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fetch_status: Convert FetchStatus to an ES6 class. 

Signed-off-by: Anders Kaseorg <anders@zulip.com>
This commit is contained in:
Anders Kaseorg 2020-07-22 16:30:13 -07:00 committed by Tim Abbott
parent a1796325de
commit 9d90ae0e69
3 changed files with 57 additions and 58 deletions
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4
frontend_tests/node_tests/fetch_status.js
View File

@ -6,10 +6,10 @@ set_global("message_scroll", {
show_loading_newer: () => {},
});
let fetch_status = FetchStatus();
let fetch_status = new FetchStatus();
function reset() {
fetch_status = FetchStatus();
fetch_status = new FetchStatus();
}
function can_load_newer() {

109
static/js/fetch_status.js
View File

@ -1,17 +1,23 @@
const FetchStatus = function () {
const self = {};
function max_id_for_messages(messages) {
let max_id = 0;
for (const msg of messages) {
max_id = Math.max(max_id, msg.id);
}
return max_id;
}
class FetchStatus {
// The FetchStatus object tracks tracks the state of a
// message_list_data object, whether rendered in the DOM or not,
// and is the source of truth for whether the message_list_data
// object has the complete history of the view or whether more
// messages should be loaded when scrolling to the top or bottom
// of the message feed.
let loading_older = false;
let loading_newer = false;
let found_oldest = false;
let found_newest = false;
let history_limited = false;
_loading_older = false;
_loading_newer = false;
_found_oldest = false;
_found_newest = false;
_history_limited = false;
// Tracks the highest message ID that we know exist in this view,
// but are not within the contiguous range of messages we have
@ -19,61 +25,53 @@ const FetchStatus = function () {
// condition where a newly sent message races with fetching a
// group of messages that would lead to found_newest being set
// (described in detail below).
let expected_max_message_id = 0;
_expected_max_message_id = 0;
function max_id_for_messages(messages) {
let max_id = 0;
for (const msg of messages) {
max_id = Math.max(max_id, msg.id);
}
return max_id;
}
self.start_older_batch = function (opts) {
loading_older = true;
start_older_batch(opts) {
this._loading_older = true;
if (opts.update_loading_indicator) {
message_scroll.show_loading_older();
}
};
}
self.finish_older_batch = function (opts) {
loading_older = false;
found_oldest = opts.found_oldest;
history_limited = opts.history_limited;
finish_older_batch(opts) {
this._loading_older = false;
this._found_oldest = opts.found_oldest;
this._history_limited = opts.history_limited;
if (opts.update_loading_indicator) {
message_scroll.hide_loading_older();
}
};
}
self.can_load_older_messages = function () {
return !loading_older && !found_oldest;
};
can_load_older_messages() {
return !this._loading_older && !this._found_oldest;
}
self.has_found_oldest = function () {
return found_oldest;
};
has_found_oldest() {
return this._found_oldest;
}
self.history_limited = function () {
return history_limited;
};
history_limited() {
return this._history_limited;
}
self.start_newer_batch = function (opts) {
loading_newer = true;
start_newer_batch(opts) {
this._loading_newer = true;
if (opts.update_loading_indicator) {
message_scroll.show_loading_newer();
}
};
}
self.finish_newer_batch = function (messages, opts) {
finish_newer_batch(messages, opts) {
// Returns true if and only if the caller needs to trigger an
// additional fetch due to the race described below.
const found_max_message_id = max_id_for_messages(messages);
loading_newer = false;
found_newest = opts.found_newest;
this._loading_newer = false;
this._found_newest = opts.found_newest;
if (opts.update_loading_indicator) {
message_scroll.hide_loading_newer();
}
if (found_newest && expected_max_message_id > found_max_message_id) {
if (this._found_newest && this._expected_max_message_id > found_max_message_id) {
// This expected_max_message_id logic is designed to
// resolve a subtle race condition involving newly sent
// messages in a view that does not display the currently
@ -108,30 +106,31 @@ const FetchStatus = function () {
// higher than the highest ID returned in a GET /messages
// response with found_newest=true, we know the above race
// has happened and trigger an additional fetch.
found_newest = false;
this._found_newest = false;
// Resetting our tracked last message id is an important
// circuit-breaker for cases where the message(s) that we
// "know" exist were deleted or moved to another topic.
expected_max_message_id = 0;
this._expected_max_message_id = 0;
return true;
}
return false;
};
}
self.can_load_newer_messages = function () {
return !loading_newer && !found_newest;
};
can_load_newer_messages() {
return !this._loading_newer && !this._found_newest;
}
self.has_found_newest = function () {
return found_newest;
};
has_found_newest() {
return this._found_newest;
}
self.update_expected_max_message_id = function (messages) {
expected_max_message_id = Math.max(expected_max_message_id, max_id_for_messages(messages));
};
return self;
};
update_expected_max_message_id(messages) {
this._expected_max_message_id = Math.max(
this._expected_max_message_id,
max_id_for_messages(messages),
);
}
}
module.exports = FetchStatus;
window.FetchStatus = FetchStatus;

2
static/js/message_list_data.js
View File

@ -19,7 +19,7 @@ class MessageListData {
}
this.filter = filter;
this.fetch_status = FetchStatus();
this.fetch_status = new FetchStatus();
}
all_messages() {