local utils = require('libs/utils')

local function noTitleFn()
  return ""
end

local function createWriteWithColor(textColor, backgroundColor, givenWin)
  local win = givenWin or term
  local originalTextColor = nil
  local originalBackgroundColor = nil

  if textColor then
    originalTextColor = win.getTextColor()
    win.setTextColor(textColor)
  end

  if backgroundColor then
    originalBackgroundColor = win.getBackgroundColor()
    win.setBackgroundColor(backgroundColor)
  end

  return function(str)
    win.write(str)

    if originalTextColor then
      win.setTextColor(originalTextColor)
    end

    if originalBackgroundColor then
      win.setBackgroundColor(originalBackgroundColor)
    end
  end
end

local function getTotalCount(countersMap)
  local total = 0
  for _, counterPayload in pairs(countersMap) do
    if counterPayload then
      total = total + (counterPayload.count or 0)
    end
  end
  return total
end

local function dropN(t, n)
  local result = {}

  for k,v in pairs(t) do
    if n == 0 then
      result[k] = v
    else
      n = n - 1
    end
  end

  return result
end

local function takeN(t, n)
  local result = {}

  for k,v in pairs(t) do
    if n == 0 then
      break
    end
    result[k] = v
    n = n - 1
  end

  return result
end

local TITLE_MARGIN = 1

local function renderCountersMap(win, countersMap, selectedCounter, titleFn)
  local writeRegular = createWriteWithColor(colors.white, colors.black, win)
  local writeSelected = createWriteWithColor(colors.black, colors.white, win)

  win.setCursorPos(1, 1)
  local _, height = win.getSize()
  -- local nbCounters = utils.sizeof(countersMap)
  -- local totalCount = getTotalCount(countersMap)

  local topMargin = 0
  local bottomMargin = 0

  if titleFn ~= noTitleFn then
    writeRegular('custom title: ' .. titleFn(countersMap, selectedCounter))
    topMargin = TITLE_MARGIN
  end

  local availableHeight = height - topMargin - bottomMargin

  local selectedPage = math.floor(selectedCounter / availableHeight) + 1
  -- local totalPages = (nbCounters % availableHeight) + 1

  local nbElementsToOmit = (selectedPage - 1) * availableHeight
  local displayedCounters = takeN(dropN(countersMap, nbElementsToOmit), availableHeight)

  local cursorYIndex = 1 + topMargin
  for k,v in pairs(displayedCounters) do
    win.setCursorPos(1, cursorYIndex)

    local line = tostring(v.name) .. ' ' .. tostring(v.count)

    if k == selectedCounter then
      writeSelected(line)
    else
      writeRegular(line)
    end

    cursorYIndex = cursorYIndex + 1
  end
end

local function CountersSelector(initialCountersMap, config)
  local countersMap = utils.shallowClone(initialCountersMap)
  local counterMax = config.counterMax
  local titleFn = config.titleFn or noTitleFn

  if not counterMax then
    error('no counterMax found in CountersSelector config')
  end

  if utils.sizeof(countersMap) == 0 then
    error('empty countersMap provided')
  end

  local selectedCounter = 1
  local nbCounters = utils.sizeof(countersMap)
  local globalCounter = getTotalCount(countersMap)

  if globalCounter > counterMax then
    error('counter cannot be greater than the counterMax')
  end

  local topHeight = 0
  if titleFn ~= noTitleFn then
    topHeight = 1
  end

  term.clear()
  local width, height = term.getSize()
  local mainWin = window.create(term.current(), 1, 1 + topHeight, width, height - topHeight)

  local shouldContinue = true
  while shouldContinue do
    mainWin.clear()
    renderCountersMap(mainWin, countersMap, selectedCounter, titleFn)
    local _, keyPressed, _ = os.pullEvent('key')

    if keyPressed == keys.up then
      selectedCounter = math.max(1, selectedCounter - 1)
    elseif keyPressed == keys.down then
      selectedCounter = math.min(nbCounters, selectedCounter + 1)
    elseif keyPressed == keys.left and globalCounter > 0 then
      local counterPayload = countersMap[selectedCounter]
      if counterPayload and counterPayload.count and counterPayload.count > 0 then
        countersMap[selectedCounter] = {
          count = counterPayload.count - 1,
          name = counterPayload.name
        }
        globalCounter = globalCounter - 1
      end
    elseif keyPressed == keys.right and globalCounter < counterMax then
      local counterPayload = countersMap[selectedCounter]
      if counterPayload and counterPayload.count then
        countersMap[selectedCounter] = {
          count = counterPayload.count + 1,
          name = counterPayload.name
        }
        globalCounter = globalCounter + 1
      end
    elseif keyPressed == keys.enter then
      shouldContinue = false
    end
  end

  return countersMap, selectedCounter
end

return CountersSelector