add modules directory and lssi, the first module!

modules/README.md

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+# Modules
+Modules are extentions to the EatIt plugin manager that aren't necessary for
+running it. Every module will be in it's own sub directory in order to keep 
+documentation relative to the individual modules.
+
+## List of modules
+- `lssi.lua` Lua Script Script Injector for modifing files post install
+
+## Installing
+Installing a module can be done through EatIt like so:
+```lua
+plugins = { -- the plugins you want to load
+  { 'https://git.squi.bid/eat-it',
+    file = 'modules/moddir/module.lua',
+    dir = 'scripts',
+  },
+}
+```
+
+## For Devs
+Please add a table in the global scope called 'mod' as this may be used in the
+future. It should look like this:
+```lua
+mod = {
+  version = 'version',
+  author = 'autor name',
+}
+```

modules/lssi/LSSI.md

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+# Using lssi
+Any plugin can be modified by lssi by doing the following in the eatit-cfg.lua:
+```lua
+plugins = { -- the  plugins you want to load
+  { 'https://git.squi.bid/eat-it',
+    file = 'eatit.lua',
+    dir = 'scripts',
+    lssi = {
+        -- code                  line
+        { 'print("hello world")', 'G' },
+    }
+  },
+}
+```
+The line option can be 'g' for top of file, 'G' for bottom of file, or any 
+number in between.

modules/lssi/lssi.lua

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+--[[
+Eat It - a Mpv plugin manager
+
+Copyright © 2023 squibid
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+]]
+
+-- NOTE: This is a POC and will most likely be reimplimented using diff files
+-- with git
+-- or we might want to generate a diff file from the requested changes
+-- and check if the diffs match in content
+
+--[[ 
+                           Lua Script Script Injector
+Takes an input file and code then, it outputs a file with your code in there.
+]]--
+
+local mp = require('mp')
+
+mod = {
+  version = 'ALPHA 1', -- the current version of lssi
+  author = 'squibid',
+}
+
+-- load the eatit config file
+dofile(mp.command_native({'expand-path', '~~/eatit-cfg.lua'}))
+
+-- helper functions
+local function tablelength(T)
+  local count = 0
+  for _ in pairs(T) do count = count + 1 end
+  return count
+end
+
+local function fileexists(name)
+   local f = io.open(name, 'r')
+   if f ~= nil then io.close(f) return true else return false end
+end
+
+local function logwrite(string)
+  if opts.logging.log then
+    io.write(os.date(opts.logging.logdate) .. ' ' .. string .. '\n')
+  end
+end
+
+local function openlog()
+  if opts.logging.log then -- log if asked to
+    -- get our logfile's full path
+    fn = mp.command_native({'expand-path', opts.logging.logfile})
+
+    f = io.open(fn, 'a') -- open file buffer
+    io.output(f) -- set it as default
+  end
+end
+
+local function closelog()
+  if opts.logging.log then
+    io.close(f)
+  end
+end
+
+local function inject(infile, l, outfile)
+  local inf = io.open(infile, 'r')
+  local infcont = {}
+  for i in inf:lines() do
+    table.insert(infcont, i)
+  end
+  inf:close()
+
+  -- don't do anything if there is already code injected into the file
+  if string.find(infcont[1], "-- code injected by lssi") then
+    logwrite('code is already injected into ' .. infile)
+    return
+  end
+  logwrite('Injecting code into ' .. infile)
+
+  for i in pairs(l) do
+    -- add requested line below existing line
+    if l[i][2] == 'G' then
+      infcont[tablelength(infcont)] = infcont[tablelength(infcont)] .. '\n' .. l[i][1]
+    elseif l[i][2] == 'g' then
+      infcont[1] = l[i][1] .. '\n' .. infcont[1]
+    else
+      infcont[l[i][2]] = (infcont[l[i][2]]) .. '\n' .. l[i][1]
+    end
+  end
+
+  local outf = io.open(outfile, 'w')
+
+  -- we inject metadata to prevent writing to the file more than once
+  infcont[1] = "-- code injected by lssi " .. mod.version .. '\n' .. infcont[1]
+  for i, v in ipairs(infcont) do
+    outf:write(v .. '\n')
+  end
+
+  io.close(outf)
+end
+
+local function checkandinject()
+  openlog()
+
+  for i = 1, tablelength(plugins) do
+    -- get the file we want to inject our code into
+    local f = mp.command_native({'expand-path', '~~/'}) ..
+      '/' .. plugins[i]['dir'] ..
+      '/' .. plugins[i]['file']
+
+    -- check if the plugin has been configured with lssi
+    if plugins[i]['lssi'] then
+      -- and the file we are trying to modify actually exists
+      if fileexists(f) then
+        -- inject it! no going back now
+        inject(f, plugins[i]['lssi'], f)
+      else
+        logwrite('Failed to inject code into "' ..
+          plugins[i]['file'] .. '" file does not exist')
+      end
+    end
+  end
+
+  closelog()
+end
+
+checkandinject()