local Observable = require "rx.observable"
local util = require "rx.util"

--- Returns an Observable that buffers values from the original and produces them as multiple
-- values.
-- @arg {number} size - The size of the buffer.
function Observable:buffer(size)
    if not size or type(size) ~= "number" then
        error("Expected a number")
    end

    return Observable.create(function(observer)
        local buffer = {}

        local function emit()
            if #buffer > 0 then
                observer:onNext(util.unpack(buffer))
                buffer = {}
            end
        end

        local function onNext(...)
            local values = {...}
            for i = 1, #values do
                table.insert(buffer, values[i])
                if #buffer >= size then
                    emit()
                end
            end
        end

        local function onError(message)
            emit()
            return observer:onError(message)
        end

        local function onCompleted()
            emit()
            return observer:onCompleted()
        end

        return self:subscribe(onNext, onError, onCompleted)
    end)
end