-- Here be nightmares
-- Seriously, don't look

local util = require("covid19.util")
local gfx = require("covid19.gfx")
local bigfont = require("bigfont")

local Plot = {}

local HEIGHT_MAP = {"\144", "\148", "\149"}
local X_TICK_FREQUENCY = 8
local Y_TICK_FREQUENCY = 2

function Plot.new(t, x, y, w, h, title, colour)
  local plot = {
    t = t,
    x = x,
    y = y,
    w = w,
    h = h,
    title = title,
    colour = colour,
    min = math.huge,
    max = 1,
    scaleHeight = (h - 2) * 3
  }

  function plot:addData(data)
    self.data = data

    for _, datum in pairs(data) do
      local v = datum.value
      if v > self.max then self.max = v end
      if v < self.min then self.min = v end
    end
  end

  function plot:scalePoint(value)
    return math.ceil((value / self.max) * self.scaleHeight)
  end

  function plot:drawTick(x, maxPoints, now)
    local time = now - (24 * 60 * 60 * (maxPoints - x))
    local date = os.date("%m/%d", time)

    t.setCursorPos(self.x + x, self.y + self.h + 3)
    t.write("|")
    t.setCursorPos(self.x + x - 2, self.y + self.h + 4)
    t.write(date)
  end

  function plot:draw()
    local now = math.floor(os.epoch("utc") / 1000)

    t.setTextColour(colour)
    bigfont.writeOn(t, 1, title, x, y)
    gfx.drawBox(t, x, y + 3, w, h)

    t.setTextColour(colours.lightGrey)

    local maxPoints = math.min(w - 2, #self.data)
    local start = #self.data - maxPoints
    for i = 1, maxPoints do
      local datum = self.data[i + start]
      local scaled = self:scalePoint(datum.value)
      local y = (self.h - math.floor(scaled / 3))
      local barHeight = self.h - y
      local barStart = self.y + 2 + y

      for j = barStart, barStart + barHeight do
        t.setCursorPos(self.x + i, j)

        if j == barStart then
          t.write(HEIGHT_MAP[((scaled - 1) % 3) + 1])
        else
          t.write("\149")
        end
      end
    end

    -- x-axis ticks
    for i = 1, maxPoints, X_TICK_FREQUENCY do
      plot:drawTick(i, maxPoints, now)
    end
    plot:drawTick(maxPoints, maxPoints, now)

    -- y-axis ticks
    for i = 1, self.h, Y_TICK_FREQUENCY do
      local val = math.floor((((self.max - self.min) / self.h) * i))
      if i == 1 then val = self.min
      elseif i == self.h then val = self.max end

      --print(val, self.h, self.min, self.max)

      t.setCursorPos(self.x + self.w + 1, self.y + self.h - i + 3)
      t.write(util.formatCommas(val))
    end
  end

  return plot
end

return Plot