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Merge pull request #3 from PureSwift/feature/evaluation
Added Predicate evaluation engine
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| // | ||
| // File.swift | ||
| // | ||
| // | ||
| // Created by Alsey Coleman Miller on 4/13/20. | ||
| // | ||
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| import Foundation | ||
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| /// Context for evaluating predicates. | ||
| public struct PredicateContext: Equatable, Hashable { | ||
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| public typealias KeyPath = PredicateKeyPath | ||
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| public var locale: Locale? | ||
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| public var values: [KeyPath: Value] | ||
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| public init(values: [KeyPath: Value], | ||
| locale: Locale? = nil) { | ||
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| self.values = values | ||
| self.locale = locale | ||
| } | ||
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| public subscript(keyPath: KeyPath) -> Value? { | ||
| return values[keyPath] | ||
| } | ||
| } | ||
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| internal extension PredicateContext { | ||
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| func value(for expression: Expression) throws -> Value { | ||
| switch expression { | ||
| case let .value(value): | ||
| return value | ||
| case let .keyPath(keyPath): | ||
| if let value = self[keyPath] { | ||
| return value | ||
| } else { | ||
| // try to find collection | ||
| if let values = collection(for: keyPath) { | ||
| return .collection(values) | ||
| } else { | ||
| throw PredicateError.invalidKeyPath(keyPath) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| private extension PredicateContext { | ||
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| func collection(for keyPath: PredicateKeyPath) -> [Value]? { | ||
| var remainderKeys = [PredicateKeyPath.Key]() | ||
| var keyPath = keyPath | ||
| repeat { | ||
| // try again with smaller keyPath | ||
| defer { | ||
| let lastKey = keyPath.removeLast() | ||
| remainderKeys.append(lastKey) | ||
| } | ||
| let countPath = keyPath.appending(.operator(.count)) | ||
| guard let countValue = self[countPath], | ||
| let count = NSNumber(value: countValue)?.uintValue | ||
| else { continue } | ||
| let values = (0 ..< count) | ||
| .map { keyPath.appending(.index($0)).appending(contentsOf: remainderKeys) } | ||
| .compactMap { self[$0] } | ||
| guard values.count == Int(count) | ||
| else { return nil } | ||
| return values | ||
| } while keyPath.keys.isEmpty == false | ||
| return nil | ||
| } | ||
| } | ||
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| // MARK: - ExpressibleByDictionaryLiteral | ||
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| extension PredicateContext: ExpressibleByDictionaryLiteral { | ||
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| public init(dictionaryLiteral elements: (PredicateKeyPath, Value)...) { | ||
| self.init(values: [PredicateKeyPath: Value](uniqueKeysWithValues: elements)) | ||
| } | ||
| } | ||
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| // MARK: - PredicateEvaluatable | ||
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| extension PredicateContext: PredicateEvaluatable { | ||
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| public func evaluate(with predicate: Predicate) throws -> Bool { | ||
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| switch predicate { | ||
| case let .value(value): | ||
| return value | ||
| case let .comparison(comparison): | ||
| return try evaluate(with: comparison) | ||
| case let .compound(compound): | ||
| return try evaluate(with: compound) | ||
| } | ||
| } | ||
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| internal func evaluate(with predicate: Comparison) throws -> Bool { | ||
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| let lhs = try value(for: predicate.left) | ||
| let rhs = try value(for: predicate.right) | ||
| return try lhs.compare(rhs, operator: predicate.type, modifier: predicate.modifier, options: predicate.options) | ||
| } | ||
| } |
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