-- Build a list of valid configuration values up for debug messages.

local defaultConfigKeys = {}
for key in pairs(defaultConfig) do
	table.insert(defaultConfigKeys, key)
end

local Config = {}

function Config.new()
	local self = {}

	self._currentConfig = setmetatable({}, {
		__index = function(_, key)
			local message = (
				"Invalid global configuration key %q. Valid configuration keys are: %s"
			):format(
				tostring(key),
				table.concat(defaultConfigKeys, ", ")
			)

			error(message, 3)
		end
	})

	-- We manually bind these methods here so that the Config's methods can be
	-- used without passing in self, since they eventually get exposed on the
	-- root Roact object.
	self.set = function(...)
		return Config.set(self, ...)
	end

	self.get = function(...)
		return Config.get(self, ...)
	end

	self.scoped = function(...)
		return Config.scoped(self, ...)
	end

	self.set(defaultConfig)

	return self
end

function Config:set(configValues)
	-- Validate values without changing any configuration.
	-- We only want to apply this configuration if it's valid!
	for key, value in pairs(configValues) do
		if defaultConfig[key] == nil then
			local message = (
				"Invalid global configuration key %q (type %s). Valid configuration keys are: %s"
			):format(
				tostring(key),
				typeof(key),
				table.concat(defaultConfigKeys, ", ")
			)

			error(message, 3)
		end

		-- Right now, all configuration values must be boolean.
		if typeof(value) ~= "boolean" then
			local message = (
				"Invalid value %q (type %s) for global configuration key %q. Valid values are: true, false"
			):format(
				tostring(value),
				typeof(value),
				tostring(key)
			)

			error(message, 3)
		end

		self._currentConfig[key] = value
	end
end

function Config:get()
	return self._currentConfig
end

function Config:scoped(configValues, callback)
	local previousValues = {}
	for key, value in pairs(self._currentConfig) do
		previousValues[key] = value
	end

	self.set(configValues)

	local success, result = pcall(callback)

	self.set(previousValues)

	assert(success, result)
end

return Config
