-- MMC.lua — Memory/FS Controller (AtlasOS v2.0)
-- in[1]  = mem_rx  ← CMC.out[4] (FS request)
-- in[3]  = mem_read ← Memory.out[1]
-- out[1] = mem_tx  → CMC.in[2] (FS response)
-- out[5] = mem_data → Memory.in[1]
-- out[6] = mem_write → Memory.in[2]

local SEG_SIZE = 8192
local MAX_INODES = 64
local ROOT_INO = 1

local function parseMsg(msg)
  local p = msg:find("|")
  return p and msg:sub(1, p - 1) or msg, p and msg:sub(p + 1) or nil
end

local function split(str, sep)
  local t = {}
  if not str then return t end
  for s in str:gmatch("[^" .. sep .. "]+") do
    t[#t + 1] = s
  end
  return t
end

local inodes = {}
local dirs = {}
local files = {}
local users = {}
local sb = { seg_size = SEG_SIZE, max_inodes = MAX_INODES, root_ino = ROOT_INO }

local function fsSerialize()
  local lines = {}
  lines[#lines + 1] = "V|1"
  lines[#lines + 1] = "S|" .. sb.seg_size .. "|" .. sb.max_inodes .. "|" .. sb.root_ino
  for _, u in pairs(users) do
    lines[#lines + 1] = "U|" .. u.uid .. "|" .. u.name .. "|" .. u.gid .. "|" .. u.home .. "|" .. (u.hash or "-")
  end
  for i = 1, MAX_INODES do
    local ino = inodes[i]
    if ino then
      lines[#lines + 1] = "I|" .. ino.ino .. "|" .. ino.typ .. "|" .. ino.mode .. "|" .. ino.uid .. "|" .. ino.gid .. "|" .. ino.size .. "|" .. ino.mtime .. "|"
      if ino.typ == "d" and dirs[ino.ino] then
        local entries = {}
        for _, e in ipairs(dirs[ino.ino]) do
          entries[#entries + 1] = e.name .. ":" .. e.ino
        end
        lines[#lines + 1] = "D|" .. ino.ino .. "|" .. table.concat(entries, "|")
      elseif ino.typ == "f" and files[ino.ino] then
        lines[#lines + 1] = "F|" .. ino.ino .. "|" .. files[ino.ino]
      end
    end
  end
  return table.concat(lines, "\n")
end

local function fsDeserialize(str)
  inodes = {}
  dirs = {}
  files = {}
  users = {}
  sb = { seg_size = SEG_SIZE, max_inodes = MAX_INODES, root_ino = ROOT_INO }
  if not str or #str == 0 then return false end
  for line in str:gmatch("[^\n]+") do
    local typ = line:sub(1, 1)
    local rest = line:sub(3)
    if typ == "V" then
    elseif typ == "S" then
      local parts = split(rest, "|")
      if #parts >= 3 then
        sb.seg_size = tonumber(parts[1]) or SEG_SIZE
        sb.max_inodes = tonumber(parts[2]) or MAX_INODES
        sb.root_ino = tonumber(parts[3]) or ROOT_INO
      end
    elseif typ == "U" then
      local parts = split(rest, "|")
      if #parts >= 4 then
        users[tonumber(parts[1])] = { uid = tonumber(parts[1]), name = parts[2], gid = tonumber(parts[3]), home = parts[4], hash = parts[5] or "-" }
      end
    elseif typ == "I" then
      local parts = split(rest, "|")
      if #parts >= 7 then
        local ino = tonumber(parts[1])
        inodes[ino] = { ino = ino, typ = parts[2], mode = parts[3], uid = tonumber(parts[4]), gid = tonumber(parts[5]), size = tonumber(parts[6]), mtime = tonumber(parts[7]) or 0 }
      end
    elseif typ == "D" then
      local parts = split(rest, "|")
      if #parts >= 2 then
        local ino = tonumber(parts[1])
        local entries = {}
        for i = 2, #parts do
          local eparts = split(parts[i], ":")
          if #eparts >= 2 then
            entries[#entries + 1] = { name = eparts[1], ino = tonumber(eparts[2]) }
          end
        end
        dirs[ino] = entries
      end
    elseif typ == "F" then
      local parts = split(rest, "|")
      if #parts >= 2 then
        local ino = tonumber(parts[1])
        local content = parts[2] or ""
        for i = 3, #parts do
          content = content .. "|" .. parts[i]
        end
        files[ino] = content
      end
    end
  end
  return next(inodes) ~= nil
end

local function findInodeByPath(path)
  if not path or #path == 0 then path = "/" end
  local parts = split(path, "/")
  local cur = inodes[sb.root_ino]
  if not cur then return nil end
  if path == "/" then return cur end
  local curIno = sb.root_ino
  for i = 1, #parts do
    local name = parts[i]
    if #name > 0 then
      local found = false
      local dentries = dirs[curIno]
      if dentries then
        for _, e in ipairs(dentries) do
          if e.name == name then
            curIno = e.ino
            cur = inodes[curIno]
            found = true
            break
          end
        end
      end
      if not found then return nil end
    end
  end
  return cur and inodes[curIno] or nil
end

local respSeq = 0

local function processReq(req)
  local op, rest = parseMsg(req)
  if not op then return "ERR|EINVAL" end
  respSeq = respSeq + 1
  local seqStr = tostring(respSeq) .. "|"

  if op == "STAT" then
    local path = rest or "/"
    local ino = findInodeByPath(path)
    if not ino then return "ERR|" .. seqStr .. "ENOENT" end
    return "OK|" .. seqStr .. ino.ino .. "|" .. ino.typ .. "|" .. ino.mode .. "|" .. ino.uid .. "|" .. ino.gid .. "|" .. ino.size .. "|" .. ino.mtime

  elseif op == "READ" then
    local parts = split(rest or "", "|")
    local path = parts[1] or ""
    local offset = tonumber(parts[2]) or 0
    local len = tonumber(parts[3]) or 8192
    local ino = findInodeByPath(path)
    if not ino then return "ERR|" .. seqStr .. "ENOENT" end
    if ino.typ ~= "f" then return "ERR|" .. seqStr .. "EISDIR" end
    local content = files[ino.ino] or ""
    local data = content:sub(offset + 1, offset + len)
    return "OK|" .. seqStr .. data

  elseif op == "LS" then
    local path = rest or "/"
    local ino = findInodeByPath(path)
    if not ino then return "ERR|" .. seqStr .. "ENOENT" end
    if ino.typ ~= "d" then return "ERR|" .. seqStr .. "ENOTDIR" end
    local dentries = dirs[ino.ino]
    if not dentries then return "OK|" .. seqStr end
    local names = {}
    for _, e in ipairs(dentries) do
      names[#names + 1] = e.name
    end
    return "OK|" .. seqStr .. table.concat(names, "|")

  elseif op == "STATFS" then
    local total = sb.seg_size
    local used = #fsSerialize()
    return "OK|" .. seqStr .. total .. "|" .. used

  elseif op == "CHDIR" then
    local path = rest or "/"
    local ino = findInodeByPath(path)
    if not ino then return "ERR|" .. seqStr .. "ENOENT" end
    if ino.typ ~= "d" then return "ERR|" .. seqStr .. "ENOTDIR" end
    return "OK|" .. seqStr .. path

  elseif op == "WRITE" then
    return "ERR|" .. seqStr .. "EROFS"
  end

  return "ERR|" .. seqStr .. "EINVAL"
end

local function defaultFS()
  inodes = {}
  dirs = {}
  files = {}
  users = {}

  users[0] = { uid = 0, name = "root", gid = 0, home = "/", hash = "-" }
  users[100] = { uid = 100, name = "captain", gid = 10, home = "/home/captain", hash = "-" }

  local function mkIno(num, typ, mode, uid, gid, size)
    inodes[num] = { ino = num, typ = typ, mode = mode, uid = uid, gid = gid, size = size or 0, mtime = 0 }
  end

  local function mkDir(num, entries)
    dirs[num] = entries
  end

  local function mkFile(num, content)
    files[num] = content or ""
    local sz = #(content or "")
    if inodes[num] then inodes[num].size = sz end
  end

  mkIno(1, "d", "755", 0, 0, 0)
  mkDir(1, { { name = ".", ino = 1 }, { name = "..", ino = 1 }, { name = "home", ino = 2 }, { name = "etc", ino = 4 } })

  mkIno(2, "d", "755", 0, 0, 0)
  mkDir(2, { { name = ".", ino = 2 }, { name = "..", ino = 1 }, { name = "captain", ino = 5 } })

  mkIno(5, "d", "700", 100, 10, 0)
  mkDir(5, { { name = ".", ino = 5 }, { name = "..", ino = 2 }, { name = "readme.txt", ino = 3 } })

  mkIno(3, "f", "644", 100, 10, 0)
  mkFile(3, "Welcome to AtlasOS v2.0!\n")

  mkIno(4, "d", "755", 0, 0, 0)
  mkDir(4, { { name = ".", ino = 4 }, { name = "..", ino = 1 }, { name = "man", ino = 6 } })

  mkIno(6, "d", "755", 0, 0, 0)
  mkDir(6, {
    { name = ".", ino = 6 }, { name = "..", ino = 4 },
    { name = "help", ino = 7 }, { name = "echo", ino = 8 },
    { name = "clear", ino = 9 }, { name = "color", ino = 10 },
    { name = "status", ino = 11 }, { name = "ls", ino = 12 },
    { name = "cat", ino = 13 }, { name = "cd", ino = 14 },
    { name = "stat", ino = 15 }, { name = "man", ino = 16 },
  })

  mkIno(7, "f", "644", 0, 0, 0)
  mkFile(7, [[NAME
     help - display help information

SYNOPSIS
     help

DESCRIPTION
     Show a list of all available commands with their usage
     and description.
]])

  mkIno(8, "f", "644", 0, 0, 0)
  mkFile(8, [[NAME
     echo - display a line of text

SYNOPSIS
     echo <text>

DESCRIPTION
     Write the given text to the terminal output.
]])

  mkIno(9, "f", "644", 0, 0, 0)
  mkFile(9, [[NAME
     clear - clear the terminal screen

SYNOPSIS
     clear

DESCRIPTION
     Clear all text from the terminal display.
]])

  mkIno(10, "f", "644", 0, 0, 0)
  mkFile(10, [[NAME
     color - set terminal text color

SYNOPSIS
     color <R> <G> <B>

DESCRIPTION
     Change the text color for subsequent output.
     Each value must be 0-255 (red, green, blue).
]])

  mkIno(11, "f", "644", 0, 0, 0)
  mkFile(11, [[NAME
     status - show system status

SYNOPSIS
     status

DESCRIPTION
     Display system information including current user,
     working directory, and memory usage.
]])

  mkIno(12, "f", "644", 0, 0, 0)
  mkFile(12, [[NAME
     ls - list directory contents

SYNOPSIS
     ls [-la] [path]

DESCRIPTION
     List contents of a directory. If no path is given,
     list the current directory.

OPTIONS
     -a    Include hidden entries (. and ..)
     -l    Long format (detailed listing)
]])

  mkIno(13, "f", "644", 0, 0, 0)
  mkFile(13, [[NAME
     cat - concatenate and display files

SYNOPSIS
     cat <path>

DESCRIPTION
     Read a file and display its contents on the terminal.
]])

  mkIno(14, "f", "644", 0, 0, 0)
  mkFile(14, [[NAME
     cd - change the working directory

SYNOPSIS
     cd [path]

DESCRIPTION
     Change the current working directory. If no path
     is given, go to root (/). Supports both absolute
     and relative paths.
]])

  mkIno(15, "f", "644", 0, 0, 0)
  mkFile(15, [[NAME
     stat - show file metadata

SYNOPSIS
     stat <path>

DESCRIPTION
     Display metadata for a file or directory, including
     inode number, type, permissions, owner, group, size,
     and modification time.
]])

  mkIno(16, "f", "644", 0, 0, 0)
  mkFile(16, [[NAME
     man - display manual page

SYNOPSIS
     man <command>

DESCRIPTION
     Display the manual page for a command. Manual pages
     are stored in /etc/man/.

EXAMPLE
     man ls
     man cat

SEE ALSO
     help
]])

  local str = fsSerialize()
  out[5] = str
  out[6] = 1
end

local fsLoaded = false
local prevReq = ""
local writePending = false

inp = {}

function upd()
  if not fsLoaded then
    local memStr = inp[3] or ""
    if #memStr > 0 and fsDeserialize(memStr) then
      fsLoaded = true
    else
      fsLoaded = true
      defaultFS()
      writePending = true
    end
  end

  if writePending then
    local str = fsSerialize()
    out[5] = str
    out[6] = 1
    writePending = false
  end

  if inp[1] ~= nil then
    local req = tostring(inp[1])
    if #req == 0 then
      prevReq = ""
    elseif req ~= prevReq then
      prevReq = req
      local resp = processReq(req)
      out[1] = resp
    end
  else
    prevReq = ""
  end

  table.clear(inp)
end