-- System: CPU load as a per-core equaliser, memory, and every temperature.
--
-- The hwmon bindings and temperature ceilings below are host-specific, which
-- is why they live here rather than in lib/data.lua: that file is the part
-- that ports to another machine, this is the part that does not.

local card = require 'lib.card'
local data = require 'lib.data'

local M = {}

-- chip, file, label, warn, crit.
--
-- Ceilings are per sensor because a single pair cannot serve both: 70C is
-- unremarkable on a CPU package and alarming on an NVMe. Starting values,
-- easy to retune once real numbers under load are known.
local TEMPS = {
  { 'k10temp',      'temp1_input', 'CPU',   75, 90 },
  { 'k10temp',      'temp3_input', 'CCD1',  75, 90 },
  { 'nvme',         'temp1_input', 'NVME',  60, 70 },
  { 'gigabyte_wmi', 'temp2_input', 'BOARD', 60, 70 },
  { 'gigabyte_wmi', 'temp3_input', 'BOARD', 60, 70 },
}

-- One counter per core, created on first draw and kept for the process's life:
-- load is a delta between samples, so the state has to outlive the frame.
local counters = {}
local total_counter = data.new_cpu_counter()

-- Read once, not per frame. Neither can change without a reboot, and
-- re-reading /proc/cpuinfo every two seconds for a constant is waste: the file
-- repeats its model-name line once per thread.
--
-- `false` is the cached miss, distinct from nil meaning "not looked up yet",
-- so an absent DMI table is not re-read on every draw.
local cpu_name, board = nil, nil

local function hardware()
  if cpu_name == nil then
    cpu_name = data.cpu_model(data.slurp('/proc/cpuinfo') or '') or false
  end
  if board == nil then
    local dmi = '/sys/devices/virtual/dmi/id/'
    board = data.board_name(data.slurp(dmi .. 'board_vendor'),
                            data.slurp(dmi .. 'board_name')) or false
  end
  return cpu_name or nil, board or nil
end

function M.draw(cr, rect, colors)
  local inner = card.card(cr, rect, colors)
  local function clamp(v, lo, hi) return math.max(lo, math.min(hi, v)) end

  local stat = data.slurp('/proc/stat')
  local agg_total, agg_idle = data.cpu_times(stat or '')
  local load = total_counter:sample(agg_total, agg_idle)
  local load_txt = load and string.format('%d%%', math.floor(load + 0.5)) or '--'
  local cores = data.per_cpu_times(stat or '')
  local temp_n = #TEMPS
  local cpu_txt, board_txt = hardware()

  -- Fluid type. One base size S drives the label, headline, RAM and every
  -- temperature row; the equaliser then absorbs the vertical room left over,
  -- so the card fills its cell and S shrinks only where a row would overrun
  -- the width. card.fit_unit supplies the width side of that.
  local LABEL_F, BIG_F, ROW_F = 0.30, 1.0, 0.32
  local groups = {
    { { card.title_str(card.ICON.system, 'CPU'), card.FONT_MONO, LABEL_F },
      { load_txt, card.FONT_HEAVY, BIG_F } },
    { { cpu_txt or '', card.FONT_MONO, ROW_F } },
    { { board_txt or '', card.FONT_MONO, ROW_F } },
    { { 'RAM', card.FONT_MONO, ROW_F }, { '999.9G / 999.9G', card.FONT_MONO, ROW_F } },
  }
  for _, t in ipairs(TEMPS) do
    groups[#groups + 1] = { { t[3], card.FONT_MONO, ROW_F },
                            { '888\u{00B0}', card.FONT_MONO, ROW_F } }
  end
  -- Height the non-equaliser content needs, in units of S, plus a reserve for
  -- the equaliser band. The smaller of that budget and the width fit is S.
  -- The two identification rows come out of the equaliser's budget: it is the
  -- card's designated slack absorber, so it is what gives up the height.
  local id_rows = (cpu_txt and 1 or 0) + (board_txt and 1 or 0)
  local fixed_units = 1.00 + 1.13 + temp_n * ROW_F * 1.8 + 0.10
    + id_rows * ROW_F * 1.5
  local S = clamp(math.min(inner.h * 0.96 / (fixed_units + 1.7),
    card.fit_unit(cr, inner.w * 0.96, groups, 100)), 10, 72)
  local label_size = S * LABEL_F
  local big_size   = S * BIG_F
  local row_size   = S * ROW_F

  local y = inner.y

  -- Aggregate load, the headline number. It takes the header line, right
  -- aligned like the big value on every other card, with the label top-left.
  card.font(cr, card.FONT_HEAVY, big_size, false)
  card.rgba(cr, load and card.threshold(load, 25, 75, colors) or colors.label)
  card.text_right(cr, inner.x + inner.w, y + big_size, load_txt)

  card.font(cr, card.FONT_MONO, label_size, false)
  card.title(cr, inner.x, y + label_size, card.ICON.system, 'CPU', colors)

  -- The hardware this card is about, under the header. Truncated by character,
  -- never by byte: a model string can carry a multi-byte character and half of
  -- one draws as a replacement box.
  -- Two accents rather than one label colour: the rows name two different
  -- pieces of hardware, and giving each its own hue separates them at a glance
  -- without a prefix like 'CPU:' eating the width. `heading` and `highlight`
  -- are the two roles that carry no state meaning, so they can stand for an
  -- identity; ok/warning/critical could not, since those say how something is
  -- doing and these strings never change.
  local id_y = y + big_size + row_size * 0.2
  if cpu_txt or board_txt then
    card.font(cr, card.FONT_MONO, row_size, false)
    local id_limit = math.max(8, math.floor(inner.w / (row_size * 0.55)))
    if cpu_txt then
      card.rgba(cr, colors.heading)
      card.text(cr, inner.x, id_y, card.truncate(cpu_txt, id_limit))
      id_y = id_y + row_size * 1.5
    end
    if board_txt then
      card.rgba(cr, colors.highlight)
      card.text(cr, inner.x, id_y, card.truncate(board_txt, id_limit))
      id_y = id_y + row_size * 1.5
    end
  end

  -- The equaliser: one bar per core, rising from a common baseline. It takes
  -- the room left between the header and the RAM/temperature block, so it is
  -- the card's slack absorber.
  -- Below the identification rows when there are any, otherwise where it was.
  local eq_top = (cpu_txt or board_txt) and (id_y + S * 0.10) or (y + big_size + S * 0.30)
  local bar_h  = S * 0.18
  local step   = row_size * 1.8
  -- The floor was a flat 18px. With the identification rows above it the
  -- equaliser can genuinely run out of room, and a fixed floor means it keeps
  -- height it does not have and the temperature rows draw over it. Zero is a
  -- legitimate outcome: the guard below skips the band when it has no height.
  local eh = clamp((inner.y + inner.h) - eq_top - (S * 1.13 + temp_n * step),
    0, math.huge)
  local n = #cores
  if n > 0 and eh >= 8 then
    local gap = math.max(2, inner.w * 0.006)
    local bw = (inner.w - gap * (n - 1)) / n
    -- Below about 3px a row of sixteen bars is an illegible smear; drop to the
    -- aggregate bar instead of drawing one.
    if bw >= 3 then
      for i, c in ipairs(cores) do
        counters[i] = counters[i] or data.new_cpu_counter()
        local pct = counters[i]:sample(c.total, c.idle) or 0
        card.vbar(cr, inner.x + (i - 1) * (bw + gap), eq_top + eh, bw, eh,
          pct / 100, card.threshold(pct, 25, 75, colors), colors)
      end
    else
      card.bar(cr, inner.x, eq_top + eh - bar_h, inner.w, bar_h, (load or 0) / 100,
        card.threshold(load or 0, 25, 75, colors), colors)
    end
  end
  local ey = eq_top + eh + S * 0.30

  -- Memory. MemAvailable, not free: it already excludes reclaimable cache, so
  -- it is the figure a person recognises as "used".
  local mem = data.mem_info(data.slurp('/proc/meminfo') or '')
  if mem then
    local frac = mem.used / mem.total
    card.font(cr, card.FONT_MONO, row_size, false)
    card.rgba(cr, colors.label)
    card.text(cr, inner.x, ey, 'RAM')
    card.rgba(cr, colors.value)
    card.text_right(cr, inner.x + inner.w, ey,
      string.format('%s / %s', card.human(mem.used * 1024), card.human(mem.total * 1024)))
    ey = ey + S * 0.30
    card.bar(cr, inner.x, ey, inner.w, bar_h, frac,
      card.threshold(frac * 100, 25, 75, colors), colors)
    ey = ey + bar_h + S * 0.35
  end

  -- Temperatures, each against its own ceiling.
  card.font(cr, card.FONT_MONO, row_size, false)
  for _, t in ipairs(TEMPS) do
    if ey + step > inner.y + inner.h then break end   -- out of room: stop
    local v = data.sensor(t[1], t[2])
    card.rgba(cr, colors.label)
    card.text(cr, inner.x, ey, t[3])
    card.rgba(cr, v and card.threshold(v, t[4], t[5], colors) or colors.label)
    card.text_right(cr, inner.x + inner.w, ey,
      v and string.format('%d\u{00B0}', v) or '--')
    ey = ey + step
  end
end

return M