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

--- Returns a new Observable that produces a single boolean value representing whether or not the
-- specified value was produced by the original.
-- @arg {*} value - The value to search for.  == is used for equality testing.
-- @returns {Observable}
function Observable:contains(value)
    return Observable.create(function(observer)
        local subscription

        local function onNext(...)
            local args = util.pack(...)

            if #args == 0 and value == nil then
                observer:onNext(true)
                if subscription then
                    subscription:unsubscribe()
                end
                return observer:onCompleted()
            end

            for i = 1, #args do
                if args[i] == value then
                    observer:onNext(true)
                    if subscription then
                        subscription:unsubscribe()
                    end
                    return observer:onCompleted()
                end
            end
        end

        local function onError(e)
            return observer:onError(e)
        end

        local function onCompleted()
            observer:onNext(false)
            return observer:onCompleted()
        end

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