#!/usr/bin/env bash
#
# Minio Cloud Storage, (C) 2014-2016 Minio, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

_init() {

    shopt -s extglob

    ## Minimum required versions for build dependencies
    GIT_VERSION="1.0"
    GO_VERSION="1.7.1"
    OSX_VERSION="10.8"
    KNAME=$(uname -s)
    ARCH=$(uname -m)
}

## FIXME:
## In OSX, 'readlink -f' option does not exist, hence
## we have our own readlink -f behaviour here.
## Once OSX has the option, below function is good enough.
## 
## readlink() {
##     return /bin/readlink -f "$1"
## }
##
readlink() {
    TARGET_FILE=$1

    cd `dirname $TARGET_FILE`
    TARGET_FILE=`basename $TARGET_FILE`

    # Iterate down a (possible) chain of symlinks
    while [ -L "$TARGET_FILE" ]
    do
        TARGET_FILE=$(env readlink $TARGET_FILE)
        cd `dirname $TARGET_FILE`
        TARGET_FILE=`basename $TARGET_FILE`
    done

    # Compute the canonicalized name by finding the physical path
    # for the directory we're in and appending the target file.
    PHYS_DIR=`pwd -P`
    RESULT=$PHYS_DIR/$TARGET_FILE
    echo $RESULT
}

## FIXME:
## In OSX, 'sort -V' option does not exist, hence
## we have our own version compare function.
## Once OSX has the option, below function is good enough.
##
## check_minimum_version() {
##     versions=($(echo -e "$1\n$2" | sort -V))
##     return [ "$1" == "${versions[0]}" ]
## }
##
check_minimum_version() {
    IFS='.' read -r -a varray1 <<< "$1"
    IFS='.' read -r -a varray2 <<< "$2"

    for i in "${!varray1[@]}"; do
        if [[ ${varray1[i]} < ${varray2[i]} ]]; then
            return 0
        elif [[ ${varray1[i]} > ${varray2[i]} ]]; then
            return 1
        fi
    done

    return 0
}

assert_is_supported_arch() {
    case "${ARCH}" in
        x86_64 | amd64 | aarch64 | arm* )
            return
            ;;
        *)
            echo "ERROR"
            echo "Arch '${ARCH}' not supported."
            echo "Supported Arch: [x86_64, amd64, aarch64, arm*]"
            exit 1
    esac
}

assert_is_supported_os() {
    case "${KNAME}" in
        Linux | FreeBSD )
            return
            ;;
        Darwin )
            osx_host_version=$(env sw_vers -productVersion)
            if ! check_minimum_version "${OSX_VERSION}" "${osx_host_version}"; then
                echo "ERROR"
                echo "OSX version '${osx_host_version}' not supported."
                echo "Minimum supported version: ${OSX_VERSION}"
                exit 1
            fi
            return
            ;;
        *)
            echo "ERROR"
            echo "OS '${KNAME}' is not supported."
            echo "Supported OS: [Linux, FreeBSD, Darwin]"
            exit 1
    esac
}

assert_check_golang_env() {
    if ! which go >/dev/null 2>&1; then
        echo "ERROR"
        echo "Cannot find go binary in your PATH configuration, please refer to Go installation document at"
        echo "https://docs.minio.io/docs/how-to-install-golang"
        exit 1
    fi

    installed_go_version=$(go version | sed 's/^.* go\([0-9.]*\).*$/\1/')
    if ! check_minimum_version "${GO_VERSION}" "${installed_go_version}"; then
        echo "ERROR"
        echo "Go version '${installed_go_version}' not supported."
        echo "Minimum supported version: ${GO_VERSION}"
        exit 1
    fi

    if [ -z "${GOPATH}" ]; then
        echo "ERROR"
        echo "GOPATH environment variable missing, please refer to Go installation document"
        echo "https://docs.minio.io/docs/how-to-install-golang"
        exit 1
    fi

}

assert_check_deps() {
    installed_git_version=$(git version | awk '{print $NF}')
    if ! check_minimum_version "${GIT_VERSION}" "${installed_git_version}"; then
        echo "ERROR"
        echo "Git version '${installed_git_version}' not supported."
        echo "Minimum supported version: ${GIT_VERSION}"
        exit 1
    fi
}

main() {
    ## Check for supported arch
    assert_is_supported_arch

    ## Check for supported os
    assert_is_supported_os

    ## Check for Go environment
    assert_check_golang_env

    ## Check for dependencies
    assert_check_deps
}

_init && main "$@"