From cc437b8cd450e142261485ab88589e91ec78da41 Mon Sep 17 00:00:00 2001
From: Koitharu <nvasya95@gmail.com>
Date: Fri, 21 Mar 2025 13:13:58 +0200
Subject: [PATCH] [ExHentai] Pages preview support

---
 .../parsers/site/all/ExHentaiParser.kt        | 35 ++++++++++++-
 .../kotatsu/parsers/util/CSSBackground.kt     | 52 +++++++++++++++++++
 .../koitharu/kotatsu/parsers/util/Jsoup.kt    |  3 ++
 3 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 src/main/kotlin/org/koitharu/kotatsu/parsers/util/CSSBackground.kt

diff --git a/src/main/kotlin/org/koitharu/kotatsu/parsers/site/all/ExHentaiParser.kt b/src/main/kotlin/org/koitharu/kotatsu/parsers/site/all/ExHentaiParser.kt
index af6f048f..06dc2a9b 100644
--- a/src/main/kotlin/org/koitharu/kotatsu/parsers/site/all/ExHentaiParser.kt
+++ b/src/main/kotlin/org/koitharu/kotatsu/parsers/site/all/ExHentaiParser.kt
@@ -13,6 +13,7 @@ import org.jsoup.nodes.Element
 import org.koitharu.kotatsu.parsers.MangaLoaderContext
 import org.koitharu.kotatsu.parsers.MangaParserAuthProvider
 import org.koitharu.kotatsu.parsers.MangaSourceParser
+import org.koitharu.kotatsu.parsers.bitmap.Rect
 import org.koitharu.kotatsu.parsers.config.ConfigKey
 import org.koitharu.kotatsu.parsers.core.LegacyPagedMangaParser
 import org.koitharu.kotatsu.parsers.exception.AuthRequiredException
@@ -258,7 +259,7 @@ internal class ExHentaiParser(
 			MangaPage(
 				id = generateUid(url),
 				url = url,
-				preview = null,
+				preview = a.children().firstOrNull()?.extractPreview(),
 				source = source,
 			)
 		}
@@ -318,6 +319,22 @@ internal class ExHentaiParser(
 				)
 			}
 		}
+		val imageRect = response.request.url.fragment?.split(',')
+		if (imageRect != null && imageRect.size == 4) {
+			// rect: top,left,right,bottom
+			return context.redrawImageResponse(response) { bitmap ->
+				val srcRect = Rect(
+					left = imageRect[0].toInt(),
+					top = imageRect[1].toInt(),
+					right = imageRect[2].toInt(),
+					bottom = imageRect[3].toInt(),
+				)
+				val dstRect = Rect(0, 0, srcRect.width, srcRect.height)
+				val result = context.createBitmap(dstRect.width, dstRect.height)
+				result.drawBitmap(bitmap, srcRect, dstRect)
+				result
+			}
+		}
 		return response
 	}
 
@@ -394,6 +411,22 @@ internal class ExHentaiParser(
 		return result
 	}
 
+	private fun Element.extractPreview(): String? {
+		val bg = backgroundOrNull() ?: return null
+		return buildString {
+			append(bg.url)
+			append('#')
+			// rect: left,top,right,bottom
+			append(bg.left)
+			append(',')
+			append(bg.top)
+			append(',')
+			append(bg.right)
+			append(',')
+			append(bg.bottom)
+		}
+	}
+
 	private fun getNextTimestamp(root: Element): Long {
 		return root.getElementById("unext")
 			?.attrAsAbsoluteUrlOrNull("href")
diff --git a/src/main/kotlin/org/koitharu/kotatsu/parsers/util/CSSBackground.kt b/src/main/kotlin/org/koitharu/kotatsu/parsers/util/CSSBackground.kt
new file mode 100644
index 00000000..ecbf8cbf
--- /dev/null
+++ b/src/main/kotlin/org/koitharu/kotatsu/parsers/util/CSSBackground.kt
@@ -0,0 +1,52 @@
+package org.koitharu.kotatsu.core.parser
+
+import org.jsoup.nodes.Element
+import org.koitharu.kotatsu.parsers.util.attrOrNull
+import org.koitharu.kotatsu.parsers.util.nullIfEmpty
+import org.koitharu.kotatsu.parsers.util.splitByWhitespace
+
+/**
+ * Utility class for parsing the `background` property of css
+ */
+public class CSSBackground private constructor(
+	public val url: String,
+	public val left: Int,
+	public val top: Int,
+	public val width: Int,
+	public val height: Int,
+) {
+
+	public val right: Int
+		get() = left + width
+
+	public val bottom: Int
+		get() = top + height
+
+	internal companion object {
+
+		fun parse(element: Element): CSSBackground? {
+			val style = element.attrOrNull("style") ?: return null
+			val attrs = style.split(';').associate {
+				val trimmed = it.trim()
+				trimmed.substringBefore(':') to trimmed.substringAfter(':', "")
+			}
+			val width = attrs["width"]?.toPx() ?: return null
+			val height = attrs["height"]?.toPx() ?: return null
+			val bg = attrs["background"]?.substringAfter("url")?.splitByWhitespace() ?: return null
+			val url = bg.firstOrNull()?.removeSurrounding("(", ")")?.nullIfEmpty() ?: return null
+			val x = bg.getOrNull(1)?.toPx() ?: 0
+			val y = bg.getOrNull(2)?.toPx() ?: 0
+			return CSSBackground(
+				url = url,
+				left = -x,
+				top = y,
+				width = width,
+				height = height,
+			)
+		}
+
+		private fun String.toPx(): Int? {
+			return removeSuffix("px").toIntOrNull()
+		}
+	}
+}
diff --git a/src/main/kotlin/org/koitharu/kotatsu/parsers/util/Jsoup.kt b/src/main/kotlin/org/koitharu/kotatsu/parsers/util/Jsoup.kt
index 47f38e1b..5e9d39ac 100644
--- a/src/main/kotlin/org/koitharu/kotatsu/parsers/util/Jsoup.kt
+++ b/src/main/kotlin/org/koitharu/kotatsu/parsers/util/Jsoup.kt
@@ -7,6 +7,7 @@ import org.jsoup.nodes.Element
 import org.jsoup.select.Elements
 import org.jsoup.select.QueryParser
 import org.jsoup.select.Selector
+import org.koitharu.kotatsu.core.parser.CSSBackground
 import org.koitharu.kotatsu.parsers.InternalParsersApi
 import org.koitharu.kotatsu.parsers.exception.ParseException
 import kotlin.contracts.contract
@@ -189,6 +190,8 @@ public fun Element.requireSrc(): String = parseNotNull(src()) {
 	"Image src not found"
 }
 
+public fun Element.backgroundOrNull(): CSSBackground? = CSSBackground.parse(this)
+
 public fun Element.metaValue(itemprop: String): String? = getElementsByAttributeValue("itemprop", itemprop)
 	.firstNotNullOfOrNull { element ->
 		element.attrOrNull("content")