VLC player command runner extension, see https://dbx-12.de/?linux/vlc-command-runner for instructions

command-runner.conf

# comma-separated list of commands to run when playback is started
on_play_commands=
# comma-separated list of commands to run when playback is paused
on_pause_commands=
# comma-separated list of commands to run when playback is stopped
on_stop_commands=

command-runner.lua

local cfgPath = ""
local options = {
    on_play_commands = {},
    on_pause_commands = {},
    on_stop_commands = {},
}

local last_called = {
    playing = 0,
    paused = 0,
    stopped = 0
}

--region methods called by vlc

---descriptor Describes the extension for VLC
function descriptor()
    return {
        title = "Command runner",
        version = "1.0",
        author = "dbx12",
        url = "http://dbx-12.de/?linux/vlc-command-runner",
        shortdesc = "Command runner",
        description = "This extension triggers commands on your machine when playback is started, paused or stopped.",
        capabilities = {
            "playing-listener",
            "menu"
        }
    }
end

---activate called when the extension is activated
function activate()
    cfgPath = vlc.config.configdir() .. "/command-runner.conf"
    if file_exists(cfgPath) == false then
        write_config_file(cfgPath)
        log_info("Config file is missing, empty config file generated at "..cfgPath)
        log_info("After editing this file, you should reload the extension config with View > Command Runner > Reload config")
    else
        load_config(cfgPath)
    end
end

---deactivate called when the extension is deactivated
function deactivate()
end

---meta_changed called when meta information changes
function meta_changed()
end

---playing_changed called when the playback status changes
function playing_changed()
    local status = vlc.playlist.status()
    if debounce(status) then
        return
    end
    if status == "playing" then
        run_commands(options.on_play_commands)
    elseif status == "paused" then
        run_commands(options.on_pause_commands)
    elseif status == "stopped" then
        run_commands(options.on_stop_commands)
    end
end

---menu contains the entries in the menu
function menu()
    return {"Reload config"}
end

---trigger_menu is called when a menu entry is clicked
---@param action_id number 1-based id of the entry that was clicked
function trigger_menu(action_id)
    if action_id == 1 then
        load_config()
    end
end

--endregion

---debounce prevents calling the commands too fast in case VLC calls `playing_changed()` more than once per state change
---@param action string
function debounce(action)
    local now = os.time()
    if last_called[action] == now then
        log_dbg(action.." was called too fast after the last call. Ignoring this one.")
        return true
    end
    last_called[action] = now
    return false
end

---run_commands runs specified commands with os.execute
---@param commands table list of commands to execute
function run_commands(commands)
    for _, command in pairs(commands) do
        log_dbg("Running command: "..command)
        os.execute(command)
    end
end

--region log functions
function log_dbg(message)
    vlc.msg.dbg("[command runner] "..message)
end

function log_info(message)
    vlc.msg.info("[command runner] "..message)
end
--endregion

--region Config file handling

function load_config()
    log_dbg("Loading config from: " .. cfgPath)
    local lines = lines_from(cfgPath)
    for _, line in pairs(lines) do
        -- only process line if it does not start with a #
        if string.match(line, "^%s*#") == nil then
            parsed = parse_line(line)
            if string.match(parsed.key, "_commands") then
                options[parsed.key] = parse_list(parsed.value)
            else
                options[parsed.key] = parsed.value
            end
        end
    end
end

function parse_line(line)
    local key, value
    for k, v in string.gmatch(line, "([a-z_]+)=(.*)") do
        key = k
        value = v
    end
    return { key = key, value = value }
end

function parse_list(value)
    local values = {}
    for v in string.gmatch(value, "([^,]+)") do
        table.insert(values, v)
    end
    return values
end

-- source: https://github.com/michaelbull/vlc-credit-skipper/blob/84211bc6e08596d2626be6f58bf8a3beec6db728/credit-skipper.lua#L206
function lines_from(cfgFile)
    local lines = {}

    for line in io.lines(cfgFile) do
        lines[#lines + 1] = line
    end
    return lines
end

-- source: https://github.com/michaelbull/vlc-credit-skipper/blob/84211bc6e08596d2626be6f58bf8a3beec6db728/credit-skipper.lua#L200
function file_exists(file)
    local f = io.open(file, "rb")
    if f then
        f:close()
    end
    return f ~= nil
end

---write_config_file writes the default config (no commands at all) to `cfgPath`
function write_config_file()
    content=[=[
# comma-separated list of commands to run when playback is started
on_play_commands=
# comma-separated list of commands to run when playback is paused
on_pause_commands=
# comma-separated list of commands to run when playback is stopped
on_stop_commands=
]=]
    local fd = io.open(cfgPath, "wb")
    fd:write(content)
    fd:close()
end

--endregion