trunk_notes_lua_usage.txt

# Some helpful info on how Lua works and how it interfaces with Trunk Notes.



{{lua Multiply.lua, 5, 10}}
n1 = args[1]
n2 = args[2]
return n1 * n2




# some people on the internet say ... (dotdotdot) should return a table of all the arguments, something like:
return ...
# haven't figured out how to get it to work yet, though




A wiki page is a Lua table (a hash) describing the page. The following attributes are available:
contents – the actual contents of the page
arguments – the list of arguments taken from the query string




page = wiki.get(title)
string.find(page.contents, "text")
is_a_front = false
for _, tag in pairs(page.tags) do
  if tag == "Front" then
    is_a_front = true
  end
end
if is_a_front then
    _, title_end = string.find(page.contents, "#Countdown\n")
    if title_end then
      _,_,first_plot = string.find(page.contents, "(%* .*)", title_end)
      if first_plot then
        title_list = title_list .. first_plot .. " ([[" .. title .. "]])\n"
      end
    end
end




string.find() will find the first instance of its second argument in its first, returning two values - where the match starts, and where the match ends. In other words:
string.find('foobar', 'foo') -->1  3
string.find('foobar', 'bar') -->4  6
actually, it returns two values plus any captures. Because string.find() knows regular expressions ("patterns").




Lua Arrays
http://www.lua.org/pil/11.1.html



# Helpful code example from
# https://github.com/evitiello/TrunkNotesScripts
-- Displays the last 20 pages that have been modified.
function string.starts(String,Start)
   return string.sub(String,1,string.len(Start))==Start
end
returnString = ""
pageTimes = {}
pageTimeMapping = {}
for pageIteration, pageTitle in ipairs(wiki.titles()) do
  pageUpdatedTime = wiki.get(pageTitle).updated
  table.insert(pageTimes, pageUpdatedTime)
  pageTimeMapping[pageUpdatedTime] = pageTitle
end
table.sort(pageTimes, function(a,b) return a>b end)
for i=1,5 do
  returnString = returnString .. "[[" .. pageTimeMapping[pageTimes[i]] .. "]]\n"
end
return returnString




Lua Online Interpreter: http://www.lua.org/cgi-bin/demo




The string.find function has an optional third parameter: an index that tells where in the subject string to start the search. This parameter is useful when we want to process all the indices where a given pattern appears. We search for a new pattern repeatedly, each time starting after the position where we found the previous one. As an example, the following code makes a table with the positions of all newlines in a string:
local t = {}                       -- table to store the indices
local i = 0
while true do
  i = string.find(s, "\n", i+1)    -- find 'next' newline
  if i == nil then break end
  table.insert(t, i)
end




# Use string.sub to return slices of a string
text = "name = Anna"
print(string.sub(text, 4, 6))




# Using not to reverse booleans
x = 10
if not (z == 11) then
print(x)
end
-- returns 10