Yet more fun with pandoc lua

[Albert Krewinkel <albert+pandoc-9EawChwDxG8hFhg+JK9F0w@public.gmane.org>]

#!/usr/bin/env -S pandoc lua
-- This Lua script can be used as a very simple task manager. It allows
-- to manage tasks in a plain Markdown file `panjour.md`. E.g., if this
-- script is saved as file `panjour` and given executable permissions,
-- then the following works:
--
--     # Add two tasks to the file.
--     ./panjour add Dabble with Lua
--     ./panjour add Use some '*Markdown*'
--
--     # List all tasks
--     ./panjour list
--
--     # Mark a task as DONE
--     ./panjour done Dabble with Lua
--
-- The code here is unpolished; the main goal was to try and write a
-- full Lua program built on top of pandoc.

local panjour_file = (os.getenv 'PANJOUR_FILE') or 'panjour.md'
local format = 'markdown'
warn '@on'

local TaskManager = {
  done_marker = pandoc.Inlines{pandoc.Str '☒', pandoc.Space()},
  todo_marker = pandoc.Inlines{pandoc.Str '☐', pandoc.Space()},
}

function TaskManager:new(filename)
  local fh = io.open(filename, 'r+')
  if not doc then
    doc = pandoc.read(fh:read 'a', format)
  end
  local mgr = {
    document = doc,
    file_handle = fh,
  }
  setmetatable(mgr, self)
  self.__index = self
  return mgr
end

function TaskManager:add_task (task)
  local item = {pandoc.Plain(self.todo_marker .. task)}
  for i, blk in ipairs(self.document.blocks) do
    if blk.t == 'BulletList' then
      blk.content:insert(item)
      goto done
    end
  end
  self.document.blocks:insert(
    pandoc.BulletList{item}
  )
  ::done::
  return self
end

function TaskManager:mark_task_as_done (task)
  local todo_item = pandoc.Blocks{pandoc.Plain(self.todo_marker..task)}
  local done_item = pandoc.Blocks{pandoc.Plain(self.done_marker..task)}
  local found = false
  self.document = self.document:walk {
    BulletList = function (ul)
      if not found then
        local li, idx = ul.content:find(todo_item)
        if idx then
          found = true
          ul.content[idx] = {pandoc.Plain(self.done_marker .. task)}
        elseif ul.content:find(done_item) then
          found = true
          warn('Item already marked as done!')
        end
        return ul
      end
    end
  }
  if not found then
    local msg = 'task not found: "%s"'
    error(msg:format(pandoc.utils.stringify(task)))
  end
  return self
end

function TaskManager:list ()
  self:write_doc(io.stdout)
end

function TaskManager:write_doc (fh)
  local out = pandoc.write(self.document, format)
  fh = fh or self.file_handle
  fh:seek('set')
  fh:write(out)
end

function TaskManager:__gc()
  self.file_handle:close()
end

local action = arg[1]
local task_args = pandoc.List{}
for i=2, #arg do
  task_args:insert(arg[i])
end
local task = pandoc.utils.blocks_to_inlines(
  pandoc.read(table.concat(task_args, ' '), format).blocks
)

local task_manager = TaskManager:new(panjour_file)

if action == 'add' then
  task_manager:add_task(task)
  task_manager:write_doc()
elseif action == 'done' then
  task_manager:mark_task_as_done(task)
  task_manager:write_doc()
elseif action == 'list' then
  task_manager:list()
else
  local msg = 'Unknown or missing action. Bailing out.\n'
  io.stderr:write(msg)
  os.exit(1)
end


-- 
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe  e836 388d c0b2 1f63 1124

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