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/*
This source file is part of the Swift.org open source project
Copyright (c) 2021-2023 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
See https://swift.org/CONTRIBUTORS.txt for Swift project authors
*/
import Foundation
/**
A utility type that computes highlighted lines for diffs between ``Code``
elements in a ``TutorialSection``'s ``Step``s.
The logic is tricky, so here's a diagram of what is going on here:
```
Start
|
N -- < `previousFile`? > ----------------------- Y
| |
N -- < Previous `Code`? > -- Y N -- < `reset`? > -- Y
| | | |
[ ] N -- < `name` match? > -- Y Compare [ ]
| |
[ ] N -- < `reset`? > -- Y
| |
Compare [ ]
```
*/
public struct LineHighlighter {
/**
A local utility type to hold incremental results.
*/
private struct IncrementalResult {
/// The previous ``Code`` element to compare.
/// If this is the first ``Step``'s ``Code``, this will be `nil`.
let previousCode: Code?
/// The highlight results accumulated so far.
let results: [Result]
init(previousCode: Code? = nil, results: [Result] = []) {
self.previousCode = previousCode
self.results = results
}
}
/**
The final resulting highlights for a given file.
*/
struct Result {
/// The file to be highlighted (or not).
let file: ResourceReference
/// The highlights to apply when displaying this file.
let highlights: [Highlight]
}
/**
A single line's highlight.
*/
public struct Highlight: Codable, Equatable {
/// The line to highlight.
public let line: Int
/// If non-`nil`, the column to start the highlight.
public let start: Int?
/// If non-`nil`, the length of the highlight in columns.
public let length: Int?
/// Creates a new highlight for a single line.
///
/// - Parameters:
/// - line: The line to highlight.
/// - start: The column in which to start the highlight.
/// - length: The character length of the highlight.
public init(line: Int, start: Int? = nil, length: Int? = nil) {
self.line = line
self.start = start
self.length = length
}
}
/// The ``DocumentationContext`` to use for loading file lines.
private let context: DocumentationContext
/// The ``TutorialSection`` whose ``Steps`` will be analyzed for their code highlights.
private let tutorialSection: TutorialSection
/// The topic reference of the tutorial whose section will be analyzed for their code highlights.
private let tutorialReference: ResolvedTopicReference
init(context: DocumentationContext, tutorialSection: TutorialSection, tutorialReference: ResolvedTopicReference) {
self.context = context
self.tutorialSection = tutorialSection
self.tutorialReference = tutorialReference
}
/// The lines in the `resource` file.
private func lines(of resource: ResourceReference) -> [String]? {
let fileContent: String?
// Check if the file is a local asset that can be read directly from the context
if let fileData = try? context.resource(with: resource) {
fileContent = String(data: fileData, encoding: .utf8)
}
// Check if the file needs to be resolved to read its content
else if let asset = context.resolveAsset(named: resource.path, in: tutorialReference) {
fileContent = try? String(contentsOf: asset.data(bestMatching: DataTraitCollection()).url, encoding: .utf8)
}
// Couldn't find the file reference's content
else {
fileContent = nil
}
return fileContent?.splitByNewlines
}
/// Returns the line highlights between two files.
private func lineHighlights(old: ResourceReference, new: ResourceReference) -> Result {
// Retrieve the contents of the current file and the file we're comparing against.
guard let oldLines = lines(of: old), let newLines = lines(of: new) else {
return Result(file: new, highlights: [])
}
let diff = newLines.difference(from: oldLines)
// Convert the insertion offsets to `Highlight` values.
let highlights = diff.insertions.compactMap { insertion -> Highlight? in
guard case .insert(let offset, _, _) = insertion else { return nil }
// Use 1-based indexing for line numbers.
// TODO: Collect intra-line diffs.
return Highlight(line: offset + 1)
}
return Result(file: new, highlights: highlights)
}
/// Returns the line highlights between two ``Code`` elements.
private func lineHighlights(old: Code?, new: Code) -> Result {
if let previousFileOverride = new.previousFileReference {
guard !new.shouldResetDiff else {
return Result(file: new.fileReference, highlights: [])
}
return lineHighlights(old: previousFileOverride, new: new.fileReference)
}
guard let old,
old.fileName == new.fileName,
!new.shouldResetDiff else {
return Result(file: new.fileReference, highlights: [])
}
return lineHighlights(old: old.fileReference, new: new.fileReference)
}
/// The highlights to apply for the given ``TutorialSection``.
var highlights: [Result] {
return tutorialSection.stepsContent?.steps
.compactMap { $0.code }
.reduce(IncrementalResult(), { (incrementalResult, newCode) -> IncrementalResult in
let result = lineHighlights(old: incrementalResult.previousCode, new: newCode)
return IncrementalResult(previousCode: newCode, results: incrementalResult.results + [result])
}).results ?? []
}
}
|
