#!/bin/bash
set -euo pipefail

# tools. change paths if necessary.
abootimg=abootimg       # https://github.com/ggrandou/abootimg
unsquashfs=unsquashfs   # https://android.googlesource.com/platform/external/squashfs-tools
ext2rd=ext2rd           # https://github.com/qmfrederik/extfstools
cpio=cpio
openssl=openssl

# https://toengel.net/philipsblog/firmware-download/
if [[ "$#" -lt 1 ]]; then
    echo "Usage: $0 <update.zip>" >&2
    exit 1
fi

passfile="$(dirname "$(readlink -f "$0")")/passfile.txt"
if [[ ! -e "$passfile" ]]; then
    echo "passfile.txt not found (looked at $passfile)" >&2
    echo "try: make -C $(dirname "$passfile") $(basename "$passfile")" >&2
    exit 1
fi

zipfile="$1"
outdir="${zipfile%.zip}"
if [[ "$outdir" == "$zipfile" ]]; then
    outdir="${zipfile}.out"
fi

echo "Unpacking $zipfile to $outdir"

# Unpack *.upg file from .zip into temporary directory. Extract the upg file
# to outdir.

tmpdir="$(mktemp -d)"
trap "rm -rf '$tmpdir'" EXIT

unzip -d "$tmpdir" "$zipfile"

upgfiles=("$tmpdir"/*.upg)
if [[ "${#upgfiles[@]}" -ne 1 ]]; then
    echo "update.zip '$zipfile' contains ${#upgfiles[@]}, want exactly one" >&2
    echo "update.zip contents:" >&2
    ls -l -R "$tmpdir" >&2
    exit 1
fi

# The .upg file is an Android recovery update.zip.
upgfile="${upgfiles[0]}"
unzip -d "$outdir" "$upgfile"
rm -f "$upgfile"

# Decrypt .zip files
rc=0
for enczip in "$outdir"/*.zip; do
    deczip="${enczip}.dec"
    if ! "$openssl" enc -d -aes-256-cbc -md md5 -p -pass file:"$passfile" -out "$deczip" -in "$enczip"; then
        echo "Failed to decrypt $enczip" >&2
        rc=1
        continue
    fi

    if ! file -bi "$deczip" | grep -q '^application/zip'; then
        echo "WARNING: $deczip might not be a .zip file, not renaming" >&2
        rc=1
        continue
    fi

    mv -vf "$deczip" "$enczip"
done

# Unpack all .zip files
for zip in "$outdir"/*.zip; do
    if ! unzip -d "$outdir" "$zip"; then
        echo "Unpacking $zip failed, not removing" >&2
        rc=1
        continue
    fi

    img="${zip%.zip}" # system.img.zip -> system.img, for system.img.{sh,lst}.
    rm -vf "$zip" "$img".sh "$img".lst
done

# Concatenate system image
if ! cat "$outdir"/system?.img > "$outdir"/system.img; then
    echo "Concatenating system images failed" >&2
    rc=1
else
    rm -vf "$outdir"/system?.img
fi

# Extract boot images
if ! which "$abootimg" 2>/dev/null; then
    echo "$abootimg is not installed, not unpacking boot images" >&2
    rc=1
else
    for img in "$outdir"/{boot,factory,recovery}.img; do
        abs="$(readlink -f "$img")" # for the subshell which has a different $PWD
        imgdir="${img%.img}"
        mkdir -p "$imgdir"
        if ! (cd "$imgdir" && "$abootimg" -x "$abs"); then
            echo "Extracting $img to $imgdir failed" >&2
            rc=1
            continue
        fi
        rm -vf "$img"

        # Extract initrd
        initrd="${imgdir}/initrd.img"
        initrddir="${initrd%.img}"
        mkdir -p "$initrddir"
        if ! gzip -cd "$initrd" | "$cpio" -D "$initrddir" -id; then
            echo "Extracting $initrd to $initrddir failed" >&2
            rc=1
            continue
        fi
        rm -vf "$initrd"
    done
fi

# Extract rootfs and 3rd_file
if ! which "$unsquashfs" 2>/dev/null; then
    echo "$unsquashfs is not installed, not unpacking rootfs" >&2
    rc=1
else
    if ! mv "$outdir"/3rd_file "$outdir"/3rd_file.bin; then
        echo "Renaming 3rd_file failed" >&2
        rc=1
    fi
    for img in "$outdir"/{3rd_file,rootfs}.bin; do
        imgdir="${img%.bin}"
        if ! "$unsquashfs" -d "$imgdir" -li "$img"; then
            echo "Extracting $img to $imgdir failed" >&2
            rc=1
            continue
        fi
        rm -vf "$img"
    done
fi

# Extract system.img
if ! which "$ext2rd" 2>/dev/null; then
    echo "$ext2rd is not installed, not unpacking system image" >&2
    rc=1
else
    img="$outdir"/system.img
    imgdir="${img%.img}"
    mkdir -p "$imgdir"
    if ! "$ext2rd" "$img" ./:"$imgdir"; then
        echo "Extracting $img to $imgdir failed" >&2
        rc=1
    else
        rm -vf "$img"
    fi
fi

# The End
if (( rc )); then
    echo "Warnings encountered; please check output!" >&2
fi
echo "Unpacked $zipfile to $outdir, have fun!"
exit "$rc"