#!/bin/sh
set -eu

REPO='basecamp/once'
IMAGE_REF=''
RELEASE_JSON=''

main() {
    os=$(detect_os)
    arch=$(detect_arch)
    ensure_docker "$os"
    fetch_latest_release
    install_once "$os" "$arch"
    run_once
}

detect_os() {
    case "$(uname -s)" in
        Linux*)  echo "linux" ;;
        Darwin*) echo "darwin" ;;
        *)       echo "Unsupported OS: $(uname -s)" >&2; exit 1 ;;
    esac
}

detect_arch() {
    case "$(uname -m)" in
        x86_64)  echo "amd64" ;;
        aarch64) echo "arm64" ;;
        arm64)   echo "arm64" ;;
        *)       echo "Unsupported architecture: $(uname -m)" >&2; exit 1 ;;
    esac
}

ensure_docker() {
    os="$1"

    if docker info > /dev/null 2>&1; then
        DOCKER_MODE=normal
        return
    fi

    if command -v docker > /dev/null 2>&1; then
        if [ "$os" = "darwin" ]; then
            echo "Docker Desktop is installed but not running."
            echo "Please start Docker Desktop and try again."
            exit 1
        fi
        DOCKER_MODE=sudo
        return
    fi

    if [ "$os" = "darwin" ]; then
        echo "Docker is required. Install Docker Desktop from"
        echo "https://www.docker.com/products/docker-desktop"
        exit 1
    fi

    echo "Installing Docker..."
    if is_root; then
        sh -c "$(curl -fsSL https://get.docker.com)" > /dev/null 2>&1
    else
        curl -fsSL https://get.docker.com | sudo sh > /dev/null 2>&1
    fi

    if ! is_root; then
        sudo usermod -aG docker "$USER"
    fi

    DOCKER_MODE=sg
}

install_once() {
    os="$1"
    arch="$2"

    version=$(latest_version)
    echo "Installing once ${version}..."

    binary="once-${os}-${arch}"
    asset_url=$(get_asset_url "$binary")

    if [ -z "$asset_url" ]; then
        echo "Could not find release asset: ${binary}" >&2
        exit 1
    fi

    if [ "$os" = "linux" ]; then
        install_dir="/usr/bin"
    else
        install_dir="/usr/local/bin"
    fi

    tmpfile=$(mktemp)
    download "$asset_url" "$tmpfile" "application/octet-stream"

    if is_root; then
        install -m 755 "$tmpfile" "${install_dir}/once"
    else
        sudo install -m 755 "$tmpfile" "${install_dir}/once"
    fi
    rm -f "$tmpfile"

    echo "Installed once to ${install_dir}/once"
}

run_once() {
    install_flag=""
    if [ -n "$IMAGE_REF" ]; then
        install_flag="--install=${IMAGE_REF}"
    fi

    case "$DOCKER_MODE" in
        normal)
            exec once ${install_flag} < /dev/tty
            ;;
        sudo)
            exec sudo once ${install_flag} < /dev/tty
            ;;
        sg)
            sg docker -c "once ${install_flag}" < /dev/tty
            ;;
    esac
}

# Private

fetch_latest_release() {
    RELEASE_JSON=$(download "https://api.github.com/repos/${REPO}/releases/latest" -)
}

latest_version() {
    echo "$RELEASE_JSON" | awk '/"tag_name"/ { gsub(/.*"tag_name": *"/, ""); gsub(/".*/, ""); print; exit }'
}

get_asset_url() {
    binary="$1"
    echo "$RELEASE_JSON" | awk -v binary="$binary" '
        /"url":.*api\.github\.com.*assets/ {
            u = $0; gsub(/.*"url": *"/, "", u); gsub(/".*/, "", u)
        }
        /"name":/ && index($0, "\"" binary "\"") { print u; exit }
    '
}

download() {
    url="$1"
    output="$2"
    accept="${3:-}"

    if command -v curl > /dev/null 2>&1; then
        set -- -fsSL -o "$output"
        [ -n "${GITHUB_TOKEN:-}" ] && set -- "$@" -H "Authorization: token ${GITHUB_TOKEN}"
        [ -n "$accept" ] && set -- "$@" -H "Accept: $accept"
        curl "$@" "$url"
    elif command -v wget > /dev/null 2>&1; then
        set -- -q -O "$output"
        [ -n "${GITHUB_TOKEN:-}" ] && set -- "$@" --header="Authorization: token ${GITHUB_TOKEN}"
        [ -n "$accept" ] && set -- "$@" --header="Accept: $accept"
        wget "$@" "$url"
    else
        echo "curl or wget is required" >&2
        exit 1
    fi
}

is_root() {
    [ "$(id -u)" -eq 0 ]
}

main