89 lines
2.5 KiB
Swift
89 lines
2.5 KiB
Swift
import Foundation
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import CryptoKit
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final class FileUpdateChecker {
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private static let hashesFileName = "hashes.json"
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private let input: URL
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private var hashesFile: URL {
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input.appendingPathComponent(FileUpdateChecker.hashesFileName)
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}
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/**
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The hashes of all accessed files from the previous run
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The key is the relative path to the file from the source
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*/
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private var previousFiles: [String : Data] = [:]
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/**
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The paths of all files which were accessed, with their new hashes
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This list is used to check if a file was modified, and to write all accessed files back to disk
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*/
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private var accessedFiles: [String : Data] = [:]
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private var source: String {
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"FileUpdateChecker"
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}
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init(input: URL) {
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self.input = input
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guard hashesFile.exists else {
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log.add(info: "No file hashes loaded, regarding all content as new", source: source)
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return
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}
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let data: Data
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do {
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data = try Data(contentsOf: hashesFile)
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} catch {
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log.add(
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warning: "File hashes could not be read, regarding all content as new",
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source: source,
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error: error)
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return
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}
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do {
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self.previousFiles = try JSONDecoder().decode(from: data)
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} catch {
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log.add(
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warning: "File hashes could not be decoded, regarding all content as new",
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source: source,
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error: error)
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return
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}
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}
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func fileHasChanged(at path: String) -> Bool {
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guard let oldHash = previousFiles[path] else {
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// Image wasn't used last time, so treat as new
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return true
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}
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guard let newHash = accessedFiles[path] else {
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// Each image should have been loaded once
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// before using this function
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fatalError()
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}
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return oldHash != newHash
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}
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func didLoad(_ data: Data, at path: String) {
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accessedFiles[path] = SHA256.hash(data: data).data
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}
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func writeDetectedFileChangesToDisk() {
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do {
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let encoder = JSONEncoder()
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encoder.outputFormatting = .prettyPrinted
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let data = try encoder.encode(accessedFiles)
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try data.write(to: hashesFile)
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} catch {
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log.add(warning: "Failed to save file hashes", source: source, error: error)
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}
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}
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}
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