#!/bin/bash
# Bail if another agent is in the same phase-group as us.
#
#   $1 = our pid file name (e.g. "pid-12345")
#   $2 = the phase we're about to enter (e.g. "surface", "observe")
#   cwd = state dir
#
# Also refreshes our own pid file with the current phase on each call,
# so concurrent agents can read each other's phase by cat'ing the pid
# files in the state dir.
#
# Phase groups: "surface" vs everything else ("post-surface"). We allow
# at most one agent per group to be alive at a time — so surface can run
# at a higher frequency than the slower organize/observe tail.
#
# Exit 0 = continue, exit 1 = bail (another agent in our group is alive).

shopt -s nullglob

my_pid_file="$1"
my_phase="$2"

# Refresh our own pid file with the current phase.
printf '%s' "$my_phase" > "$my_pid_file"

group_of() {
    if [[ "$1" == "surface" ]]; then
        echo "surface"
    else
        echo "post-surface"
    fi
}

my_group=$(group_of "$my_phase")

for f in pid-*; do
    [[ "$f" == "$my_pid_file" ]] && continue
    pid="${f#pid-}"
    if ! kill -0 "$pid" 2>/dev/null; then
        rm -f "$f"   # stale pid file, clean up
        continue
    fi
    other_phase=$(cat "$f" 2>/dev/null)
    other_group=$(group_of "$other_phase")
    if [[ "$my_group" == "$other_group" ]]; then
        exit 1
    fi
done

exit 0