#!/usr/bin/env bash
# fix_kivy_sdl2.sh — make Kivy use the system SDL2 (Wayland-capable).
#
# THE PROBLEM
# -----------
# Kivy's PyPI wheel bundles a private SDL2 in ``Kivy.libs/`` that is compiled
# WITHOUT the Wayland video driver. Verified on this Pi:
#
#   Kivy.libs/libSDL2-2-87637523.0.so.0.3000.7  ->  x11, KMSDRM, offscreen, dummy, evdev
#   /usr/lib/aarch64-linux-gnu/libSDL2-2.0.so.0 ->  x11, wayland, KMSDRM, offscreen, dummy, evdev
#
# On Raspberry Pi OS "Trixie" the desktop is Wayland/labwc and there is no
# X server running, so the bundled build cannot create a window at all:
#
#   [CRITICAL] Unable to find any valuable Window provider.
#   sdl2 - RuntimeError: b'wayland,x11,dummy not available'
#
# Substituting the system library under Kivy's bundled filename resolves it
# (verified: "WINDOW OK size=(800, 600)").
#
# WHY A SYMLINK AND NOT A COPY
# ----------------------------
# The symlink survives ``pip install --upgrade kivy`` overwriting the file, is
# reversible, and keeps the distro's security updates in effect. A copy would
# silently become stale.
#
# Usage:
#   bash linux/fix_kivy_sdl2.sh            # apply (idempotent)
#   bash linux/fix_kivy_sdl2.sh --check    # report only, change nothing
#   bash linux/fix_kivy_sdl2.sh --revert   # remove the symlink

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
ROOT_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
VENV_DIR="${KIWY_VENV:-$ROOT_DIR/.venv}"
BACKUP_DIR="$VENV_DIR/.kivy-sdl2-backup"
SYSTEM_SDL2="/usr/lib/aarch64-linux-gnu/libSDL2-2.0.so.0"

MODE="apply"
case "${1:-}" in
    --check)  MODE="check" ;;
    --revert) MODE="revert" ;;
    "")       MODE="apply" ;;
    *) echo "Unknown option: $1" >&2; exit 2 ;;
esac

if [ ! -d "$VENV_DIR" ]; then
    echo "ERROR: virtualenv not found at $VENV_DIR" >&2
    echo "       Set KIWY_VENV=/path/to/venv if it lives elsewhere." >&2
    exit 1
fi

KIVY_LIBS="$(find "$VENV_DIR" -maxdepth 5 -type d -name 'Kivy.libs' 2>/dev/null | head -1)"
if [ -z "$KIVY_LIBS" ]; then
    echo "No Kivy.libs directory found under $VENV_DIR — nothing to do."
    echo "(Kivy is probably installed from apt, which uses the system SDL2 already.)"
    exit 0
fi

# Kivy names the bundled library with a hash, so locate it by pattern rather
# than hard-coding the version. Symlinks must be matched too: once the fix is
# applied the original file IS a symlink, and skipping it would make this
# script wrongly conclude that nothing is bundled.
BUNDLED="$(find "$KIVY_LIBS" -maxdepth 1 -name 'libSDL2-2-*.so*' 2>/dev/null | head -1)"

# Fallback: ask the compiled extension which SDL2 it actually loads. This is
# authoritative and also covers a future Kivy layout change.
if [ -z "$BUNDLED" ]; then
    EXT="$(find "$VENV_DIR" -maxdepth 6 -name '_window_sdl2*.so' 2>/dev/null | head -1)"
    if [ -n "$EXT" ]; then
        NEEDED="$(ldd "$EXT" 2>/dev/null | awk '/libSDL2-2-/ {print $3; exit}')"
        [ -n "$NEEDED" ] && BUNDLED="$NEEDED"
    fi
fi

echo "Kivy.libs : $KIVY_LIBS"
echo "bundled   : ${BUNDLED:-<none>}"
echo "system    : $SYSTEM_SDL2"

if [ ! -e "$SYSTEM_SDL2" ]; then
    echo "ERROR: system SDL2 not found at $SYSTEM_SDL2" >&2
    echo "       Install it with:  sudo apt install libsdl2-2.0-0" >&2
    exit 1
fi

# Report the video drivers compiled into a library, so the fix is verifiable.
report_drivers() {
    local lib="$1"
    local py="${VENV_DIR}/bin/python"
    [ -x "$py" ] || py="$(command -v python3)"
    "$py" - "$lib" <<'PY' 2>/dev/null || echo "  (could not inspect drivers)"
import ctypes, sys
try:
    s = ctypes.CDLL(sys.argv[1])
    s.SDL_GetNumVideoDrivers.restype = ctypes.c_int
    s.SDL_GetVideoDriver.restype = ctypes.c_char_p
    s.SDL_GetVideoDriver.argtypes = [ctypes.c_int]
    n = s.SDL_GetNumVideoDrivers()
    print('  drivers:', ', '.join(s.SDL_GetVideoDriver(i).decode() for i in range(n)))
except Exception as exc:
    print('  (inspection failed:', exc, ')')
PY
}

case "$MODE" in
    revert)
        if [ -L "$BUNDLED" ]; then
            rm -f "$BUNDLED"
            if [ -f "$BACKUP_DIR/$(basename "$BUNDLED")" ]; then
                cp -a "$BACKUP_DIR/$(basename "$BUNDLED")" "$BUNDLED"
                echo "Reverted to the original bundled SDL2."
            else
                echo "Removed the symlink. Reinstall Kivy to restore the bundled library:"
                echo "  $VENV_DIR/bin/pip install --force-reinstall kivy"
            fi
        else
            echo "Nothing to revert (no symlink in place)."
        fi
        exit 0
        ;;

    check)
        echo
        if [ -L "$BUNDLED" ]; then
            echo "STATUS: fixed (bundled name points at the system SDL2)"
            report_drivers "$BUNDLED"
        else
            echo "STATUS: NOT fixed — Kivy is using its own SDL2"
            report_drivers "$BUNDLED"
        fi
        echo
        echo "system SDL2:"
        report_drivers "$SYSTEM_SDL2"
        exit 0
        ;;

    apply)
        if [ -z "$BUNDLED" ]; then
            echo "No bundled libSDL2 found — Kivy already uses the system SDL2."
            exit 0
        fi

        if [ -L "$BUNDLED" ]; then
            echo "Already fixed (symlink in place). Verifying..."
            report_drivers "$BUNDLED"
            exit 0
        fi

        # Keep a copy of the original so --revert works without a reinstall.
        mkdir -p "$BACKUP_DIR"
        if [ ! -f "$BACKUP_DIR/$(basename "$BUNDLED")" ]; then
            cp -a "$BUNDLED" "$BACKUP_DIR/"
            echo "Backed up original -> $BACKUP_DIR/$(basename "$BUNDLED")"
        fi

        ln -sf "$SYSTEM_SDL2" "$BUNDLED"
        echo "Symlinked $BUNDLED -> $SYSTEM_SDL2"
        echo
        echo "Resulting drivers:"
        report_drivers "$BUNDLED"
        echo
        echo "Done. Kivy can now create a Wayland window."
        echo "NOTE: re-run this script after any 'pip install --upgrade kivy'."
        ;;
esac