#!/bin/bash

set -euo pipefail

# Version and checksums for godel. Values are populated by the godel "dist" task.
VERSION=2.40.0
DARWIN_AMD64_CHECKSUM=c0ddf9c67b8bbad9bb362687f79437ca1bf9e9076bc36b212d1be2b659bf23bd
DARWIN_ARM64_CHECKSUM=2de3ff5e61ebba985e2ab80fbc4ca0add0db34cac5fa4b7776c1b50d1e53463b
LINUX_AMD64_CHECKSUM=d489cd497218e68a5bd26ad6efa73ff6775e94b653b232585061ad07efdbd684
LINUX_ARM64_CHECKSUM=c1e03926e7f032e895b25e320f490c3ea696e505b44b27cb5b9014bcd24c4d16

# Downloads file at URL to destination path using wget or curl. Prints an error and exits if wget or curl is not present.
function download {
    local url=$1
    local dst=$2

    # determine whether wget, curl or both are present
    set +e
    command -v wget >/dev/null 2>&1
    local wget_exists=$?
    command -v curl >/dev/null 2>&1
    local curl_exists=$?
    set -e

    # if one of wget or curl is not present, exit with error
    if [ "$wget_exists" -ne 0 -a "$curl_exists" -ne 0 ]; then
        echo "wget or curl must be present to download distribution. Install one of these programs and try again or install the distribution manually."
        exit 1
    fi

    if [ "$wget_exists" -eq 0 ]; then
        # attempt download using wget
        echo "Downloading $url to $dst..."
        local progress_opt=""
        if wget --help | grep -q '\--show-progress'; then
            progress_opt="-q --show-progress"
        fi
        set +e
        wget -O "$dst" $progress_opt "$url"
        rv=$?
        set -e
        if [ "$rv" -eq 0 ]; then
            # success
            return
        fi

        echo "Download failed using command: wget -O $dst $progress_opt $url"

        # curl does not exist, so nothing more to try: exit
        if [ "$curl_exists" -ne 0 ]; then
            echo "Download failed using wget and curl was not found. Verify that the distribution URL is correct and try again or install the distribution manually."
            exit 1
        fi
        # curl exists, notify that download will be attempted using curl
        echo "Attempting download using curl..."
    fi

    # attempt download using curl
    echo "Downloading $url to $dst..."
    set +e
    curl -f -L -o "$dst" "$url"
    rv=$?
    set -e
    if [ "$rv" -ne 0 ]; then
        echo "Download failed using command: curl -f -L -o $dst $url"
        if [ "$wget_exists" -eq 0 ]; then
            echo "Download failed using wget and curl. Verify that the distribution URL is correct and try again or install the distribution manually."
        else
            echo "Download failed using curl and wget was not found. Verify that the distribution URL is correct and try again or install the distribution manually."
        fi
        exit 1
    fi
}

# verifies that the provided checksum matches the computed SHA-256 checksum of the specified file. If not, echoes an
# error and exits.
function verify_checksum {
    local file=$1
    local expected_checksum=$2
    local computed_checksum=$(compute_sha256 $file)
    if [ "$expected_checksum" != "$computed_checksum" ]; then
        echo "SHA-256 checksum for $file did not match expected value."
        echo "Expected: $expected_checksum"
        echo "Actual:   $computed_checksum"
        exit 1
    fi
}

# computes the SHA-256 hash of the provided file. Uses openssl, shasum or sha1sum program.
function compute_sha256 {
    local file=$1
    if command -v openssl >/dev/null 2>&1; then
        # print SHA-256 hash using openssl
        openssl dgst -sha256 "$file" | sed -E 's/SHA256\(.*\)= //'
    elif command -v shasum >/dev/null 2>&1; then
        # Darwin systems ship with "shasum" utility
        shasum -a 256 "$file" | sed -E 's/[[:space:]]+.+//'
    elif command -v sha256sum >/dev/null 2>&1; then
        # Most Linux systems ship with sha256sum utility
        sha256sum "$file" | sed -E 's/[[:space:]]+.+//'
    else
        echo "Could not find program to calculate SHA-256 checksum for file"
        exit 1
    fi
}

# Verifies that the tgz file at the provided path contains the paths/files that would be expected in a valid gödel
# distribution with the provided version.
function verify_dist_tgz_valid {
    local tgz_path=$1
    local version=$2

    local expected_paths=("godel-$version/" "godel-$version/bin/darwin-amd64/godel" "godel-$version/bin/darwin-arm64/godel" "godel-$version/bin/linux-amd64/godel" "godel-$version/bin/linux-arm64/godel" "godel-$version/wrapper/godelw" "godel-$version/wrapper/godel/config/")
    local files=($(tar -tf "$tgz_path"))

    # this is a double-for loop, but fine since $expected_paths is small and bash doesn't have good primitives for set/map/list manipulation
    for curr_line in "${files[@]}"; do
        # if all expected paths have been found, terminate
        if [[ ${#expected_paths[*]} == 0 ]]; then
            break
        fi

        # check for expected path and splice out if match is found
        idx=0
        for curr_expected in "${expected_paths[@]}"; do
            if [ "$curr_expected" = "$curr_line" ]; then
                expected_paths=(${expected_paths[@]:0:idx} ${expected_paths[@]:$(($idx + 1))})
                break
            fi
            idx=$idx+1
        done
    done

    # if any expected paths still remain, raise error and exit
    if [[ ${#expected_paths[*]} > 0 ]]; then
        echo "Required paths were not present in $tgz_path: ${expected_paths[@]}"
        exit 1
    fi
}

# Verifies that the gödel binary in the distribution reports the expected version when called with the "version"
# argument. Assumes that a valid gödel distribution directory for the given version exists in the provided directory.
function verify_godel_version {
    local base_dir=$1
    local version=$2
    local os=$3
    local arch=$4

    local expected_output="godel version $version"
    local version_output=$($base_dir/godel-$version/bin/$os-$arch/godel version)

    if [ "$expected_output" != "$version_output" ]; then
        echo "Version reported by godel executable did not match expected version: expected \"$expected_output\", was \"$version_output\""
        exit 1
    fi
}

# directory of godelw script
SCRIPT_HOME=$(cd "$(dirname "$0")" && pwd)

# use $GODEL_HOME or default value
GODEL_BASE_DIR=${GODEL_HOME:-$HOME/.godel}

# determine OS
OS=""
EXPECTED_CHECKSUM=""
case "$(uname)-$(uname -m)" in
    Darwin-x86_64)
        OS=darwin
        ARCH=amd64
        EXPECTED_CHECKSUM=$DARWIN_AMD64_CHECKSUM
        ;;
    Darwin-arm64)
        OS=darwin
        ARCH=arm64
        EXPECTED_CHECKSUM=$DARWIN_ARM64_CHECKSUM
        ;;
    Linux-x86_64)
        OS=linux
        ARCH=amd64
        EXPECTED_CHECKSUM=$LINUX_AMD64_CHECKSUM
        ;;
    Linux-aarch64)
        OS=linux
        ARCH=arm64
        EXPECTED_CHECKSUM=$LINUX_ARM64_CHECKSUM
        ;;
    *)
        echo "Unsupported operating system-architecture: $(uname)-$(uname -m)"
        exit 1
        ;;
esac

# path to godel binary
CMD=$GODEL_BASE_DIR/dists/godel-$VERSION/bin/$OS-$ARCH/godel

# godel binary is not present -- download distribution
if [ ! -f "$CMD" ]; then
    # get download URL
    PROPERTIES_FILE=$SCRIPT_HOME/godel/config/godel.properties
    if [ ! -f "$PROPERTIES_FILE" ]; then
        echo "Properties file must exist at $PROPERTIES_FILE"
        exit 1
    fi
    DOWNLOAD_URL=$(cat "$PROPERTIES_FILE" | sed -E -n "s/^distributionURL=//p")
    if [ -z "$DOWNLOAD_URL" ]; then
        echo "Value for property \"distributionURL\" was empty in $PROPERTIES_FILE"
        exit 1
    fi
    DOWNLOAD_CHECKSUM=$(cat "$PROPERTIES_FILE" | sed -E -n "s/^distributionSHA256=//p")

    # create downloads directory if it does not already exist
    mkdir -p "$GODEL_BASE_DIR/downloads"

    # download tgz and verify its contents
    # Download to unique location that includes PID ($$) and use trap ensure that temporary download file is cleaned up
    # if script is terminated before the file is moved to its destination.
    DOWNLOAD_DST=$GODEL_BASE_DIR/downloads/godel-$VERSION-$$.tgz
    download "$DOWNLOAD_URL" "$DOWNLOAD_DST"
    trap 'rm -rf "$DOWNLOAD_DST"' EXIT
    if [ -n "$DOWNLOAD_CHECKSUM" ]; then
        verify_checksum "$DOWNLOAD_DST" "$DOWNLOAD_CHECKSUM"
    fi
    verify_dist_tgz_valid "$DOWNLOAD_DST" "$VERSION"

    # create temporary directory for unarchiving, unarchive downloaded file and verify directory
    TMP_DIST_DIR=$(mktemp -d "$GODEL_BASE_DIR/tmp_XXXXXX" 2>/dev/null || mktemp -d -t "$GODEL_BASE_DIR/tmp_XXXXXX")
    trap 'rm -rf "$TMP_DIST_DIR"' EXIT
    tar zxvf "$DOWNLOAD_DST" -C "$TMP_DIST_DIR" >/dev/null 2>&1
    verify_godel_version "$TMP_DIST_DIR" "$VERSION" "$OS" "$ARCH"

    # rename downloaded file to remove PID portion
    mv "$DOWNLOAD_DST" "$GODEL_BASE_DIR/downloads/godel-$VERSION.tgz"

    # if destination directory for distribution already exists, remove it
    if [ -d "$GODEL_BASE_DIR/dists/godel-$VERSION" ]; then
        rm -rf "$GODEL_BASE_DIR/dists/godel-$VERSION"
    fi

    # ensure that parent directory of destination exists
    mkdir -p "$GODEL_BASE_DIR/dists"

    # move expanded distribution directory to destination location. The location of the unarchived directory is known to
    # be in the same directory tree as the destination, so "mv" should always work.
    mv "$TMP_DIST_DIR/godel-$VERSION" "$GODEL_BASE_DIR/dists/godel-$VERSION"

    # edge case cleanup: if the destination directory "$GODEL_BASE_DIR/dists/godel-$VERSION" was created prior to the
    # "mv" operation above, then the move operation will move the source directory into the destination directory. In
    # this case, remove the directory. It should always be safe to remove this directory because if the directory
    # existed in the distribution and was non-empty, then the move operation would fail (because non-empty directories
    # cannot be overwritten by mv). All distributions of a given version are also assumed to be identical. The only
    # instance in which this would not work is if the distribution purposely contained an empty directory that matched
    # the name "godel-$VERSION", and this is assumed to never be true.
    if [ -d "$GODEL_BASE_DIR/dists/godel-$VERSION/godel-$VERSION" ]; then
        rm -rf "$GODEL_BASE_DIR/dists/godel-$VERSION/godel-$VERSION"
    fi
fi

verify_checksum "$CMD" "$EXPECTED_CHECKSUM"

# execute command
$CMD --wrapper "$SCRIPT_HOME/$(basename "$0")" "$@"