--[[
  altlog.lua 
  Verson: 1.0

  A Lua script for EdgeTX to log on demand the maximum altitude (from the "Alt+" telemetry sensor) 
  to a CSV file.

  USAGE
  -----
    EdgeTX Special Function -> Lua Script:  altlog

  WHAT IT DOES
  ============
  On activation it:
  1. Builds a log filename from the model name and today's date:
    /LOGS/modelname_ALT_yyyy-mm-dd.csv
  2. Creates the file (with a header row) if it doesn't already exist.
  3. Reads the "Alt+" telemetry sensor (max altitude).
  4. Appends one line: either
      2026-08-12 15:23:26, 45 m
    or, if no telemetry is available:
      2026-08-12 15:23:26, no ALT+ telemetry

  INSTALLATION
  ============
  1. Rename the file to altlog.lua (if different)
  2. Copy the file to /SCRIPTS/FUNCTIONS/ on the SD card or flash memory.
  3. In MODEL -> Special Functions, add a new special function:
      Trigger: <whatever switch you want to trigger the log, e.g. a momentary SA>
      Function: 'Lua Script'
      Value: altlog.lua
      Repeat: 1x
      Enable: checked

  To avoid writing dozens of lines every time you hold the
  switch, make sure that Repeat is set to 1x.

  To record launch heights with an RC-Soar DLG template, identify the SF which calls out the
  launch height, and use the same switch to trigger the script.

  CODE NOTES
  ==========
  - Change ALT_SENSOR below if your telemetry uses a different sensor
    name for altitude.
  - Telemetry presence is detected via RSSI: if RSSI is 0, we treat
    telemetry as unavailable.
  - Model names are sanitised (spaces and punctuation become "_") so
    they're safe to use in a filename.

  LICENSE
  =======
  Copyright (c) Mike Shellim
  This script is provided under the GNU General Public License v3.
  https://www.gnu.org/licenses/gpl-3.0.en.html
]]

local LOG_DIR    = "/LOGS/"
local ALT_SENSOR = "Alt+" -- '+' so that maximum height is logged, not current height

local function sanitise(name)
  return (string.gsub(name, "[^%w%-]", "_"))
end

local function twoDigits(n)
  return string.format("%02d", n)
end

local function buildTimestamps()
  local dt = getDateTime()
  local dateStr = string.format("%04d-%02d-%02d", dt.year, dt.mon, dt.day)
  local timeStr = string.format("%s:%s:%s",
    twoDigits(dt.hour), twoDigits(dt.min), twoDigits(dt.sec))
  return dateStr, dateStr .. " " .. timeStr
end

local function logFilePath(dateStr)
  local modelName = sanitise(model.getInfo().name or "model")
  return LOG_DIR .. modelName .. "_ALT_" .. dateStr .. ".csv"
end

local function fileExists(path)
  local f = io.open(path, "r")
  if f then
    io.close(f)
    return true
  end
  return false
end

local function writeRecord()
  local dateStr, timestamp = buildTimestamps()
  local path = logFilePath(dateStr)
  local isNew = not fileExists(path)

  local f = io.open(path, "a")
  if not f then
    -- Couldn't open (e.g. /LOGS missing on the SD card) - nothing more
    -- we can do from here.
    return
  end

  if isNew then
    io.write(f, "time, altitude\n")
  end

  local telemetryOk = getRSSI() ~= 0
  local alt = getValue(ALT_SENSOR)

  local line
  if telemetryOk and alt ~= nil then
    line = string.format("%s, %.2f", timestamp, alt)
  else
    line = string.format("%s, no %s telemetry", timestamp, ALT_SENSOR)
  end

  io.write(f, line .. "\n")
  io.close(f)
end

local function init()
end

local function run(event)
  writeRecord()
  return 0
end

return { init = init, run = run }