local rtfs, internal = {}, {}
local proxy = {}
proxy.cacheSize = 8
local ieformat = ">BI8I8c47" -- ftype, start, len, name
local iesize = string.packsize(ieformat)
local sbformat = ">c4I2I8c18" -- "rtfs" magic, version, index size in entries, label. label length subject to change.
local ftypes = {
 unused = 0x00,
 empty = 0x01,
 file = 0x10,
 tfile = 0x11,
 dfile = 0x12,
 directory = 0x20,
}

function proxy:log(message,level)
 syslog(message,level or syslog.debug,"rtfs:"..self.label)
end

-- data mangling functions
local function fnormalize(s)
 return table.concat(fs.segments(s),"/")
end
function proxy:cSOI(n)
 n=n-1
 local ms = self.capacity / self.blockSize
 local ePS = self.blockSize // iesize
 local s = n // ePS
 local so = self.blockSize - iesize - ((n % ePS) * iesize)
 local eo = so + iesize
 return ms - s, so+1, eo
end

-- just for ease-of-use
local function getProxy(addr)
 if type(addr) == "string" then
  return component.proxy(component.get(addr,"partition") or component.get(addr) or addr)
 end
 return addr
end

-- cache stuff
function proxy:cacheClean()
 while #self.cache > self.cacheSize do
  table.remove(self.cache, 1)
 end
end
function proxy:cachedRead(s)
 for k,v in ipairs(self.cache) do
  if v[1] == s then
   self.cacheHits = self.cacheHits + 1
   return v[2]
  end
 end
 self.cache[#self.cache + 1] = {s, self.d.readSector(s)}
 self.cacheMisses = self.cacheMisses + 1
 return self.cache[#self.cache][2]
end
function proxy:cachedWrite(s,d)
 for k,v in ipairs(self.cache) do
  if v[1] == s then
   table.remove(self.cache, k)
  end
 end
 self.cache[#self.cache + 1] = {s, d}
 self:cacheClean()
 return self.d.writeSector(s,d)
end

-- superblock stuff
function proxy:updateSB()
 self:cachedWrite(1,string.pack(sbformat, "rtfs", 0, self.isize, self.label))
end 
function proxy:setISize(n)
 if self.isize ~= n then
  self.isize = n
  self:updateSB()
 end
end

-- index I/O
function proxy:readIEntry(n)
 local sector, sstart, send = self:cSOI(n)
 local rt = {string.unpack(ieformat,self:cachedRead(sector):sub(sstart, send))}
 rt[4] = rt[4]:gsub("\0","")
 rt[5] = nil
 return table.unpack(rt)
end
function proxy:writeIEntry(n,et,es,el,en)
 local ne = string.pack(ieformat, et, es, el, en)
 local sector, sstart, send = self:cSOI(n)
 local fi, ft = self:findIEntry(nil,nil,nil,nil,sector)
 if fi then
  self:log("auto-compact triggered")
  if not (ft[1] == ftypes.empty or ft[1] == ftypes.dfile or ftypes[1] == ftypes.tfile) then
   self:log("automatic defragment triggered from:" .. debug.traceback())
   assert(not self.runningDefragment, "recursive defragment triggered")
   self:defragment()
  end
  n = self:compactIndex(n) or self.isize + 1
  sector, sstart, send = self:cSOI(n)
 end
 local pes = self:cachedRead(sector)
 local ns = pes:sub(1, sstart - 1) .. ne .. pes:sub(send + 1)
 self:cachedWrite(sector, ns)
 self:setISize(math.max(self.isize, n))
end
function proxy:allIEntries()
 local i = 0
 return function()
  if i < self.isize then
   i = i + 1
   return i, self:readIEntry(i)
  end
  return nil
 end
end
 
-- index maintenance
function proxy:compactIndex(ti) -- number -- number -- Compact the index, optionally returning the new index of *ti*.
 while self.runningCompact do -- wait for any existing compact run to complete
  coroutine.yield()
 end
 self.runningCompact = true
 -- look for contingous free space
 local ri
 for i, tp, st, sl, n in self:allIEntries() do
  if tp == ftypes.empty or tp == ftypes.dfile then
   local ni, nt = self:findIEntry(nil,st+sl)
   if ni and nt then
   if nt[1] == ftypes.empty or nt[1] == ftypes.dfile then
    self:writeIEntry(i,tp,st,sl+nt[3],n)
    self:writeIEntry(ni,ftypes.unused,0,0,"")
   end
   end
  end
 end
 -- reverse walk to move any unused indexes
 for i = self.isize, 1, -1 do
  local ne = self:nextEntry() or self.isize
  local ft = {self:readIEntry(i)}
  if ne < i then
   -- modify any open handles to point at the new index
   for k,v in pairs(self.handles) do
    if v.fi == i then
     v.fi = ne
    end
   end
   self:writeIEntry(ne, table.unpack(ft))
   ri = (ti == i) and ne or ri -- track the requested index
  elseif ft[1] ~= ftypes.unused then
   self:setISize(i)
   break
  end
 end
 -- resize the free space / tentative file at the end of the FS to match the index size
 local li, ls = 0, 0
 local lt
 for i, tp, st, sl, n in self:allIEntries() do
  if st+sl > ls then
   li, ls = i, st+sl
   lt = {tp, st, sl, n}
  end
 end
 if lt[1] == ftypes.empty or lt[1] == ftypes.dfile or lt[1] == ftypes.tfile then
  local lastsec = (self.capacity / self.blockSize) - math.ceil(self.isize / (self.blockSize / iesize))
  self:writeIEntry(li, lt[1], lt[2], lastsec - lt[2] - 1, lt[4])
  -- modify the file handle in memory, if applicable
  if lt[1] == ftypes.tfile then
   for k,v in ipairs(self.handles) do
    if v.fi == li then
     v.ft[3] = lastsec - lt[2]
     v.maxWrite = v.ft[3] * self.blockSize
    end
   end
  end
 end
 self.runningCompact = false
 return ri
end

-- mostly just for debugging
function proxy:dumpIndex()
 print(" # ty init  len  end name")
 for i, tp, st, sl, n in self:allIEntries() do
--  print(string.format("%2x %2x %4x %4x %4x %s",i,tp,st,sl,st+sl-1, n))
  print(string.format("%2i %2i %4i %4i %4i %s",i,tp,st,sl,st+sl-1, n))
 end
end

-- index searching
function proxy:findIEntry(et,es,el,en,ef) -- number number number string number -- Find an entry matching all provided parameters and ignoring any not specified.
 local ri, rt
 for i, tp, st, sl, n in self:allIEntries() do
  local sf = st + sl - 1
  if (et or tp) == tp and (es or st) == st and (el or sl) == sl and (en or n) == n and (ef or sf) == sf then
   ri, rt = i, {self:readIEntry(i)}
   break
  end
 end
 return ri, rt
end
function proxy:nextEntry()
 local ni = self.isize+1
 for i, tp, st, sl, n in self:allIEntries() do
  if tp == ftypes.unused or tp == ftypes.dfile then
   ni = i
   break
  end
 end
 return ni
end

-- file allocation
function proxy:bestFree()
 local ri, sri
 local bs, sbs = 0, 0
 for i, tp, st, sl, n in self:allIEntries() do
  if tp == ftypes.empty or tp == ftypes.dfile then
   if sl > bs then
    sri, sbs = ri, bs
    ri, bs = i, sl
   end
  end
 end
 return bs/2 > sbs and ri or sri, bs/2 > sbs
end
function proxy:allocateNew(name)
 self:compactIndex()
 local lfi,lfis = self:bestFree()
 local lf = {self:readIEntry(lfi)}
 local new
 if lfis then
  new = {ftypes.tfile, lf[2] + math.floor(lf[3]/2), math.ceil(lf[3]/2), name}
  lf[3] = math.floor(lf[3] / 2)
  self:writeIEntry(lfi, table.unpack(lf))
  local ni = self:nextEntry()
  self:writeIEntry(ni, table.unpack(new))
  self:setISize(math.max(ni,self.isize))
  return self:findIEntry(ftypes.tfile,nil,nil,name)
--  return ni, new
 else
  new = {ftypes.tfile, lf[2], lf[3], name}
  self:writeIEntry(lfi, table.unpack(new))
  return lfi, new
 end
 return false
end

function proxy:relocateBlocks(start, len, dest, loud)
 local ot = os.getTimeout()
 os.setTimeout(0.00001) -- disable coroutine.yield's delay
 io.write(loud and "\27[s" or "")
 for i = 0, len-1 do
  local buffer = self.d.readSector(start+i)
  self.d.writeSector(dest+i, buffer)
  io.write(loud and string.format("\27[u\27[2K%i/%i %i -> %i", i+1, len, start+i, dest+i) or "")
  coroutine.yield()
 end
 io.write(loud and " done!\n" or "")
 os.setTimeout(ot)
 return true
end
function proxy:relocateFile(n,dest,loud)
 local ft = {self:readIEntry(n)}
 -- modify any writing handles to write to the destination before doing anything
 local realLen
 for k,v in pairs(self.handles) do
  print(n, v.ft[1])
  if v.ft[1] == n and (v.w or v.a) then
   print("found file handle")
   v.ft[2] = dest
   realLen = v.currentSector
  end
 end
 self:relocateBlocks(ft[2],realLen or ft[3],dest,loud)
 local w, e = pcall(self.writeIEntry,self,n,ft[1],dest,ft[3],ft[4])
 -- modify any reading handles to read from the destination after moving the data
 for k,v in pairs(self.handles) do
  if v.ft[1] == n and v.r then
   v.ft[2] = dest
  end
 end
 return w, {ft[1], dest, ft[3], ft[4]}
end

function proxy:defragment(loud)
 loud=true
 while self.runningDefragment do
  coroutine.yield()
 end
 self.runningDefragment = true
 for i, tp, _, _, _ in self:allIEntries() do
  if tp == ftypes.empty or tp == ftypes.dfile then
   self:writeIEntry(i, ftypes.unused, 0, 0, "")
  end
 end
 local ftab = {}
 local fsec, lsec = 2, (self.capacity / self.blockSize) - math.ceil(self.isize / (self.blockSize / iesize))
 for i, tp, st, sl, n in self:allIEntries() do
  if tp ~= ftypes.empty and tp ~= ftypes.dfile and sl > 0 then
   ftab[#ftab+1] = {i, tp, st, sl, n}
  end
 end
 -- sort files in order of their start sector
 table.sort(ftab, function(a,b)
  return a[3] < b[3]
 end)
 -- move files closer to the start if applicable
 local deferred = {}
 for k, ft in ipairs(ftab) do
  io.write(loud and string.format("%i/%i: %s\n",k,#ftab,ft[5]) or "")
  if ft[3] ~= fsec then
   local w, dt = self:relocateFile(ft[1], fsec, loud)
   deferred[#deferred+1] = (not w and dt) or nil
  end
  fsec = fsec + ft[4]
 end
 self:writeIEntry(self:nextEntry(), ftypes.empty, fsec, lsec-fsec, "")
 for k,v in ipairs(deferred) do
  self:writeIEntry(self:nextEntry(), table.unpack(v))
 end
 self.runningDefragment = false
end

-- handle management
function proxy:openFile(name,mode)
 name = fnormalize(name)
 local handle = {}
 for c in mode:gmatch(".") do
  handle[c] = true
 end
 local fi,ft = self:findIEntry(ftypes.file, nil, nil, name)
 if handle.r then
  if not fi then
   return false, "file not found"
  end
  handle.currentSector, handle.fi, handle.ft = 0, fi, ft
 elseif handle.w or handle.a then
  handle.writeBuffer, handle.writeCounter = "", 0
  local oft = ft
  fi, ft = self:allocateNew(name)
  if oft and handle.a then
   assert(ft[3] >= oft[3], "no extent large enough for relocated file")
   handle.writeBuffer = self.d.readSector(oft[2] + oft[3] - 1):gsub("\0+$","")
   handle.currentSector, handle.writeCounter = oft[3]-1, ((oft[3]-1) * 512) + #handle.writeBuffer
   self:log(string.format("appending %s, CS: %i, WC: %i, WB: %i", name, handle.currentSector, handle.writeCounter, #handle.writeBuffer))
   self:relocateBlocks(oft[2], oft[3], ft[2])
  end
  handle.fi, handle.ft, handle.maxWrite, handle.writeCounter, handle.currentSector = fi, ft, ft[3] * self.blockSize, handle.writeCounter or 0, handle.currentSector or 0
 end
 self.handles[#self.handles+1] = handle
 return #self.handles
end
function proxy:closeHandle(h)
 local handle = self.handles[h]
 if handle.w or handle.a then
  local ft = handle.ft
  self.d.writeSector(ft[2] + handle.currentSector, handle.writeBuffer .. ("\0"):rep(self.blockSize - #handle.writeBuffer))
  local fs = ft[3] - math.ceil(handle.writeCounter / self.blockSize)
  local ni, nt = self:findIEntry(nil, ft[2] + ft[3])
  if ni and (nt[1] == ftypes.empty or nt[1] == ftypes.dfile) then
   fs = fs + nt[3]
  else
   ni = self:nextEntry()
  end
  while self:findIEntry(ftypes.file,nil,nil,ft[4]) do
   local di, dt = self:findIEntry(ftypes.file, nil, nil, ft[4])
   dt[1] = ftypes.dfile
   self:writeIEntry(di, table.unpack(dt))
   self:log(string.format("marking entry %i for %s as deleted", di, dt[4]))
  end
  ft[1], ft[3] = ftypes.file, math.ceil(handle.writeCounter / self.blockSize)
  self:writeIEntry(handle.fi, table.unpack(ft))
  self:writeIEntry(ni, ftypes.empty, ft[2] + ft[3], fs, "")
  self:setISize(math.max(handle.fi,ni,self.isize))
 end
 self.handles[h] = nil
 return true
end

-- handle I/O
function proxy:writeHandle(h,s)
 local handle = self.handles[h]
 if s:len() + handle.writeCounter > handle.maxWrite then
  self:log("no space left in extent", syslog.error)
  return false, "no space left in extent"
 end
 handle.writeCounter = handle.writeCounter + s:len()
 handle.writeBuffer = handle.writeBuffer .. s
 while #handle.writeBuffer > self.blockSize do
  self.d.writeSector(handle.ft[2] + handle.currentSector, handle.writeBuffer:sub(1,self.blockSize))
  handle.currentSector = handle.currentSector + 1
  handle.writeBuffer = handle.writeBuffer:sub(self.blockSize+1)
 end
 return true
end
function proxy:readHandle(h,s)
 local handle = self.handles[h]
 if handle.currentSector <= handle.ft[3] - 1 then
  local rb = self.d.readSector(handle.ft[2] + handle.currentSector):gsub("\0+$","")
  handle.currentSector = handle.currentSector + 1
  return rb
 else
  return nil
 end
end

-- primarily for debugging
function proxy:getHandle(h)
 return self.handles[h]
end

----------

function rtfs.mount(d)
 d=getProxy(d)
 local p = setmetatable({}, {__index=proxy})
 local magic, version, isize, label = string.unpack(sbformat,d.readSector(1))
 assert(magic == "rtfs", "incorrect magic")
 if magic ~= "rtfs" then error("incorrect magic") end
 p.d = d
 p.fstype = "rtfs"
 p.cache, p.handles = {}, {}
 p.cacheHits, p.cacheMisses = 0, 0
 p.blockSize, p.capacity, p.label, p.isize = d.getSectorSize(), d.getCapacity(), label:gsub("\0",""), isize

 -- FS proxy functions
 function p.exists(name)
  name = fnormalize(name)
  for i, tp, st, sl, n in p:allIEntries() do
   if (tp == ftypes.file or tp == ftypes.directory) and n == name then
    return true
   end
  end
 end
 function p.isDirectory(name)
  name = fnormalize(name)
  return p:findIEntry(ftypes.directory, nil, nil, name) ~= nil
 end
 function p.size(name)
  name = fnormalize(name)
  local fi, ft = p:findIEntry(ftypes.file, nil, nil, name)
  if not fi and ft then return 0 end
  return ft[3] * p.blockSize
 end
 function p.spaceUsed()
  local c = 0
  for i, tp, st, sl, n in p:allIEntries() do
   if tp == ftypes.file then
    c = c + sl
   end
  end
  return c*p.blockSize
 end
 function p.spaceTotal()
  return p.capacity - (math.ceil(p.isize / (p.blockSize / iesize))*p.blockSize) - p.blockSize
 end
 p.isReadOnly = p.d.isReadOnly

 function p.list(name)
  name = fnormalize(name)
  local rt = {}
  for i, tp, st, sl, n in p:allIEntries() do
   local seg = fs.segments(n)
   local pn = table.concat(seg,"/",1,#seg-1)
   local fn = seg[#seg]
   if (tp == ftypes.file or tp == ftypes.directory) and pn == name then
    rt[#rt+1] = fn .. ((tp == ftypes.directory and "/") or "")
   end
  end
  return rt
 end
 function p.makeDirectory(name)
  name = fnormalize(name)
  if #name < 1 or p:findIEntry(nil,nil,nil,name) then return false end
  local ni = p:nextEntry()
  p:writeIEntry(ni, ftypes.directory, 0, 0, name)
  p:setISize(math.max(p.isize, ni))
  return true
 end
 function p.remove(name)
  name = fnormalize(name)
  local fi, ft = p:findIEntry(ftypes.file, nil, nil, name)
  if fi then
   ft[1] = ftypes.dfile
   p:writeIEntry(fi, table.unpack(ft))
  end
  local fi, ft = p:findIEntry(ftypes.directory, nil, nil, name)
  if fi then
   error("removing dirs not implemented")
  end
 end
 function p.rename(from, to)
  from, to = fnormalize(from), fnormalize(to)
  if p.exists(from) then
   if p.exists(to) then
    p.remove(to)
   end
   local fi, ft = p:findIEntry(p.isDirectory(name) and ftypes.directory or ftypes.file, nil, nil, to)
   ft[4] = to
   p:writeIEntry(fi, table.unpack(ft))
  end
 end
 function p.lastModified()
  return 0
 end

 function p.open(name, mode)
  name, mode = fnormalize(name), mode or "r"
  return p:openFile(name, mode)
 end
 function p.write(h,v)
  return p:writeHandle(h,v)
 end
 function p.read(h,v)
  return p:readHandle(h,v)
 end
 function p.close(h)
  return p:closeHandle(h)
 end

 function p.getLabel()
  return p.label
 end
 function p.setLabel(label)
  p.label = label
  p:updateSB()
 end
 return p
end

function rtfs.format(d,label)
 d=getProxy(d)
 print(d.address)
 d.writeSector(1, string.pack(sbformat,"rtfs", 0, 1, label or ""))
 rtfs.mount(d):writeIEntry(1, ftypes.empty, 2, (d.getCapacity() / d.getSectorSize()) - 2, "")
end

return rtfs