local mtar = require "libmtar"
local w, lz16 = pcall(require, "liblz16")
if not w then lz16 = nil end

pkgfs = {}
pkgfs.files = {}
local findex = {}
local handles = {}
local hc = 0

local function rfalse()
 return false
end
local function rzero()
 return 0
end

pkgfs.component = {seek = rfalse, makeDirectory = rfalse, write = rfalse, rename = rfalse, setlabel = rfalse, spaceUsed = rzero, spaceTotal = rzero, lastModified = rzero, address = "pkgfs"}

local function fopen(path,comp)
 local f
 if comp and lz16 then
  f = lz16.open(path,"rb")
 else
  f = io.open(path,"rb")
 end
 return f
end

local function fnormalize(s)
 return table.concat(fs.segments(s),"/")
end

function pkgfs.component.exists(path)
 path = fnormalize(path)
 return findex[path] and true
end

function pkgfs.component.list(path)
 path = fnormalize(path).."/"
 local ft,rt = {},{}
 for k,v in pairs(findex) do
  k="/"..k
  if k:match(path.."([^/]+)/.+") then
   ft[k:match(path.."([^/]+)/.+").."/"] = true
  elseif k:match(path.."([^/]+)") then
   ft[k:match(path.."([^/]+)")] = true
  end
 end
 for k,v in pairs(ft) do
  rt[#rt+1] = k
 end
 return rt
end
function pkgfs.component.isDirectory(path)
 path = fnormalize(path).."/"
 for k,v in pairs(findex) do
  k="/"..k
  if k:match(path.."([^/]+)/.+") then
   return true
  end
 end
 return false
end
function pkgfs.component.size(path)
 path=fnormalize(path)
 if not findex[path] then return false end
 local f = fopen(findex[path][1], findex[path][2])
 for fname, read, fsize in mtar.iter(f) do
  if fname == path then
   return fsize
  end
 end
 return false
end

function pkgfs.component.open(path,mode)
 path=fnormalize(path)
 if mode:find("w") or mode:find("a") or not findex[path] then
  return false
 end
 local f = fopen(findex[path][1],findex[path][2])
 for fname,read,fsize in mtar.iter(f) do
  if fname == path then
   hc = hc + 1
   handles[hc] = {read, f}
   return hc
  end
 end
end

function pkgfs.component.read(handle, n)
 if not handles[handle] then return false end
 local rv = handles[handle][1](n)
 if not rv then return nil end
 if rv:len() < 1 then return nil end
 return rv
end

function pkgfs.component.close(handle)
 if not handles[handle] then return false end
 handles[handle][2]:close()
 handles[handle] = nil
 return true
end

local function index()
 findex = {}
 for k,v in pairs(pkgfs.files) do
  fname, comp = v[1], v[2]
  if fname:sub(1,1) ~= "/" then
   fname = "/"..fnormalize(os.getenv("PWD").."/"..fname)
  end
  local f = fopen(fname,comp)
  if not f then error("unable to open file "..fname) end
  for name, read, fsize in mtar.iter(f) do
   findex[fnormalize(name)] = {fname,comp}
  end
  f:close()
 end
 return true
end

function pkgfs.add(fname,comp) -- string boolean -- boolean -- Add a package as specified in *fname* to the pkgfs component. If *comp* is true, read it as a LZ16-compressed package.
 pkgfs.files[#pkgfs.files+1] = {fname,comp}
 return index()
end
function pkgfs.remove(fname) -- string -- boolean -- Removes the package specified by *fname* from the pkgfs index.
 for k,v in pairs(pkgfs.files) do
  if v[1] == fname then
   table.remove(pkgfs.files,k)
  end
 end
 return index()
end

fs.makeDirectory("/pkg")
fs.mount("/pkg",pkgfs.component)
for _,file in ipairs(fs.list("/boot/pkg/")) do
 if file:sub(-5) == ".mtar" then
  pcall(pkgfs.add,"/boot/pkg/"..file)
 elseif file:sub(-9) == ".mtar.lss" then
  pcall(pkgfs.add,"/boot/pkg/"..file,true)
 end
end
return pkgfs