From 99e0eb4c2a96be9fe0e77f54d89c27937d0465a6 Mon Sep 17 00:00:00 2001
From: Konstantin Nazarov <mail@knazarov.com>
Date: Sun, 12 Sep 2021 17:16:30 +0100
Subject: [PATCH] Add rss feed

---
 Makefile   |   5 ++-
 bin/rss.sh | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+), 1 deletion(-)
 create mode 100755 bin/rss.sh

diff --git a/Makefile b/Makefile
index c9c27f7..af84264 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ PROJECTS_DST := $(patsubst content/projects/%,$(ODIR)/projects/%/index.html,$(PR
 POSTS_SRC := $(wildcard content/posts/*)
 POSTS_DST := $(patsubst content/posts/%,$(ODIR)/posts/%/index.html,$(POSTS_SRC))
 
-all: $(PAGES_DST) $(PROJECTS_DST) $(POSTS_DST) $(ODIR)/style.css $(ODIR)/index.html $(ODIR)/posts/index.html
+all: $(PAGES_DST) $(PROJECTS_DST) $(POSTS_DST) $(ODIR)/style.css $(ODIR)/index.html $(ODIR)/posts/index.html $(ODIR)/rss.xml
 
 $(ODIR)/%/index.html: content/pages/%/note.md
 	mkdir -p "$(dir $@)"
@@ -25,6 +25,9 @@ $(ODIR)/posts/%/index.html: content/posts/%/note.md
 $(ODIR)/posts/index.html: $(POSTS_SRC)
 	./bin/toc.sh content/posts "/posts" | awk -f ./bin/markdown.awk | ./bin/page.sh Posts > "$@"
 
+$(ODIR)/rss.xml: $(POSTS_SRC)
+	./bin/rss.sh content/posts "https://knazarov.com" "/posts" > "$@"
+
 $(ODIR)/index.html: content/index.md
 	cat content/index.md | ./bin/mdpage.sh --notitle > "$@"
 
diff --git a/bin/rss.sh b/bin/rss.sh
new file mode 100755
index 0000000..ead0b66
--- /dev/null
+++ b/bin/rss.sh
@@ -0,0 +1,113 @@
+#!/bin/bash
+
+remove_nbsp() {
+	sed 's#\&nbsp;# #g'
+}
+
+date_rfc_822() {
+	date -j '+%a, %d %b %Y %H:%M:%S %z'
+}
+
+date_to_rfc_822() {
+	date -f "%Y-%m-%dT%H:%M:%SZ" -j '+%a, %d %b %Y %H:%M:%S %z' "$1T00:00:00Z"
+}
+
+get_header() {
+	HFILE="$1"
+	HEADER="$2"
+
+	FILTER="{ \
+		if (match(\$0, /^$HEADER: /)) {print substr(\$0, RLENGTH+1, length(\$0) - RLENGTH)}; \
+		if (\$0~/^$/) {exit}; \
+		if (!\$0~/^[^ ]*: .*$/) {exit}; \
+	}"
+
+	awk "$FILTER" "$HFILE"
+}
+
+list_items() {
+	DIR="$1"
+
+	pushd "$DIR" > /dev/null
+	find . ! -path . -type d  | while read -r FN
+	do
+		PAGE="$(echo "$FN" | sed 's/^\.\///g')"
+		#echo "FILE: $PAGE"
+
+		MD="$PAGE/note.md"
+		if [ ! -f "$MD" ]; then
+			echo "$MD doesn't exist"
+			exit 1;
+		fi
+
+		SUBJECT="$(get_header "$MD" "Subject")"
+		FDATE="$(get_header "$MD" "X-Date" | sed 's/T.*$//g')"
+
+		if [ -z "$SUBJECT" ]; then
+			echo "No subject in $MD"
+			exit 1
+		fi
+
+		if [ -z "$FDATE" ] && [ "$NODATE" == "0" ]; then
+			echo "No date in $MD"
+			exit 1
+		fi
+
+		echo "$FDATE $PAGE $SUBJECT"
+	done	
+	popd > /dev/null
+}
+
+render_item() {
+	base_url="$1"
+	item="$2"
+
+	site_url="$(echo "$base_url"| sed 's#\(.*//.*\)/.*#\1#')"
+
+	date=$(echo "$item"|awk '{print $1}')
+	url=$(echo "$item"|awk '{print $2}')
+	title=$(echo "$item"| cut -d ' ' -f 3- )
+
+	guid="$base_url/$(echo "$url" | sed 's#^/##')"
+
+	cat <<-EOF
+		<item>
+		<guid>$guid</guid>
+		<link>$guid</link>
+		<pubDate>$(date_to_rfc_822 "$date")</pubDate>
+		<title>$title</title>
+		</item>
+
+	EOF
+}
+
+render_items() {
+	base_url="$1"
+
+	while read -r i
+	do render_item "$1" "$i"
+	done
+}
+
+render_feed() {
+	url="$1"
+	title=$(echo "$2" | remove_nbsp)
+	description="$3"
+
+	base_url="$(echo "$url" | cut -d '/' -f1-3)"
+
+	cat <<-EOF
+		<?xml version="1.0" encoding="UTF-8"?>
+		<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
+		<channel>
+		<atom:link href="$url" rel="self" type="application/rss+xml" />
+		<title>$title</title>
+		<description>$description</description>
+		<link>$base_url/</link>
+		<lastBuildDate>$(date_rfc_822)</lastBuildDate>
+		$(cat)
+		</channel></rss>
+	EOF
+}
+
+list_items "$1" | sort | render_items "$2$3" | render_feed "$2" "Konstantin Nazarov" "test"