#!/usr/bin/env bash
set -Eeuo pipefail

usage() {
    cat <<'EOF'
Quicksh docker 0.1.0 — Docker client and daemon diagnostics
Usage: bash docker.sh [--help|-h|--version]

Reports the client version and checks the active Docker endpoint with docker info.
Honors the existing Docker context and environment, which may point to a remote
daemon. Output never includes full daemon information or endpoint addresses.
Uses a 10-second timeout when the timeout tool is available.
Exit 1 means the client is missing, unusable, or the daemon check failed.
Never installs Docker, starts services, or changes groups/socket permissions.
EOF
}

guidance() {
    local ID=unknown
    if [[ -r /etc/os-release ]]; then
        # shellcheck disable=SC1091
        if ! . /etc/os-release; then
            printf 'quicksh docker: could not read OS identification.\n' >&2
            return 1
        fi
    fi
    printf '\nInstallation and setup guidance:\n'
    case "$ID" in
        arch)
            printf '  Arch Linux: https://wiki.archlinux.org/title/Docker\n'
            printf '  Review the docker package and service setup in the Arch documentation.\n'
            ;;
        ubuntu)
            printf '  Ubuntu: https://docs.docker.com/engine/install/ubuntu/\n'
            printf '  Follow the official repository and package instructions for your release.\n'
            ;;
        *) printf '  Use your distribution documentation: https://docs.docker.com/engine/install/\n' ;;
    esac
    printf '  Docker group membership grants root-level privileges on the host.\n'
    printf '  Consider rootless Docker; never make the socket world-writable.\n'
}

main() {
    if (( $# > 1 )); then
        printf 'quicksh docker: expected at most one option. Use --help.\n' >&2
        return 2
    fi
    case "${1:-}" in
        --help|-h) usage; return ;;
        --version) printf 'Quicksh docker 0.1.0\n'; return ;;
        '') ;;
        *) printf 'quicksh docker: unsupported option: %s. Use --help.\n' "$1" >&2; return 2 ;;
    esac

    printf 'Quicksh docker 0.1.0\n'
    if ! command -v docker >/dev/null 2>&1; then
        printf 'Docker client: not found in PATH. This is not a daemon permission error.\n' >&2
        guidance
        return 1
    fi
    if ! docker --version; then
        printf 'quicksh docker: the installed client failed to report its version.\n' >&2
        return 1
    fi

    local diagnostic status
    local -a limit=()
    if command -v timeout >/dev/null 2>&1; then
        limit=(timeout 10s)
    else
        printf 'No timeout tool: the endpoint check may wait; press Ctrl-C to cancel.\n'
    fi
    if diagnostic=$("${limit[@]}" docker info --format '{{.ServerVersion}}' 2>&1); then
        printf 'Docker daemon: reachable using the active endpoint.\n'
        return 0
    else
        status=$?
    fi

    # Classify locally without echoing daemon diagnostics, which can contain endpoints.
    if (( status == 124 || status == 137 )); then
        printf 'Docker daemon check timed out. Check the active context and connectivity.\n' >&2
    elif [[ "${diagnostic,,}" == *'permission denied'* || "${diagnostic,,}" == *'access is denied'* ]]; then
        printf 'Docker is installed, but the endpoint reported insufficient permissions.\n' >&2
        printf 'Check the socket owner, active context, and rootless setup before changing access.\n' >&2
    else
        printf 'Docker is installed, but the active daemon endpoint is not reachable.\n' >&2
        printf 'Possible causes: stopped service, incorrect context, credentials, or network failure.\n' >&2
    fi
    guidance
    return 1
}

main "$@"