#!/usr/bin/env bash
set -euo pipefail

if ! command -v mmsg >/dev/null 2>&1; then
  echo "error: mmsg not found" >&2
  exit 1
fi

mode="${1:-all}"
case "$mode" in
  all|single) ;;
  *)
    echo "usage: $(basename "$0") [single]" >&2
    exit 2
    ;;
esac

mapfile -t outputs < <(mmsg -O | awk 'NF { print $1 }')
out_count=${#outputs[@]}

if (( out_count == 0 )); then
  echo "error: no monitors detected" >&2
  exit 1
fi
if (( out_count == 1 )); then
  echo "info: only one monitor connected, nothing to move"
  exit 0
fi
if (( out_count > 2 )); then
  echo "error: script supports max 2 monitors, found ${out_count}" >&2
  exit 2
fi

active="$(mmsg -g -o | awk '$2=="selmon" && $3=="1" { print $1; exit }')"
if [[ -z "$active" ]]; then
  active="${outputs[0]}"
fi

target=""
for out in "${outputs[@]}"; do
  if [[ "$out" != "$active" ]]; then
    target="$out"
    break
  fi
done

if [[ -z "$target" ]]; then
  echo "error: failed to determine target monitor" >&2
  exit 1
fi

get_active_tag() {
  local mon="$1"
  local active_mask
  active_mask="$(mmsg -g -t | awk -v m="$mon" '$1==m && $2=="tags" && $3 ~ /^[0-9]+$/ && $4 ~ /^[0-9]+$/ { print $4; exit }')"
  if [[ ! "$active_mask" =~ ^[0-9]+$ ]]; then
    echo 1
    return
  fi

  for tag in {1..9}; do
    if (( active_mask & (1 << (tag - 1)) )); then
      echo "$tag"
      return
    fi
  done
  echo 1
}

get_tag_clients() {
  local mon="$1" tag="$2"
  local n
  n="$(mmsg -g -t | awk -v m="$mon" -v t="$tag" '$1==m && $2=="tag" && $3==t { print $5; exit }')"
  if [[ "$n" =~ ^[0-9]+$ ]]; then
    echo "$n"
  else
    echo 0
  fi
}

get_total_clients() {
  local mon="$1"
  local n
  n="$(mmsg -g -t | awk -v m="$mon" '$1==m && $2=="clients" { print $3; exit }')"
  if [[ "$n" =~ ^[0-9]+$ ]]; then
    echo "$n"
  else
    echo 0
  fi
}

if [[ "$mode" == "single" ]]; then
  echo "move-single: active=${active} target=${target}"
  mmsg -o "$active" -s -d "tagmon,${target},1" >/dev/null
  echo "move-single: done"
  exit 0
fi

target_tag="$(get_active_tag "$target")"
source_total="$(get_total_clients "$active")"

if (( source_total == 0 )); then
  echo "info: no windows on active monitor (${active})"
  exit 0
fi

echo "move-all: active=${active} target=${target} target_tag=${target_tag} total=${source_total}"

moved=0
for tag in {1..9}; do
  while :; do
    before="$(get_tag_clients "$active" "$tag")"
    (( before > 0 )) || break

    mmsg -o "$active" -s -t "$tag" >/dev/null
    mmsg -o "$active" -s -d "tagcrossmon,${target_tag},${target}" >/dev/null
    mmsg -s -d "focusmon,${active}" >/dev/null || true

    after="$(get_tag_clients "$active" "$tag")"
    if (( after < before )); then
      (( moved += (before - after) ))
    else
      echo "warn: no progress on tag=${tag}; stopping this tag"
      break
    fi
  done
done

left="$(get_total_clients "$active")"
echo "move-all: done moved=${moved} left_on_source=${left} from=${active} to=${target} tag=${target_tag}"