mirror of
https://github.com/github/semantic.git
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169 lines
3.9 KiB
Swift
169 lines
3.9 KiB
Swift
/// A patch to some part of a `Syntax` tree.
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public enum Patch<A>: CustomDebugStringConvertible {
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case Replace(A, A)
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case Insert(A)
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case Delete(A)
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public var state: (before: A?, after: A?) {
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switch self {
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case let .Replace(a, b):
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return (a, b)
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case let .Insert(b):
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return (nil, b)
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case let .Delete(a):
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return (a, nil)
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}
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}
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public var inverse: Patch {
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switch self {
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case let .Replace(a, b):
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return .Replace(b, a)
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case let .Insert(b):
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return .Delete(b)
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case let .Delete(a):
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return .Insert(a)
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}
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}
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// MARK: CustomDebugStringConvertible
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public var debugDescription: String {
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switch self {
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case let .Replace(a, b):
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return ".Replace(\(String(reflecting: a)), \(String(reflecting: b)))"
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case let .Insert(b):
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return ".Insert(\(String(reflecting: b)))"
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case let .Delete(a):
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return ".Delete(\(String(reflecting: a)))"
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}
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}
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}
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// MARK: - Functor
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extension Patch {
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public func map<B>(@noescape transform: A throws -> B) rethrows -> Patch<B> {
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switch self {
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case let .Replace(a, b):
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return try .Replace(transform(a), transform(b))
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case let .Delete(a):
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return try .Delete(transform(a))
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case let .Insert(b):
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return try .Insert(transform(b))
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}
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}
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}
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// MARK: - Equality
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extension Patch {
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public static func equals(param: (A, A) -> Bool)(_ left: Patch, _ right: Patch) -> Bool {
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return Optional.equals(param)(left.state.before, right.state.before)
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&& Optional.equals(param)(left.state.after, right.state.after)
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}
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}
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// MARK: - Cost calculations
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extension Patch {
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/// Returns a function which computes the size of a `patch` as the sum of the sizes of its terms, as computed by `size`.
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public static func sum(@noescape size: A throws -> Int)(_ patch: Patch) rethrows -> Int {
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return try (patch.state.before.map(size) ?? 0) + (patch.state.after.map(size) ?? 0)
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}
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/// Returns a function which computes the size of a `patch` as the absolute difference of the sizes of its terms, as computed by `size`.
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public static func difference(@noescape size: A throws -> Int)(_ patch: Patch) rethrows -> Int {
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return try abs((patch.state.before.map(size) ?? 0) - (patch.state.after.map(size) ?? 0))
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}
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}
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extension Patch where A: TermType {
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/// Computes the size of a `patch` as the sum of the sizes of its terms.
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public static func sum(patch: Patch) -> Int {
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return sum { $0.size } (patch)
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}
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/// Computes the size of a `patch` as the absolute difference of the sizes of its terms.
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public static func difference(patch: Patch) -> Int {
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return difference { $0.size } (patch)
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}
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}
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// MARK: - JSON
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extension Patch {
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public func JSON(ifLeaf: A -> Doubt.JSON) -> Doubt.JSON {
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switch self {
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case let .Replace(a, b):
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return [
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"replace": [
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"before": ifLeaf(a),
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"after": ifLeaf(b),
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]
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]
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case let .Insert(b):
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return [
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"insert": ifLeaf(b),
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]
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case let .Delete(a):
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return [
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"delete": ifLeaf(a)
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]
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}
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}
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}
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extension Patch where A: CustomJSONConvertible {
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public var JSON: Doubt.JSON {
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return JSON { $0.JSON }
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}
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}
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// MARK: - PatchType
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/// A hack to enable constrained extensions on `Free<Leaf, Annotation, Patch<Term: CofreeType where Term.Leaf == Leaf, Term.Annotation == Annotation>`.
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public protocol PatchType {
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typealias Element
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var state: (before: Element?, after: Element?) { get }
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var inverse: Self { get }
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init(replacing before: Element, with after: Element)
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init(deleting before: Element)
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init(inserting after: Element)
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}
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extension Patch: PatchType {
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public init(replacing before: A, with after: A) {
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self = .Replace(before, after)
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}
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public init(deleting before: A) {
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self = .Delete(before)
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}
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public init(inserting after: A) {
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self = .Insert(after)
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}
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}
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extension PatchType where Element: CofreeType, Element.Annotation == Range<String.Index> {
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public func JSON(a a: String, b: String) -> Doubt.JSON {
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return [
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"before": state.before.map { $0.JSON(a) } ?? nil,
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"after": state.after.map { $0.JSON(b) } ?? nil,
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]
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}
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}
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