includes multiple files

filter.lua

@@ -1,18 +1,34 @@
-function File2Block(filename)
-    local fh = io.open(filename, "r")
-    if not fh then
-        io.stderr:write("Cannot open file: " .. filename .. "\n")
-        return { pandoc.Plain { pandoc.Str("[Error: cannot read file " .. filename .. "]") } }
+
+local function words(s)
+    local res = {}
+    for part in s:gmatch("[^,]+") do                -- split by commas
+        local trimmed = part:match("^%s*(.-)%s*$")  -- remove leading/trailing spaces
+        if trimmed ~= "" then
+            table.insert(res, trimmed)
+        end
+    end
+    return res
+end
+
+local function label2Block(labels)
+    local contents = ""
+    for _,l in ipairs(words(labels)) do
+        -- use file for now.
+        local fh = io.open(l, "r")
+        if not fh then
+            io.stderr:write("Cannot open file: " .. l .. "\n")
+            return { pandoc.Plain { pandoc.Str("[Error: cannot read file " .. l .. "]") } }
+        end
+        contents = contents .. fh:read("*a")
+        fh:close()
     end
-    local contents = fh:read("*a")
-    fh:close()
     return { pandoc.Plain { pandoc.Str(contents) } }
 end
 
 function Div(e)
     local include = e.attributes["include"]
     if include then
-        local blocks = File2Block(include)
+        local blocks = label2Block(include)
         -- Replace the Div contents
         return pandoc.Div(blocks, e.attr)
     end