-- 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.

-- svc-t.lua : terminal

local _, _, retTbl, title = ...

assert(retTbl, "need to alert creator")

if title ~= nil then
 assert(type(title) == "string", "title must be string")
end

local function rW()
 return string.format("%04x", math.random(0, 65535))
end

local id = "neo.pub.t/" .. rW() .. rW() .. rW() .. rW()
local closeNow = false

-- Terminus Registration State --

local tReg = neo.requireAccess("r." .. id, "registration")
local sendSigs = {}

-- Display State --
-- unicode.safeTextFormat'd lines.
-- The size of this must not go below 1.
local console = {}
-- This must not go below 3.
local conW = 40
local conCX, conCY = 1, 1
local conSCX, conSCY = 1, 1
-- Performance
local consoleShown = {}
local conCYShown
for i = 1, 14 do
 console[i] = (" "):rep(conW)
end

-- Line Editing State --
-- Nil if line editing is off.
-- In this case, the console height
--  must be adjusted accordingly.
local leText = ""
-- These are NOT nil'd out,
--  particularly not the history buffer.
local leCX = 1
local leHistory = {
 -- Size = history buffer size
 "", "", "", ""
}
local function cycleHistoryUp()
 local backupFirst = leHistory[1]
 for i = 1, #leHistory - 1 do
  leHistory[i] = leHistory[i + 1]
 end
 leHistory[#leHistory] = backupFirst
end
local function cycleHistoryDown()
 local backup = leHistory[1]
 for i = 2, #leHistory do
  backup, leHistory[i] = leHistory[i], backup
 end
 leHistory[1] = backup
end

-- Window --

local window = neo.requireAccess("x.neo.pub.window", "window")(conW, #console + 1, title)

-- Core Terminal Functions --

local function setSize(w, h)
 conW = w
 for i = 1, #console do
  consoleShown[i] = nil
 end
 while #console < h do
  table.insert(console, "")
 end
 while #console > h do
  table.remove(console, 1)
 end
 for i = 1, #console do
  console[i] = unicode.sub(console[i], 1, w) .. (" "):rep(w - unicode.len(console[i]))
 end
 if leText then
  window.setSize(w, h + 1)
 else
  window.setSize(w, h)
 end
 conCX, conCY = 1, h
end

local function setLineEditing(state)
 if state and not leText then
  leText = ""
  leCX = 1
  setSize(conW, #console)
 elseif leText and not state then
  leText = nil
  setSize(conW, #console)
 end
end

local function draw(i)
 if console[i] then
  window.span(1, i, console[i], 0, 0xFFFFFF)
  if i == conCY and not leText then
   window.span(conCX, i, unicode.sub(console[i], conCX, conCX), 0xFFFFFF, 0)
  end
 elseif leText then
  window.span(1, i, require("lineedit").draw(conW, unicode.safeTextFormat(leText, leCX)), 0xFFFFFF, 0)
 end
end
local function drawDisplay()
 for i = 1, #console do
  if consoleShown[i] ~= console[i] or i == conCY or i == conCYShown then
   draw(i)
   consoleShown[i] = console[i]
  end
 end
 conCYShown = conCY
end

-- Terminal Visual --

local function consoleSD()
 for i = 1, #console - 1 do
  console[i] = console[i + 1]
 end
 console[#console] = (" "):rep(conW)
end
local function consoleSU()
 local backup = (" "):rep(conW)
 for i = 1, #console do
  backup, console[i] = console[i], backup
 end
end

local function consoleCLS()
 for i = 1, #console do
  console[i] = (" "):rep(conW)
 end
 conCX, conCY = 1, 1
end

local function writeFF()
 if conCY ~= #console then
  conCY = conCY + 1
 else
  consoleSD()
 end
end

local function writeData(data)
 -- handle data until completion
 while #data > 0 do
  local char = unicode.sub(data, 1, 1)
  --neo.emergency("svc-t.data: " .. char:byte())
  data = unicode.sub(data, 2)
  -- handle character
  if char == "\t" then
   -- not ideal, but allowed
   char = " "
  end
  if char == "\r" then
   conCX = 1
  elseif char == "\x00" then
   -- caused by TELNET \r rules
  elseif char == "\n" then
   conCX = 1
   writeFF()
  elseif char == "\a" then
   -- Bell (er...)
  elseif char == "\b" then
   conCX = math.max(1, conCX - 1)
  elseif char == "\v" or char == "\f" then
   writeFF()
  else
   local charL = unicode.wlen(char)
   if (conCX + charL - 1) > conW then
    conCX = 1
    writeFF()
   end
   local spaces = (" "):rep(charL - 1)
   console[conCY] = unicode.sub(console[conCY], 1, conCX - 1) .. char .. spaces .. unicode.sub(console[conCY], conCX + charL)
   conCX = conCX + charL
   -- Cursor can be (intentionally!) off-screen here
  end
 end
end

local function writeANSI(s)
 --neo.emergency("svc-t.ansi: " .. s)
 -- This supports just about enough to get by.
 if s == "c" then
  consoleCLS()
  return
 end
 local pfx = s:sub(1, 1)
 local cmd = s:sub(#s)
 if pfx == "[" then
  local np = tonumber(s:sub(2, -2)) or 1
  if cmd == "A" then
   conCY = conCY - np
  elseif cmd == "B" then
   conCY = conCY + np
  elseif cmd == "C" then
   conCX = conCX + np
  elseif cmd == "D" then
   conCX = conCX - np
  elseif cmd == "f" or cmd == "H" then
   local p = s:find(";")
   if not p then
    conCY = np
    conCX = 1
   else
    conCY = tonumber(s:sub(2, p - 1)) or 1
    conCX = tonumber(s:sub(p + 1, -2)) or 1
   end
  elseif cmd == "J" then
   consoleCLS()
  elseif cmd == "K" then
   if s == "[K" or s == "[0K" then
    -- bash needs this
    console[conCY] = unicode.sub(console[conCY], 1, conCX - 1) .. (" "):rep(1 + conW - conCX)
   else
    console[conCY] = (" "):rep(conW)
   end
  elseif cmd == "n" then
   if s == "[6n" then
    for _, v in pairs(sendSigs) do
     v("data", "\x1b[" .. conY .. ";" .. conX .. "R")
    end
   end
  elseif cmd == "s" then
   conSCX, conSCY = conCX, conCY
  elseif cmd == "u" then
   conCX, conCY = conSCX, conSCY
  end
 end
 conCX = math.min(math.max(math.floor(conCX), 1), conW)
 conCY = math.min(math.max(math.floor(conCY), 1), #console)
end

-- The Terminus --

local tvBuildingCmd = ""
local tvBuildingUTF = ""
local tvSubnegotiation = false
local function incoming(s)
 tvBuildingCmd = tvBuildingCmd .. s
 -- Flush Cmd
 while #tvBuildingCmd > 0 do
  if tvBuildingCmd:byte() == 255 then
   -- It's a command. Uhoh.
   if #tvBuildingCmd < 2 then break end
   local cmd = tvBuildingCmd:byte(2)
   local param = tvBuildingCmd:byte(3)
   local cmdLen = 2
   -- Command Lengths
   if cmd >= 251 and cmd <= 254 then cmdLen = 3 end
   if #tvBuildingCmd < cmdLen then break end
   if cmd == 240 then
    -- SE
    tvSubnegotiation = false
   elseif cmd == 250 then
    -- SB
    tvSubnegotiation = true
   elseif cmd == 251 and param == 1 then
    -- WILL ECHO (respond with DO ECHO, disable line editing)
    -- test using io.write("\xFF\xFB\x01")
    for _, v in pairs(sendSigs) do
     v("telnet", "\xFF\xFD\x01")
    end
    setLineEditing(false)
   elseif cmd == 252 and param == 1 then
    -- WON'T ECHO (respond with DON'T ECHO, enable line editing)
    for _, v in pairs(sendSigs) do
     v("telnet", "\xFF\xFE\x01")
    end
    setLineEditing(true)
   elseif cmd == 251 or cmd == 252 then
    -- WILL/WON'T (x) (respond with DON'T (X))
    local res = "\xFF\xFE" .. string.char(param)
    for _, v in pairs(sendSigs) do
     v("telnet", res)
    end
   elseif cmd == 253 or cmd == 254 then
    -- DO/DON'T (x) (respond with WON'T (X))
    local res = "\xFF\xFC" .. string.char(param)
    for _, v in pairs(sendSigs) do
     v("telnet", res)
    end
   elseif cmd == 255 then
    if not tvSubnegotiation then
     tvBuildingUTF = tvBuildingUTF .. "\xFF"
    end
   end
   tvBuildingCmd = tvBuildingCmd:sub(cmdLen + 1)
  else
   if not tvSubnegotiation then
    tvBuildingUTF = tvBuildingUTF .. tvBuildingCmd:sub(1, 1)
   end
   tvBuildingCmd = tvBuildingCmd:sub(2)
  end
 end
 -- Flush UTF/Display
 while #tvBuildingUTF > 0 do
  local head = tvBuildingUTF:byte()
  local len = 1
  local handled = false
  if head == 27 then
   local h2 = tvBuildingUTF:byte(2)
   if h2 == 91 then
    for i = 3, #tvBuildingUTF do
     local cmd = tvBuildingUTF:byte(i)
     if cmd >= 0x40 and cmd <= 0x7E then
      writeANSI(tvBuildingUTF:sub(2, i))
      len = i
      handled = true
      break
     end
    end
   elseif h2 then
    len = 2
    writeANSI(tvBuildingUTF:sub(2, 2))
    handled = true
   end
   if not handled then break end
  end
  if not handled then
   if head < 192 then
    len = 1
   elseif head < 224 then
    len = 2
   elseif head < 240 then
    len = 3
   elseif head < 248 then
    len = 4
   elseif head < 252 then
    len = 5
   elseif head < 254 then
    len = 6
   end
   if #tvBuildingUTF < len then
    break
   end
   -- verified one full character...
   writeData(tvBuildingUTF:sub(1, len))
  end
  tvBuildingUTF = tvBuildingUTF:sub(len + 1)
 end
end

do
 tReg(function (_, pid, sendSig)
  sendSigs[pid] = sendSig
  return {
   id = "x." .. id,
   pid = neo.pid,
   write = function (text)
    incoming(tostring(text))
    drawDisplay()
   end
  }
 end, true)

 if retTbl then
  coroutine.resume(coroutine.create(retTbl), {
   access = "x." .. id,
   close = function ()
    closeNow = true
    neo.scheduleTimer(0)
   end
  })
 end
end

local control = false

local function key(a, c)
 if control then
  if c == 203 and conW > 8 then
   setSize(conW - 1, #console)
   return
  elseif c == 200 and #console > 1 then
   setSize(conW, #console - 1)
   return
  elseif c == 205 then
   setSize(conW + 1, #console)
   return
  elseif c == 208 then
   setSize(conW, #console + 1)
   return
  end
 end
 -- so with the reserved ones dealt with...
 if not leText then
  -- Line Editing not active.
  -- For now support a bare minimum.
  for _, v in pairs(sendSigs) do
   if a == "\x03" then
    v("telnet", "\xFF\xF4")
   elseif c == 199 then
    v("data", "\x1b[H")
   elseif c == 201 then
    v("data", "\x1b[5~")
   elseif c == 207 then
    v("data", "\x1b[F")
   elseif c == 209 then
    v("data", "\x1b[6~")
   elseif c == 203 then
    v("data", "\x1b[D")
   elseif c == 205 then
    v("data", "\x1b[C")
   elseif c == 200 then
    v("data", "\x1b[A")
   elseif c == 208 then
    v("data", "\x1b[B")
   elseif a == "\r" then
    v("data", "\r\n")
   elseif a then
    v("data", a)
   end
  end
 elseif not control then
  -- Line Editing active and control isn't involved
  if c == 200 or c == 208 then
   -- History cursor up (history down)
   leText = leHistory[#leHistory]
   leCX = unicode.len(leText) + 1
   if c == 208 then
    cycleHistoryUp()
   else
    cycleHistoryDown()
   end
   return
  end
  local lT, lC, lX = require("lineedit").key(a, c, leText, leCX)
  leText = lT or leText
  leCX = lC or leCX
  if lX == "nl" then
   cycleHistoryUp()
   leHistory[#leHistory] = leText
   -- the whole thing {
   local fullText = leText .. "\r\n"
   writeData(fullText)
   drawDisplay()
   for _, v in pairs(sendSigs) do
    v("data", fullText)
   end
   -- }
   leText = ""
   leCX = 1
  end
 end
end

while not closeNow do
 local e = {coroutine.yield()}
 if e[1] == "k.procdie" then
  sendSigs[e[3]] = nil
 elseif e[1] == "x.neo.pub.window" then
  if e[3] == "close" then
   break
  elseif e[3] == "clipboard" then
   for i = 1, unicode.len(e[4]) do
    local c = unicode.sub(e[4], i, i)
    if c ~= "\r" then
     if c == "\n" then
      c = "\r"
     end
     key(c, 0)
    end
   end
   draw(#console + 1)
  elseif e[3] == "key" then
   if e[5] == 29 or e[5] == 157 then
    control = e[6]
   elseif e[6] then
    key(e[4] ~= 0 and unicode.char(e[4]), e[5])
    draw(#console + 1)
   end
  elseif e[3] == "line" then
   draw(e[4])
  end
 end
end