All communication consists of messages that are one line of
human-readable UTF-8 text (with no terminating newline), optionally
followed by a single newline and arbitrary (potentialy even binary)
data.

The WebSocket distinction between 'text' and 'binary' frames has no
meaning for us for messages that don't contain additional binary data;
such messages can be either 'binary' or 'text' from the WebSocket
point of view even if we require them (the single line) to be
UTF-8. In other words, an implementation is free to send such a
single-line message as a WebSocket 'binary' frame, and the receiving
implementation must treat that equally as if it was a 'text' frame.

The WebSocket protocol says that 'text' frames are to be "interpreted"
as UTF-8, so it is probably best to indeed use 'binary' frames for
messages that contain optional non-UTF-8 data.

The protocol is not a request-response one. Messages may be sent in
either direction at any time, either in response to some message, or
spontaneously. For 'tile' messages, the client may send a bunch of
tile requests without waiting for return messages. The server may send
tiles proactively (guessing what the client might need). Etc.

client -> server
================

canceltiles

    All outstanding tile messages from the client to the server are
    dropped and will not be handled, except tile messages with an id
    parameter. There is no guarantee of exactly which tile: messages
    might still be sent back to the client.

downloadas name=<fileName> id=<id> format=<document format> options=<SkipImages, etc>

    Exports the current document to the desired format and returns a download URL
    The id identifies the request on the client. id can take following values:
    * 'print': When request for download is basically for print purposes
    * 'slideshow': When request for download is for showing slideshow
    * 'export': Just a simple download

getchildid

    Requests the child id so that it knows where the files needs to be sent when it is
    inserted in the document

gettextselection mimetype=<mimeType>

    Request selection's content

paste mimetype=<mimeType>
<binaryPasteData>

    Paste content at the current cursor position.

insertfile name=<name> type=<type>

    Inserts the file with the name <name> into the document, we currently support type = 'graphic'

key type=<type> char=<charcode> key=<keycode>

    <type> is 'input' or 'up', <charcode> and <keycode> are numbers.

load <pathname>

    Deprecated.

load [part=<partNumber>] url=<url> [timestamp=<time>] [lang=<locale>] [options=<options>]

    part is an optional parameter. <partNumber> is a number.

    timestamp is an optional parameter.  <time> is provided in microseconds
    since the Unix epoch - midnight, January 1, 1970.

    lang specifies the locale to which we should switch before loading the
    document

    options are the whole rest of the line, not URL-encoded, and must be valid JSON.

loolclient <major.minor[-patch]>

    Upon connection, a client must announce the version number it supports.
    Major: an integer that must always match between client and server,
           otherwise there are no guarantees of any sensible
           compatibility. This is bumped when API changes.
    Minor: an integer is more flexible and is at the discretion of either party.
           Security fixes that do not alter the API would bump the minor version number.
    Patch: an optional string that is informational.

mouse type=<type> x=<x> y=<y> count=<count>

    <type> is 'buttondown', 'buttonup' or 'move', others are numbers.

ping

    requests a 'pong' server message.

renderfont font=<font> char=<characters>

    requests the rendering of the given font.
    The font parameter is URL encoded
    The char parameter is URL encoded

requestloksession

    requests the initialization of a LOK process in an attempt to predict the user's
    interaction with the document

resetselection

saveas url=<url> format=<format> options=<options>

    <url> is a URL, encoded. <format> is also URL-encoded, i.e. spaces as %20 and it can be empty
    options are the whole rest of the line, not URL-encoded, and can be empty

selecttext type=<type> x=<x> y=<y>

    <type> is 'start', 'end' or 'reset', <x> and <y> are numbers.

selectgraphic type=<type> x=<x> y=<y>

    <type> is 'start' or 'end' <x> and <y> are numbers.

setclientpart part=<partNumber>

    Informs the server that the client changed to part <partNumber>.

status

styles

tile part=<partNumber> width=<width> height=<height> tileposx=<xpos> tileposy=<ypos> tilewidth=<tileWidth> tileheight=<tileHeight> [timestamp=<time>] [id=<id> broadcast=<yesOrNo>] [oldhash=<hash>]

    Parameters are numbers except broadcast which is 'yes' or 'no' and
    hash which is a 64-bit hash. (There is no need for the client to
    parse it into a number, it can be treated as an opaque string.)

    Note: id must be echoed back in the response verbatim. It and the
    following parameter, broadcast, are used when rendering slide
    previews of presentation documents, and not for anything else. It
    is only useful to loleaflet and will break it if not returned in
    the response.

tilecombine <parameters>

    Accepts same parameters as the 'tile' message except that
    parameters 'tileposx', 'tileposy' and 'oldhash' are
    comma-separated lists, and the number of elements in each must be
    same.

uno <command>

    <command> is a line of text.

save dontTerminateEdit=<value> dontSaveIfUnmodified=<value>

    A wrapper over UNO save command. A non-zero <value> is considered true.
    'dontTerminateEdit' means not terminating the edit session in
    spreadsheets when saving the document. In most cases, you should set it to
    non-zero. 'dontSaveIfUnmodified' when set to non-zero skips saving the document when it is
    unmodified.

clientvisiblearea x=<x> y=<y> width=<width> height=<height>

    Invokes lok::Document::setClientVisibleArea().

useractive

    Sent when the user regains focus or clicks within the active area to
    disable the inactive state.
    Will send invalidation and update notifications to force refreshing the screen.

    See 'userinactive'.

userinactive

    Sent when the user has switched tabs or away from the Browser altogether.
    It should throttle updates until the user is active again.

    See 'useractive'.

closedocument

    This gives document owners the ability to terminate all sessions currently
    having that document opened. This functionality is enabled only in case WOPI
    host mentions 'EnableOwnerTermination' flag in its CheckFileInfo response

server -> client
================

loolserver <loolwsd version> <loolwsd git hash> <major.minor[-patch]>

    Upon connection, the server must announce the version number it supports.
    Major: an integer that must always match between client and server,
           otherwise there are no guarantees of any sensible
           compatibility. This is bumped when API changes.
    Minor: an integer is more flexible and is at the discretion of either party.
           Security fixes that do not alter the API would bump the minor version number.
    Patch: an optional string that is informational.

lokitversion <JSON string>

    JSON string contains version information in format:
    {ProductName: <>, ProductVersion: <>, ProductExtension: <>, BuildId: <>}

    Eg: {"ProductName": "LibreOffice",
         "ProductVersion": "5.3",
         "ProductExtension": ".0.0.alpha0",
         "BuildId": "<full 40 char git hash>"}

contextmenu: <json description of the context menu>

    When the user right-clicks in the document, the content of the context
    menu is sent back via this callback.

    The structure of the context menu is a JSON, and looks like:

        {
            "menu": [
                { "text": "label text1", "type": "command", "command": ".uno:Something1", "enabled": "true" },
                { "text": "label text2", "type": "command", "command": ".uno:Something2", "enabled": "false" },
                { "type": "separator" },
                { "text": "label text2", "type": "menu", "menu": [ { ... }, { ... }, ... ] },
                ...
            ]
        }

downloadas: jail=<jail directory> dir=<a tmp dir> name=<name> port=<port>

    The client should then request http://server:port/jail/dir/name in order to download
    the document

error: cmd=<command> kind=<kind> [code=<error_code>] [params=1,2,3,...,N]
<freeErrorText>

    <command> is the command part of the corresponding client->server
    message that caused the error.

    <command> can also take following values:
    'internal': for errors generated without directly corresponding to a client
    message.
    'storage': for errors pertaining to storage (filesysytem, wopi etc.)

    <kind> is some single-word classification

    <code> (when provided) further specifies the error as forwarded from
    LibreOffice

close: <reason>

    Ask a client to close the websocket connection with <reason>.
    Exactly similar fields are also available in WebSocket protocol's
    CLOSE frame, but some browser implementation (google-chrome) doesn't seem to
    handle that well. This is a temporary application-level close websocket
    to circumvent the same.

    <reason> can have following values:
    * ownertermination - If the session close is due to 'Document owner'
    terminating the session.
    (Document owner is the one who has the file ownership and hence have the
    ability to kill all other sessions if EnableOwnerTermination flag in WOPI
    CheckFileInfo is 'true' (assumed to be 'false' by default).

    * shuttingdown - Sent when the server is going down in a graceful fashion.
    The server doesn't disconnect from clients yet, but starts
    saving document and tearing down internals.

    * recycling - The last message sent from the server when it is gracefully
    shutting down to let clients know they can try connecting
    after a short interval.

getchildid: id=<id>

    Returns the child id

invalidatetiles: part=<partNumber> x=<x> y=<y> width=<width> height=<height>

    All parameters are numbers. Tells the client to invalidate any
    cached tiles for the document area specified (in twips), at any
    zoom level.

invalidatetiles: EMPTY

nextmessage: size=<byteSize>

    <byteSize> is the size, in bytes, of the next message, in case it
    is "large". (In practice, nextmessage: messages precede each tile:
    message). Can be ignored by clients using an API that can read
    arbitrarily large buffers from a WebSocket (like JavaScript), but
    must be handled by clients that cannot (like those using Poco
    1.6.0.

pong rendercount=<num>

    sent in reply to a 'ping' message, where <num> is the total number
    of rendered tiles of the document.

status: type=<typeName> parts=<numberOfParts> current=<currentPartNumber> width=<width> height=<height> viewid=<viewId> [partNames]

    <typeName> is 'text, 'spreadsheet', 'presentation', 'drawing' or 'other. Others are numbers.
    if the document has multiple parts and those have names, part names follow separated by '\n'

styles: {"styleFamily": ["styles in family"], etc. }

statechanged: <key>=<value>

    Notifies client of state changed events of <key>.
    Eg: 'statechanged: .uno:Undo=enabled'

textselectioncontent: <content>

    Current selection's content

tile: part=<partNumber> width=<width> height=<height> tileposx=<xpos> tileposy=<ypos> tilewidth=<tileWidth> tileheight=<tileHeight> [timestamp=<time>] [renderid=<id>] [hash=<hash>]
<binaryPngImage>

    The parameters from the corresponding 'tile' command.

    In a debug build, the renderid is either a unique identifier,
    different for each actual call to LibreOfficeKit to render a tile,
    or the string 'cached' if the tile was found in the cache. hash is
    a hash of the tile contents, and can be included by the client in
    the next 'tile' message requesting the same tile.

Each LOK_CALLBACK_FOO_BAR callback except
LOK_CALLBACK_INVALIDATE_TILES causes a corresponding message to the
client, consisting of the FOO_BAR part in lowercase, without
underscore, followed by a colon, space and the callback
payload. (LOK_CALLBACK_INVALIDATE_TILES causes an invalidatetiles:
message as documented above.) For instance:

invalidatecursor: <payload>

The payload contains a rectangle describing the cursor position.

The communication between the parent process (the one keeping open the
Websocket connections to the clients) and a child process (handling
one document through LibreOfficeKit) uses the same protocol, with
the following additions and changes:

unocommandresult: <payload>

Callback that an UNO command has finished.
See LOK_CALLBACK_UNO_COMMAND_RESULT for details.

invalidateviewcursor:

    Per-view cursor position invalidation. JSON payload.

textviewselection:

    Per-view text selection bounds. JSON payload.

cellviewcursor:

    Per-view cell cursor position. JSON payload.

graphicviewselection:

    Per-view graphic selection. JSON payload.

viewcursorvisible:

    Per-view cursor visible. JSON payload.

viewlock:

    Per-view lock rectangle. JSON payload.

viewinfo: <payload>

    Message is sent everytime there is any change in view information.
    <payload> consists of an array of JSON objects. Structure of JSON
    objects is like : {"id": <viewid>, "username": <Full Name of the user>}

redlinetablechanged:

    Signals that the redlines table has been modified.
    Redlines are used for tracking changes.

comment:

    Signals that comment has either been added, removed or modified. See
    LOK_CALLBACK_COMMENT for JSON structure.

celladdress: <payload>

    Message is sent anytime the content of the address input box should be updated.
    The <payload> is a string representing the new content.

stats: <key> <value>

    Contains statistical data. Eg: 'stats: wopiloadduration 5' means that
    wopi calls made in loading of document took 5 seconds.

perm: <permission>

    <permission> can be one of 'edit', 'view', 'readonly'. Client must
    change the UI accordingly (disabling buttons etc.)

wopi: <JSON>

     Sent only in case storage is WOPI. Contains WOPI related
     capabilities/information for loleaflet to act accordingly.

     Properties mentioned:
     + PostMessageOrigin: See WOPI specs for more information
     + HideSaveOption: (boolean): If loleaflet should hide the save options
     + HidePrintOption: (boolean): If loleaflet should hide print options
     + HideExportOption: (boolean): If loleaflet should hide the export options
       this implies 'Download as' options in file menu

child -> parent
===============

curpart: part=<partNumber>

    Sent to the parent process before certain messages that the parent
    needs to act on in addition to passing them on to the client, like
    invalidatetiles:

errortoall: cmd=<command> kind=<kind> [code=<error_code>]

    Causes the parent to send the corresponding error: message to all
    clients.

nextmessage: size=<upperlimit>

    each tile: message sent from the child to the parent is preceded
    by a nextmessage: message that gives an upper limit on the size of
    the tile: message that will follow. (We assume it is only tile:
    messages that can be "large".) Once we depend on Poco 1.6.1, where
    one doesn't need to use a pre-allocated buffer when receiving
    WebSocket messages, this will go away.

saveas: url=<url>

    <url> is a URL of the destination, encoded. Sent from the child to the
    parent after a saveAs() completed.

client-<sessionId> <Payload Message>

    Forwarding message between a child and its parent session.
    The payload message is forwarded to the ClientSession.

parent -> child
===============

child-<sessionId> <Payload Message>

    Forwarding message between a parent and its child session.
    The payload message is forwarded to the ChildSession.

disconnect

    Signals to the child that the client for the respective connection
    has disconnected.

exit

    Signals to the child that the process must end and exit.

Admin console
===============

Client can query admin console to get information about currently opened
documents. Following information about the document is exposed:

* PID of the process hosting the document
* Number of client views opening this document
* Name of the document (URL encoded)
* Memory consumed by the process (in kilobytes)
* Elapsed time since first view of document was opened (in seconds)

Admin console can also opt to get notified of various events on the server. For
example, getting notified when a new document is opened or closed. Notifications
are commands sent from server to the client over established websocket.

Before doing anything, clients must authenticate by providing an auth token with
'auth' command.

client -> admin
==============

auth jwt=<jwtToken>

    Authenticate the client with provided jwtToken. This is necessary before any
    other command.

subscribe <space seperated list of commands>

    Where list of commands are the ones that client wants to get notified
    about. For eg. 'subscribe adddoc rmdoc'

version

    Queries the server for current version of lokit and loolserver. See
    'lokitversion' and 'loolserver' in admin -> client for the format of
    response message.

documents

    Queries the server for list of opened documents. See `documents` command
    in admin -> client section for format of the response message

total_mem

    Queries for total memory being consumed by the server in kilobytes.
    This includes processes - loolwsd, loolforkit, and child processes
    hosting various documents

active_docs_count

    Returns total number of documents opened

active_users_count

    Returns total number of users connected. This is a summation of number
    of views opened of each document.

settings

    Queries the server for configurable settings from admin console.

set <setting1=value1> <setting2=value2> ...

    Sets a particular setting (must be one returned as response to
    `settings` command) to value.

    There are only 4 configurable settings as of now.

    mem_stats_size: Number of memory consumed values that server caches
    atmost.
    mem_stats_interval: Time after which server calculates its total memory
    consumption
    cpu_stats_size: Number of cpu usage values that server caches atmost.
    cpu_stats_interval: Time after which server calculates its total cpu
    usage.

    Note: cpu stats gathering is a TODO, so  not functional as of now.

kill <pid>

     <pid> process id of the document to kill. All sessions of document would be
     killed. There is no way yet to kill individual sessions.

admin -> client
===============

Commands marked with [*] are notifications that are delivered only if client is
subscribed to these commands using `subscribe` (see client->admin
section). Others are just response messages to some client command.

[*] adddoc <pid> <filename> <viewid> <memory consumed>

    <pid> process id hosting the document
    <filename> URL encoded name of the file
    <viewid> string identifying the view of this document
    <memory consumed> RSS of <pid> in kilobytes

[*] rmdoc <pid> <viewid>

    <pid> process id hosting the document
    <viewid> view which was closed

[*] mem_stats <memory consumed>

    <memory consumed> in kilobytes sent from admin -> client after every
    mem_stats_interval (see `set` command for list of settings)

[*] propchange <pid> <property> <new-value>

    Notifies of a property change on a pid's property. Properties can
    include:
       "mem" <memory consumed> - in kilobytes of the process.

[*] resetidle <pid>

    <pid> process id hosting the document
    reset the idle time counter for the document

InvalidAuthToken

    This is sent when invalid auth token is provided in 'auth' command. See
    above.

NotAuthenticated

    When client sends an admin command that requires authentication.

documents <pid> <filename> <number of views> <memory consumed> <elapsed time> <idle time>
<pid> <filename> ....
...

    <elapsed time> is in seconds since the first view of the document was opened
    <idle time> is in seconds since some user did something in his view of the document (even just moving
        the insertion cursor)
    <number of views> Number of users/views opening this(<pid>) document
    Other parameters are same as mentioned in `adddoc`

    Each set document attributes is separated by a newline.

total_mem <memory>

    <memory> in kilobytes

active_docs_count <count>

active_users_count <count>

settings <setting1=value1> <setting2=value2> ...

    Current value of each configurable setting.

mem_stats <comma separated list of memory consumed values>

     The length of the list is equal to the value of setting
     mem_stats_size`

loolserver <JSON string>

    The returned JSON string contains information in the following format:
    {Version: <>, Hash: <>}

    Eg: {"Version": "master..",
         "Hash": "4897710"}

lokitversion <JSON string>

    JSON string contains version information in format:
    {ProductName: <>, ProductVersion: <>, ProductExtension: <>, BuildId: <>}

    Eg: {"ProductName": "LibreOffice",
         "ProductVersion": "5.3",
         "ProductExtension": ".0.0.alpha0",
         "BuildId": "<full 40 char git hash>"}
