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package org.terst.feedreader.data
import org.terst.feedreader.readability.ConsentNotice
import org.terst.feedreader.readability.ArticleLitter
import org.terst.feedreader.readability.UnrenderedTex
/** What a cached `articles.extractedContent` value turned out to be worth. */
data class CachedExtraction(
/** The content to show, or null if there is nothing usable. */
val content: String?,
/**
* True when a cached consent notice was thrown away. The caller has nothing to
* show and should extract again -- the cache is the reason the article looked
* broken, so dropping it silently would just leave a blank reader.
*/
val discardedConsentNotice: Boolean,
/**
* True when a cached extraction holding raw TeX source was thrown away -- it was
* extracted before extraction knew how to render maths (see [UnrenderedTex]).
*/
val discardedUnrenderedTex: Boolean = false
) {
/**
* True when something was thrown away, whatever it was: there is nothing to show and
* the caller has to extract again.
*/
val discarded: Boolean get() = discardedConsentNotice || discardedUnrenderedTex
}
/**
* Reads a cached extraction, dropping it if it is the site's cookie/consent notice
* rather than the article, or if it is an older extraction whose maths never got
* rendered.
*
* Needed because the extractor's own guard can only keep a bad extraction from
* being written in future. The reported bug ("reader mode just extracts cookie
* disclaimer", with `extractedContent cached: true`) was already on disk: every
* subsequent open read it straight back out, so no amount of fixing the extractor
* would have changed what the user saw. A poisoned row is cleared here rather than
* in a schema migration, so it is repaired whenever the article is next opened --
* including for anything extracted before this check existed.
*
* [clearCache] is passed in rather than taking the DAO so this stays a plain
* decision that can be tested without a database.
*/
suspend fun loadCachedExtraction(
cached: String?,
clearCache: suspend () -> Unit
): CachedExtraction {
val discard = when {
ConsentNotice.looksLikeConsentNotice(cached) ->
CachedExtraction(content = null, discardedConsentNotice = true)
// Same shape of problem, different cause: this one was extracted before extraction
// rendered maths, so it holds the TeX source the page shipped.
UnrenderedTex.looksLikeUnrenderedTex(cached) ->
CachedExtraction(
content = null,
discardedConsentNotice = false,
discardedUnrenderedTex = true
)
else -> null
} ?: return CachedExtraction(
// Recirculation widgets are deliberately not in the `discard` list above. A cached
// article carrying the publisher's promo blocks is a good article with litter in it,
// not a poisoned row: cleaning it in place shows the right thing immediately, where
// discarding it would throw away a usable body and fetch the identical one back.
content = ArticleLitter.strip(cached),
discardedConsentNotice = false
)
clearCache()
return discard
}
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