Add support for lists in html2md

2021/2/README.md

@@ -4,7 +4,11 @@ Now, you need to figure out how to pilot this thing.
 
 It seems like the submarine can take a series of commands like `forward 1`, `down 2`, or `up 3`:
 
-`forward X``X``down X`__increases__`X``up X`__decreases__`X`Note that since you're on a submarine, `down` and `up` affect your __depth__, and so they have the opposite result of what you might expect.
+- `forward X` increases the horizontal position by `X` units.
+- `down X` __increases__ the depth by `X` units.
+- `up X` __decreases__ the depth by `X` units.
+
+Note that since you're on a submarine, `down` and `up` affect your __depth__, and so they have the opposite result of what you might expect.
 
 The submarine seems to already have a planned course (your puzzle input). You should probably figure out where it's going. For example:
 
@@ -19,7 +23,14 @@ forward 2
 
 Your horizontal position and depth both start at `0`. The steps above would then modify them as follows:
 
-`forward 5``5``5``down 5``5``5``forward 8``8``13``up 3``3``2``down 8``8``10``forward 2``2``15`After following these instructions, you would have a horizontal position of `15` and a depth of `10`. (Multiplying these together produces `150`.)
+- `forward 5` adds `5` to your horizontal position, a total of `5`.
+- `down 5` adds `5` to your depth, resulting in a value of `5`.
+- `forward 8` adds `8` to your horizontal position, a total of `13`.
+- `up 3` decreases your depth by `3`, resulting in a value of `2`.
+- `down 8` adds `8` to your depth, resulting in a value of `10`.
+- `forward 2` adds `2` to your horizontal position, a total of `15`.
+
+After following these instructions, you would have a horizontal position of `15` and a depth of `10`. (Multiplying these together produces `150`.)
 
 Calculate the horizontal position and depth you would have after following the planned course. __What do you get if you multiply your final horizontal position by your final depth?__
 
@@ -29,11 +40,24 @@ Based on your calculations, the planned course doesn't seem to make any sense. Y
 
 In addition to horizontal position and depth, you'll also need to track a third value, __aim__, which also starts at `0`. The commands also mean something entirely different than you first thought:
 
-`down X`__increases__`X``up X`__decreases__`X``forward X``X`__multiplied by__`X`Again note that since you're on a submarine, `down` and `up` do the opposite of what you might expect: "down" means aiming in the positive direction.
+- `down X` __increases__ your aim by `X` units.
+- `up X` __decreases__ your aim by `X` units.
+- `forward X` does two things:
+  - It increases your horizontal position by `X` units.
+  - It increases your depth by your aim __multiplied by__ `X`.
+
+Again note that since you're on a submarine, `down` and `up` do the opposite of what you might expect: "down" means aiming in the positive direction.
 
 Now, the above example does something different:
 
-`forward 5``5``5``0``down 5``5``5``forward 8``8``13``5``8*5=40``up 3``3``2``down 8``8``10``forward 2``2``15``10``2*10=20``60`After following these new instructions, you would have a horizontal position of `15` and a depth of `60`. (Multiplying these produces `900`.)
+- `forward 5` adds `5` to your horizontal position, a total of `5`. Because your aim is `0`, your depth does not change.
+- `down 5` adds `5` to your aim, resulting in a value of `5`.
+- `forward 8` adds `8` to your horizontal position, a total of `13`. Because your aim is `5`, your depth increases by `8*5=40`.
+- `up 3` decreases your aim by `3`, resulting in a value of `2`.
+- `down 8` adds `8` to your aim, resulting in a value of `10`.
+- `forward 2` adds `2` to your horizontal position, a total of `15`.  Because your aim is `10`, your depth increases by `2*10=20` to a total of `60`.
+
+After following these new instructions, you would have a horizontal position of `15` and a depth of `60`. (Multiplying these produces `900`.)
 
 Using this new interpretation of the commands, calculate the horizontal position and depth you would have after following the planned course. __What do you get if you multiply your final horizontal position by your final depth?__
 

scripts/html2md.py

@@ -24,6 +24,10 @@ def __init__(self, *, convert_charrefs: bool = ...) -> None:
       self.tags: list[tuple[str, HTMLAttributes]] = []
       # Whether or not we're inside the main article
       self.is_in_article = False
+      # The ul depth
+      self.list_depth = 0
+      # Whether the last seen ul was nested
+      self.list_was_nested = False
 
   def handle_starttag(self, tag: str, attrs: HTMLAttributes) -> None:
       self.tags.append((tag, attrs))
@@ -40,6 +44,15 @@ def handle_starttag(self, tag: str, attrs: HTMLAttributes) -> None:
           print("```")
         else:
           print("`", end="")
+      elif tag == "li":
+        print("  " * (self.list_depth - 1) + "- ", end="")
+      elif tag == "ul":
+        self.list_depth += 1
+        if self.list_depth == 1:
+          self.list_was_nested = False
+        elif self.list_depth > 1:
+          self.list_was_nested = True
+          print()
 
   def handle_endtag(self, tag: str) -> None:
       self.tags.pop()
@@ -60,6 +73,16 @@ def handle_endtag(self, tag: str) -> None:
           print("```\n")
         else:
           print("`", end="")
+      elif tag == "li":
+        print()
+      elif tag == "ul":
+        self.list_depth -= 1
+        # As a nested ul resides within a li tag two newlines will be printed
+        # for the last li. As we don't have a lookahead, best we can do is to
+        # keep track of last seen nested ul and add another newline when we
+        # leave a non-nested ul
+        if not self.list_was_nested and self.list_depth == 0:
+          print()
 
   @property
   def current_tag(self) -> tuple[str, HTMLAttributes] | None:
@@ -92,6 +115,8 @@ def handle_data(self, data: str) -> None:
       print(data, end="")
     elif tag == "span":
       print(data, end="")
+    elif tag == "li":
+      print(data, end="")
 
 def main():
   parser = CustomParser()