164 lines
7 KiB
ABNF
164 lines
7 KiB
ABNF
; Left-Factored ABNF Grammar for Markdown with Embedded HTML
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; Based on RFC 5234 (ABNF) syntax - no negative lookahead operators
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; Top-level document structure
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document = *( block-element / CRLF )
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; Block-level elements (true left-factoring with unique prefixes)
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block-element = heading-block /
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blockquote-block /
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unordered-list-block /
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ordered-list-block /
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fenced-code-block /
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indented-code-block /
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horizontal-rule-block /
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html-block /
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paragraph-block
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; Headings (must start with #)
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heading-block = "#" heading-rest
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heading-rest = [ 1*5"#" ] *WSP *( inline-element ) line-ending
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; Blockquotes (must start with >)
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blockquote-block = ">" blockquote-rest
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blockquote-rest = [ WSP ] *( inline-element ) line-ending
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*( ">" [ WSP ] *( inline-element ) line-ending )
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; Unordered lists (must start with *, -, or + followed by space)
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unordered-list-block = unordered-list-item 1*( unordered-list-item )
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unordered-list-item = unordered-marker list-item-content
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unordered-marker = ( "*" / "-" / "+" ) WSP
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list-item-content = *( inline-element ) line-ending
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*( list-continuation )
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list-continuation = 2*WSP *( inline-element ) line-ending
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; Ordered lists (must start with digit(s) followed by . and space)
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ordered-list-block = ordered-list-item 1*( ordered-list-item )
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ordered-list-item = ordered-marker list-item-content
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ordered-marker = 1*DIGIT "." WSP
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; Fenced code blocks (must start with ``` or ~~~)
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fenced-code-block = code-fence fenced-code-rest
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fenced-code-rest = [ language-info ] line-ending
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*( code-line )
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code-fence line-ending
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code-fence = "```" / "~~~"
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language-info = 1*( ALPHA / DIGIT / "-" / "+" / "." )
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code-line = *VCHAR line-ending
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; Indented code blocks (must start with 4+ spaces followed by non-space)
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indented-code-block = 4*WSP VCHAR indented-code-rest
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indented-code-rest = *VCHAR line-ending
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*( 4*WSP *VCHAR line-ending )
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; Horizontal rules (must start with 3+ of same character)
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horizontal-rule-block = hr-pattern hr-rest
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hr-pattern = 3*"*" / 3*"-" / 3*"_"
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hr-rest = *( WSP / "*" / "-" / "_" ) line-ending
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; HTML blocks (must start with <)
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html-block = "<" html-block-rest
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html-block-rest = html-tag-block / html-comment-block / html-declaration-block
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html-tag-block = tag-name *( WSP attribute ) [ WSP ] [ "/" ] ">"
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*( html-content )
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[ "</" tag-name ">" ]
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line-ending
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html-comment-block = "!--" *( CHAR ) "-->" line-ending
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html-declaration-block = "!" 1*ALPHA *( WSP / VCHAR ) ">" line-ending
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; Paragraphs (everything else that doesn't match above patterns)
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paragraph-block = paragraph-text-line 1*( paragraph-continuation )
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paragraph-text-line = paragraph-first-element *( inline-element ) line-ending
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paragraph-continuation = paragraph-first-element *( inline-element ) line-ending
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; First element of paragraph - anything that's not a block starter
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paragraph-first-element = emphasis / strong / code-span / link / image /
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html-inline / line-break / escaped-char / plain-text
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; Inline elements
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inline-element = emphasis / strong / code-span / link / image /
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html-inline / line-break / escaped-char / plain-text
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; Emphasis and strong (left-factored by delimiter)
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emphasis = emphasis-asterisk / emphasis-underscore
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strong = strong-asterisk / strong-underscore
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emphasis-asterisk = "*" emphasis-content-asterisk "*"
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emphasis-underscore = "_" emphasis-content-underscore "_"
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strong-asterisk = "**" strong-content-asterisk "**"
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strong-underscore = "__" strong-content-underscore "__"
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; Content within emphasis/strong (simplified - no nesting for clarity)
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emphasis-content-asterisk = 1*( escaped-char / plain-text-no-asterisk )
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emphasis-content-underscore = 1*( escaped-char / plain-text-no-underscore )
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strong-content-asterisk = 1*( escaped-char / plain-text-no-double-asterisk )
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strong-content-underscore = 1*( escaped-char / plain-text-no-double-underscore )
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; Code spans
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code-span = "`" code-span-content "`" /
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"``" code-span-content-double "``" /
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"```" code-span-content-triple "```"
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code-span-content = 1*( %x20-5F / %x61-10FFFF ) ; Everything except `
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code-span-content-double = *( %x20-5F / %x61-10FFFF / "`" )
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code-span-content-triple = *( %x20-5F / %x61-10FFFF / "`" / "``" )
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; Links and images (left-factored by opening bracket)
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link = "[" link-content "]" link-destination
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image = "!" "[" alt-text "]" link-destination
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link-content = 1*( escaped-char / plain-text-no-bracket )
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alt-text = 1*( escaped-char / plain-text-no-bracket )
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link-destination = "(" url [ WSP title ] ")" /
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"[" reference-id "]"
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reference-id = 1*( ALPHA / DIGIT / WSP )
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url = 1*( %x21-29 / %x2B-10FFFF ) ; Everything except space and )
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title = DQUOTE title-content-dquote DQUOTE /
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"'" title-content-squote "'" /
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"(" title-content-paren ")"
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title-content-dquote = *( %x20-21 / %x23-10FFFF ) ; Everything except "
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title-content-squote = *( %x20-26 / %x28-10FFFF ) ; Everything except '
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title-content-paren = *( %x20-28 / %x2A-10FFFF ) ; Everything except )
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; Inline HTML
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html-inline = "<" html-inline-content
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html-inline-content = tag-name *( WSP attribute ) [ WSP ] [ "/" ] ">" /
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entity-name ";"
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entity-name = 1*( ALPHA / DIGIT )
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; HTML attributes and tag content
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tag-name = ALPHA *( ALPHA / DIGIT / "-" / ":" )
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attribute = attribute-name [ "=" attribute-value ]
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attribute-name = ( ALPHA / "_" / ":" ) *( ALPHA / DIGIT / "-" / "_" / ":" / "." )
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attribute-value = DQUOTE attribute-value-dquote DQUOTE /
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"'" attribute-value-squote "'" /
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attribute-value-unquoted
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attribute-value-dquote = *( %x20-21 / %x23-10FFFF ) ; Everything except "
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attribute-value-squote = *( %x20-26 / %x28-10FFFF ) ; Everything except '
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attribute-value-unquoted = 1*( %x21-22 / %x24-26 / %x28-2F / %x30-3D / %x3F-10FFFF )
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html-content = *( %x20-3B / %x3D-10FFFF ) ; Everything except <
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; Line breaks and escaped characters
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line-break = 2*WSP line-ending
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escaped-char = "\" VCHAR
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; Plain text variations (to avoid conflicts)
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plain-text = 1*plain-text-char
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plain-text-char = %x20-21 / %x23-29 / %x2B-2F / %x30-3B / %x3D /
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%x3F-40 / %x41-5A / %x5C / %x5E-5F / %x61-7A /
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%x7C / %x7E-10FFFF
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plain-text-no-asterisk = %x20-29 / %x2B-10FFFF
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plain-text-no-underscore = %x20-5E / %x60-10FFFF
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plain-text-no-double-asterisk = 1*( %x20-29 / %x2B-10FFFF ) ; Simplified
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plain-text-no-double-underscore = 1*( %x20-5E / %x60-10FFFF ) ; Simplified
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plain-text-no-bracket = %x20-5A / %x5C-10FFFF
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; Basic definitions
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line-ending = CRLF / LF / CR
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WSP = SP / HTAB
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ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
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DIGIT = %x30-39 ; 0-9
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SP = %x20 ; Space
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HTAB = %x09 ; Horizontal tab
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CR = %x0D ; Carriage return
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LF = %x0A ; Line feed
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CRLF = CR LF ; Internet standard newline
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DQUOTE = %x22 ; Double quote
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VCHAR = %x21-7E ; Visible ASCII characters
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