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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
struct HandWrittenParticipant: Participant {
static var name: String { "HandWritten" }
static func graphemeBreakProperty() throws -> (String) -> GraphemeBreakEntry? {
graphemeBreakPropertyData(forLine:)
}
}
// Try to parse a Unicode scalar off the input
private func parseScalar(_ str: inout Substring) -> Unicode.Scalar? {
let val = str.eat(while: { $0.isHexDigit })
guard !val.isEmpty else { return nil }
// Subtle potential bug: if this init fails, we need to restore
// str.startIndex. Because of how this is currently called, the bug wont
// manifest now, but could if the call site is changed.
return Unicode.Scalar(hex: val)
}
// Useful for testing the testing framework
private var forceFailure: Bool { false }
private func graphemeBreakPropertyData(
forLine line: String
) -> GraphemeBreakEntry? {
var line = line[...]
guard let lower = parseScalar(&line) else {
// Comment or whitespace line
return nil
}
let upper: Unicode.Scalar
if line.peek(".") {
guard !line.eat(exactly: "..").isEmpty else {
fatalError("Parse error")
}
guard let s = parseScalar(&line) else {
fatalError("Parse error")
}
upper = s
} else {
upper = lower
}
line.eat(while: { !$0.isLetter })
let name = line.eat(while: { $0.isLetter || $0 == "_" })
guard let prop = Unicode.GraphemeBreakProperty(name) else {
return nil
}
// For testing our framework
if forceFailure, lower == Unicode.Scalar(0x07FD) {
return nil
}
return GraphemeBreakEntry(lower ... upper, prop)
}
//
// MARK: Eat Convenience Overloads
//
extension Collection where SubSequence == Self {
// TODO: optionality of return? Probably a good idea to signal if something happened...
// TODO: worth having?
@discardableResult
internal mutating func eat() -> Element? {
self.eat(count: 1).first
}
@discardableResult
internal mutating func eat(count n: Int = 0) -> SubSequence {
let idx = self.index(self.startIndex, offsetBy: n, limitedBy: self.endIndex) ?? self.endIndex
return self.eat(upTo: idx)
}
@discardableResult
internal mutating func eat(one predicate: (Element) -> Bool) -> Element? {
guard let elt = self.first, predicate(elt) else { return nil }
return eat()
}
}
extension Collection where SubSequence == Self, Element: Equatable {
@discardableResult
internal mutating func eat(one e: Element) -> Element? {
self.eat(one: { (other: Element) in other == e })
}
@discardableResult
internal mutating func eat(many e: Element) -> SubSequence {
self.eat(while: { (other: Element) in other == e })
}
internal func peek(_ e: Element) -> Bool {
self.first == e
}
@discardableResult
internal mutating func eat<S: Sequence>(exactly s: S) -> SubSequence where S.Element == Element {
var idx = startIndex
for e in s {
guard idx < endIndex, e == self[idx] else {
idx = startIndex
break
}
formIndex(after: &idx)
}
return eat(upTo: idx)
}
}
extension Collection where SubSequence == Self, Element: Hashable {
@discardableResult
internal mutating func eat(oneIn s: Set<Element>) -> Element? {
self.eat(one: { s.contains($0) })
}
@discardableResult
internal mutating func eat(whileIn s: Set<Element>) -> SubSequence {
self.eat(while: { s.contains($0) })
}
}
extension Collection where SubSequence == Self {
@discardableResult
internal mutating func eat(upTo idx: Index) -> SubSequence {
defer { self = self[idx...] }
return self[..<idx]
}
@discardableResult
internal mutating func eat(
while predicate: (Element) -> Bool
) -> SubSequence {
eat(upTo: self.firstIndex(where: { !predicate($0) }) ?? endIndex)
}
}
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