andros
15eb8acbd0
- FeedCache actor: conditional GET with ETag/Last-Modified, returns 304 hits from cache - PartialFeedFetcher: Range requests for header-only Discover fetches and date-filtered timeline fetches (2 requests instead of 3 per feed) - TimelineFetcher: AsyncStream-based streaming emits posts as each feed arrives instead of waiting for all feeds - TimelineViewModel: consumes stream progressively so posts appear immediately on first feed - Discover uses header-only fetch (16 KB vs full file) - maxConcurrentDownloads raised from 10 to 20
58 lines
2.1 KiB
Swift
58 lines
2.1 KiB
Swift
import Foundation
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/// In-memory store for HTTP conditional GET headers (ETag / Last-Modified).
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///
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/// When `FeedFetcher` receives a successful response it stores the server's
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/// caching headers here. On the next request for the same URL it sends
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/// `If-None-Match` / `If-Modified-Since`; a 304 response lets it return
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/// the cached body without re-downloading or re-parsing.
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///
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/// `FeedCache.shared` is the default singleton. Tests can create isolated
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/// instances (`FeedCache()`) to avoid cross-test pollution.
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public actor FeedCache: Sendable {
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public static let shared = FeedCache()
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private struct Entry {
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var etag: String?
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var lastModified: String?
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var content: String
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}
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private var store: [String: Entry] = [:]
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// MARK: - Write
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/// Stores caching headers and body for `url`.
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/// Does nothing when neither `etag` nor `lastModified` is present
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/// (no usable validator means a conditional GET would always get 200).
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public func record(url: URL, etag: String?, lastModified: String?, content: String) {
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guard etag != nil || lastModified != nil else { return }
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store[url.absoluteString] = Entry(etag: etag, lastModified: lastModified, content: content)
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}
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/// Removes the cache entry for `url`. Call before a forced refresh.
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public func invalidate(_ url: URL) {
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store.removeValue(forKey: url.absoluteString)
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}
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// MARK: - Read
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/// Returns the conditional request headers to include for `url`.
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/// Both values are `nil` when no entry exists.
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public func conditionalHeaders(for url: URL) -> (ifNoneMatch: String?, ifModifiedSince: String?) {
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guard let entry = store[url.absoluteString] else { return (nil, nil) }
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return (entry.etag, entry.lastModified)
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}
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/// Returns the previously cached body for `url`, or `nil` when not cached.
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public func cachedContent(for url: URL) -> String? {
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store[url.absoluteString]?.content
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}
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/// Returns `true` when a cache entry exists for `url`.
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public func has(_ url: URL) -> Bool {
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store[url.absoluteString] != nil
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}
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}
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