From 7e65b1deef086d12cff6a129857a8ba335b4eccf Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Mon, 24 Jan 2022 23:54:32 +0100
Subject: util.xtemplate: Yet another string template library

This one takes a stanza as input

Roughly based on util.interpolation
---
 teal-src/util/xtemplate.tl | 101 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 teal-src/util/xtemplate.tl

(limited to 'teal-src/util')

diff --git a/teal-src/util/xtemplate.tl b/teal-src/util/xtemplate.tl
new file mode 100644
index 00000000..b3bdc400
--- /dev/null
+++ b/teal-src/util/xtemplate.tl
@@ -0,0 +1,101 @@
+-- render(template, stanza) --> string
+-- {path} --> stanza:find(path)
+-- {{ns}name/child|each({ns}name){sub-template}}
+
+--[[
+template ::= "{" path ("|" name ("(" args ")")? (template)? )* "}"
+path ::= defined by util.stanza
+name ::= %w+
+args ::= anything with balanced ( ) pairs
+]]
+
+local s_gsub = string.gsub;
+local s_match = string.match;
+local s_sub = string.sub;
+local t_concat = table.concat;
+
+local st = require "util.stanza";
+
+local type escape_t = function (string) : string
+local type filter_t = function (string, string | st.stanza_t, string) : string | st.stanza_t, boolean
+local type filter_coll = { string : filter_t }
+
+local function render(template : string, root : st.stanza_t, escape : escape_t, filters : filter_coll) : string
+	escape = escape or st.xml_escape;
+
+	return (s_gsub(template, "%b{}", function(block : string) : string
+		local inner = s_sub(block, 2, -2);
+		local path, pipe, pos = s_match(inner, "^([^|]+)(|?)()");
+		if not path is string then return end
+		local value : string | st.stanza_t
+		if path == "." then
+			value = root;
+		elseif path == "#" then
+			value = root:get_text();
+		else
+			value = root:find(path);
+		end
+		local is_escaped = false;
+
+		while pipe == "|" do
+			local func, args, tmpl, p = s_match(inner, "^(%w+)(%b())(%b{})()", pos as integer);
+			if not func then func, args, p = s_match(inner, "^(%w+)(%b())()", pos as integer); end
+			if not func then func, tmpl, p = s_match(inner, "^(%w+)(%b{})()", pos as integer); end
+			if not func then func, p = s_match(inner, "^(%w+)()", pos as integer); end
+			if not func then break end
+			if tmpl then tmpl = s_sub(tmpl, 2, -2); end
+			if args then args = s_sub(args, 2, -2); end
+
+			if func == "each" and tmpl and st.is_stanza(value) then
+				if not args then value, args = root, path; end
+				local ns, name = s_match(args, "^(%b{})(.*)$");
+				if ns then ns = s_sub(ns, 2, -2); else name, ns = args, nil; end
+				if ns == "" then ns = nil; end
+				if name == "" then name = nil; end
+				local out, i = {}, 1;
+				for c in (value as st.stanza_t):childtags(name, ns) do
+					out[i], i = render(tmpl, c, escape, filters), i + 1;
+				end
+				value = t_concat(out);
+				is_escaped = true;
+			elseif func == "and" and tmpl then
+				local condition = value;
+				if args then condition = root:find(args); end
+				if condition then
+					value = render(tmpl, root, escape, filters);
+					is_escaped = true;
+				end
+			elseif func == "or" and tmpl then
+				local condition = value;
+				if args then condition = root:find(args); end
+				if not condition then
+					value = render(tmpl, root, escape, filters);
+					is_escaped = true;
+				end
+			elseif filters and filters[func] then
+				local f = filters[func];
+				if args == nil then
+					value, is_escaped = f(value, tmpl);
+				else
+					value, is_escaped = f(args, value, tmpl);
+				end
+			else
+				error("No such filter function: " .. func);
+			end
+			pipe, pos = s_match(inner, "^(|?)()", p as integer);
+		end
+
+		if value is string then
+			if not is_escaped then value = escape(value); end
+			return value;
+		elseif st.is_stanza(value) then
+			value = value:get_text();
+			if value then
+				return escape(value);
+			end
+		end
+		return "";
+	end));
+end
+
+return { render = render };
-- 
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