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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift open source project
//
// Copyright (c) 2014-2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
fileprivate enum SnippetVisibility {
case shown
case hidden
}
fileprivate extension StringProtocol {
/// If the string is a line comment, attempt to parse
/// a ``SnippetVisibility`` with `mark: show` or `mark: hide`.
var parsedVisibilityMark: SnippetVisibility? {
guard var comment = parsedLineCommentText else {
return nil
}
comment = comment.drop { $0.isWhitespace }
if comment.lowercased().starts(with: "mark: show") {
return SnippetVisibility.shown
} else if comment.lowercased().starts(with: "mark: hide") {
return SnippetVisibility.hidden
} else {
return nil
}
}
/// If the string is a line comment starting with `"//"`, return the
/// contents with the comment marker stripped.
var parsedLineCommentText: Self.SubSequence? {
var trimmed = self.drop { $0.isWhitespace }
guard trimmed.starts(with: "//") else {
return nil
}
trimmed.removeFirst(2)
return trimmed
}
var isEmptyOrWhiteSpace: Bool {
return self.isEmpty || self.allSatisfy { $0.isWhitespace }
}
}
fileprivate extension String {
mutating func removeLeadingAndTrailingNewlines() {
while self.starts(with: "\n") {
self.removeFirst(1)
}
while self.suffix(1) == "\n" {
self.removeLast(1)
}
}
/// Returns a re-indented string with the most indentation removed
/// without changing the relative indentation between lines. This is
/// useful for re-indenting some inner part of a block of nested code.
mutating func trimExtraIndentation() {
var lines = self.split(separator: "\n", maxSplits: Int.max,
omittingEmptySubsequences: false)
lines = Array(lines
.drop(while: { $0.isEmptyOrWhiteSpace })
.reversed()
.drop(while: { $0.isEmptyOrWhiteSpace })
.reversed())
let minimumIndentation = lines.map {
guard !$0.isEmpty else {
return Int.max
}
return $0.prefix { $0 == " " }.count
}.min() ?? 0
guard minimumIndentation > 0 else {
return
}
self = lines.map { $0.dropFirst(minimumIndentation) }
.joined(separator: "\n")
}
}
/// Extracts a ``Snippet`` structure from Swift source code.
///
/// - todo: In order to support different styles of comments, it might be
/// better to adopt SwiftSyntax if possible in the future.
struct PlainTextSnippetExtractor {
var source: String
var explanation = ""
var presentationCode = ""
private var currentVisibility = SnippetVisibility.shown
init(source: String) {
self.source = source
let lines = source.split(separator: "\n", omittingEmptySubsequences: false)
var lastExplanationLine = "..."
var lastPresentationCodeLine = "..."
for line in lines {
if let visibility = line.parsedVisibilityMark {
self.currentVisibility = visibility
continue
}
guard case .shown = currentVisibility else {
continue
}
if var comment = line.parsedLineCommentText,
comment.starts(with: "!") {
comment.removeFirst(1)
comment = comment.drop { $0.isWhitespace }
if lastExplanationLine.isEmptyOrWhiteSpace && comment.isEmptyOrWhiteSpace {
continue
}
print(comment, to: &explanation)
lastExplanationLine = String(comment)
} else {
if lastPresentationCodeLine.isEmptyOrWhiteSpace && line.isEmptyOrWhiteSpace {
continue
}
print(line, to: &presentationCode)
lastPresentationCodeLine = String(line)
}
}
self.explanation
.removeLeadingAndTrailingNewlines()
self.presentationCode
.removeLeadingAndTrailingNewlines()
self.presentationCode
.trimExtraIndentation()
}
}
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