#!/bin/bash
set -euo pipefail
# The build container (Dockerfile.ubuntu) runs as native ARM64, but Tauri's
# AppImage bundler downloads and runs linuxdeploy-x86_64.AppImage — an x86_64
# binary that bundles the app's shared library dependencies (GTK, WebKit, …)
# into the AppDir so the AppImage is self-contained on any x86_64 Linux system.
# Without intervention the ARM64 kernel cannot execute it and returns "Exec
# format error". binfmt_misc is a Linux kernel feature that maps file magic
# bytes to an interpreter; by registering a handler here, the kernel
# automatically prepends QEMU to any x86_64 ELF execution, making x86_64
# binaries work transparently inside the ARM64 container without any changes to
# the code that invokes them.
#
# Register an x86_64 binfmt_misc handler so the ARM64 kernel transparently
# routes x86_64 ELF executables through QEMU. This is needed because Tauri's
# AppImage bundler downloads and runs linuxdeploy-x86_64.AppImage.
#
# binfmt_misc registration format:
#   :name:type:offset:magic:mask:interpreter:flags
#
# The magic matches an x86_64 ELF executable header:
#   \x7fELF  — ELF magic
#   \x02     — 64-bit (EI_CLASS)
#   \x01     — little-endian (EI_DATA)
#   \x01     — version
#   \x00...  — OS/ABI + padding (bytes 7-15)
#   \x02\x00 — ET_EXEC (executable)
#   \x3e\x00 — x86-64 machine type
#
# The mask has \x00 for bytes 7-15 (the padding area). A zero mask bit means
# "don't check this byte". This is necessary because AppImages embed the
# two-byte marker 'AI' in bytes 8-9 of the ELF padding. The standard x86_64
# mask checks those bytes exactly (\xff), so it rejects AppImages. With the
# permissive mask both plain ELFs and AppImages are intercepted.
#
# echo (not printf): the \x.. sequences must reach the kernel binfmt_misc
# parser as literal text (e.g. the four characters \, x, 7, f), which the
# kernel then interprets as byte values. printf would expand them to raw bytes
# first, the parser would misread the entry, and the broken handler would
# intercept ARM64 binaries and route them through QEMU, breaking the container.
mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc 2>/dev/null || true
echo ':qemu-x86_64-appimage:M::\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x3e\x00:\xff\xff\xff\xff\xff\xfe\xfe\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfe\xff\xff\xff:/usr/bin/qemu-x86_64-static:' \
  > /proc/sys/fs/binfmt_misc/register 2>/dev/null || true
export APPIMAGE_EXTRACT_AND_RUN=1
# linuxdeploy-plugin-gtk.sh calls pkg-config to find GTK 3; on an ARM64 host
# with amd64 multiarch the default search path misses the amd64 .pc files.
export PKG_CONFIG_PATH=/usr/lib/x86_64-linux-gnu/pkgconfig:/usr/share/pkgconfig
# Ubuntu 24.04 installs gtk-query-immodules-3.0 under the t64 directory.
# The plugin needs it in PATH; binfmt-misc handles it as x86_64 via QEMU.
export PATH=/usr/lib/x86_64-linux-gnu/libgtk-3-0t64:$PATH
npm exec -- tauri build \
  --config '{"build":{"beforeBuildCommand":""}}' \
  --target x86_64-unknown-linux-gnu \
  --bundles appimage
cp target/x86_64-unknown-linux-gnu/release/bundle/appimage/*.AppImage /output/