local ui = require("ui")

TICK_MS = 50

local INSET = 30
local BLACK, WHITE, RED = gui.color(0, 0, 0), gui.color(255, 255, 255), gui.color(255, 0, 0)
local ACCENT = gui.color(0, 120, 255)

local screen, message
local mode = "menu"
local samples, pending, armed = {}, nil, false

local buildMenu, startCalibration, cycleRotation

-- Two inset targets give a raw-per-pixel slope; extrapolate it to the screen edges.
-- Exposed as a global so test/settings_calibration.lua can exercise it.
function computeCalibration(s1, s2, w, h, inset)
  local sx = (s2.x - s1.x) / (w - 2 * inset)
  local sy = (s2.y - s1.y) / (h - 2 * inset)
  return math.floor(s1.x - sx * inset), math.floor(s1.y - sy * inset),
         math.floor(s2.x + sx * inset), math.floor(s2.y + sy * inset)
end

local function target(n)
  -- Calibration always runs in the rotation-0 frame, so use panel geometry.
  if n == 1 then return INSET, INSET end
  return 320 - INSET, 480 - INSET
end

local function drawTarget(n)
  local x, y = target(n)
  gui.clear(WHITE)
  gui.drawText("tap the cross", 10, 10, BLACK, WHITE)
  gui.drawLine(x - 12, y, x + 12, y, RED)
  gui.drawLine(x, y - 12, x, y + 12, RED)
end

local function finishCalibration()
  local ok = sys.setCalibration(computeCalibration(samples[1], samples[2], 320, 480, INSET))
  message = ok and "calibration saved" or "save failed"
  mode = "menu"
  gui.setRotation(sys.getRotation() / 90)
  buildMenu()
end

function startCalibration()
  message = nil
  mode = "calibrate"
  samples, pending, armed = {}, nil, false
  gui.setRotation(0)
  drawTarget(1)
end

function cycleRotation()
  local ok = sys.setRotation((sys.getRotation() + 90) % 360)
  message = ok and "rotation saved" or "save failed"
  buildMenu()  -- the frame changed size, so lay out again
end

function buildMenu()
  local items = {
    pad = 12,
    gap = 8,
    ui.text("settings"),
    ui.button{label = "calibrate touch", on_press = startCalibration},
    ui.button{label = "rotation: " .. sys.getRotation() .. " deg", on_press = cycleRotation},
    ui.button{label = "exit", on_press = sys.exit},
  }
  if message then items[#items + 1] = ui.text(message) end
  items.color, items.bg = BLACK, WHITE
  items.press_bg, items.press_color = ACCENT, WHITE
  screen = ui.screen(ui.box(items))
end

function setup()
  buildMenu()
end

function draw()
  if mode == "menu" then screen:draw() end
end

function on_touch_down(x, y)
  if mode == "menu" then screen:down(x, y) end
end

function on_touch_up(x, y)
  if mode == "menu" then screen:up(x, y) end
end

function on_tick()
  if mode ~= "calibrate" then return end
  local rx, ry = input.getRawTouch()
  if not armed then
    if not rx then armed = true end
    return
  end
  if rx then
    pending = {x = rx, y = ry}
  elseif pending then
    samples[#samples + 1] = pending
    pending = nil
    if #samples == 1 then
      drawTarget(2)
    else
      finishCalibration()
    end
  end
end