1 files changed, 133 insertions, 0 deletions
diff --git a/markdown_it/rules_inline/strikethrough.py b/markdown_it/rules_inline/strikethrough.py
new file mode 100644
index 0000000..107ea26
--- /dev/null
+++ b/markdown_it/rules_inline/strikethrough.py
@@ -0,0 +1,133 @@
+# ~~strike through~~
+from __future__ import annotations
+
+from .state_inline import Delimiter, StateInline
+
+
+def tokenize(state: StateInline, silent: bool):
+    """Insert each marker as a separate text token, and add it to delimiter list"""
+    start = state.pos
+    marker = state.srcCharCode[start]
+
+    if silent:
+        return False
+
+    if marker != 0x7E:  # /* ~ */
+        return False
+
+    scanned = state.scanDelims(state.pos, True)
+    length = scanned.length
+    ch = chr(marker)
+
+    if length < 2:
+        return False
+
+    if length % 2:
+        token = state.push("text", "", 0)
+        token.content = ch
+        length -= 1
+
+    i = 0
+    while i < length:
+        token = state.push("text", "", 0)
+        token.content = ch + ch
+        state.delimiters.append(
+            Delimiter(
+                **{
+                    "marker": marker,
+                    "length": 0,  # disable "rule of 3" length checks meant for emphasis
+                    "jump": i // 2,  # for `~~` 1 marker = 2 characters
+                    "token": len(state.tokens) - 1,
+                    "end": -1,
+                    "open": scanned.can_open,
+                    "close": scanned.can_close,
+                }
+            )
+        )
+
+        i += 2
+
+    state.pos += scanned.length
+
+    return True
+
+
+def _postProcess(state: StateInline, delimiters: list[Delimiter]):
+
+    loneMarkers = []
+    maximum = len(delimiters)
+
+    i = 0
+    while i < maximum:
+        startDelim = delimiters[i]
+
+        if startDelim.marker != 0x7E:  # /* ~ */
+            i += 1
+            continue
+
+        if startDelim.end == -1:
+            i += 1
+            continue
+
+        endDelim = delimiters[startDelim.end]
+
+        token = state.tokens[startDelim.token]
+        token.type = "s_open"
+        token.tag = "s"
+        token.nesting = 1
+        token.markup = "~~"
+        token.content = ""
+
+        token = state.tokens[endDelim.token]
+        token.type = "s_close"
+        token.tag = "s"
+        token.nesting = -1
+        token.markup = "~~"
+        token.content = ""
+
+        if (
+            state.tokens[endDelim.token - 1].type == "text"
+            and state.tokens[endDelim.token - 1].content == "~"
+        ):
+
+            loneMarkers.append(endDelim.token - 1)
+
+        i += 1
+
+    # If a marker sequence has an odd number of characters, it's split
+    # like this: `~~~~~` -> `~` + `~~` + `~~`, leaving one marker at the
+    # start of the sequence.
+    #
+    # So, we have to move all those markers after subsequent s_close tags.
+    #
+    while loneMarkers:
+        i = loneMarkers.pop()
+        j = i + 1
+
+        while (j < len(state.tokens)) and (state.tokens[j].type == "s_close"):
+            j += 1
+
+        j -= 1
+
+        if i != j:
+            token = state.tokens[j]
+            state.tokens[j] = state.tokens[i]
+            state.tokens[i] = token
+
+
+def postProcess(state: StateInline):
+    """Walk through delimiter list and replace text tokens with tags."""
+    tokens_meta = state.tokens_meta
+    maximum = len(state.tokens_meta)
+    _postProcess(state, state.delimiters)
+
+    curr = 0
+    while curr < maximum:
+        try:
+            curr_meta = tokens_meta[curr]
+        except IndexError:
+            pass
+        else:
+            if curr_meta and "delimiters" in curr_meta:
+                _postProcess(state, curr_meta["delimiters"])
+        curr += 1