1 files changed, 90 insertions, 0 deletions
diff --git a/markdown_it/rules_block/lheading.py b/markdown_it/rules_block/lheading.py
new file mode 100644
index 0000000..f26e2af
--- /dev/null
+++ b/markdown_it/rules_block/lheading.py
@@ -0,0 +1,90 @@
+# lheading (---, ==)
+import logging
+
+from ..ruler import Ruler
+from .state_block import StateBlock
+
+LOGGER = logging.getLogger(__name__)
+
+
+def lheading(state: StateBlock, startLine: int, endLine: int, silent: bool):
+
+    LOGGER.debug("entering lheading: %s, %s, %s, %s", state, startLine, endLine, silent)
+
+    level = None
+    nextLine = startLine + 1
+    ruler: Ruler = state.md.block.ruler
+    terminatorRules = ruler.getRules("paragraph")
+
+    # if it's indented more than 3 spaces, it should be a code block
+    if state.sCount[startLine] - state.blkIndent >= 4:
+        return False
+
+    oldParentType = state.parentType
+    state.parentType = "paragraph"  # use paragraph to match terminatorRules
+
+    # jump line-by-line until empty one or EOF
+    while nextLine < endLine and not state.isEmpty(nextLine):
+        # this would be a code block normally, but after paragraph
+        # it's considered a lazy continuation regardless of what's there
+        if state.sCount[nextLine] - state.blkIndent > 3:
+            nextLine += 1
+            continue
+
+        # Check for underline in setext header
+        if state.sCount[nextLine] >= state.blkIndent:
+            pos = state.bMarks[nextLine] + state.tShift[nextLine]
+            maximum = state.eMarks[nextLine]
+
+            if pos < maximum:
+                marker = state.srcCharCode[pos]
+
+                # /* - */  /* = */
+                if marker == 0x2D or marker == 0x3D:
+                    pos = state.skipChars(pos, marker)
+                    pos = state.skipSpaces(pos)
+
+                    # /* = */
+                    if pos >= maximum:
+                        level = 1 if marker == 0x3D else 2
+                        break
+
+        # quirk for blockquotes, this line should already be checked by that rule
+        if state.sCount[nextLine] < 0:
+            nextLine += 1
+            continue
+
+        # Some tags can terminate paragraph without empty line.
+        terminate = False
+        for terminatorRule in terminatorRules:
+            if terminatorRule(state, nextLine, endLine, True):
+                terminate = True
+                break
+        if terminate:
+            break
+
+        nextLine += 1
+
+    if not level:
+        # Didn't find valid underline
+        return False
+
+    content = state.getLines(startLine, nextLine, state.blkIndent, False).strip()
+
+    state.line = nextLine + 1
+
+    token = state.push("heading_open", "h" + str(level), 1)
+    token.markup = chr(marker)
+    token.map = [startLine, state.line]
+
+    token = state.push("inline", "", 0)
+    token.content = content
+    token.map = [startLine, state.line - 1]
+    token.children = []
+
+    token = state.push("heading_close", "h" + str(level), -1)
+    token.markup = chr(marker)
+
+    state.parentType = oldParentType
+
+    return True