energy graph monitor

-- graph_ui.lua  (run on your graph‐UI computer)

-- Peripheral wrapping & term redirect
rednet.open("left")
local mon = assert(peripheral.wrap("monitor_4"), "Monitor not found")
term.redirect(mon)

-- Configuration
local HISTORY_MAX = 100    -- number of data points to keep
local INTERVAL    = 1     -- seconds between samples

-- histories
local feHistory  = {}
local pctHistory = {}

-- Subpixel hi-res line helpers (2x2 per char cell)
local subpixelGrid = {}

local function setSubpixel(gx, gy, col)
  local cx = math.floor((gx-1)/2)+1
  local cy = math.floor((gy-1)/2)+1
  local sx = (gx-1)%2
  local sy = (gy-1)%2
  local bit = sy*2 + sx -- 0..3
  subpixelGrid[cy] = subpixelGrid[cy] or {}
  local cell = subpixelGrid[cy][cx] or {mask=0, col=col}
  cell.mask = bit32.bor(cell.mask, bit32.lshift(1, bit))
  cell.col = col or cell.col
  subpixelGrid[cy][cx] = cell
end

local function drawLine(x1, y1, x2, y2, col)
  x1 = math.floor(x1 * 2 + 0.5)
  y1 = math.floor(y1 * 2 + 0.5)
  x2 = math.floor(x2 * 2 + 0.5)
  y2 = math.floor(y2 * 2 + 0.5)
  local dx = math.abs(x2 - x1)
  local dy = math.abs(y2 - y1)
  local sx = x1 < x2 and 1 or -1
  local sy = y1 < y2 and 1 or -1
  local err = dx - dy
  while true do
    setSubpixel(x1, y1, col)
    if x1 == x2 and y1 == y2 then break end
    local e2 = 2 * err
    if e2 > -dy then err = err - dy; x1 = x1 + sx end
    if e2 <  dx then err = err + dx; y1 = y1 + sy end
  end
end

local function renderSubpixels(mon)
  for y, row in pairs(subpixelGrid) do
    for x, cell in pairs(row) do
      mon.setCursorPos(x, y)
      mon.setTextColor(cell.col or colors.white)
      mon.write(string.char(128 + (cell.mask or 0)))
    end
  end
  mon.setTextColor(colors.white)
end

local function clearSubpixels()
  subpixelGrid = {}
end

local function addTimestamp()
  if not feHistory.timestamps then feHistory.timestamps = {} end
  local t = textutils.formatTime(os.time(), true)
  table.insert(feHistory.timestamps, t)
  if #feHistory.timestamps > HISTORY_MAX then
    table.remove(feHistory.timestamps, 1)
  end
end

local function drawBackground()
  mon.setBackgroundColor(colors.black)
  mon.clear()
  clearSubpixels()

  local w, h = mon.getSize()
  local left, top     = 3, 3
  local right, bottom = w - 2, h - 2
  local graph_w       = right - left
  local graph_h       = bottom - top

  if #feHistory == 0 then
    return left, top, right, bottom, graph_w, graph_h, 0, 1, 1
  end

  -- compute FE history min/max including zero
  local minV, maxV = feHistory[1], feHistory[1]
  for i = 2, #feHistory do
    local v = feHistory[i]
    if v < minV then minV = v end
    if v > maxV then maxV = v end
  end
  minV = math.min(minV, 0)
  maxV = math.max(maxV, 0)
  local range = maxV - minV
  if range == 0 then range = 1 end  -- **SAFEGUARD for zero range**

  -- draw horizontal zero line as subpixels (use gray)
  local zero_t = (0 - minV) / range
  local zero_y = bottom - math.floor(zero_t * graph_h + 0.5)
  drawLine(left, zero_y, right, zero_y, colors.gray)

  -- draw fixed vertical grey bars and "seconds ago" labels at the bottom
  local divisions = 10 -- number of spaces, so 10 bars (adjust as you want)
  local labelRow = bottom + 1
  local stepDiv = graph_w / divisions
  for d = 0, divisions do
    local x = left + math.floor(d * stepDiv + 0.5)
    drawLine(x, top, x, bottom, colors.gray)
    -- offset label in seconds ago
    local secondsAgo = (divisions - d) * INTERVAL * math.floor(HISTORY_MAX / divisions)
    mon.setCursorPos(x-2, labelRow)
    mon.setTextColor(colors.lightGray)
    mon.write("-" .. tostring(secondsAgo))
    mon.setTextColor(colors.white)
  end

  return left, top, right, bottom, graph_w, graph_h, minV, maxV, range
end

local function drawPctGraph(left, top, right, bottom, gw, gh)
  if #pctHistory == 0 then return end
  local step   = gw / (HISTORY_MAX - 1)
  local offset = HISTORY_MAX - #pctHistory

  local px, py
  for i, p in ipairs(pctHistory) do
    local x = left + math.floor((offset + i - 1) * step + 0.5)
    local y = bottom - math.floor((p / 100) * gh + 0.5)
    if px then drawLine(px, py, x, y, colors.red) end
    px, py = x, y
  end
end

local function drawFEGraph(left, top, right, bottom, gw, gh, vmin, vmax, vrange)
  if #feHistory == 0 then return end
  if vrange == 0 then vrange = 1 end  -- **SAFEGUARD for zero range**
  local step   = gw / (HISTORY_MAX - 1)
  local offset = HISTORY_MAX - #feHistory

  local px, py
  for i, v in ipairs(feHistory) do
    local x = left + math.floor((offset + i - 1) * step + 0.5)
    local t = (v - vmin) / vrange
    local y = bottom - math.floor(t * gh + 0.5)
    if px then drawLine(px, py, x, y, colors.lime) end
    px, py = x, y
  end
end

local function drawPctLabels(left, bottom, gw, gh, offset)
  if #pctHistory == 0 then return end
  local minIdx, maxIdx = 1, 1
  for i = 2, #pctHistory do
    if pctHistory[i] < pctHistory[minIdx] then minIdx = i end
    if pctHistory[i] > pctHistory[maxIdx] then maxIdx = i end
  end
  local currIdx = #pctHistory
  local function labelPoint(idx)
    local p = pctHistory[idx]
    local x = left + math.floor((offset + idx - 1) * gw / (HISTORY_MAX - 1) + 0.5)
    local y = bottom - math.floor((p / 100) * gh + 0.5)
    local lbl = string.format("%.1f%%", p)
    mon.setBackgroundColor(colors.black)
    mon.setTextColor(colors.white)
    mon.setCursorPos(x - math.floor(#lbl/2), y - 1)
    mon.write(lbl)
  end
  labelPoint(minIdx)
  labelPoint(maxIdx)
  labelPoint(currIdx)
end

local function drawFELabels(left, bottom, gw, gh, offset, vmin, vrange)
  if #feHistory == 0 then return end
  if vrange == 0 then vrange = 1 end  -- **SAFEGUARD for zero range**
  local minIdx, maxIdx = 1, 1
  for i = 2, #feHistory do
    if feHistory[i] < feHistory[minIdx] then minIdx = i end
    if feHistory[i] > feHistory[maxIdx] then maxIdx = i end
  end
  local currIdx = #feHistory
  local function labelPoint(idx)
    local v = feHistory[idx]
    local x = left + math.floor((offset + idx - 1) * gw / (HISTORY_MAX - 1) + 0.5)
    local t = (v - vmin) / vrange
    local y = bottom - math.floor(t * gh + 0.5)
    local lbl = string.format("%d", math.floor(v + 0.5))
    mon.setBackgroundColor(colors.black)
    mon.setTextColor(colors.white)
    mon.setCursorPos(x - math.floor(#lbl/2), y - 1)
    mon.write(lbl)
  end
  labelPoint(minIdx)
  labelPoint(maxIdx)
  labelPoint(currIdx)
end

-- Initialize display
mon.setTextScale(0.5)
mon.setBackgroundColor(colors.black)
mon.clear()

-- Main loop: sample at INTERVAL, redraw both graphs
local prevEnergy = nil
local timer = os.startTimer(INTERVAL)
while true do
  local ev, id = os.pullEvent()
  if ev == "timer" and id == timer then
    local _, data = rednet.receive("generator_status")
    if data then
      local energy = data.totalEnergy or 0
      local pct    = data.accPct or 0

      -- Calculate FE/t from energy delta
      local fe
      if prevEnergy ~= nil then
        fe = (energy - prevEnergy) / (INTERVAL * 20)
      else
        fe = 0
      end
      prevEnergy = energy

      -- update histories
      table.insert(feHistory,  fe)
      table.insert(pctHistory, pct)
      addTimestamp()
      if #feHistory  > HISTORY_MAX then table.remove(feHistory, 1)  end
      if #pctHistory > HISTORY_MAX then table.remove(pctHistory, 1) end

      -- draw background and get layout
      local left, top, right, bottom, gw, gh, vmin, vmax, vrange =
        drawBackground()
      drawPctGraph( left, top, right, bottom, gw, gh )
      drawFEGraph( left, top, right, bottom, gw, gh, vmin, vmax, vrange )
      renderSubpixels(mon)
      local offsetPct = HISTORY_MAX - #pctHistory
      drawPctLabels(left, bottom, gw, gh, offsetPct)
      local offsetFE = HISTORY_MAX - #feHistory
      drawFELabels(left, bottom, gw, gh, offsetFE, vmin, vrange)
    end
    timer = os.startTimer(INTERVAL)
  end
end