qemush/bin/qemush

#!/bin/bash
# version=0.2.0

# Function to re-exec the script as another user via sudo (only if needed)
exec_as() {
    local user
    user="$1"
    shift

    if [ "$(whoami)" != "$user" ]; then
        exec sudo -u "$user" "$0" "$@"
    fi
}

# Exec the script as qemu
exec_as qemu "$@"

# Directories used in the program
bin="${HOME}/launchers"
images="${HOME}/disks"

# Environment
PATH="${bin}:${HOME}/bin:${PATH}"
EDITOR="${EDITOR:-nvim}"
export QEMUSH_NAME

# Aliases
alias ls='ls --color=auto'
alias exec='exec '
if [ -t 1 ]; then
    alias pretty_cat='source-highlight --failsafe -f esc --style-file=esc.style -i'
else
    alias pretty_cat=cat
fi
shopt -s expand_aliases

# Set a restrictive umask to make sure qemu user files are private
umask 027

# Function to print a colored error
perror() {
    >&2 printf '\033[1;31mERROR:\033[0m \033[1m%s\033[0m\n' "$*"
}

# Function to show the usage
public_help() {
    local name
    name="$(basename "$0")"

    exec cat << EOF
${name}: usage:
  ${name} active                           - (default behaviour) list active VMs
  ${name} start <VM name>                  - start a VM
  ${name} watch <VM name>                  - attach VM screen session
  ${name} ls                               - list available VMs
  ${name} edit <VM name>                   - edit VM launching script
  ${name} rm <VM name>                     - delete launch script
  ${name} diskls                           - list available disk images
  ${name} diskadd <disk name> <size>       - create a disk image
  ${name} diskrm <disk name>               - delete disk image
  ${name} shell                            - start a shell as user qemu
  ${name} help                             - show this help
  ${name} add <path to script> [<VM name>] - add a launching script
  ${name} do <command>                     - run shell input as user qemu
  ${name} depcheck                         - check if script dependencies are met
EOF
}

# Function to throw an invalid usage error (skill issue)
error_usage() {
    perror "Invalid usage"
    >&2 public_help
    return 1
}

# Function to start a virtual machine ; fails if the virtual machine is
# already started thanks to tmux
public_start() {
    QEMUSH_NAME="$1"
    shift

    exec tmux new-session \
        -s "$QEMUSH_NAME" \
        "$QEMUSH_NAME" \
        "$@"
}

# Attach to a running virtual machine output, the latest opened if no
# argument is provided
public_watch() {
    [ -n "$1" ] && set -- -t "$1"

    exec tmux attach "$@"
}

# List running virtual machines
public_active() {
    exec tmux list-sessions
}

# List available virtual machines entrypoints
public_ls() {
    echo "Available machines:"
    exec ls "$bin"
}

# Create a copy-on-write disk for a virtual machine
public_diskadd() {
    QEMUSH_NAME="$1"
    shift

    exec qemu-img create -f qcow2 "$(pathof disk)" "$1"
}

# Delete a disk
public_diskrm() {
    QEMUSH_NAME="$1"
    shift

    exec rm -vi -- "$(pathof disk)"
}

# List available disks
public_diskls() {
    echo "Available disks:"
    exec ls "$images"
}

# Edit a virtual machine entrypoint with a text editor
public_edit() {
    local file="${bin}/${1}"
    "$EDITOR" "$file"
    [ -f "$file" ] && exec chmod u+x "$file"
}

# Delete a virtual machine entrypoint
public_rm() {
    exec rm -vi -- "${bin}/${1}"
}

# Invoke bash as qemu user in its home directory
public_shell() {
    cd || return
    exec bash -i
}

# Output the content of an entrypoint, with coloration if on a virtual
# terminal
public_cat() {
    pretty_cat "${bin}/${1}"
}

# Copy a file in entrypoints folder
public_add() {
    trap return EXIT
    set -e

    local name
    name="${2:-$(basename "$1")}"
    cp -v -i -- "$1" "${bin}/${2}"
    chmod 740 "${bin}/${name}"

    set +e
    trap - EXIT
}

# Run shell commands as qemu
public_do() {
    exec sh -c "$*"
}

# Retrieve user requested function
function="$1"
shift

# Defauts to `active` if no function is supplied; else checks for a public
# function named after the argument; else fails
if [ -z "$function" ]; then
    public_active
elif declare -F | cut -d \  -f 3- | grep '^public_' | sed 's/^public_//' | grep -q "^${function}$"; then
    "public_${function}" "$@"
else
    error_usage
fi