#!/bin/sh
# Installs the newest Termilly on Debian or Ubuntu (64-bit):
#
#   curl -fsSL https://termilly.com/install.sh | sh
#
# It reads https://termilly.com/downloads/latest.json, downloads the package named there, checks its SHA-256
# against that file and installs it with apt, which brings .NET and WebKitGTK with it. It's short on purpose,
# so you can read it before you run it. TERMILLY_SITE points it at another server, for testing.
set -eu

# Everything is in main, which runs on the last line: a download cut short runs nothing.
main() {
    site="${TERMILLY_SITE:-https://termilly.com}"

    command -v apt-get >/dev/null 2>&1 || fail "This script is for Debian and Ubuntu (it needs apt). Other systems: $site/#download"
    command -v curl >/dev/null 2>&1 || fail "This script needs curl: sudo apt install curl"
    command -v sha256sum >/dev/null 2>&1 || fail "This script needs sha256sum (coreutils)."
    arch="$(dpkg --print-architecture)"
    [ "$arch" = amd64 ] || fail "Termilly is built for 64-bit PCs (amd64), and this one is $arch."

    sudo=""
    if [ "$(id -u)" -ne 0 ]; then
        command -v sudo >/dev/null 2>&1 || fail "Installing needs root: run this as root, or install sudo."
        sudo=sudo
    fi

    # latest.json may be on one line or spread over several: without the whitespace, the "linux" part is
    # {"deb":"<url>","sha256":"<hash>"} either way.
    manifest="$(fetch "$site/downloads/latest.json")" || fail "Couldn't read $site/downloads/latest.json."
    manifest="$(printf '%s' "$manifest" | tr -d ' \t\r\n')"
    version="$(field "$manifest" version)"
    linux="$(printf '%s' "$manifest" | sed -n 's/.*"linux":{\([^}]*\)}.*/\1/p')"
    url="$(field "$linux" deb)"
    sum="$(field "$linux" sha256)"
    [ -n "$version" ] && [ -n "$url" ] && [ -n "$sum" ] || fail "$site/downloads/latest.json doesn't name a Linux package."

    # apt reads the package as its own user (_apt), so the folder and the file are readable by everyone.
    dir="$(mktemp -d)"
    trap 'rm -rf "$dir"' EXIT
    chmod 755 "$dir"
    deb="$dir/termilly_amd64.deb"

    echo "Downloading Termilly $version"
    fetch "$url" > "$deb" || fail "Couldn't download $url."
    chmod 644 "$deb"
    echo "$sum  $deb" | sha256sum -c --status - || fail "The download doesn't match the SHA-256 in latest.json, so it wasn't installed. Try again later."

    echo "Installing it with apt"
    $sudo apt-get update -qq || fail "apt-get update failed."
    $sudo apt-get install -y "$deb" || fail "apt-get couldn't install the package."
    echo "Termilly $version is installed. Start it from your applications, or type termilly in a terminal."
}

# HTTPS only, redirects too (http:// only when TERMILLY_SITE asks for it).
fetch() {
    case "$1" in
        https://*) curl -fsSL --proto =https --proto-redir =https "$1" ;;
        *) curl -fsSL --proto-redir =https "$1" ;;
    esac
}

# The string value of a key in compact JSON: field '{"a":"b"}' a prints b.
field() {
    printf '%s' "$1" | sed -n "s/.*\"$2\":\"\([^\"]*\)\".*/\1/p"
}

fail() {
    echo "termilly install: $1" >&2
    exit 1
}

main "$@"