feat(single): Impelement emphasis span elements

1 files changed, 39 insertions, 2 deletions

diff --git a/single.awk b/single.awk
index 726f519..9195576 100644
--- a/single.awk
+++ b/single.awk
@@ -9,12 +9,12 @@
 #     [ ] Lists
 #     [x] Code blocks
 #     [x] Horizontal rules
-# [ ] Span elements
+# [.] Span elements
 #     [ ] Links
 #         [ ] Inline
 #         [ ] Reference
-#     [ ] Emphasis
 #     [ ] Code
+#     [x] Emphasis
 #     [ ] Images
 #         [ ] Inline
 #         [ ] Reference
@@ -150,6 +150,43 @@ inside_codeblock && ! /^[ \t]*$/ {
 	not_paragraph = 1
 }
 
+# Emphasis
+function sub_match(replacement) {
+	$0 = substr($0, 1, RSTART - 1) replacement substr($0, RSTART + RLENGTH)
+}
+function surround(brace, left, right, blen) {
+	if (blen == "") { blen = length(brace) }
+	if (match($0, brace "[^" brace "]+" brace)) {
+		elem = left substr($0, RSTART + blen, RLENGTH - 2*blen) right
+		sub_match(elem)
+		return 1;
+	}
+	return 0
+}
+function gsurround(brace, left, right, blen) {
+	while (surround(brace, left, right, blen)) {}
+
+	if (blen == 1) {
+		gsub("\\\\", "", brace)
+		## Surrounding a single character span with spaces should make it a
+		## literal char. This is inelegant but functional.
+		gsub(" " left  " ", " " brace " ")
+		gsub(" " right " ", " " brace " ")
+	}
+}
+
+{
+	## Make sure <em> is on the inside for long chains
+	## E.g. *****a***** will be the same as ****_a_****
+	surround("___"      , "<strong><em>", "</em></strong>")
+	surround("\\*\\*\\*", "<strong><em>", "</em></strong>", 3)
+
+	gsurround("__"    , "<strong>", "</strong>")
+	gsurround("_"     , "<em>"    , "</em>")
+	gsurround("\\*\\*", "<strong>", "</strong>", 2)
+	gsurround("\\*"   , "<em>"    , "</em>", 1)
+}
+
 # Paragraph
 emptyP1 && !empty0 && !not_paragraph { $0 = "<p>" $0 }
 !emptyP1 && empty0 && !not_paragraph_p1 { P1 = P1 "</p>" }