#!/bin/sh
# Cycle focus through visible X windows (next or previous).
# Usage: window_cycle.sh next | prev
# POSIX-compliant; works without a window manager.

# Get direction argument
case "$1" in
    next) DIR="next" ;;
    prev) DIR="prev" ;;
    *)
        echo "Usage: $0 next | prev" >&2
        exit 1
        ;;
esac

# Get all visible window IDs (space-separated)
WINDOWS=$(xdotool search --onlyvisible -class . | tr '\n' ' ')

# Get the currently focused window ID
CURRENT=$(xdotool getwindowfocus)

NEXT=""
PREV=""
LAST=""
FOUND=0

for ID in $WINDOWS; do
    if [ "$DIR" = "next" ]; then
        # Find next window
        if [ "$FOUND" -eq 1 ]; then
            NEXT=$ID
            break
        fi
        if [ "$ID" = "$CURRENT" ]; then
            FOUND=1
        fi
    else
        # Find previous window
        if [ "$ID" = "$CURRENT" ]; then
            if [ -z "$PREV" ]; then
                PREV=$LAST
            fi
            break
        fi
        PREV=$ID
        LAST=$ID
    fi
done

# Wrap around if needed
if [ "$DIR" = "next" ]; then
    if [ -z "$NEXT" ]; then
        for ID in $WINDOWS; do
            NEXT=$ID
            break
        done
    fi
    TARGET=$NEXT
else
    if [ -z "$PREV" ]; then
        for ID in $WINDOWS; do
            PREV=$ID
        done
    fi
    TARGET=$PREV
fi

# Focus the chosen window
xdotool windowfocus "$TARGET"