#!/usr/bin/env bash
# version=0.8.0

# Re-exec the script as qemu via sudo (only if needed)
[ "$(whoami)" != qemu ] && exec sudo -E -H -u qemu -- "$0" "$@"

# Environment
PATH="${HOME}/launchers:${HOME}/bin:${PATH}"

# Aliases
alias ls='ls --color=auto'
alias exec='exec '
shopt -s expand_aliases

# Set a restrictive umask to make sure qemu user files are private
umask 7027

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

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

    exec cat << EOF
${name}: usage:
  ${name} running                          - (default behaviour) list running VMs
  ${name} ls                               - list available VMs
  ${name} add <path to script> [<VM name>] - add a launching script
  ${name} edit <VM name>                   - edit VM launching script
  ${name} start <VM name>                  - start a VM
  ${name} attach <VM name>                 - attach to the VM monitor socket
  ${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} do <shell code>                  - run shell input as user qemu
  ${name} spice <running VM> [<TCP port>]  - expose a SPICE socket to TCP
  ${name} help                             - show this help
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
public_start() {
    export QEMUSH_NAME="$1"

    set -- "$@" \
        -name "$QEMUSH_NAME" \
        -monitor "unix:$(pathof socket),server,nowait" \
        -daemonize

    if ! "$@"; then
        perror "error launching virtual machine \"${QEMUSH_NAME}\""
        return 2
    fi
}

# Attach to a running virtual machine output, the latest opened if no
# argument is provided
public_attach() {
    export QEMUSH_NAME="$1"

    exec socat -,rawer,escape=15 "UNIX-CONNECT:$(pathof socket)"
}

# List running virtual machines
public_running() {
    cd || return

    echo "Running machines:"
    exec ls -t sockets/monitors
}

# List available virtual machines entrypoints
public_ls() {
    cd || return

    echo "Available machines:"
    exec ls launchers
}

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

    exec qemu-img create -f qcow2 "$(pathof disk)" "$2"
}

# Delete a disk
public_diskrm() {
    for disk in "$@"; do
        export QEMUSH_NAME="$disk"

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

# List available disks
public_diskls() {
    cd || return

    echo "Available disks:"
    exec ls disks
}

# Edit a virtual machine entrypoint with a text editor
public_edit() {
    file="launchers/${1}"
    # I don't even know why shellcheck gives me this warning
    # shellcheck disable=2209
    [ -z "$EDITOR" ] && EDITOR=vi

    set -e
    cd
    touch -- "$file"
    chmod u+x -- "$file"
    exec "$EDITOR" -- "$file"
}

# Delete a virtual machine entrypoint
public_rm() {
    cd ~/launchers || return

    exec rm -vi -- "$@"
}

# 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() {
    cd ~/launchers || return

    exec cat -- "$@"
}

# Copy a file in entrypoints folder
public_add() {
    if [ -z "$1" ]; then
        perror "specify the path of a launching script you want to add"
        return 1
    fi

    if [ -n "$2" ]; then
        destination="$2"
    else
        destination=$(basename "$1")
    fi
    destination="${HOME}/launchers/${destination}"

    trap return EXIT
    set -e

    cp -vi -- "$1" "$destination"
    chmod 0740 -- "$destination"

    set +e
    trap - EXIT
}

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

# Expose SPICE via TCP
public_spice() {
    export QEMUSH_NAME="$1"

    if [ -n "$2" ]; then
        port=$2
    else
        port=$(first-free-port 5900)
    fi

    exec tmux new -d -s "TCP port ${port} -> ${QEMUSH_NAME}" \
        socat TCP-LISTEN:"${port},reuseaddr,fork" UNIX-CLIENT:"$(pathof spice)"
}

function_exists() {
    declare -F \
        | cut -d \  -f 3- \
        | grep '^public_' \
        | sed 's/^public_//' \
        | grep -q "^${1}\$"
}

# Defauts to `active` if no function is supplied; else checks for a public
# function named after the argument; else fails
if [ -z "$1" ]; then
    public_running
elif function_exists "$1"; then
    function=$1
    shift

    "public_${function}" "$@"
else
    error_usage
fi