| // Copyright 2017 The Tulsi Authors. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| /// TODO(b/65199212): Move this back into TulsiParameter once Xcode 8.3 is available. |
| /// Origin of a TulsiParameter, which has precedence: |
| /// (high) explicitly provided (ie argument) <- options (ie config) <- project <- Fallback (low) |
| public enum Source: Int { |
| /// Provided by an argument or flag. Highest precedence. |
| case explicitlyProvided |
| |
| /// Provided by a TulsiOption. |
| case options |
| |
| /// Provided by a Tulsi Project. |
| case project |
| |
| /// default, back up value in cases where a value is needed. Lowest precedence. |
| case fallback |
| |
| /// Returns true if self is higher priority than the other. |
| public func isHigherPriorityThan(_ other: Source) -> Bool { |
| return self.rawValue < other.rawValue; |
| } |
| } |
| |
| /// Struct representing a value that is read in the following precedence: |
| /// (high) explicitly provided (ie argument) <- options (ie config) <- project <- Fallback (low) |
| public struct TulsiParameter<T> { |
| |
| public let value: T |
| public let source: Source |
| |
| init(value: T, source: Source) { |
| self.value = value |
| self.source = source |
| } |
| |
| init?(value: T?, source: Source) { |
| guard let value = value else { return nil } |
| self.init(value: value, source: source) |
| } |
| |
| /// Returns true if self is higher priority than the other. |
| public func isHigherPriorityThan(_ other: TulsiParameter<T>) -> Bool { |
| return self.source.isHigherPriorityThan(other.source) |
| } |
| |
| /// Reduces self with given TulsiParameter, returning the value with the higher priority (or self |
| /// if the priorities are equal). |
| public func reduce(_ other: TulsiParameter<T>?) -> TulsiParameter<T> { |
| if let other = other, other.isHigherPriorityThan(self) { |
| return other |
| } |
| return self |
| } |
| } |