import std/[nre, sequtils]

const CSI = "\x1b["
const RESET_FORMATTING* = "\x1b[0m"
const ANSI_ESCAPE_CODE_ENDINGS*: seq[char] = toSeq('A'..'Z') & toSeq('a'..'z')
let FORMATTING_REGEX* = re("\x1b\\[([0-9;]*)([a-zA-Z])")

type
  CursorType* = enum
    ctBlockBlink = 1, ctBlock, ctUnderlineBlink, ctUnderline, ctBarBlink, ctBar

  EraseMode* = enum
    emToEnd, emToStart, emAll

  TerminalColors* = enum
    cBlack, cRed, cGreen, cYellow, cBlue, cMagenta, cCyan, cWhite


proc stripFormatting*(text: string): string =
  text.replace(FORMATTING_REGEX, "")

proc stripAnsi*(text: string): string = stripFormatting(text)

func ansiAwareSubstring*(s: string, start, length: int): string =
  result = ""
  var curAnsiEscCode = ""
  var i = 0
  var visibleLen = 0

  while i < len(s) and visibleLen < length:

    if len(s) > i + len(CSI) and
      # We need to notice ANSI escape codes...
       s[i..<i + len(CSI)] == CSI:
      var j = i + len(CSI)
      while j < s.len and s[j] notin ANSI_ESCAPE_CODE_ENDINGS: j += 1

      # and remember it if we're before the start of the substring
      if i < start: curAnsiEscCode = s[i..j]

      # or add it without increasing our substring length
      else: result.add(s[i..j])

      # either way we want to pick up after it
      i = j

    else:
      result.add(s[i])
      visibleLen += 1

    i += 1

  result = curAnsiEscCode & result

func color*(text: string, fg = cWhite, bg = cBlack): string =
  return CSI & $int(fg) & ";" & $(int(bg) + 40) & "m" & text & RESET_FORMATTING


func color*(text: string, fg: TerminalColors): string =
  return CSI & $int(fg) & "m" & text & RESET_FORMATTING


func color*(text: string, bg: TerminalColors): string =
  return CSI & $(int(bg) + 40) & "m" & text & RESET_FORMATTING


func invert*(text: string): string = return CSI & "7m" & text & RESET_FORMATTING
func striketrough*(text: string): string = return CSI & "9m" & text & RESET_FORMATTING


func eraseDisplay*(mode = emToEnd): string = return CSI & $int(mode) & "J"
func eraseLine*(mode = emToEnd): string = return CSI & $int(mode) & "K"


func blinkSlow*(text: string): string = return CSI & "5m" & text & RESET_FORMATTING
func blinkFast*(text: string): string = return CSI & "6m" & text & RESET_FORMATTING


func cursorUp*(n: int = 1): string = return CSI & $int(n) & "A"
func cursorDown*(n: int = 1): string = return CSI & $int(n) & "B"
func cursorForward*(n: int = 1): string = return CSI & $int(n) & "C"
func cursorBackward*(n: int = 1): string = return CSI & $int(n) & "D"
func cursorNextLine*(n: int = 1): string = return CSI & $int(n) & "E"
func cursorPrevLine*(n: int = 1): string = return CSI & $int(n) & "F"
func cursorHorizontalAbsolute*(col: int): string = return CSI & $int(col) & "G"


func cursorPosition*(row, col: int): string =
  return CSI & $int(row) & ";" & $int(col) & "H"


proc cursorType*(ct: CursorType): string = return CSI & $int(ct) & " q"
func saveCursorPosition*(): string = return CSI & "s"
func restoreCursorPosition*(): string = return CSI & "u"


func scrollUp*(n: int = 1): string = return CSI & $int(n) & "S"
func scrollDown*(n: int = 1): string = return CSI & $int(n) & "T"


proc write*(f: File, x, y: int, text: string) =
  f.write(cursorPosition(y, x) & text)


proc write*(x, y: int, text: string) =
  stdout.write(cursorPosition(y, x) & text)


proc setCursorType*(ct: CursorType) = stdout.write(cursorType(ct))
proc setCursorPosition*(x, y: int) = stdout.write(cursorPosition(y, x))
proc hideCursor*() = stdout.write(CSI & "?25l")
proc showCursor*() = stdout.write(CSI & "?25l")