Add markdown parser

1 files changed, 96 insertions, 0 deletions

diff --git a/src/main/kotlin/moe/nea/blog/md/MarkdownParser.kt b/src/main/kotlin/moe/nea/blog/md/MarkdownParser.kt
new file mode 100644
index 0000000..86b92d2
--- /dev/null
+++ b/src/main/kotlin/moe/nea/blog/md/MarkdownParser.kt
@@ -0,0 +1,96 @@
+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 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 == ' ' }
+        return Pair(Word(text.substring(0, nextSpecial)), text.substring(nextSpecial))
+    }
+
+    fun parseInlineText(text: String): MarkdownFormat {
+        val seq = mutableListOf<MarkdownFormat>()
+        var remaining = text
+        var lastToken: MarkdownFormat = Begin()
+        while (remaining.isNotEmpty()) {
+            val (tok, next) = parseInlineTextOnce(lastToken, remaining)
+            seq.add(tok)
+            lastToken = tok
+            remaining = next
+        }
+        return collapseInlineFormat(seq)
+    }
+
+    fun collapseInlineFormat(sequence: List<MarkdownFormat>): MarkdownFormat {
+        return FormatSequence(sequence)
+    }
+
+    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)
+    }
+}
+