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local unpack = unpack or table.unpack
local PromisePrototype = {}
function PromisePrototype:__run_handler(func, ...)
local values = {pcall(func, ...)}
if table.remove(values, 1) then
self:__resolve_raw(unpack(values))
else
self:__reject_raw(values[1])
end
end
function PromisePrototype:__add_child(promise)
if self.state == "resolved" then
promise:__resolve(unpack(self.values))
elseif self.state == "rejected" then
promise:__reject(self.reason)
else
table.insert(self.__children, promise)
end
end
function PromisePrototype:__resolve_raw(...)
self.state = "resolved"
self.values = {...}
self.reason = nil
for _, child in ipairs(self.__children) do
child:resolve(...)
end
end
function PromisePrototype:__reject_raw(reason)
self.state = "rejected"
self.values = nil
self.reason = reason
local any_child = false
for _, child in ipairs(self.__children) do
child:reject(reason)
end
assert(any_child, "Uncaught (in promise): " .. reason)
end
function PromisePrototype:then_(on_resolve, on_reject)
local promise = Promise()
promise.__on_resolve = on_resolve
promise.__on_reject = on_reject
self:__add_child(promise)
return promise
end
function PromisePrototype:catch(func)
local promise = Promise(function() end)
promise.__on_reject = func
self:__add_child(promise)
return promise
end
function PromisePrototype:resolve(...)
assert(self.state == "pending")
if self.__on_resolve then
self:__run_handler(self.__on_resolve, ...)
else
self:__resolve_raw(...)
end
end
function PromisePrototype:reject(reason)
assert(self.state == "pending")
if self.__on_reject then
self:__run_handler(self.__on_reject, reason)
else
self:__reject_raw(reason)
end
end
Promise = setmetatable({}, {
__call = function(_, resolver)
local promise = setmetatable({
state = "pending",
__children = {},
}, {__index = PromisePrototype})
if resolver then
resolver(
function(...)
promise:resolve(...)
end,
function(...)
promise:reject(...)
end
)
end
return promise
end
})
function Promise.resolve(...)
local args = {...}
return Promise(function(resolve)
resolve(unpack(args))
end)
end
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