#!/usr/bin/env bash
#
# Your build script should simply source this script, optionally override any build hooks and then invoke `build`.
# The build product should be available under `build-<platform>~/out`, under the library path.
# 
# Hook lifecycle:
# - build
#     - initialize
#         - needs
#     - clean & exit (only if script was ran with "clean" argument)
#     - prepare
#         - clean
#         - config
#     - target
#         - prepare
#         - configure
#         - build
#     - finalize
#         - merge
#         - clean
#
# You can override any of these hooks to provide a custom implementation or call their underscore variant to delegate to the default implementation.
# For example:
# target_prepare() { make -s distclean; }
# target_configure() { _target_configure "$@" --enable-minimal; }
set -e

# needs <binary> ...
#
# Utility for ensuring all tools needed by the script are installed prior to starting.
needs() { _needs "$@"; }
_needs() {
    local failed=0
    for tool; do
        hash "$tool" || { echo >&2 "Missing: $tool.  Please install this tool."; (( failed++ )); }
    done

    return $failed
}

# initialize <prefix> <platform>
#
# The build script invokes this once prior to all other actions if the user wants a clean slate.
initialize() { _initialize "$@"; }
_initialize() {
    initialize_needs "$@"
}

# initialize_needs <prefix> <platform>
#
# Check if all tools needed for the default implementations are available.
#
# By default, this will check for `libtool` (for libtoolize), `automake` (for aclocal) and `autoconf` (for autoreconf).
initialize_needs() { _initialize_needs "$@"; }
_initialize_needs() {
    if [[ $platform = windows ]]; then
        needs cmd
        export VSINSTALLDIR="${VSINSTALLDIR:-$(cd "$(cygpath -F 0x002a)/Microsoft Visual Studio"/*/*/Common7/.. && pwd)}"
        [[ -e "$VSINSTALLDIR/Common7/Tools/VsMSBuildCmd.bat" ]] || { echo >&2 "Missing: msbuild.  Please install 'Build Tools for Visual Studio'."; return 1; }
    else
        needs libtool automake autoconf
    fi
}

# clean <prefix> <platform>
#
# Fully clean up the library code, restoring it to a pristine state.
#
# By default, this will wipe the prefix, run `make distclean` and `git clean -fdx`.
clean() { _clean "$@"; }
_clean() {
    rm -rf "$prefix"

    if [[ $platform = windows ]]; then
        printf '"%%VSINSTALLDIR%%\Common7\Tools\VsMSBuildCmd.bat" && msbuild /t:Clean' > .clean.bat
        cmd //c .clean.bat
        rm -f .clean.bat
    fi

    [[ ! -e Makefile ]] || make -s distclean
    [[ ! -e .git ]] || git clean -fdx
}

# prepare <prefix> <platform> [ <arch> ... ]
#
# Configure the library for building the <arch>s on this machine.
# The build script invokes this once prior to building each of its targets.
# The <prefix> has been newly created.
#
# By default, this will run `autoreconf`.
prepare() { _prepare "$@"; }
_prepare() {
    prepare_clean "$@"
    prepare_config "$@"
}

# prepare_clean <prefix> <platform> [ <arch> ... ]
#
# Perform any necessary clean-up of the library code prior to building.
#
# By default, this will wipe and re-create the prefix.
prepare_clean() { _prepare_clean "$@"; }
_prepare_clean() {
    local prefix=$1 platform=$2; shift 2

    rm -rf "$prefix"
    install -d "$prefix"
}

# prepare_config <prefix> <platform> [ <arch> ... ]
#
# Configure the library for building the <arch>s on this machine.
#
# By default, this will run `autoreconf`.
prepare_config() { _prepare_config "$@"; }
_prepare_config() {
    local prefix=$1 platform=$2; shift 2

    [[ $platform = windows ]] && return

    [[ -e configure ]] || autoreconf --verbose --install --symlink 2> >(sed 's/^\([^:]*\):[0-9]\{1,\}: /\1: /')
}

# target <prefix> <platform> <arch>
#
# Build the library for the given <arch> and <platform> into the given <prefix>.
# The build script invokes this function when it's ready to build the library's code.
# Generic platform-specific environment setup has been done.
target() { _target "$@"; }
_target() {
    target_prepare "$@"
    target_configure "$@"
    target_build "$@"
}

# target_prepare <prefix> <platform> <arch>
#
# Prepare the library configuration for building the target.
#
# By default, this will run `make clean` if a Makefile is found.
target_prepare() { _target_prepare "$@"; }
_target_prepare() {
    local prefix=$1 platform=$2 arch=$3; shift 3

    [[ $platform = windows ]] && return

    [[ ! -e Makefile ]] || make -s clean
}

# target_configure <prefix> <platform> <arch> [ <args> ... ]
#
# Configure the library for building the target.
#
# By default, this will run `./configure --host=<host> --prefix=<prefix>/<arch> --disable-shared <args>`.
target_configure() { _target_configure "$@"; }
_target_configure() {
    local prefix=$1 platform=$2 arch=$3; shift 3

    case "$platform" in
        'windows')
            return
        ;;
        'android')
            host=( "$SDKROOT"/*-android* ) host=${host##*/}

            set -- --with-sysroot="$SDKROOT/sysroot" "$@"
        ;;
        'ios')
            [[ $arch = *arm* ]] && host=arm || host=$arch
            host+=-apple

            set -- --disable-shared "$@"
        ;;
    esac

    ./configure ${host:+--host="$host"} --prefix="$prefix/$arch" "$@"
}

# target_build <prefix> <platform> <arch>
#
# Build the library code for the target.
#
# By default, this will run `make check install`.
target_build() { _target_build "$@"; }
_target_build() {
    local prefix=$1 platform=$2 arch=$3; shift 3

    if [[ $platform = windows ]]; then
        # I cannot for the life of me figure out how to pass this command directly into cmd.
        printf '"%%VSINSTALLDIR%%\Common7\Tools\VsMSBuildCmd.bat" && msbuild /t:Rebuild /p:Configuration=ReleaseDLL;Platform=%s;OutDir=%s' "$arch" "$(cygpath -w "${prefix##$PWD/}/$arch/")" > .build.bat
        cmd //c .build.bat
        rm -f .build.bat
    else
        local cores=$(getconf NPROCESSORS_ONLN 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null ||:)
        make -j"${cores:-3}" install
    fi
}

# finalize <prefix> <platform> [ <arch> ... ]
#
# Prepare the final build product.
# The build script invokes this once after a successful build of all targets.
finalize() { _finalize "$@"; }
_finalize() {
    finalize_merge "$@"
    finalize_clean "$@"
}

# finalize_merge <prefix> <platform> [ <arch> ... ]
#
# Merge all targets into a product the application can use, available at `<prefix>/out`.
#
# By default, this will copy the headers to `<prefix>/out/include`, install libraries into `<prefix>/out/lib` and mark the output product as successful.
finalize_merge() { _finalize_merge "$@"; }
_finalize_merge() {
    local prefix=$1 platform=$2; shift 2

    [[ -e "$prefix/$1/include" ]] && mv -f -- "$prefix/$1/include" "$prefix/out/"

    mkdir -p "$prefix/out/lib"
    case "$platform" in
        'windows')
            for arch; do
                install -d "$prefix/out/lib/$arch"
                install -p "$prefix/Win32/"*.lib "$prefix/out/lib/"
            done
        ;;
        'macos'|'ios')
            for lib in "$prefix/$1/lib/"*; do
                if lipo -info "$lib" >/dev/null 2>&1; then
                    local lib=("${lib##*/}") libs=("${@/#/$prefix/}") libs=("${libs[@]/%//lib/$lib}")
                    lipo -create "${libs[@]}" -output "$prefix/out/lib/$lib"
                fi
            done
        ;;
        'android')
            for arch; do
                local abi=$arch
                case "$arch" in
                    'arm')      abi='armeabi-v7a' ;;
                    'arm64')    abi='arm64-v8a' ;;
                esac
                install -d "$prefix/out/lib/$abi"
                install -p "$prefix/$arch/lib/"*.so "$prefix/out/lib/$abi"
            done
        ;;
    esac

    touch "$prefix/out/.success"
}

# finalize_clean <prefix> [ <arch> ... ]
#
# Clean up the library after a successful build (eg. housekeeping of temporary files).
#
# By default, this will run `make clean`.
finalize_clean() { _finalize_clean "$@"; }
_finalize_clean() {
    [[ ! -e Makefile ]] || make -s clean
}

# build <name> [<platform>]
#
# Build the library <name> (found at ../<name>) for platform <platform> (or "host" if unspecified).
build() { _build "$@"; }
_build() {
    local name=$1 platform=${2:-host}
    local path="../$name"
    [[ $path = /* ]] || path="${BASH_SOURCE%/*}/$path"
    cd "$path"

    if [[ $platform = host ]]; then
        case "$(uname -s)" in
            'Darwin') platform='macos' archs=( "$(uname -m)" ) ;;
        esac
    fi
    if (( ! ${#archs[@]} )); then
        case "$platform" in
            'macos') archs=( 'x86_64' ) ;;
            'ios') archs=( 'i386' 'x86_64' 'armv7' 'armv7s' 'arm64' ) ;;
            'android') archs=( 'arm' 'arm64' 'x86' 'x86_64' ) ;;
            'windows') archs=( 'Win32' 'x64' ) ;;
        esac
    fi

    local prefix="$PWD/build-$platform~"
    initialize "$prefix" "$platform"

    # "clean" argument wipes the lib clean and exits. If .success exists in prefix output, skip build.
    if [[ ${BASH_ARGV[@]:(-1)} = clean ]]; then
        clean "$prefix" "$platform"
        exit
    elif [[ -e "$prefix"/out/.success ]]; then
        echo >&2 "Skipping build for $platform: output product already built successfully."
        exit
    fi

    # Prepare the output location and build configuration.
    prepare "$prefix" "$platform" "${archs[@]}"

    # Repeat the build for each individual architecture.
    for arch in "${archs[@]}"; do (

        # Set up a base environment for the platform.
        case "$platform" in
            'windows')
            ;;
            'macos')
                SDKROOT="$(xcrun --show-sdk-path --sdk macosx)"
                export PATH="$(xcrun --show-sdk-platform-path --sdk macosx)/usr/bin:$PATH"
                export CFLAGS="-arch $arch -flto -O2 -g -isysroot $SDKROOT -mmacosx-version-min=${MACOSX_DEPLOYMENT_TARGET:-10.8} $CFLAGS"
                export LDFLAGS="-arch $arch -flto -isysroot $SDKROOT -mmacosx-version-min=${MACOSX_DEPLOYMENT_TARGET:-10.8} $LDFLAGS"
                export CPPFLAGS="$CFLAGS $CPPFLAGS"
            ;;
            'ios')
                case "$arch" in
                    *'arm'*)
                        SDKROOT="$(xcrun --show-sdk-path --sdk iphoneos)"
                        export PATH="$(xcrun --show-sdk-platform-path --sdk iphoneos)/usr/bin:$PATH"
                        export CFLAGS="-arch $arch -mthumb -fembed-bitcode -flto -O2 -g -isysroot $SDKROOT -mios-version-min=${IPHONEOS_DEPLOYMENT_TARGET:-8.0} $CFLAGS"
                        export LDFLAGS="-arch $arch -mthumb -fembed-bitcode -flto -isysroot $SDKROOT -mios-version-min=${IPHONEOS_DEPLOYMENT_TARGET:-8.0} $LDFLAGS"
                        export CPPFLAGS="$CFLAGS $CPPFLAGS"
                    ;;
                    *)
                        SDKROOT="$(xcrun --show-sdk-path --sdk iphonesimulator)"
                        export PATH="$(xcrun --show-sdk-platform-path --sdk iphonesimulator)/usr/bin:$PATH"
                        export CFLAGS="-arch $arch -flto -O2 -g -isysroot $SDKROOT -mios-simulator-version-min=${IPHONEOS_DEPLOYMENT_TARGET:-8.0} $CFLAGS"
                        export LDFLAGS="-arch $arch -flto -isysroot $SDKROOT -mios-simulator-version-min=${IPHONEOS_DEPLOYMENT_TARGET:-8.0} $LDFLAGS"
                        export CPPFLAGS="$CFLAGS $CPPFLAGS"
                    ;;
                esac
            ;;
            'android')
                [[ -x $ANDROID_NDK_HOME/build/ndk-build ]] || { echo >&2 "Android NDK not found.  Please set ANDROID_NDK_HOME."; return 1; }

                SDKROOT="$prefix/$arch/ndk"
                # Platform 21 is lowest that supports x86_64
                "$ANDROID_NDK_HOME/build/tools/make-standalone-toolchain.sh" --force --install-dir="$SDKROOT" --platform='android-21' --arch="$arch"
                export PATH="$SDKROOT/bin:$PATH"
                export CFLAGS="-O2 -g $CFLAGS"
                export LDFLAGS="-avoid-version $LDFLAGS"
                export CC='clang'

                # For GCC:
                # arm    CFLAGS="-march=armv7-a -mfloat-abi=softfp -mfpu=vfpv3-d16 -mthumb" LDFLAGS="-Wl,--fix-cortex-a8"
                # arm64  CFLAGS="-march=armv8-a"
                # x86    CFLAGS="-march=i686 -mtune=intel -mssse3 -mfpmath=sse -m32"
                # x86_64 CFLAGS="-march=x86-64 -msse4.2 -mpopcnt -m64 -mtune=intel"
            ;;
        esac

        target "$prefix" "$platform" "$arch"
    ); done

    finalize "$prefix" "$platform" "${archs[@]}"
}