n.LastChild = child
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} else {
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n.FirstChild = child
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n.LastChild = child
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}
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}
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// InsertBefore inserts 'sibling' immediately before 'n'.
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// It panics if either node is nil.
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func (n *Node) InsertBefore(sibling *Node) {
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sibling.Unlink()
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sibling.Prev = n.Prev
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if sibling.Prev != nil {
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sibling.Prev.Next = sibling
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}
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sibling.Next = n
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n.Prev = sibling
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sibling.Parent = n.Parent
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if sibling.Prev == nil {
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sibling.Parent.FirstChild = sibling
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}
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}
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// IsContainer returns true if 'n' can contain children.
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func (n *Node) IsContainer() bool {
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switch n.Type {
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case Document:
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fallthrough
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case BlockQuote:
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fallthrough
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case List:
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fallthrough
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case Item:
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fallthrough
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case Paragraph:
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fallthrough
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case Heading:
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fallthrough
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case Emph:
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fallthrough
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case Strong:
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fallthrough
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case Del:
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fallthrough
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case Link:
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fallthrough
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case Image:
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fallthrough
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case Table:
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fallthrough
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case TableHead:
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fallthrough
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case TableBody:
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fallthrough
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case TableRow:
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fallthrough
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case TableCell:
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return true
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default:
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return false
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}
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}
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// IsLeaf returns true if 'n' is a leaf node.
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func (n *Node) IsLeaf() bool {
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return !n.IsContainer()
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}
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func (n *Node) canContain(t NodeType) bool {
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if n.Type == List {
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return t == Item
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}
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if n.Type == Document || n.Type == BlockQuote || n.Type == Item {
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return t != Item
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}
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if n.Type == Table {
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return t == TableHead || t == TableBody
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}
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if n.Type == TableHead || n.Type == TableBody {
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return t == TableRow
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}
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if n.Type == TableRow {
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return t == TableCell
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}
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return false
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}
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// WalkStatus allows NodeVisitor to have some control over the tree traversal.
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// It is returned from NodeVisitor and different values allow Node.Walk to
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// decide which node to go to next.
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type WalkStatus int
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const (
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// GoToNext is the default traversal of every node.
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GoToNext WalkStatus = iota
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// SkipChildren tells walker to skip all children of current node.
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SkipChildren
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// Terminate tells walker to terminate the traversal.
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Terminate
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)
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// NodeVisitor is a callback to be called when traversing the syntax tree.
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// Called twice for every node: once with entering=true when the branch is
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// first visited, then with entering=false after all the children are done.
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type NodeVisitor func(node *Node, entering bool) WalkStatus
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// Walk is a convenience method that instantiates a walker and starts a
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// traversal of subtree rooted at n.
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func (n *Node) Walk(visitor NodeVisitor) {
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w := newNodeWalker(n)
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for w.current != nil {
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status := visitor(w.current, w.entering)
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switch status {
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case GoToNext:
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w.next()
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case SkipChildren:
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w.entering = false
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w.next()
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case Terminate:
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return
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}
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}
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}
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type nodeWalker struct {
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current *Node
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root *Node
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entering bool
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}
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func newNodeWalker(root *Node) *nodeWalker {
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return &nodeWalker{
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current: root,
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root: root,
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entering: true,
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}
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}
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func (nw *nodeWalker) next() {
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if (!nw.current.IsContainer() || !nw.entering) && nw.current == nw.root {
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nw.current = nil
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return
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}
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if nw.entering && nw.current.IsContainer() {
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if nw.current.FirstChild != nil {
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nw.current = nw.current.FirstChild
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nw.entering = true
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} else {
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nw.entering = false
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}
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} else if nw.current.Next == nil {
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nw.current = nw.current.Parent
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nw.entering = false
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} else {
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nw.current = nw.current.Next
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nw.entering = true
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}
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}
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func dump(ast *Node) {
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fmt.Println(dumpString(ast))
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}
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func dumpR(ast *Node, depth int) string {
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if ast == nil {
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return ""
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}
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indent := bytes.Repeat([]byte("\t"), depth)
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content := ast.Literal
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if content == nil {
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content = ast.content
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}
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result := fmt.Sprintf("%s%s(%q)\n", indent, ast.Type, content)
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for n := ast.FirstChild; n != nil; n = n.Next {
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result += dumpR(n, depth+1)
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}
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return result
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}
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func dumpString(ast *Node) string {
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return dumpR(ast, 0)
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}
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