import unicode
import strutils
import terminal
import strformat
import posix

import keycodes

type
  EditorState* = ref object
    # config
    prompt: string # prompt to display
    maxRowsGoal: int # if terminal resizes, how to compute max rows
    # positive: it will set max rows to maxRowsGoal, or terminal height, whichever is lower
    # negative: it will set it to terminal height - maxRowsGoal or terminal height, whichever is lower
    # 0: terminal height

    # state reached during execution
    x: int # current cursor x position on screen
    bx: int # current x position in buffer (not same as x due to UTF-8)
    y: int # which row are we editing
    size: int # size of the row being edited in characters
    buffer: seq[string] # current text
    history: seq[seq[string]] # past texts
    historyIndex: int # where are we in history
    cols: int # number of columns in the terminal
    maxRows: int # max number of rows allowed

# for editors
var editors: seq[EditorState]

# resize support
onSignal(28):
  discard

proc newEditor*(prompt: string = "> ", multiline: bool = true): EditorState =
  new(result)
  result.prompt = prompt
  result.maxRowsGoal = if multiline: 0 else: 1
  result.buffer.add("")
  editors.add(result)

proc destroyEditor*(oldEditor: EditorState) =
  for i in 0..editors.high():
    let ed = editors[i]
    if ed == oldEditor:
      editors.del(i)
      return

proc render(ed: EditorState) =
  eraseLine()
  setCursorXPos(0)
  write stdout, ed.prompt
  write stdout, ed.buffer[ed.y]

template cline(ed: EditorState): var string =
  ed.buffer[ed.y]

proc read*(ed: EditorState): string =
  ed.render()
  while true:
    let key = getKey()
    case key:
    of jkEnter.int:
      break
    of jkBackspace.int:
      if ed.x == 0:
        discard # merge two lines TODO
      elif ed.x > ed.cline().high():
        ed.cline() = ed.cline[0..ed.cline().high()-1]
        dec ed.x
        dec ed.bx
      else:
        # TODO UTF8
        ed.cline() = ed.cline[0..ed.x-1] & ed.cline[ed.x+1..ed.cline().high()]
        dec ed.x
        dec ed.bx
    else:
      if key > 31 and key < 127:
        # ascii char
        let ch = key.char()
        if ed.x == 0:
          ed.cline() = $ch & ed.cline
        elif ed.x > ed.cline.high():
          ed.cline() = ed.cline & $ch
        else:
          ed.cline() = ed.cline[0..ed.x-1] & $ch & ed.cline[ed.x..ed.cline().high()]
        inc ed.x
        inc ed.bx

    ed.render()
  
  # return val
  result = ed.buffer.join("\n")

  # cleanup
  write(stdout, "\n")
  ed.history.add(ed.buffer)
  ed.buffer = @[""]
  ed.y = 0
  ed.x = 0