feat: add /proc and /sys parsers with fixture tests

Parsers take file contents as a string, not a path, so they test
against committed fixtures with no filesystem mocking.

hwmon is globbed by its name file rather than a fixed index, carried
over from the old config: indices drift across kernel reorders and a
stale one silently reads a different chip.

Failure returns nil, never 0. A sensor reading 0 C is legitimate, so 0
cannot double as an error value.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/lib/data.lua b/lib/data.lua
new file mode 100644
index 0000000..96fc172
--- /dev/null
+++ b/lib/data.lua
@@ -0,0 +1,75 @@
+-- Readers for /proc and /sys.
+--
+-- Every function takes the file *contents* as a string rather than reading the
+-- file itself, so the parsers are testable against fixtures without mocking the
+-- filesystem. The thin read-and-parse wrappers live at the bottom.
+
+local M = {}
+
+-- Aggregate CPU jiffies from /proc/stat. Returns total, idle.
+-- iowait counts as idle: a core waiting on disk is not doing work, and
+-- treating it as busy makes a disk-bound system look CPU-bound.
+function M.cpu_times(stat)
+  local line = stat:match('^cpu%s+([^\n]+)')
+  if not line then return nil, nil end
+  local v = {}
+  for n in line:gmatch('%d+') do v[#v + 1] = tonumber(n) end
+  if #v < 5 then return nil, nil end
+  local total = 0
+  for _, n in ipairs(v) do total = total + n end
+  return total, v[4] + v[5]  -- idle + iowait
+end
+
+-- /proc/meminfo, values in kB as the file states them.
+function M.mem_info(meminfo)
+  local function field(name)
+    return tonumber(meminfo:match(name .. ':%s+(%d+)'))
+  end
+  local total = field('MemTotal')
+  local available = field('MemAvailable')
+  if not (total and available) then return nil end
+  return {
+    total = total,
+    free = field('MemFree'),
+    available = available,
+    -- MemAvailable already excludes reclaimable cache, so this is the figure a
+    -- user recognises as "used", unlike total-free which counts cache.
+    used = total - available,
+  }
+end
+
+-- hwmon temp*_input is millidegrees C. Returns whole degrees, or nil.
+-- nil rather than 0 on failure: 0 C is a legitimate reading.
+function M.millidegrees(s)
+  if not s then return nil end
+  local n = tonumber(s:match('^%s*(-?%d+)'))
+  if not n then return nil end
+  return math.floor(n / 1000 + 0.5)
+end
+
+-- Read a whole file, returning nil if it cannot be read. Used by the wrappers
+-- so a vanished sysfs path degrades to nil instead of raising.
+function M.slurp(path)
+  local f = io.open(path, 'r')
+  if not f then return nil end
+  local s = f:read('*a')
+  f:close()
+  return s
+end
+
+-- Find a hwmon directory by the exact contents of its `name` file.
+--
+-- Globbing by name, never by a fixed hwmon index: indices drift across kernel
+-- and hardware reorders, and a stale index silently reports a different chip.
+-- Carried over from the previous conky config, where this was the hard-won bit.
+function M.hwmon_dir(name)
+  local p = io.popen('grep -lx ' .. ("%q"):format(name)
+    .. ' /sys/class/hwmon/hwmon*/name 2>/dev/null')
+  if not p then return nil end
+  local hit = p:read('*l')
+  p:close()
+  if not hit then return nil end
+  return hit:match('^(.*)/name$')
+end
+
+return M