book-reader/app/src/main/java/com/aryan/reader/paginatedreader/HtmlParser.kt
Aryan dff236fa7f
feat(epub): overhaul border system to support individual sides and radii (#44)
- Refactored `BlockStyle` to replace unified border/radius fields with explicit properties for all four sides and corners.
- Overhauled `CssParser` to correctly handle CSS border shorthands (`border-bottom`, `border-width`, etc.) and multi-value `border-radius`.
- Implemented `drawCssBorders` custom modifier to render side-specific borders, styles (dashed/dotted), and background clipping.
- Updated `Paginator` measurement logic to calculate block height and splitting points based on individual side widths.
2026-03-08 10:31:07 +05:30

601 lines
No EOL
26 KiB
Kotlin

/*
* Episteme Reader - A native Android document reader.
* Copyright (C) 2026 Episteme
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* mail: epistemereader@gmail.com
*/
package com.aryan.reader.paginatedreader
import android.graphics.BitmapFactory
import android.os.Build
import timber.log.Timber
import androidx.annotation.RequiresApi
import androidx.compose.ui.graphics.isSpecified
import androidx.compose.ui.text.ParagraphStyle
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.Density
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.isSpecified
import org.jsoup.Jsoup
import org.jsoup.nodes.Element
import org.jsoup.nodes.Node
import org.jsoup.nodes.TextNode
import org.jsoup.select.Selector
import java.io.File
import java.net.URLDecoder
import java.nio.file.Paths
private val unsupportedPseudoElementRegex = Regex("::?(before|after|first-letter|first-line|marker|selection)", RegexOption.IGNORE_CASE)
private fun Element.getCfiPath(): String {
val path = mutableListOf<Int>()
var currentNode: Node? = this
while (currentNode != null && (currentNode !is Element || currentNode.tagName() != "body")) {
val parent = currentNode.parent() ?: break
val children = parent.childNodes().filter { node ->
node is Element || (node is TextNode && node.text().trim().isNotEmpty())
}
val nodeIndex = children.indexOf(currentNode)
if (nodeIndex == -1) {
currentNode = parent
continue
}
val cfiIndex = (nodeIndex * 2) + 2
path.add(0, cfiIndex)
currentNode = parent
}
path.add(0, 4)
return "/" + path.joinToString("/")
}
private fun String.capitalizeWords(): String =
split(' ').joinToString(" ") { word ->
if (word.isNotEmpty()) word.replaceFirstChar { it.titlecase() } else ""
}
/**
* The public entry point for converting HTML to a list of [SemanticBlock]s.
* This function sets up a parsing context and delegates the work to a [SemanticHtmlParser] instance.
*/
@RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
fun htmlToSemanticBlocks(
html: String,
cssRules: OptimizedCssRules,
textStyle: TextStyle,
chapterAbsPath: String,
extractionBasePath: String,
density: Density,
fontFamilyMap: Map<String, FontFamily>,
constraints: Constraints,
imageDimensionsCache: Map<String, Pair<Float, Float>> = emptyMap(),
mathSvgCache: Map<String, String> = emptyMap()
): List<SemanticBlock> {
return SemanticHtmlParser(
cssRules,
textStyle,
chapterAbsPath,
extractionBasePath,
density,
fontFamilyMap,
constraints,
imageDimensionsCache,
mathSvgCache
).parse(html)
}
/**
* A stateful parser that holds the context for a single HTML-to-SemanticBlock conversion.
*/
@RequiresApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
private class SemanticHtmlParser(
cssRules: OptimizedCssRules,
private val textStyle: TextStyle,
private val chapterAbsPath: String,
private val extractionBasePath: String,
private val density: Density,
fontFamilyMap: Map<String, FontFamily>,
private val constraints: Constraints,
private val imageDimensionsCache: Map<String, Pair<Float, Float>>,
private val mathSvgCache: Map<String, String>
) {
private val styleCache = mutableMapOf<String, CssStyle>()
private var combinedRules: OptimizedCssRules = cssRules
private val currentFontFamilyMap: MutableMap<String, FontFamily> = fontFamilyMap.toMutableMap()
private var nextBlockIndex = 0
fun parse(html: String): List<SemanticBlock> {
val document = Jsoup.parse(html, chapterAbsPath)
val inlineCssContent = document.head().select("style").joinToString(separator = "\n") { it.data() }
if (inlineCssContent.isNotBlank()) {
Timber.d("Found inline <style> content in $chapterAbsPath. Parsing...")
val inlineParseResult = CssParser.parse(
cssContent = inlineCssContent,
cssPath = chapterAbsPath,
baseFontSizeSp = textStyle.fontSize.value,
density = density.density,
constraints = constraints,
isDarkTheme = false // Semantic parsing is always theme-agnostic
)
if (inlineParseResult.fontFaces.isNotEmpty()) {
val newFonts = loadFontFamilies(inlineParseResult.fontFaces, extractionBasePath)
if (newFonts.isNotEmpty()) {
currentFontFamilyMap.putAll(newFonts)
}
}
combinedRules = combinedRules.merge(inlineParseResult.rules)
}
val body = document.body()
return body.children().flatMap { childElement ->
parseNodeToSemanticBlocks(childElement, getElementStyle(body))
}
}
private fun parseNodeToSemanticBlocks(
element: Element,
inheritedStyle: CssStyle
): List<SemanticBlock> {
val elementOwnStyle = getElementStyle(element)
val finalBlockStyle = elementOwnStyle.blockStyle.copy(
listStyleType = elementOwnStyle.blockStyle.listStyleType ?: inheritedStyle.blockStyle.listStyleType,
listStyleImage = elementOwnStyle.blockStyle.listStyleImage ?: inheritedStyle.blockStyle.listStyleImage
)
val finalStyle = elementOwnStyle.copy(
spanStyle = inheritedStyle.spanStyle.merge(elementOwnStyle.spanStyle),
paragraphStyle = inheritedStyle.paragraphStyle.merge(elementOwnStyle.paragraphStyle),
blockStyle = finalBlockStyle,
fontFamilies = elementOwnStyle.fontFamilies.ifEmpty { inheritedStyle.fontFamilies },
fontSize = if (elementOwnStyle.fontSize.isSpecified) elementOwnStyle.fontSize else inheritedStyle.fontSize,
textTransform = elementOwnStyle.textTransform ?: inheritedStyle.textTransform,
hyphens = elementOwnStyle.hyphens ?: inheritedStyle.hyphens,
fontVariantNumeric = elementOwnStyle.fontVariantNumeric ?: inheritedStyle.fontVariantNumeric,
textEmphasis = elementOwnStyle.textEmphasis ?: inheritedStyle.textEmphasis
)
if (finalStyle.display == "none") return emptyList()
return elementToSemanticBlocks(element, finalStyle)
}
private fun getElementDescriptor(element: Element): String {
return buildString {
append(element.tagName())
val id = element.id()
if (id.isNotEmpty()) append('#').append(id)
val classes = element.classNames()
if (classes.isNotEmpty()) append('.').append(classes.sorted().joinToString("."))
}
}
private fun getElementStyle(element: Element): CssStyle {
val cacheKey = getElementDescriptor(element)
val baseStyle = styleCache.getOrPut(cacheKey) {
val potentialRules = mutableListOf<CssRule>()
combinedRules.byTag[element.tagName()]?.let { potentialRules.addAll(it) }
element.id().takeIf { it.isNotEmpty() }?.let { id ->
combinedRules.byId[id]?.let { potentialRules.addAll(it) }
}
element.classNames().forEach { className ->
combinedRules.byClass[className]?.let { potentialRules.addAll(it) }
}
potentialRules.addAll(combinedRules.otherComplex)
val matchingRules = potentialRules.filter { rule ->
if (unsupportedPseudoElementRegex.containsMatchIn(rule.selector.selector)) return@filter false
try {
element.`is`(rule.selector.selector)
} catch (e: Selector.SelectorParseException) {
Timber.w(e, "Jsoup failed to parse selector '${rule.selector.selector}'.")
false
}
}
matchingRules.sortedBy { it.selector.specificity }.fold(CssStyle()) { acc, rule ->
acc.merge(rule.style)
}
}
var elementStyle = baseStyle
val inlineStyleAttribute = element.attr("style")
if (inlineStyleAttribute.isNotBlank()) {
val inlineStyle = CssParser.parseProperties(inlineStyleAttribute, textStyle.fontSize.value, density.density, constraints, onlyImportant = false, isDarkTheme = false)
elementStyle = elementStyle.merge(inlineStyle)
}
element.attr("align").takeIf { it.isNotBlank() }?.let { align ->
val textAlign = when (align.lowercase()) {
"center" -> TextAlign.Center; "right" -> TextAlign.End
"justify" -> TextAlign.Justify; "left" -> TextAlign.Start
else -> null
}
if (textAlign != null) {
elementStyle = elementStyle.merge(CssStyle(paragraphStyle = ParagraphStyle(textAlign = textAlign)))
}
}
return elementStyle
}
private fun elementToSemanticBlocks(
element: Element,
elementStyle: CssStyle
): List<SemanticBlock> {
val elementId = element.id().ifBlank { null }
val cfi = element.getCfiPath()
if (element.tagName().equals("br", ignoreCase = true)) {
return listOf(SemanticSpacer(style = elementStyle, elementId = elementId, cfi = cfi, isExplicitLineBreak = true, blockIndex = nextBlockIndex++))
}
if (elementStyle.blockStyle.display == "flex") {
val children = element.children().flatMap { child ->
parseNodeToSemanticBlocks(child, elementStyle)
}
return listOf(SemanticFlexContainer(children, elementStyle, elementId, cfi, blockIndex = nextBlockIndex++))
}
val result = when (val tagName = element.tagName().lowercase()) {
"div", "header", "section", "article", "aside", "main", "footer", "nav", "figure" -> {
val hasBoxStyles = elementStyle.blockStyle.backgroundColor.isSpecified ||
elementStyle.blockStyle.borderTop != null ||
elementStyle.blockStyle.borderRight != null ||
elementStyle.blockStyle.borderBottom != null ||
elementStyle.blockStyle.borderLeft != null ||
elementStyle.blockStyle.padding != BoxBorders() ||
elementStyle.blockStyle.borderTopLeftRadius > 0.dp ||
elementStyle.blockStyle.borderTopRightRadius > 0.dp ||
elementStyle.blockStyle.borderBottomRightRadius > 0.dp ||
elementStyle.blockStyle.borderBottomLeftRadius > 0.dp
if (hasBoxStyles) {
val children = element.children().flatMap { child ->
parseNodeToSemanticBlocks(child, elementStyle)
}
listOf(SemanticFlexContainer(children, elementStyle, elementId, cfi, blockIndex = nextBlockIndex++))
} else {
parseContainer(element, elementStyle)
}
}
"svg" -> parseSvgElementToSemantic(element, elementStyle)?.let { listOf(it) } ?: emptyList()
"table" -> parseTableElementToSemantic(element, elementStyle)?.let { listOf(it) } ?: emptyList()
"math-placeholder" -> parseMathPlaceholderToSemantic(element, elementStyle)
"img" -> parseImageElementToSemantic(element, elementStyle)?.let { listOf(it) } ?: emptyList()
"h1", "h2", "h3", "h4", "h5", "h6" -> {
val (text, spans) = buildSemanticTextAndSpans(element, elementStyle)
if (text.isNotBlank()) {
val level = tagName.substring(1).toIntOrNull() ?: 1
listOf(SemanticHeader(level, text, spans, elementStyle, elementId, cfi, blockIndex = nextBlockIndex++))
} else emptyList()
}
"hr" -> listOf(SemanticSpacer(style = elementStyle, elementId = elementId, cfi = cfi, blockIndex = nextBlockIndex++))
"ul", "ol" -> parseListElementToSemantic(element, elementStyle)
else -> {
if (element.isBlock) {
parseContainer(element, elementStyle)
} else {
val (text, spans) = buildSemanticTextAndSpans(element, elementStyle)
if (text.isNotBlank()) {
listOf(SemanticParagraph(text, spans, elementStyle, elementId, cfi, blockIndex = nextBlockIndex++))
} else emptyList()
}
}
}
return if (elementId != null && result.isNotEmpty()) {
val first = result.first()
if (first.elementId == null) {
listOf(first.withElementId(elementId)) + result.drop(1)
} else result
} else result
}
private fun parseContainer(element: Element, style: CssStyle): List<SemanticBlock> {
val children = mutableListOf<SemanticBlock>()
val textNodesBuffer = mutableListOf<Node>()
fun flushTextBuffer() {
if (textNodesBuffer.isEmpty()) return
val (text, spans) = buildSemanticTextAndSpansFromNodes(textNodesBuffer, style)
if (text.isNotBlank()) {
children.add(SemanticParagraph(text, spans, style, element.id().ifBlank { null }, element.getCfiPath(), blockIndex = nextBlockIndex++)) }
textNodesBuffer.clear()
}
element.childNodes().forEach { node ->
if (node is Element) {
val isEffectivelyBlock = node.isBlock || node.tagName().lowercase() in listOf("img", "svg", "math-placeholder", "hr")
if (isEffectivelyBlock) {
flushTextBuffer()
children.addAll(parseNodeToSemanticBlocks(node, style))
} else {
textNodesBuffer.add(node)
}
} else {
textNodesBuffer.add(node)
}
}
flushTextBuffer()
return children
}
private fun buildSemanticTextAndSpans(
rootElement: Element,
rootStyle: CssStyle
): Pair<String, List<SemanticSpan>> {
return buildSemanticTextAndSpansFromNodes(rootElement.childNodes(), rootStyle)
}
private fun buildSemanticTextAndSpansFromNodes(
nodes: List<Node>,
rootStyle: CssStyle
): Pair<String, List<SemanticSpan>> {
val textBuilder = StringBuilder()
val spans = mutableListOf<SemanticSpan>()
fun processNode(node: Node, inheritedStyle: CssStyle) {
when (node) {
is TextNode -> {
var text = node.wholeText.replace('\n', ' ')
when (inheritedStyle.textTransform) {
"uppercase" -> text = text.uppercase()
"lowercase" -> text = text.lowercase()
"capitalize" -> text = text.capitalizeWords()
}
textBuilder.append(text)
}
is Element -> {
if (node.tagName().lowercase() == "br") {
textBuilder.append('\n'); return
}
val currentElementStyle = getElementStyle(node)
val newStyle = inheritedStyle.merge(currentElementStyle)
val startIndex = textBuilder.length
node.childNodes().forEach { processNode(it, newStyle) }
val endIndex = textBuilder.length
val elementId = node.id().ifBlank { null }
val isAnchor = node.tagName().lowercase() == "a" || elementId != null
// Capture span if it has content OR if it has an ID (anchor)
if (startIndex < endIndex || elementId != null) {
val href = if (node.tagName().lowercase() == "a") node.attr("href").ifBlank { null } else null
spans.add(SemanticSpan(
start = startIndex,
end = endIndex,
style = newStyle,
linkHref = href,
tag = node.tagName().lowercase(),
elementId = elementId // Pass the ID here
))
}
}
}
}
nodes.forEach { processNode(it, rootStyle) }
var processedText = textBuilder.toString()
if (processedText.isNotEmpty() && processedText.last().isWhitespace()) {
// 1. Find the index where trailing whitespace begins
var newLength = processedText.length
while (newLength > 0 && processedText[newLength - 1].isWhitespace()) {
newLength--
}
// 2. Cut the text
processedText = processedText.substring(0, newLength)
// 3. Filter or Cap spans so they don't point to indices that no longer exist
val adjustedSpans = spans.mapNotNull { span ->
if (span.start >= newLength) {
// Span started in the whitespace area, remove it
null
} else if (span.end > newLength) {
// Span ended in the whitespace area, cap it
span.copy(end = newLength)
} else {
span
}
}
return processedText to adjustedSpans
}
return processedText to spans
}
private fun parseMathPlaceholderToSemantic(element: Element, style: CssStyle): List<SemanticBlock> {
val uniqueId = element.id()
val svgContent = mathSvgCache[uniqueId]
val altText = element.attr("alttext").ifBlank { "Equation" }
var svgWidth: String? = null
var svgHeight: String? = null
var svgViewBox: String? = null
if (svgContent != null) {
val svgDoc = Jsoup.parse(svgContent)
svgDoc.selectFirst("svg")?.let {
svgWidth = it.attr("width")
svgHeight = it.attr("height")
svgViewBox = it.attr("viewBox")
}
}
return listOf(
SemanticMath(
svgContent, altText, svgWidth, svgHeight, svgViewBox,
isFromMathJax = true, style = style,
elementId = element.id().ifBlank { null }, cfi = element.getCfiPath(), blockIndex = nextBlockIndex++
)
)
}
private fun parseSvgElementToSemantic(svgElement: Element, style: CssStyle): SemanticBlock? {
val children = svgElement.children()
val imageElement = children.firstOrNull()?.takeIf { children.size == 1 && it.tagName() == "image" }
if (imageElement != null) {
Timber.d("Detected SVG acting as a wrapper for an image. Parsing as SemanticImage.")
val href = imageElement.attr("href").ifBlank { imageElement.attr("xlink:href") }
if (href.isBlank()) return null
val imageFile = resolveImagePath(href) ?: return null
val (width, height) = imageDimensionsCache[imageFile.absolutePath] ?: run {
try {
BitmapFactory.Options().apply { inJustDecodeBounds = true }
.also { BitmapFactory.decodeFile(imageFile.absolutePath, it) }
.let { Pair(it.outWidth.toFloat(), it.outHeight.toFloat()) }
} catch (_: Exception) {
Pair(null, null)
}
}
return SemanticImage(
path = imageFile.absolutePath,
altText = svgElement.selectFirst("title")?.text() ?: "Cover Image",
intrinsicWidth = width,
intrinsicHeight = height,
style = style,
elementId = svgElement.id().ifBlank { null },
cfi = svgElement.getCfiPath(),
blockIndex = nextBlockIndex++
)
}
Timber.d("Parsing genuine SVG content into SemanticMath block.")
val title = svgElement.selectFirst("title")?.text()
val desc = svgElement.selectFirst("desc")?.text()
val altText = title ?: desc ?: "SVG Image"
return SemanticMath(
svgContent = svgElement.outerHtml(),
altText = altText,
style = style,
elementId = svgElement.id().ifBlank { null },
cfi = svgElement.getCfiPath(),
svgWidth = svgElement.attr("width").ifBlank { null },
svgHeight = svgElement.attr("height").ifBlank { null },
svgViewBox = svgElement.attr("viewBox").ifBlank { null },
isFromMathJax = false,
blockIndex = nextBlockIndex++
)
}
private fun parseImageElementToSemantic(element: Element, style: CssStyle): SemanticBlock? {
val src = element.attr("src")
if (src.isBlank()) return null
val imageFile = resolveImagePath(src) ?: return null
if (imageFile.extension.equals("svg", ignoreCase = true)) {
return try {
val svgContent = imageFile.readText()
val svgElement = Jsoup.parseBodyFragment(svgContent).body().children().firstOrNull()
svgElement?.let { parseSvgElementToSemantic(it, style) }
} catch (e: Exception) {
Timber.e(e, "Failed to read SVG from <img> tag: ${imageFile.path}")
null
}
}
val (width, height) = imageDimensionsCache[imageFile.absolutePath] ?: run {
try {
BitmapFactory.Options().apply { inJustDecodeBounds = true }
.also { BitmapFactory.decodeFile(imageFile.absolutePath, it) }
.let { Pair(it.outWidth.toFloat(), it.outHeight.toFloat()) }
} catch (_: Exception) {
Pair(null, null)
}
}
return SemanticImage(
path = imageFile.absolutePath,
altText = element.attr("alt"),
intrinsicWidth = width,
intrinsicHeight = height,
style = style,
elementId = element.id().ifBlank { null },
cfi = element.getCfiPath(),
blockIndex = nextBlockIndex++
)
}
private fun resolveImagePath(src: String): File? {
if (src.isBlank()) return null
val decodedSrc = try { URLDecoder.decode(src, "UTF-8") } catch (_: Exception) { src }
val parentPath = File(chapterAbsPath).parent ?: ""
val relativePath = Paths.get(parentPath, decodedSrc).normalize().toString()
val fromRelativeFile = File(extractionBasePath, relativePath)
try {
if (fromRelativeFile.exists()) return fromRelativeFile.canonicalFile
val fromRootFile = File(extractionBasePath, decodedSrc)
if (fromRootFile.exists()) return fromRootFile.canonicalFile
} catch (e: java.io.IOException) {
Timber.e(e, "Could not get canonical path for image at $src")
return null
}
Timber.w("Image not found. Tried: ${fromRelativeFile.absolutePath} and ${File(extractionBasePath, decodedSrc).absolutePath}")
return null
}
private fun parseListElementToSemantic(listElement: Element, listStyle: CssStyle): List<SemanticBlock> {
val isOrdered = listElement.tagName().lowercase() == "ol"
val items = listElement.children().mapNotNull { child ->
if (child.tagName().lowercase() != "li") return@mapNotNull null
val itemStyle = listStyle.merge(getElementStyle(child))
val (text, spans) = buildSemanticTextAndSpans(child, itemStyle)
val imageSrc = itemStyle.blockStyle.listStyleImage?.let { resolveImagePath(it)?.absolutePath }
SemanticListItem(text, spans, itemStyle, child.id().ifBlank { null }, child.getCfiPath(), 0, imageSrc, blockIndex = nextBlockIndex++)
}
return listOf(SemanticList(items, isOrdered, listStyle, listElement.id().ifBlank { null }, listElement.getCfiPath(), blockIndex = nextBlockIndex++))
}
private fun parseTableElementToSemantic(tableElement: Element, tableStyle: CssStyle): SemanticTable? {
val rows = tableElement.select("tr").mapNotNull { rowElement ->
val rowStyle = getElementStyle(rowElement)
if (rowStyle.display == "none") return@mapNotNull null
val cells = rowElement.children().mapNotNull { cellElement ->
val tagName = cellElement.tagName().lowercase()
if (tagName !in listOf("td", "th")) return@mapNotNull null
var cellCssStyle = getElementStyle(cellElement)
if (cellCssStyle.display == "none") return@mapNotNull null
if (!cellCssStyle.blockStyle.backgroundColor.isSpecified) {
if (rowStyle.blockStyle.backgroundColor.isSpecified) {
cellCssStyle = cellCssStyle.copy(
blockStyle = cellCssStyle.blockStyle.copy(
backgroundColor = rowStyle.blockStyle.backgroundColor
)
)
}
}
val cellContent = parseContainer(cellElement, cellCssStyle)
SemanticTableCell(cellContent, tagName == "th", cellElement.attr("colspan").toIntOrNull() ?: 1, cellCssStyle)
}
cells.ifEmpty { null }
}
if (rows.isEmpty()) return null
return SemanticTable(rows, tableStyle, tableElement.id().ifBlank { null }, tableElement.getCfiPath(), blockIndex = nextBlockIndex++)
}
}