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lrpc/client/web/lrpc.rb

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# LRPCResponseType represents the various types an LRPC
# response can have.
LRPCResponseType = {
Normal: 0,
Error: 1,
Channel: 2,
ChannelDone: 3,
}
# LRPCClient represents a client for the LRPC protocol
# using WebSockets and the JSON codec
class LRPCClient
def initialize(addr)
# Set self variables
@callMap = Map.new()
@enc = TextEncoder.new()
@dec = TextDecoder.new()
# Create connection to lrpc server
@conn = WebSocket.new(addr)
@conn.binaryType = "arraybuffer"
@conn.onmessage = proc do |msg|
# if msg.data is string
if msg.data.instance_of? String
# Set json to msg.data
json = msg.data
else
# Set json to decoded msg.data
json = @dec.decode(msg.data)
end
# Parse JSON string
val = JSON.parse(json)
# Get id from callMap
fns = @callMap.get(val.ID)
# If fns is undefined (key does not exist), and this is
# a normal response, return
return if !fns && val.Type == LRPCResponseType.Normal
case val.Type
when LRPCResponseType.Normal
# If fns is a channel, send the value. Otherwise,
# resolve the promise with the value.
if fns.isChannel
fns.send(val.Return)
else
fns.resolve(val.Return)
end
when LRPCResponseType.Channel
# Get channel ID from response
chID = val.Return
# Create new LRPCChannel
ch = LRPCChannel.new(self, chID)
# Set channel in map
@callMap.set(chID, ch)
# Resolve promise with channel
fns.resolve(ch)
when LRPCResponseType.ChannelDone
# Close and delete channel
fns.close()
@callMap.delete(val.ID)
when LRPCResponseType.Error
# Reject promise with error
fns.reject(val.Error)
end
# Delete item from map unless it is a channel
@callMap.delete(val.ID) unless fns.isChannel
end
end
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# call calls a method on the server with the given
# argument and returns a promise.
def callMethod(rcvr, method, arg)
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return Promise.new do |resolve, reject|
# Get random UUID (this only works with TLS)
id = crypto.randomUUID()
# Add resolve/reject functions to callMap
@callMap.set(id, {
resolve: resolve,
reject: reject,
})
# Encode data as JSON
data = @enc.encode({
Receiver: rcvr,
Method: method,
Arg: arg,
ID: id,
}.to_json())
# Send data to lrpc server
@conn.send(data.buffer)
end
end
end
# LRPCChannel represents a channel used for lrpc.
class LRPCChannel
def initialize(client, id)
# Set self variables
@client = client
@id = id
@closed = false
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# Set function variables to no-ops
@onMessage = proc {|fn|}
@onClose = proc {}
end
# isChannel is defined to allow identifying whether
# an object is a channel.
def isChannel() end
# send sends a value on the channel. This should not
# be called by the consumer of the channel.
def send(val)
return if @closed
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fn = @onMessage
fn(val)
end
# done cancels the context corresponding to the channel
# on the server side and closes the channel.
def done()
return if @closed
@client.callMethod("lrpc", "ChannelDone", @id)
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self.close()
@client._callMap.delete(@id)
end
# onMessage sets the callback to be called whenever a
# message is received. The function should have one parameter
# that will be set to the value received. Subsequent calls
# will overwrite the callback
def onMessage(fn)
@onMessage = fn
end
# onClose sets the callback to be called whenever the client
# is closed. The function should have no parameters.
# Subsequent calls will overwrite the callback
def onClose(fn)
@onClose = fn
end
# close closes the channel. This should not be called by the
# consumer of the channel. Use done() instead.
def close()
fn = @onClose
fn()
@closed = true
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end
end