Add initial jq-template.awk

scripts/jq-template.awk

@@ -0,0 +1,127 @@
+# this script assumes gawk! (busybox "awk" is not quite sufficient)
+
+# see https://github.com/docker-library/php or https://github.com/docker-library/golang for examples of usage ("apply-templates.sh")
+
+# escape an arbitrary string for passing back to jq as program input
+function jq_escape(str,          # parameters
+                   prog, e, out) # locals
+{
+	prog = "jq --raw-input --slurp ."
+	printf "%s", str |& prog
+	close(prog, "to")
+	prog |& getline out
+	e = close(prog)
+	if (e != 0) {
+		exit(e)
+	}
+	return out
+}
+
+BEGIN {
+	jq_expr_defs = ""
+	jq_expr = ""
+	agg_jq = ""
+	agg_text = ""
+
+	OPEN = "{{"
+	CLOSE = "}}"
+	CLOSE_EAT_EOL = "-" CLOSE ORS
+}
+
+function trim(str) {
+	sub(/^[[:space:]]+/, "", str)
+	sub(/[[:space:]]+$/, "", str)
+	return str
+}
+function append(str) {
+	if (jq_expr && jq_expr !~ /\($/ && str !~ /^\)/) {
+		jq_expr = jq_expr "\n+ "
+	} else if (jq_expr) {
+		jq_expr = jq_expr "\n"
+	}
+	jq_expr = jq_expr str
+}
+function append_string(str) {
+	if (!str) return
+	str = jq_escape(str)
+	append(str)
+}
+function append_jq(expr) {
+	if (!expr) return
+	expr = trim(expr)
+	if (!expr) return
+	if (expr ~ /^(def|include|import)[[:space:]]/) { # a few things need to go at the start of our "script"
+		jq_expr_defs = jq_expr_defs expr ";\n"
+		return
+	}
+	# if expr doesn't begin with ")" or end with "(", wrap it in parenthesis (so our addition chain works properly)
+	if (expr !~ /^\)/) expr = "(" expr
+	if (expr !~ /\($/) expr = expr ")"
+	append(expr)
+}
+
+{
+	line = $0 ORS
+
+	i = 0
+	if (agg_jq || (i = index(line, OPEN))) {
+		if (i) {
+			agg_text = agg_text substr(line, 1, i - 1)
+			line = substr(line, i)
+		}
+		append_string(agg_text)
+		agg_text = ""
+
+		agg_jq = agg_jq line
+		line = ""
+
+		if (!index(agg_jq, CLOSE)) {
+			next
+		}
+
+		while (i = index(agg_jq, OPEN)) {
+			line = substr(agg_jq, 1, i - 1)
+			agg_jq = substr(agg_jq, i + length(OPEN))
+			if (i = index(agg_jq, CLOSE_EAT_EOL)) {
+				expr = substr(agg_jq, 1, i - 1)
+				agg_jq = substr(agg_jq, i + length(CLOSE_EAT_EOL))
+			}
+			else {
+				i = index(agg_jq, CLOSE)
+				expr = substr(agg_jq, 1, i - 1)
+				agg_jq = substr(agg_jq, i + length(CLOSE))
+			}
+			append_string(line)
+			append_jq(expr)
+		}
+		line = agg_jq
+		agg_jq = ""
+	}
+
+	if (line) {
+		agg_text = agg_text line
+	}
+}
+
+END {
+	append_string(agg_text)
+	agg_text = ""
+
+	append_jq(agg_jq)
+	agg_jq = ""
+
+	jq_expr = "if env.version then .[env.version] else . end | (\n" jq_expr "\n)"
+	jq_expr = jq_expr_defs jq_expr
+
+	if (ENVIRON["DEBUG"]) {
+		print jq_expr > "/dev/stderr"
+	}
+
+	prog = "jq --join-output --from-file /dev/stdin versions.json"
+	printf "%s", jq_expr | prog
+
+	e = close(prog)
+	if (e != 0) {
+		exit(e)
+	}
+}