-- Copyright (C) 2018-2021 by KittenOS NEO contributors
--
-- Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.
--
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
-- THIS SOFTWARE.

-- metamachine-vgpu.lua : Virtual GPU library
-- Authors: 20kdc

return function (icecap, address, path, ro)
 if path ~= "/" then
  icecap.makeDirectory(path:sub(1, #path - 1))
 end
 local function resolvePath(p, post)
  local pth = {}
  local issue = false
  string.gsub(p, "[^\\/]+", function (str)
   if str == ".." then
    if not pth[1] then
     issue = true
    else
     table.remove(pth, #pth)
    end
   elseif str ~= "." then
    table.insert(pth, str)
   end
  end)
  if issue then
   return
  end
  local str = path
  if post then
   str = str:sub(1, #str - 1)
  end
  for k, v in ipairs(pth) do
   if k > 1 or post then
    str = str .. "/"
   end
   str = str .. v
  end
  return str
 end
 local function wrapThing(fn, post, roStop)
  -- If we're adding a "/", we get rid of the original "/".
  -- 
  local pofx = ""
  if post then
   pofx = "/"
  end
  return function (p)
   if ro and roStop then
    return false, "read-only filesystem"
   end
   p = resolvePath(p, post)
   if p then
    local nt = {pcall(fn, p .. pofx)}
    if nt[1] then
     return table.unpack(nt, 2)
    end
   end
   return nil, "no such file or directory"
  end
 end
 local function wrapStat(s)
  return wrapThing(function (px)
   local stat = icecap.stat(px)
   if stat then
    return stat[s]
   end
  end, false, false)
 end
 local handles = {}
 local lHandle = 0
 local modeMapping = {
  r = false,
  rb = false,
  w = true,
  wb = true,
  a = "append",
  ab = "append"
 }
 return {
  type = "filesystem",
  getLabel = function ()
   return "VFS"
  end,
  setLabel = function (label)
  end,
  isReadOnly = function ()
   return ro or icecap.isReadOnly()
  end,
  spaceUsed = function ()
   return icecap.spaceUsed()
  end,
  spaceTotal = function ()
   return icecap.spaceTotal()
  end,
  list = wrapThing(icecap.list, true, false),
  exists = wrapThing(function (px)
   if icecap.stat(px) then
    return true
   end
   return false
  end, false, false),
  isDirectory = wrapStat(1),
  size = wrapStat(2),
  lastModified = wrapStat(3),
  makeDirectory = wrapThing(icecap.makeDirectory, false, true),
  rename = function (a, b)
   if ro then return false, "read-only filesystem" end
   a = resolvePath(a)
   b = resolvePath(b)
   if not (a and b) then
    return nil, a
   end
   return icecap.rename(a, b)
  end,
  remove = wrapThing(icecap.remove, false, true),
  --
  open = function (p, mode)
   checkArg(1, p, "string")
   p = resolvePath(p)
   if not p then return nil, "failed to open" end
   if rawequal(mode, nil) then mode = "r" end
   if modeMapping[mode] == nil then
    error("unsupported mode " .. tostring(mode))
   end
   mode = modeMapping[mode]
   if (mode ~= false) and ro then return nil, "read-only filesystem" end
   lHandle = lHandle + 1
   handles[lHandle] = icecap.open(p, mode)
   if not handles[lHandle] then
    return nil, "failed to open"
   end
   return lHandle
  end,
  read = function (fh, len)
   checkArg(1, fh, "number")
   checkArg(2, len, "number")
   if not handles[fh] then return nil, "bad file descriptor" end
   if not handles[fh].read then return nil, "bad file descriptor" end
   return handles[fh].read(len)
  end,
  write = function (fh, data)
   checkArg(1, fh, "number")
   if not handles[fh] then return nil, "bad file descriptor" end
   if not handles[fh].write then return nil, "bad file descriptor" end
   return handles[fh].write(data)
  end,
  seek = function (fh, whence, point)
   checkArg(1, fh, "number")
   if not handles[fh] then return nil, "bad file descriptor" end
   if not handles[fh].seek then return nil, "bad file descriptor" end
   return handles[fh].seek(whence, point)
  end,
  close = function (fh)
   checkArg(1, fh, "number")
   if not handles[fh] then return nil, "bad file descriptor" end
   handles[fh].close()
   handles[fh] = nil
   return true
  end,
 }
end