#### Android...
#
# See NOTES.ANDROID for details, and don't miss platform-specific
# comments below...

{
    use File::Spec::Functions;

    my $android_ndk = {};
    my %triplet = (
        arm    => "arm-linux-androideabi",
        arm64  => "aarch64-linux-android",
        mips   => "mipsel-linux-android",
        mips64 => "mips64el-linux-android",
        x86    => "i686-linux-android",
        x86_64 => "x86_64-linux-android",
    );

    sub android_ndk {
        unless (%$android_ndk) {
            if ($now_printing =~ m|^android|) {
                return $android_ndk = { bn_ops => "BN_AUTO" };
            }

            my $ndk_var;
            my $ndk;
            foreach (qw(ANDROID_NDK_HOME ANDROID_NDK)) {
                $ndk_var = $_;
                $ndk = $ENV{$ndk_var};
                last if defined $ndk;
            }
            die "\$ANDROID_NDK_HOME is not defined"  if (!$ndk);
            if (!-d "$ndk/platforms" && !-f "$ndk/AndroidVersion.txt") {
                # $ndk/platforms is traditional "all-inclusive" NDK, while
                # $ndk/AndroidVersion.txt is so-called standalone toolchain
                # tailored for specific target down to API level.
                die "\$ANDROID_NDK_HOME=$ndk is invalid";
            }
            $ndk = canonpath($ndk);

            my $ndkver = undef;

            if (open my $fh, "<$ndk/source.properties") {
                local $_;
                while(<$fh>) {
                    if (m|Pkg\.Revision\s*=\s*([0-9]+)|) {
                        $ndkver = $1;
                        last;
                    }
                }
                close $fh;
            }

            my ($sysroot, $api, $arch);

            $config{target} =~ m|[^-]+-([^-]+)$|;	# split on dash
            $arch = $1;

            if ($sysroot = $ENV{CROSS_SYSROOT}) {
                $sysroot =~ m|/android-([0-9]+)/arch-(\w+)/?$|;
                ($api, $arch) = ($1, $2);
            } elsif (-f "$ndk/AndroidVersion.txt") {
                $sysroot = "$ndk/sysroot";
            } else {
                $api = "*";

                # see if user passed -D__ANDROID_API__=N
                foreach (@{$useradd{CPPDEFINES}}, @{$user{CPPFLAGS}}) {
                    if (m|__ANDROID_API__=([0-9]+)|) {
                        $api = $1;
                        last;
                    }
                }

                # list available platforms (numerically)
                my @platforms = sort { $a =~ m/-([0-9]+)$/; my $aa = $1;
                                       $b =~ m/-([0-9]+)$/; $aa <=> $1;
                                     } glob("$ndk/platforms/android-$api");
                die "no $ndk/platforms/android-$api" if ($#platforms < 0);

                $sysroot = "@platforms[$#platforms]/arch-$arch";
                $sysroot =~ m|/android-([0-9]+)/arch-$arch|;
                $api = $1;
            }
            die "no sysroot=$sysroot"   if (!-d $sysroot);

            my $triarch = $triplet{$arch};
            my $cflags;
            my $cppflags;

            # see if there is NDK clang on $PATH, "universal" or "standalone"
            if (which("clang") =~ m|^$ndk/.*/prebuilt/([^/]+)/|) {
                my $host=$1;
                # harmonize with gcc default
                my $arm = $ndkver > 16 ? "armv7a" : "armv5te";
                (my $tridefault = $triarch) =~ s/^arm-/$arm-/;
                (my $tritools   = $triarch) =~ s/(?:x|i6)86(_64)?-.*/x86$1/;
                $cflags .= " -target $tridefault "
                        .  "-gcc-toolchain \$($ndk_var)/toolchains"
                        .  "/$tritools-4.9/prebuilt/$host";
                $user{CC} = "clang" if ($user{CC} !~ m|clang|);
                $user{CROSS_COMPILE} = undef;
                if (which("llvm-ar") =~ m|^$ndk/.*/prebuilt/([^/]+)/|) {
                    $user{AR} = "llvm-ar";
                    $user{ARFLAGS} = [ "rs" ];
                    $user{RANLIB} = ":";
                }
            } elsif (-f "$ndk/AndroidVersion.txt") {    #"standalone toolchain"
                my $cc = $user{CC} // "clang";
                # One can probably argue that both clang and gcc should be
                # probed, but support for "standalone toolchain" was added
                # *after* announcement that gcc is being phased out, so
                # favouring clang is considered adequate. Those who insist
                # have option to enforce test for gcc with CC=gcc.
                if (which("$triarch-$cc") !~ m|^$ndk|) {
                    die "no NDK $triarch-$cc on \$PATH";
                }
                $user{CC} = $cc;
                $user{CROSS_COMPILE} = "$triarch-";
            } elsif ($user{CC} eq "clang") {
                die "no NDK clang on \$PATH";
            } else {
                if (which("$triarch-gcc") !~ m|^$ndk/.*/prebuilt/([^/]+)/|) {
                    die "no NDK $triarch-gcc on \$PATH";
                }
                $cflags .= " -mandroid";
                $user{CROSS_COMPILE} = "$triarch-";
            }

            if (!-d "$sysroot/usr/include") {
                my $incroot = "$ndk/sysroot/usr/include";
                die "no $incroot"          if (!-d $incroot);
                die "no $incroot/$triarch" if (!-d "$incroot/$triarch");
                $incroot =~ s|^$ndk/||;
                $cppflags  = "-D__ANDROID_API__=$api";
                $cppflags .= " -isystem \$($ndk_var)/$incroot/$triarch";
                $cppflags .= " -isystem \$($ndk_var)/$incroot";
            }

            $sysroot =~ s|^$ndk/||;
            $android_ndk = {
                cflags   => "$cflags --sysroot=\$($ndk_var)/$sysroot",
                cppflags => $cppflags,
                bn_ops   => $arch =~ m/64$/ ? "SIXTY_FOUR_BIT_LONG"
                                            : "BN_LLONG",
            };
        }

        return $android_ndk;
    }
}

my %targets = (
    "android" => {
        inherit_from     => [ "linux-generic32" ],
        template         => 1,
        ################################################################
        # Special note about -pie. The underlying reason is that
        # Lollipop refuses to run non-PIE. But what about older systems
        # and NDKs? -fPIC was never problem, so the only concern is -pie.
        # Older toolchains, e.g. r4, appear to handle it and binaries
        # turn out mostly functional. "Mostly" means that oldest
        # Androids, such as Froyo, fail to handle executable, but newer
        # systems are perfectly capable of executing binaries targeting
        # Froyo. Keep in mind that in the nutshell Android builds are
        # about JNI, i.e. shared libraries, not applications.
        cflags           => add(sub { android_ndk()->{cflags} }),
        cppflags         => add(sub { android_ndk()->{cppflags} }),
        cxxflags         => add(sub { android_ndk()->{cflags} }),
        bn_ops           => sub { android_ndk()->{bn_ops} },
        bin_cflags       => "-pie",
        enable           => [ ],
    },
    "android-arm" => {
        ################################################################
        # Contemporary Android applications can provide multiple JNI
        # providers in .apk, targeting multiple architectures. Among
        # them there is "place" for two ARM flavours: generic eabi and
        # armv7-a/hard-float. However, it should be noted that OpenSSL's
        # ability to engage NEON is not constrained by ABI choice, nor
        # is your ability to call OpenSSL from your application code
        # compiled with floating-point ABI other than default 'soft'.
        # (Latter thanks to __attribute__((pcs("aapcs"))) declaration.)
        # This means that choice of ARM libraries you provide in .apk
        # is driven by application needs. For example if application
        # itself benefits from NEON or is floating-point intensive, then
        # it might be appropriate to provide both libraries. Otherwise
        # just generic eabi would do. But in latter case it would be
        # appropriate to
        #
        #   ./Configure android-arm -D__ARM_MAX_ARCH__=8
        #
        # in order to build "universal" binary and allow OpenSSL take
        # advantage of NEON when it's available.
        #
        # Keep in mind that (just like with linux-armv4) we rely on
        # compiler defaults, which is not necessarily what you had
        # in mind, in which case you would have to pass additional
        # -march and/or -mfloat-abi flags. NDK defaults to armv5te.
        # Newer NDK versions reportedly require additional -latomic.
        #
        inherit_from     => [ "android", asm("armv4_asm") ],
        bn_ops           => add("RC4_CHAR"),
    },
    "android-arm64" => {
        inherit_from     => [ "android", asm("aarch64_asm") ],
        bn_ops           => add("RC4_CHAR"),
        perlasm_scheme   => "linux64",
    },

    "android-mips" => {
        inherit_from     => [ "android", asm("mips32_asm") ],
        bn_ops           => add("RC4_CHAR"),
        perlasm_scheme   => "o32",
    },
    "android-mips64" => {
        ################################################################
        # You are more than likely have to specify target processor
        # on ./Configure command line. Trouble is that toolchain's
        # default is MIPS64r6 (at least in r10d), but there are no
        # such processors around (or they are too rare to spot one).
        # Actual problem is that MIPS64r6 is binary incompatible
        # with previous MIPS ISA versions, in sense that unlike
        # prior versions original MIPS binary code will fail.
        #
        inherit_from     => [ "android", asm("mips64_asm") ],
        bn_ops           => add("RC4_CHAR"),
        perlasm_scheme   => "64",
    },

    "android-x86" => {
        inherit_from     => [ "android", asm("x86_asm") ],
        CFLAGS           => add(picker(release => "-fomit-frame-pointer")),
        bn_ops           => add("RC4_INT"),
        perlasm_scheme   => "android",
    },
    "android-x86_64" => {
        inherit_from     => [ "android", asm("x86_64_asm") ],
        bn_ops           => add("RC4_INT"),
        perlasm_scheme   => "elf",
    },

    ####################################################################
    # Backward compatible targets, (might) require $CROSS_SYSROOT
    #
    "android-armeabi" => {
        inherit_from     => [ "android-arm" ],
    },
    "android64" => {
        inherit_from     => [ "android" ],
    },
    "android64-aarch64" => {
        inherit_from     => [ "android-arm64" ],
    },
    "android64-x86_64" => {
        inherit_from     => [ "android-x86_64" ],
    },
    "android64-mips64" => {
        inherit_from     => [ "android-mips64" ],
    },
);