mirror of
https://github.com/cwinfo/matterbridge.git
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813 lines
22 KiB
Go
813 lines
22 KiB
Go
/*
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Package parser implements parser for markdown text that generates AST (abstract syntax tree).
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*/
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package parser
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import (
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"bytes"
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"fmt"
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"strings"
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"unicode/utf8"
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"github.com/gomarkdown/markdown/ast"
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)
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// Extensions is a bitmask of enabled parser extensions.
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type Extensions int
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// Bit flags representing markdown parsing extensions.
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// Use | (or) to specify multiple extensions.
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const (
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NoExtensions Extensions = 0
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NoIntraEmphasis Extensions = 1 << iota // Ignore emphasis markers inside words
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Tables // Parse tables
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FencedCode // Parse fenced code blocks
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Autolink // Detect embedded URLs that are not explicitly marked
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Strikethrough // Strikethrough text using ~~test~~
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LaxHTMLBlocks // Loosen up HTML block parsing rules
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SpaceHeadings // Be strict about prefix heading rules
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HardLineBreak // Translate newlines into line breaks
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NonBlockingSpace // Translate backspace spaces into line non-blocking spaces
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TabSizeEight // Expand tabs to eight spaces instead of four
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Footnotes // Pandoc-style footnotes
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NoEmptyLineBeforeBlock // No need to insert an empty line to start a (code, quote, ordered list, unordered list) block
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HeadingIDs // specify heading IDs with {#id}
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Titleblock // Titleblock ala pandoc
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AutoHeadingIDs // Create the heading ID from the text
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BackslashLineBreak // Translate trailing backslashes into line breaks
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DefinitionLists // Parse definition lists
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MathJax // Parse MathJax
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OrderedListStart // Keep track of the first number used when starting an ordered list.
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Attributes // Block Attributes
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SuperSubscript // Super- and subscript support: 2^10^, H~2~O.
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EmptyLinesBreakList // 2 empty lines break out of list
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Includes // Support including other files.
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Mmark // Support Mmark syntax, see https://mmark.nl/syntax
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CommonExtensions Extensions = NoIntraEmphasis | Tables | FencedCode |
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Autolink | Strikethrough | SpaceHeadings | HeadingIDs |
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BackslashLineBreak | DefinitionLists | MathJax
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)
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// The size of a tab stop.
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const (
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tabSizeDefault = 4
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tabSizeDouble = 8
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)
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// for each character that triggers a response when parsing inline data.
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type inlineParser func(p *Parser, data []byte, offset int) (int, ast.Node)
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// ReferenceOverrideFunc is expected to be called with a reference string and
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// return either a valid Reference type that the reference string maps to or
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// nil. If overridden is false, the default reference logic will be executed.
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// See the documentation in Options for more details on use-case.
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type ReferenceOverrideFunc func(reference string) (ref *Reference, overridden bool)
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// Parser is a type that holds extensions and the runtime state used by
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// Parse, and the renderer. You can not use it directly, construct it with New.
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type Parser struct {
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// ReferenceOverride is an optional function callback that is called every
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// time a reference is resolved. It can be set before starting parsing.
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//
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// In Markdown, the link reference syntax can be made to resolve a link to
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// a reference instead of an inline URL, in one of the following ways:
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//
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// * [link text][refid]
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// * [refid][]
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//
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// Usually, the refid is defined at the bottom of the Markdown document. If
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// this override function is provided, the refid is passed to the override
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// function first, before consulting the defined refids at the bottom. If
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// the override function indicates an override did not occur, the refids at
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// the bottom will be used to fill in the link details.
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ReferenceOverride ReferenceOverrideFunc
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Opts Options
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// after parsing, this is AST root of parsed markdown text
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Doc ast.Node
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extensions Extensions
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refs map[string]*reference
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refsRecord map[string]struct{}
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inlineCallback [256]inlineParser
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nesting int
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maxNesting int
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insideLink bool
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indexCnt int // incremented after every index
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// Footnotes need to be ordered as well as available to quickly check for
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// presence. If a ref is also a footnote, it's stored both in refs and here
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// in notes. Slice is nil if footnotes not enabled.
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notes []*reference
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tip ast.Node // = doc
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oldTip ast.Node
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lastMatchedContainer ast.Node // = doc
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allClosed bool
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// Attributes are attached to block level elements.
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attr *ast.Attribute
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includeStack *incStack
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}
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// New creates a markdown parser with CommonExtensions.
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//
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// You can then call `doc := p.Parse(markdown)` to parse markdown document
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// and `markdown.Render(doc, renderer)` to convert it to another format with
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// a renderer.
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func New() *Parser {
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return NewWithExtensions(CommonExtensions)
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}
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// NewWithExtensions creates a markdown parser with given extensions.
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func NewWithExtensions(extension Extensions) *Parser {
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p := Parser{
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refs: make(map[string]*reference),
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refsRecord: make(map[string]struct{}),
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maxNesting: 16,
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insideLink: false,
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Doc: &ast.Document{},
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extensions: extension,
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allClosed: true,
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includeStack: newIncStack(),
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}
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p.tip = p.Doc
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p.oldTip = p.Doc
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p.lastMatchedContainer = p.Doc
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p.inlineCallback[' '] = maybeLineBreak
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p.inlineCallback['*'] = emphasis
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p.inlineCallback['_'] = emphasis
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if p.extensions&Strikethrough != 0 {
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p.inlineCallback['~'] = emphasis
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}
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p.inlineCallback['`'] = codeSpan
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p.inlineCallback['\n'] = lineBreak
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p.inlineCallback['['] = link
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p.inlineCallback['<'] = leftAngle
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p.inlineCallback['\\'] = escape
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p.inlineCallback['&'] = entity
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p.inlineCallback['!'] = maybeImage
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if p.extensions&Mmark != 0 {
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p.inlineCallback['('] = maybeShortRefOrIndex
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}
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p.inlineCallback['^'] = maybeInlineFootnoteOrSuper
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if p.extensions&Autolink != 0 {
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p.inlineCallback['h'] = maybeAutoLink
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p.inlineCallback['m'] = maybeAutoLink
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p.inlineCallback['f'] = maybeAutoLink
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p.inlineCallback['H'] = maybeAutoLink
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p.inlineCallback['M'] = maybeAutoLink
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p.inlineCallback['F'] = maybeAutoLink
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}
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if p.extensions&MathJax != 0 {
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p.inlineCallback['$'] = math
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}
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return &p
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}
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func (p *Parser) getRef(refid string) (ref *reference, found bool) {
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if p.ReferenceOverride != nil {
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r, overridden := p.ReferenceOverride(refid)
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if overridden {
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if r == nil {
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return nil, false
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}
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return &reference{
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link: []byte(r.Link),
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title: []byte(r.Title),
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noteID: 0,
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hasBlock: false,
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text: []byte(r.Text)}, true
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}
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}
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// refs are case insensitive
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ref, found = p.refs[strings.ToLower(refid)]
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return ref, found
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}
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func (p *Parser) isFootnote(ref *reference) bool {
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_, ok := p.refsRecord[string(ref.link)]
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return ok
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}
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func (p *Parser) finalize(block ast.Node) {
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p.tip = block.GetParent()
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}
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func (p *Parser) addChild(node ast.Node) ast.Node {
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for !canNodeContain(p.tip, node) {
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p.finalize(p.tip)
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}
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ast.AppendChild(p.tip, node)
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p.tip = node
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return node
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}
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func canNodeContain(n ast.Node, v ast.Node) bool {
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switch n.(type) {
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case *ast.List:
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return isListItem(v)
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case *ast.Document, *ast.BlockQuote, *ast.Aside, *ast.ListItem, *ast.CaptionFigure:
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return !isListItem(v)
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case *ast.Table:
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switch v.(type) {
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case *ast.TableHeader, *ast.TableBody, *ast.TableFooter:
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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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case *ast.TableHeader, *ast.TableBody, *ast.TableFooter:
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_, ok := v.(*ast.TableRow)
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return ok
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case *ast.TableRow:
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_, ok := v.(*ast.TableCell)
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return ok
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}
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return false
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}
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func (p *Parser) closeUnmatchedBlocks() {
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if p.allClosed {
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return
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}
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for p.oldTip != p.lastMatchedContainer {
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parent := p.oldTip.GetParent()
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p.finalize(p.oldTip)
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p.oldTip = parent
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}
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p.allClosed = true
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}
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// Reference represents the details of a link.
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// See the documentation in Options for more details on use-case.
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type Reference struct {
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// Link is usually the URL the reference points to.
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Link string
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// Title is the alternate text describing the link in more detail.
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Title string
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// Text is the optional text to override the ref with if the syntax used was
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// [refid][]
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Text string
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}
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// Parse generates AST (abstract syntax tree) representing markdown document.
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//
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// The result is a root of the tree whose underlying type is *ast.Document
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//
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// You can then convert AST to html using html.Renderer, to some other format
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// using a custom renderer or transform the tree.
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func (p *Parser) Parse(input []byte) ast.Node {
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p.block(input)
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// Walk the tree and finish up some of unfinished blocks
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for p.tip != nil {
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p.finalize(p.tip)
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}
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// Walk the tree again and process inline markdown in each block
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ast.WalkFunc(p.Doc, func(node ast.Node, entering bool) ast.WalkStatus {
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switch node.(type) {
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case *ast.Paragraph, *ast.Heading, *ast.TableCell:
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p.Inline(node, node.AsContainer().Content)
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node.AsContainer().Content = nil
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}
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return ast.GoToNext
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})
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if p.Opts.Flags&SkipFootnoteList == 0 {
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p.parseRefsToAST()
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}
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return p.Doc
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}
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func (p *Parser) parseRefsToAST() {
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if p.extensions&Footnotes == 0 || len(p.notes) == 0 {
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return
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}
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p.tip = p.Doc
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list := &ast.List{
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IsFootnotesList: true,
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ListFlags: ast.ListTypeOrdered,
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}
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p.addBlock(&ast.Footnotes{})
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block := p.addBlock(list)
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flags := ast.ListItemBeginningOfList
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// Note: this loop is intentionally explicit, not range-form. This is
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// because the body of the loop will append nested footnotes to p.notes and
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// we need to process those late additions. Range form would only walk over
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// the fixed initial set.
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for i := 0; i < len(p.notes); i++ {
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ref := p.notes[i]
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p.addChild(ref.footnote)
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block := ref.footnote
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listItem := block.(*ast.ListItem)
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listItem.ListFlags = flags | ast.ListTypeOrdered
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listItem.RefLink = ref.link
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if ref.hasBlock {
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flags |= ast.ListItemContainsBlock
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p.block(ref.title)
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} else {
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p.Inline(block, ref.title)
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}
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flags &^= ast.ListItemBeginningOfList | ast.ListItemContainsBlock
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}
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above := list.Parent
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finalizeList(list)
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p.tip = above
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ast.WalkFunc(block, func(node ast.Node, entering bool) ast.WalkStatus {
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switch node.(type) {
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case *ast.Paragraph, *ast.Heading:
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p.Inline(node, node.AsContainer().Content)
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node.AsContainer().Content = nil
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}
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return ast.GoToNext
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})
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}
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//
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// Link references
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//
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// This section implements support for references that (usually) appear
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// as footnotes in a document, and can be referenced anywhere in the document.
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// The basic format is:
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//
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// [1]: http://www.google.com/ "Google"
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// [2]: http://www.github.com/ "Github"
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//
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// Anywhere in the document, the reference can be linked by referring to its
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// label, i.e., 1 and 2 in this example, as in:
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//
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// This library is hosted on [Github][2], a git hosting site.
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//
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// Actual footnotes as specified in Pandoc and supported by some other Markdown
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// libraries such as php-markdown are also taken care of. They look like this:
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//
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// This sentence needs a bit of further explanation.[^note]
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//
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// [^note]: This is the explanation.
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//
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// Footnotes should be placed at the end of the document in an ordered list.
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// Inline footnotes such as:
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//
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// Inline footnotes^[Not supported.] also exist.
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//
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// are not yet supported.
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// reference holds all information necessary for a reference-style links or
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// footnotes.
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//
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// Consider this markdown with reference-style links:
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//
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// [link][ref]
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//
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// [ref]: /url/ "tooltip title"
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//
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// It will be ultimately converted to this HTML:
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//
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// <p><a href=\"/url/\" title=\"title\">link</a></p>
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//
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// And a reference structure will be populated as follows:
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//
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// p.refs["ref"] = &reference{
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// link: "/url/",
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// title: "tooltip title",
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// }
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//
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// Alternatively, reference can contain information about a footnote. Consider
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// this markdown:
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//
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// Text needing a footnote.[^a]
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//
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// [^a]: This is the note
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//
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// A reference structure will be populated as follows:
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//
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// p.refs["a"] = &reference{
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// link: "a",
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// title: "This is the note",
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// noteID: <some positive int>,
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// }
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//
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// TODO: As you can see, it begs for splitting into two dedicated structures
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// for refs and for footnotes.
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type reference struct {
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link []byte
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title []byte
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noteID int // 0 if not a footnote ref
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hasBlock bool
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footnote ast.Node // a link to the Item node within a list of footnotes
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text []byte // only gets populated by refOverride feature with Reference.Text
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}
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func (r *reference) String() string {
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return fmt.Sprintf("{link: %q, title: %q, text: %q, noteID: %d, hasBlock: %v}",
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r.link, r.title, r.text, r.noteID, r.hasBlock)
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}
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// Check whether or not data starts with a reference link.
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// If so, it is parsed and stored in the list of references
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// (in the render struct).
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// Returns the number of bytes to skip to move past it,
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// or zero if the first line is not a reference.
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func isReference(p *Parser, data []byte, tabSize int) int {
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// up to 3 optional leading spaces
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if len(data) < 4 {
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return 0
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}
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i := 0
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for i < 3 && data[i] == ' ' {
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i++
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}
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noteID := 0
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// id part: anything but a newline between brackets
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if data[i] != '[' {
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return 0
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}
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i++
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if p.extensions&Footnotes != 0 {
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if i < len(data) && data[i] == '^' {
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// we can set it to anything here because the proper noteIds will
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// be assigned later during the second pass. It just has to be != 0
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noteID = 1
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i++
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}
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}
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idOffset := i
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for i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != ']' {
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i++
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}
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if i >= len(data) || data[i] != ']' {
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return 0
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}
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idEnd := i
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// footnotes can have empty ID, like this: [^], but a reference can not be
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// empty like this: []. Break early if it's not a footnote and there's no ID
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if noteID == 0 && idOffset == idEnd {
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return 0
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}
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// spacer: colon (space | tab)* newline? (space | tab)*
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i++
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if i >= len(data) || data[i] != ':' {
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return 0
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}
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i++
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for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
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i++
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}
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if i < len(data) && (data[i] == '\n' || data[i] == '\r') {
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i++
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if i < len(data) && data[i] == '\n' && data[i-1] == '\r' {
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i++
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}
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}
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for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
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i++
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}
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if i >= len(data) {
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return 0
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}
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var (
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linkOffset, linkEnd int
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titleOffset, titleEnd int
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lineEnd int
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raw []byte
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hasBlock bool
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)
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if p.extensions&Footnotes != 0 && noteID != 0 {
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linkOffset, linkEnd, raw, hasBlock = scanFootnote(p, data, i, tabSize)
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lineEnd = linkEnd
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} else {
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linkOffset, linkEnd, titleOffset, titleEnd, lineEnd = scanLinkRef(p, data, i)
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}
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if lineEnd == 0 {
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return 0
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}
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// a valid ref has been found
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ref := &reference{
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noteID: noteID,
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hasBlock: hasBlock,
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}
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if noteID > 0 {
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// reusing the link field for the id since footnotes don't have links
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ref.link = data[idOffset:idEnd]
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// if footnote, it's not really a title, it's the contained text
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ref.title = raw
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} else {
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ref.link = data[linkOffset:linkEnd]
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ref.title = data[titleOffset:titleEnd]
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}
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// id matches are case-insensitive
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id := string(bytes.ToLower(data[idOffset:idEnd]))
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p.refs[id] = ref
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return lineEnd
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}
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func scanLinkRef(p *Parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
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// link: whitespace-free sequence, optionally between angle brackets
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if data[i] == '<' {
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i++
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}
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linkOffset = i
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for i < len(data) && data[i] != ' ' && data[i] != '\t' && data[i] != '\n' && data[i] != '\r' {
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i++
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}
|
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linkEnd = i
|
|
if linkEnd < len(data) && data[linkOffset] == '<' && data[linkEnd-1] == '>' {
|
|
linkOffset++
|
|
linkEnd--
|
|
}
|
|
|
|
// optional spacer: (space | tab)* (newline | '\'' | '"' | '(' )
|
|
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
|
|
i++
|
|
}
|
|
if i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != '\'' && data[i] != '"' && data[i] != '(' {
|
|
return
|
|
}
|
|
|
|
// compute end-of-line
|
|
if i >= len(data) || data[i] == '\r' || data[i] == '\n' {
|
|
lineEnd = i
|
|
}
|
|
if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' {
|
|
lineEnd++
|
|
}
|
|
|
|
// optional (space|tab)* spacer after a newline
|
|
if lineEnd > 0 {
|
|
i = lineEnd + 1
|
|
for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
|
|
i++
|
|
}
|
|
}
|
|
|
|
// optional title: any non-newline sequence enclosed in '"() alone on its line
|
|
if i+1 < len(data) && (data[i] == '\'' || data[i] == '"' || data[i] == '(') {
|
|
i++
|
|
titleOffset = i
|
|
|
|
// look for EOL
|
|
for i < len(data) && data[i] != '\n' && data[i] != '\r' {
|
|
i++
|
|
}
|
|
if i+1 < len(data) && data[i] == '\n' && data[i+1] == '\r' {
|
|
titleEnd = i + 1
|
|
} else {
|
|
titleEnd = i
|
|
}
|
|
|
|
// step back
|
|
i--
|
|
for i > titleOffset && (data[i] == ' ' || data[i] == '\t') {
|
|
i--
|
|
}
|
|
if i > titleOffset && (data[i] == '\'' || data[i] == '"' || data[i] == ')') {
|
|
lineEnd = titleEnd
|
|
titleEnd = i
|
|
}
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
// The first bit of this logic is the same as Parser.listItem, but the rest
|
|
// is much simpler. This function simply finds the entire block and shifts it
|
|
// over by one tab if it is indeed a block (just returns the line if it's not).
|
|
// blockEnd is the end of the section in the input buffer, and contents is the
|
|
// extracted text that was shifted over one tab. It will need to be rendered at
|
|
// the end of the document.
|
|
func scanFootnote(p *Parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
|
|
if i == 0 || len(data) == 0 {
|
|
return
|
|
}
|
|
|
|
// skip leading whitespace on first line
|
|
for i < len(data) && data[i] == ' ' {
|
|
i++
|
|
}
|
|
|
|
blockStart = i
|
|
|
|
// find the end of the line
|
|
blockEnd = i
|
|
for i < len(data) && data[i-1] != '\n' {
|
|
i++
|
|
}
|
|
|
|
// get working buffer
|
|
var raw bytes.Buffer
|
|
|
|
// put the first line into the working buffer
|
|
raw.Write(data[blockEnd:i])
|
|
blockEnd = i
|
|
|
|
// process the following lines
|
|
containsBlankLine := false
|
|
|
|
gatherLines:
|
|
for blockEnd < len(data) {
|
|
i++
|
|
|
|
// find the end of this line
|
|
for i < len(data) && data[i-1] != '\n' {
|
|
i++
|
|
}
|
|
|
|
// if it is an empty line, guess that it is part of this item
|
|
// and move on to the next line
|
|
if p.isEmpty(data[blockEnd:i]) > 0 {
|
|
containsBlankLine = true
|
|
blockEnd = i
|
|
continue
|
|
}
|
|
|
|
n := 0
|
|
if n = isIndented(data[blockEnd:i], indentSize); n == 0 {
|
|
// this is the end of the block.
|
|
// we don't want to include this last line in the index.
|
|
break gatherLines
|
|
}
|
|
|
|
// if there were blank lines before this one, insert a new one now
|
|
if containsBlankLine {
|
|
raw.WriteByte('\n')
|
|
containsBlankLine = false
|
|
}
|
|
|
|
// get rid of that first tab, write to buffer
|
|
raw.Write(data[blockEnd+n : i])
|
|
hasBlock = true
|
|
|
|
blockEnd = i
|
|
}
|
|
|
|
if data[blockEnd-1] != '\n' {
|
|
raw.WriteByte('\n')
|
|
}
|
|
|
|
contents = raw.Bytes()
|
|
|
|
return
|
|
}
|
|
|
|
// isPunctuation returns true if c is a punctuation symbol.
|
|
func isPunctuation(c byte) bool {
|
|
for _, r := range []byte("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~") {
|
|
if c == r {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// isSpace returns true if c is a white-space charactr
|
|
func isSpace(c byte) bool {
|
|
return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v'
|
|
}
|
|
|
|
// isLetter returns true if c is ascii letter
|
|
func isLetter(c byte) bool {
|
|
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
|
|
}
|
|
|
|
// isAlnum returns true if c is a digit or letter
|
|
// TODO: check when this is looking for ASCII alnum and when it should use unicode
|
|
func isAlnum(c byte) bool {
|
|
return (c >= '0' && c <= '9') || isLetter(c)
|
|
}
|
|
|
|
// TODO: this is not used
|
|
// Replace tab characters with spaces, aligning to the next TAB_SIZE column.
|
|
// always ends output with a newline
|
|
func expandTabs(out *bytes.Buffer, line []byte, tabSize int) {
|
|
// first, check for common cases: no tabs, or only tabs at beginning of line
|
|
i, prefix := 0, 0
|
|
slowcase := false
|
|
for i = 0; i < len(line); i++ {
|
|
if line[i] == '\t' {
|
|
if prefix == i {
|
|
prefix++
|
|
} else {
|
|
slowcase = true
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
// no need to decode runes if all tabs are at the beginning of the line
|
|
if !slowcase {
|
|
for i = 0; i < prefix*tabSize; i++ {
|
|
out.WriteByte(' ')
|
|
}
|
|
out.Write(line[prefix:])
|
|
return
|
|
}
|
|
|
|
// the slow case: we need to count runes to figure out how
|
|
// many spaces to insert for each tab
|
|
column := 0
|
|
i = 0
|
|
for i < len(line) {
|
|
start := i
|
|
for i < len(line) && line[i] != '\t' {
|
|
_, size := utf8.DecodeRune(line[i:])
|
|
i += size
|
|
column++
|
|
}
|
|
|
|
if i > start {
|
|
out.Write(line[start:i])
|
|
}
|
|
|
|
if i >= len(line) {
|
|
break
|
|
}
|
|
|
|
for {
|
|
out.WriteByte(' ')
|
|
column++
|
|
if column%tabSize == 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
i++
|
|
}
|
|
}
|
|
|
|
// Find if a line counts as indented or not.
|
|
// Returns number of characters the indent is (0 = not indented).
|
|
func isIndented(data []byte, indentSize int) int {
|
|
if len(data) == 0 {
|
|
return 0
|
|
}
|
|
if data[0] == '\t' {
|
|
return 1
|
|
}
|
|
if len(data) < indentSize {
|
|
return 0
|
|
}
|
|
for i := 0; i < indentSize; i++ {
|
|
if data[i] != ' ' {
|
|
return 0
|
|
}
|
|
}
|
|
return indentSize
|
|
}
|
|
|
|
// Create a url-safe slug for fragments
|
|
func slugify(in []byte) []byte {
|
|
if len(in) == 0 {
|
|
return in
|
|
}
|
|
out := make([]byte, 0, len(in))
|
|
sym := false
|
|
|
|
for _, ch := range in {
|
|
if isAlnum(ch) {
|
|
sym = false
|
|
out = append(out, ch)
|
|
} else if sym {
|
|
continue
|
|
} else {
|
|
out = append(out, '-')
|
|
sym = true
|
|
}
|
|
}
|
|
var a, b int
|
|
var ch byte
|
|
for a, ch = range out {
|
|
if ch != '-' {
|
|
break
|
|
}
|
|
}
|
|
for b = len(out) - 1; b > 0; b-- {
|
|
if out[b] != '-' {
|
|
break
|
|
}
|
|
}
|
|
return out[a : b+1]
|
|
}
|
|
|
|
func isListItem(d ast.Node) bool {
|
|
_, ok := d.(*ast.ListItem)
|
|
return ok
|
|
}
|