Paragraph and heading parsing for md2html

1 files changed, 130 insertions, 0 deletions

diff --git a/src/md2html.sh b/src/md2html.sh
new file mode 100755
index 0000000..f675399
--- /dev/null
+++ b/src/md2html.sh
@@ -0,0 +1,130 @@
+#!/bin/sh
+
+# replace all * with _ for easier processing
+#
+_pre_emph () {
+    while IFS= read -r line; do
+        while [ "$line" != "${line%%\**}" ]; do
+            printf "%s_" "${line%%\**}"
+            line="${line#*\*}"
+        done
+        printf "${line}\n"
+    done
+}
+
+
+# fix any misaligned <em> and <strong> closign tags
+#
+_post_emph () {
+    while IFS= read -r line; do
+        # TODO: avoid this problem entirely?
+
+        local wrong="</strong></em>" right="</em></strong>"
+
+        while [ "$line" != "${line%%${wrong}*}" ]; do
+            printf "%s${right}" "${line%%${wrong}*}"
+            line="${line#*${wrong}}"
+        done
+        printf "${line}\n"
+    done
+}
+
+# parse emphasis in a line
+#
+#   emph [bound] <lefttag> <righttag>
+#
+_emph () {
+    local bound="$1"
+    local lefttag="$2" righttag="$3"
+
+    while IFS= read -r line; do
+        next="${line}"
+        line=
+        rightofbold=
+
+        while [ "$next" != "${next#*${bound}}" ]; do
+            leftofbold="${next%%${bound}*}"
+            rightofbold="${next#$leftofbold${bound}*}"
+            bold="${rightofbold%%${bound}*}"
+            next="${rightofbold#*${bound}}"
+            printf "%s%s%s%s" "${leftofbold}" "${lefttag}" "${bold}" "${righttag}"
+        done
+        printf "%s\n" "${next}"
+    done
+}
+
+# parse heading
+#
+#   h [heading no.]
+_h () {
+    local num=$1
+    while IFS= read -r line; do
+        s=
+
+        n=$num
+        while [ "$n" -gt "0" ]; do
+            s="#$s"
+            n=$((n-1))
+        done
+
+        case "$line" in
+            "$s "*)
+                printf "<h$num>%s</h$num>\n" "${line#$s }"
+                ;;
+            *)
+                printf "%s\n" "$line"
+                ;;
+        esac
+    done
+}
+
+# parse paragraphs
+#
+#   p
+_p () {
+    local num=$1
+    empty=true
+    while IFS= read -r line; do
+        case "$line" in
+            "#"*)
+                printf "%s\n" "$line"
+                ;;
+            "") 
+                $empty ||
+                    printf "</p>\n"
+                
+                empty=true ;;
+            *) 
+                $empty &&
+                    printf "<p>%s " "$line" ||
+                    printf "%s " "$line"
+
+                empty=false ;;
+        esac
+
+    done
+
+    $empty || {
+        printf "</p>\n"
+    }
+}
+
+
+# convert the markdown from stdin into html
+#
+md2html () {
+            _p \
+            | _pre_emph \
+            | _emph '__' "<strong>" "</strong>" \
+            | _emph '_' "<em>" "</em>" \
+            | _post_emph \
+            | _h 6 \
+            | _h 5 \
+            | _h 4 \
+            | _h 3 \
+            | _h 2 \
+            | _h 1 
+}
+
+md2html
+