aboutsummaryrefslogtreecommitdiffstats
path: root/util/promise.lua
blob: ea30898c25316f241acc35d808b8e06a0db99258 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
local promise_methods = {};
local promise_mt = { __name = "promise", __index = promise_methods };

local xpcall = require "util.xpcall".xpcall;
local unpack = table.unpack or unpack; --luacheck: ignore 113

function promise_mt:__tostring()
	return  "promise (" .. (self._state or "invalid") .. ")";
end

local function is_promise(o)
	local mt = getmetatable(o);
	return mt == promise_mt;
end

local function wrap_handler(f, resolve, reject, default)
	if not f then
		return default;
	end
	return function (param)
		local ok, ret = xpcall(f, debug.traceback, param);
		if ok then
			resolve(ret);
		else
			reject(ret);
		end
		return true;
	end;
end

local function next_pending(self, on_fulfilled, on_rejected, resolve, reject)
	table.insert(self._pending_on_fulfilled, wrap_handler(on_fulfilled, resolve, reject, resolve));
	table.insert(self._pending_on_rejected, wrap_handler(on_rejected, resolve, reject, reject));
end

local function next_fulfilled(promise, on_fulfilled, on_rejected, resolve, reject) -- luacheck: ignore 212/on_rejected
	wrap_handler(on_fulfilled, resolve, reject, resolve)(promise.value);
end

local function next_rejected(promise, on_fulfilled, on_rejected, resolve, reject) -- luacheck: ignore 212/on_fulfilled
	wrap_handler(on_rejected, resolve, reject, reject)(promise.reason);
end

local function promise_settle(promise, new_state, new_next, cbs, value)
	if promise._state ~= "pending" then
		return;
	end
	promise._state = new_state;
	promise._next = new_next;
	for _, cb in ipairs(cbs) do
		cb(value);
	end
	-- No need to keep references to callbacks
	promise._pending_on_fulfilled = nil;
	promise._pending_on_rejected = nil;
	return true;
end

local function new_resolve_functions(p)
	local resolved = false;
	local function _resolve(v)
		if resolved then return; end
		resolved = true;
		if is_promise(v) then
			v:next(new_resolve_functions(p));
		elseif promise_settle(p, "fulfilled", next_fulfilled, p._pending_on_fulfilled, v) then
			p.value = v;
		end

	end
	local function _reject(e)
		if resolved then return; end
		resolved = true;
		if promise_settle(p, "rejected", next_rejected, p._pending_on_rejected, e) then
			p.reason = e;
		end
	end
	return _resolve, _reject;
end

local function new(f)
	local p = setmetatable({ _state = "pending", _next = next_pending, _pending_on_fulfilled = {}, _pending_on_rejected = {} }, promise_mt);
	if f then
		local resolve, reject = new_resolve_functions(p);
		local ok, ret = xpcall(f, debug.traceback, resolve, reject);
		if not ok and p._state == "pending" then
			reject(ret);
		end
	end
	return p;
end

local function all(promises)
	return new(function (resolve, reject)
		local settled, results, loop_finished = 0, {}, false;
		local total = 0;
		for k, v in pairs(promises) do
			if is_promise(v) then
				total = total + 1;
				v:next(function (value)
					results[k] = value;
					settled = settled + 1;
					if settled == total and loop_finished then
						resolve(results);
					end
				end, reject);
			else
				results[k] = v;
			end
		end
		loop_finished = true;
		if settled == total then
			resolve(results);
		end
	end);
end

local function all_settled(promises)
	return new(function (resolve)
		local settled, results, loop_finished = 0, {}, false;
		local total = 0;
		for k, v in pairs(promises) do
			if is_promise(v) then
				total = total + 1;
				v:next(function (value)
					results[k] = { status = "fulfilled", value = value };
					settled = settled + 1;
					if settled == total and loop_finished then
						resolve(results);
					end
				end, function (e)
					results[k] = { status = "rejected", reason = e };
					settled = settled + 1;
					if settled == total and loop_finished then
						resolve(results);
					end
				end);
			else
				results[k] = v;
			end
		end
		loop_finished = true;
		if settled == total then
			resolve(results);
		end
	end);
end

local function join(handler, ...)
	local promises, n = { ... }, select("#", ...);
	return all(promises):next(function (results)
		return handler(unpack(results, 1, n));
	end);
end

local function race(promises)
	return new(function (resolve, reject)
		for i = 1, #promises do
			promises[i]:next(resolve, reject);
		end
	end);
end

local function resolve(v)
	return new(function (_resolve)
		_resolve(v);
	end);
end

local function reject(v)
	return new(function (_, _reject)
		_reject(v);
	end);
end

local function try(f)
	return resolve():next(function () return f(); end);
end

function promise_methods:next(on_fulfilled, on_rejected)
	return new(function (resolve, reject) --luacheck: ignore 431/resolve 431/reject
		self:_next(on_fulfilled, on_rejected, resolve, reject);
	end);
end

function promise_methods:catch(on_rejected)
	return self:next(nil, on_rejected);
end

function promise_methods:finally(on_finally)
	local function _on_finally(value) on_finally(); return value; end
	local function _on_catch_finally(err) on_finally(); return reject(err); end
	return self:next(_on_finally, _on_catch_finally);
end

return {
	new = new;
	resolve = resolve;
	join = join;
	reject = reject;
	all = all;
	all_settled = all_settled;
	race = race;
	try = try;
	is_promise = is_promise;
}