#!/bin/sh
set -eu

# Simple LTC-like line generator to feed into a PTY for development.
# It outputs lines like: "LOCK HH:MM:SS;FF 25.00"
# Configure frames-per-second via LTC_FPS environment variable (23,24,25,29,30 supported).
FPS="${LTC_FPS:-25}"

case "$FPS" in
  23) PERIOD="0.0417083"; RATE_STR="23.98" ;;
  24) PERIOD="0.0416667"; RATE_STR="24.00" ;;
  25) PERIOD="0.0400000"; RATE_STR="25.00" ;;
  29) PERIOD="0.0333667"; RATE_STR="29.97" ;;
  30) PERIOD="0.0333333"; RATE_STR="30.00" ;;
  *)  PERIOD="0.0400000"; RATE_STR="25.00"; FPS="25" ;;
esac

h=12
m=0
s=0
f=0

while true; do
  printf "[LOCK] %02d:%02d:%02d;%02d | %sfps\r\n" "$h" "$m" "$s" "$f" "$RATE_STR"

  # increment frame
  f=$((f+1))
  if [ "$f" -ge "$FPS" ]; then
    f=0
    s=$((s+1))
    if [ "$s" -ge 60 ]; then
      s=0
      m=$((m+1))
      if [ "$m" -ge 60 ]; then
        m=0
        h=$(( (h + 1) % 24 ))
      fi
    fi
  fi

  # sleep to approximate frame cadence
  sleep "$PERIOD"
done