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package moe.nea.blog.md
import moe.nea.blog.util.indentSize
import java.util.*
class MarkdownParser(source: String) {
private val lines = source.lines()
private var lineIndex = 0
private var blockIndents = 0
private val indentStack = Stack<Int>()
private val blockParsers = mutableListOf<BlockParser>()
private val inlineParsers = mutableListOf<InlineParser>()
fun findParserFor(line: String): BlockParser? {
return blockParsers.filter { it.detect(line) }
.maxByOrNull { it.prio }
}
fun readChildBlock(): MarkdownBlock? {
val peek = peekLine() ?: return null
val blockParser = findParserFor(peek) ?: ParagraphParser
return blockParser.parse(this)
}
fun pushIndent(newIndent: Int) {
require(newIndent > blockIndents)
indentStack.push(blockIndents)
blockIndents = newIndent
}
fun popIndent() {
blockIndents = indentStack.pop()
}
fun consumeLine(): String? {
val line = peekLine()
if (line != null)
lineIndex++
return line
}
fun peekLine(): String? {
if (lineIndex !in lines.indices) return null
val line = lines[lineIndex]
val indent = line.indentSize()
if (indent != null && indent < blockIndents)
return null
return line.substring(blockIndents)
}
fun parseInlineTextUntil(
text: String,
initialLookback: MarkdownFormat,
breakout: (lookback: MarkdownFormat, remaining: String) -> Boolean
): Pair<List<MarkdownFormat>, String> {
val seq = mutableListOf<MarkdownFormat>()
var remaining = text
var lastToken: MarkdownFormat = initialLookback
while (remaining.isNotEmpty()) {
val (tok, next) = parseInlineTextOnce(lastToken, remaining)
seq.add(tok)
lastToken = tok
remaining = next
if (breakout(tok, next))
break
}
return seq to remaining
}
fun parseInlineTextOnce(lookback: MarkdownFormat, text: String): Pair<MarkdownFormat, String> {
val parser = inlineParsers.find { it.detect(lookback, text) }
if (parser != null)
return parser.parse(this, text)
require(!text.isEmpty()) // TODO handle empty string
if (text[0] == ' ')
return Pair(Whitespace(), text.substring(1))
val nextSpecial = text.indexOfFirst { it in inlineParsers.flatMap { it.specialSyntax } || it == ' ' }
if (nextSpecial == 0)
return Pair(Word(text.substring(0, 1)), text.substring(1))
if (nextSpecial == -1)
return Pair(Word(text), "")
return Pair(Word(text.substring(0, nextSpecial)), text.substring(nextSpecial))
}
fun parseInlineText(text: String): MarkdownFormat {
val (tokens, rest) = parseInlineTextUntil(text, Begin()) { _, _ -> false }
require(rest.isEmpty())
return collapseInlineFormat(tokens, true)
}
private fun expandMarkdownFormats(sequence: List<MarkdownFormat>): List<MarkdownFormat> {
val elongated = mutableListOf<MarkdownFormat>()
for (markdownFormat in sequence) {
if (markdownFormat is FormatSequence) {
elongated.addAll(expandMarkdownFormats(markdownFormat.list))
} else {
elongated.add(markdownFormat)
}
}
return elongated
}
private fun collapseMarkdownFormats(
sequence: List<MarkdownFormat>,
trimWhitespace: Boolean
): MutableList<MarkdownFormat> {
val shortened = mutableListOf<MarkdownFormat>()
var last: MarkdownFormat = if (trimWhitespace) Whitespace() else Begin()
for (format in sequence) {
if (format is Whitespace && last is Whitespace) {
continue
}
last = format
shortened.add(format)
}
return shortened
}
fun collapseInlineFormat(sequence: List<MarkdownFormat>, trimWhitespace: Boolean): MarkdownFormat {
val formats = collapseMarkdownFormats(expandMarkdownFormats(sequence), trimWhitespace)
return formats.singleOrNull() ?: FormatSequence(formats)
}
fun readDocument(): Document {
val list = mutableListOf<MarkdownBlock>()
while (true) {
val block = readChildBlock() ?: break
list.add(block)
}
return Document(list)
}
fun addDefaultParsers() {
blockParsers.add(CodeBlockParser)
blockParsers.add(HeaderParser)
inlineParsers.add(ItalicsParser)
}
}
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