1 files changed, 136 insertions, 0 deletions
diff --git a/bin/md b/bin/md
new file mode 100755
index 0000000..ca08090
--- /dev/null
+++ b/bin/md
@@ -0,0 +1,136 @@
+#!/bin/sh
+
+# See https://spec.commonmark.org for reference
+md2html() {
+	awk '
+	function newblock(nb) {
+		if (text) print "<" block ">" text "</" block ">"
+		text = ""
+		block = nb ? nb : "p"
+	}
+
+	function subinline(tgl, inl) {
+		while (match($0, tgl)) {
+			if (inline[ni] == inl)
+				ni -= sub(tgl, "</" inl ">")
+			else if (sub(tgl, "<" inl ">"))
+				inline[++ni] = inl
+		}
+	}
+
+	function dolink(href, lnk) {
+		# Undo escaped html in uris
+		gsub(/&amp;/, "\\&", href)
+		gsub(/&lt;/, "<", href)
+		gsub(/&gt;/, ">", href)
+		# & can be tricky, and not standard:
+		gsub(/&/, "\\\\\\&", href)
+		gsub(/&/, "\\\\\\&", lnk)
+		return "<a href=\"" href "\">" lnk "</a>"
+	}
+
+	BEGIN { ni = 0; nl = 0; text = ""; block = "p" }
+
+	# Escape html
+	esc != "false" { gsub("&", "\\&amp;"); gsub("<", "\\&lt;"); gsub(">", "\\&gt;") }
+
+	# Horizontal rules (_ is not in markdown)
+	/^[ 	]*([-*_] ?)+[ 	]*$/ && text == "" { print "<hr>"; next }
+
+	# Tables (not in markdown)
+	# Syntax:
+	# 		Right Align| 	Center Align	|Left Align
+	/([ 	]\|)|(\|[ 	])/ {
+		if (block != "table") newblock("table")
+		nc = split($0, cells, "|")
+		$0 = "<tr>\n"
+		for (i = 1; i <= nc; i++) {
+			align = "left"
+			if (sub(/^[ 	]+/, "", cells[i])) {
+				if (sub(/[ 	]+$/, "", cells[i]))
+					align = "center"
+				else
+					align = "right"
+			}
+			sub(/[ 	]+$/, "", cells[i])
+			$0 = $0 "<td align=\"" align "\">" cells[i] "</td>\n"
+		}
+		$0 = $0 "</tr>"
+	}
+
+	# Ordered and unordered (possibly nested) lists
+	/^[ 	]*([*+-]|(([0-9]+[\.-]?)+))[ 	]/ {
+		newblock("li")
+		nnl = 1
+		while (match($0, /^[ 	]/)) { sub(/^[ 	]/,""); nnl++ }
+		while (nl > nnl) print "</" list[nl--] ">"
+		while (nl < nnl) {
+			list[++nl] = "ol"
+			if (match($0, /^[*+-]/)) list[nl] = "ul"
+			print "<" list[nl] ">"
+		}
+		sub(/^([*+-]|(([0-9]+[\.-]?)+))[ 	]/,"")
+	}
+
+	# Multi line list items
+	block == "li" { sub(/^( *)|(	*)/,"") }
+
+	# Code blocks
+	/^(    |	)/ {
+		if (block != "code") newblock("code")
+		sub(/^(    |	)/, "")
+		text = text $0 "\n"
+		next
+	}
+
+	# Paragraph
+	/^$/ { newblock(); while(nl > 0) print "</" list[nl--] ">" }
+
+	# Setex-style Headers (plus h3 with underscores)
+	/^=+$/ { block = "h" 1; next }
+	/^-+$/ { block = "h" 2; next }
+	/^_+$/ { block = "h" 3; next }
+
+	# Atx-style headers
+	/^#/ {
+		newblock()
+		match($0, /#+/)
+		n = RLENGTH
+		if (n > 6) n = 6
+		sub(/# */, "#")
+		text = substr($0, RLENGTH + 1)
+		block = "h" n
+		next
+	}
+
+	{
+		# Images
+		while (match($0, /!\[[^\]]+\]\([^\)]+\)/)) {
+			split(substr($0, RSTART, RLENGTH), a, /(!\[)|\)|(\]\()/)
+			sub(/!\[[^\]]+\]\([^\)]+\)/, "<img src=\"" a[3] "\" alt=\"" a[2] "\">")
+		}
+		# Links
+		while (match($0, /\[[^\]]+\]\([^\)]+\)/)) {
+			split(substr($0, RSTART, RLENGTH), a, /[\[\)]|(\]\()/)
+			sub(/\[[^\]]+\]\([^\)]+\)/, dolink(a[3], a[2]))
+		}
+		# Auto links (uri matching is poor)
+		na = split($0, a, /(^\()|[ 	]|([,\.\)]([ 	]|$))/)
+		for (i = 1; i <= na; i++)
+			if (match(a[i], /^(((https?|ftp|file|news|irc):\/\/)|(mailto:)).+$/))
+				sub(a[i], dolink(a[i], a[i]))
+		# Inline
+		subinline("(\\*\\*)|(__)", "strong")
+		subinline("\\*", "em")
+		subinline("`", "code")
+		text = text (text ? " " : "") $0
+	}
+
+	END {
+		while(ni > 0) text = text "</" inline[ni--] ">"
+		newblock()
+		while(nl > 0) print "</" list[nl--] ">"
+	}' "$1"
+}
+
+md2html "$1"