#!/bin/sh
# Public Linux installer. No credentials, package installs, or daemon startup.
# Each release packages Caterm and its checksum-pinned native Chrome controller.
set -eu

fail() {
    printf 'Caterm installer: %s\n' "$*" >&2
    exit 1
}

download() {
    curl --proto '=https' --proto-redir '=https' --tlsv1.2 \
        --fail --silent --show-error --location --retry 2 \
        --connect-timeout 15 --max-time 300 --output "$2" "$1" ||
        fail "Download failed: $1. Your existing installation has been kept."
}

valid_version() {
    printf '%s\n' "$1" | awk '
        /^[0-9]+\.[0-9]+\.[0-9]+$/ { valid++ }
        END { exit !(NR == 1 && valid == 1) }'
}

main() {
    version=latest
    bin_dir=
    while [ "$#" -gt 0 ]; do
        case "$1" in
            --version)
                [ "$#" -ge 2 ] || fail '--version needs X.Y.Z'
                version=${2#v}
                shift 2 ;;
            --bin-dir)
                [ "$#" -ge 2 ] || fail '--bin-dir needs an absolute directory'
                bin_dir=$2
                shift 2 ;;
            -h|--help)
                printf '%s\n' \
                    'Usage: sh install.sh [--version X.Y.Z] [--bin-dir /absolute/path]' \
                    'Linux x86_64 / ARM64, glibc 2.36+. Default: $HOME/.local/bin.' \
                    'Rerun to upgrade. Stop and restart the daemon yourself.'
                return ;;
            *) fail "Unknown option: $1" ;;
        esac
    done
    [ "$(uname -s)" = Linux ] || fail 'This installer is for Linux. Use the Mac app on macOS.'
    case "$(uname -m)" in
        x86_64|amd64) arch=x86_64 ;;
        aarch64|arm64) arch=aarch64 ;;
        *) fail "Unsupported architecture: $(uname -m)" ;;
    esac
    for tool in curl tar awk sed mktemp chmod mv cp rm readlink getconf; do
        command -v "$tool" >/dev/null 2>&1 || fail "Missing $tool; install it with your distribution's package manager."
    done
    libc=$(getconf GNU_LIBC_VERSION 2>/dev/null) ||
        fail 'A glibc Linux distribution is required; Alpine/musl is not supported.'
    printf '%s\n' "$libc" | awk '
        $1 == "glibc" { split($2, v, "."); ok = v[1] > 2 || (v[1] == 2 && v[2] >= 36) }
        END { exit !ok }' || fail "glibc 2.36 or newer is required; found $libc."
    if command -v sha256sum >/dev/null 2>&1; then
        checksum=sha256sum
    elif command -v shasum >/dev/null 2>&1; then
        checksum=shasum
    else
        fail 'sha256sum or shasum is required to verify the binary.'
    fi
    if [ -z "$bin_dir" ]; then
        [ -n "${HOME:-}" ] || fail 'HOME is unset; use --bin-dir.'
        bin_dir=$HOME/.local/bin
    fi
    case "$bin_dir" in /*) ;; *) fail '--bin-dir must be an absolute path' ;; esac
    # Only the old managed alias can be replaced by a regular executable.
    if [ -L "$bin_dir/caterm" ]; then
        [ "$(readlink "$bin_dir/caterm")" = catermd ] ||
            fail "$bin_dir/caterm is an unrelated symlink; choose another --bin-dir."
    elif [ -e "$bin_dir/caterm" ] && [ ! -f "$bin_dir/caterm" ]; then
        fail "$bin_dir/caterm is not a regular executable; choose another --bin-dir."
    fi
    remove_legacy=false
    if [ -e "$bin_dir/catermd" ] || [ -L "$bin_dir/catermd" ]; then
        if [ -L "$bin_dir/catermd" ] && [ "$(readlink "$bin_dir/catermd")" = caterm ]; then
            remove_legacy=true
        elif [ -f "$bin_dir/catermd" ] && [ ! -L "$bin_dir/catermd" ]; then
            legacy_identity=$("$bin_dir/catermd" --version 2>/dev/null) ||
                fail 'Cannot identify the old catermd; remove it manually or choose another --bin-dir.'
            case "$legacy_identity" in
                "catermd "*" (protocol "*) remove_legacy=true ;;
                *) fail 'The old catermd path is unrelated to Caterm; choose another --bin-dir.' ;;
            esac
        else
            fail 'The old catermd path is not a Caterm executable; choose another --bin-dir.'
        fi
    fi
    if [ "$version" != latest ]; then
        valid_version "$version" || fail '--version must be X.Y.Z'
    fi
    umask 077
    temporary=$(mktemp -d "${TMPDIR:-/tmp}/caterm-install.XXXXXXXX")
    stage=
    replacing=false
    committed=false
    cleanup() {
        if [ "$replacing" = true ] && [ "$committed" = false ]; then
            for name in caterm caterm-agent-browser caterm-agent-browser-LICENSE; do
                if [ -e "$stage/previous/$name" ] || [ -L "$stage/previous/$name" ]; then
                    mv -fT "$stage/previous/$name" "$bin_dir/$name"
                else
                    rm -f "$bin_dir/$name"
                fi
            done
        fi
        rm -rf "$temporary"
        if [ -n "$stage" ]; then rm -rf "$stage"; fi
    }
    trap cleanup EXIT
    trap 'exit 130' INT
    trap 'exit 143' TERM HUP
    base=https://downloads.caterm.com
    if [ "$version" = latest ]; then
        download "$base/channels/stable.json" "$temporary/stable.json"
        # Read only the publisher's numeric version field. Never evaluate a manifest.
        version=$(sed -n 's/^  "version": "\([0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\)",$/\1/p' "$temporary/stable.json")
        valid_version "$version" || fail 'Invalid stable release manifest.'
    fi
    package=caterm-linux-$arch
    archive=$package.tar.gz
    printf 'Installing Caterm %s for Linux %s into %s\n' "$version" "$arch" "$bin_dir"
    download "$base/releases/$version/$archive" "$temporary/$archive"
    download "$base/releases/$version/$archive.sha256" "$temporary/$archive.sha256"
    expected=$(awk -v name="$archive" '
        NF == 2 && $2 == name && length($1) == 64 && $1 !~ /[^0-9a-f]/ { digest = $1; valid++ }
        END { if (NR == 1 && valid == 1) print digest; else exit 1 }' "$temporary/$archive.sha256") ||
        fail 'Invalid SHA-256 file.'
    if [ "$checksum" = sha256sum ]; then
        actual=$(sha256sum "$temporary/$archive" | awk '{print $1}')
    else
        actual=$(shasum -a 256 "$temporary/$archive" | awk '{print $1}')
    fi
    [ "$actual" = "$expected" ] || fail 'SHA-256 mismatch. Your existing installation has been kept.'
    mkdir -p "$bin_dir"
    stage=$(mktemp -d "$bin_dir/.caterm-install.XXXXXXXX")
    # Extract only the expected executable as bytes, never archive paths/symlinks.
    tar -xzOf "$temporary/$archive" "$package/caterm" > "$stage/caterm" || fail 'Could not extract the daemon.'
    [ -s "$stage/caterm" ] || fail 'The downloaded executable is empty.'
    chmod 755 "$stage/caterm"
    identity=$("$stage/caterm" --version) ||
        fail 'The downloaded binary cannot run on this machine. Your existing installation has been kept.'
    case "$identity" in
        "caterm $version (protocol "*) ;;
        *) fail "Unexpected binary identity: $identity" ;;
    esac
    # Chrome Use attaches to the user's Chrome; this tool is not a browser engine.
    if [ -L "$bin_dir/caterm-agent-browser" ] || { [ -e "$bin_dir/caterm-agent-browser" ] && [ ! -f "$bin_dir/caterm-agent-browser" ]; }; then
        fail "$bin_dir/caterm-agent-browser is not a regular executable; choose another --bin-dir."
    fi
    tar -xzOf "$temporary/$archive" "$package/caterm-agent-browser" > "$stage/agent-browser" || fail 'Could not extract the Chrome controller.'
    [ -s "$stage/agent-browser" ] || fail 'The Chrome controller is empty.'
    chmod 755 "$stage/agent-browser"
    "$stage/agent-browser" --version >/dev/null || fail 'The Chrome controller cannot run on this machine.'
    tar -xzOf "$temporary/$archive" "$package/caterm-agent-browser-LICENSE" > "$stage/agent-browser-LICENSE" || fail 'Could not extract the Chrome controller license.'
    [ -s "$stage/agent-browser-LICENSE" ] || fail 'The Chrome controller license is empty.'
    if [ -L "$bin_dir/caterm-agent-browser-LICENSE" ] || { [ -e "$bin_dir/caterm-agent-browser-LICENSE" ] && [ ! -f "$bin_dir/caterm-agent-browser-LICENSE" ]; }; then
        fail 'Chrome controller license destination is not a regular file.'
    fi
    mkdir "$stage/previous"
    for name in caterm caterm-agent-browser caterm-agent-browser-LICENSE; do
        if [ -e "$bin_dir/$name" ] || [ -L "$bin_dir/$name" ]; then
            cp -P "$bin_dir/$name" "$stage/previous/$name"
        fi
    done
    replacing=true
    mv -fT "$stage/agent-browser" "$bin_dir/caterm-agent-browser"
    mv -fT "$stage/agent-browser-LICENSE" "$bin_dir/caterm-agent-browser-LICENSE"
    # GNU mv -T replaces a destination, never moves into a directory/symlink.
    mv -fT "$stage/caterm" "$bin_dir/caterm"
    committed=true
    # Retire the old command only after the verified replacement is installed.
    if [ "$remove_legacy" = true ]; then
        rm -f "$bin_dir/catermd"
    fi
    printf '%s\n' "$identity" 'Installed caterm. No services were started.'
    case ":${PATH:-}:" in
        *":$bin_dir:"*) ;;
        *) printf 'Add this directory to PATH: %s\n' "$bin_dir"
           if [ "$bin_dir" = "${HOME:-}/.local/bin" ]; then
               printf '%s\n' 'For this shell: export PATH="$HOME/.local/bin:$PATH"'
           fi ;;
    esac
    printf '%s\n' \
        'Use Add a device on caterm.com, then run its connection command.' \
        'For desktop sharing: caterm desktop doctor, then caterm connect --desktop --saved.' \
        'Desktop prerequisites and applications must be installed by you.' \
        'For Chrome: caterm plugins install chrome-use (or gmail-use), then restart Caterm.' \
        'In Chrome 144+, enable chrome://inspect/#remote-debugging and allow the connection.'
}

# Defining the whole installer before invoking it also avoids executing a
# partially downloaded function body when this script is piped into sh.
main "$@"