1 files changed, 145 insertions, 0 deletions
diff --git a/src/prompt_toolkit/formatted_text/html.py b/src/prompt_toolkit/formatted_text/html.py
new file mode 100644
index 0000000..a940ac8
--- /dev/null
+++ b/src/prompt_toolkit/formatted_text/html.py
@@ -0,0 +1,145 @@
+from __future__ import annotations
+
+import xml.dom.minidom as minidom
+from string import Formatter
+from typing import Any
+
+from .base import FormattedText, StyleAndTextTuples
+
+__all__ = ["HTML"]
+
+
+class HTML:
+    """
+    HTML formatted text.
+    Take something HTML-like, for use as a formatted string.
+
+    ::
+
+        # Turn something into red.
+        HTML('<style fg="ansired" bg="#00ff44">...</style>')
+
+        # Italic, bold, underline and strike.
+        HTML('<i>...</i>')
+        HTML('<b>...</b>')
+        HTML('<u>...</u>')
+        HTML('<s>...</s>')
+
+    All HTML elements become available as a "class" in the style sheet.
+    E.g. ``<username>...</username>`` can be styled, by setting a style for
+    ``username``.
+    """
+
+    def __init__(self, value: str) -> None:
+        self.value = value
+        document = minidom.parseString(f"<html-root>{value}</html-root>")
+
+        result: StyleAndTextTuples = []
+        name_stack: list[str] = []
+        fg_stack: list[str] = []
+        bg_stack: list[str] = []
+
+        def get_current_style() -> str:
+            "Build style string for current node."
+            parts = []
+            if name_stack:
+                parts.append("class:" + ",".join(name_stack))
+
+            if fg_stack:
+                parts.append("fg:" + fg_stack[-1])
+            if bg_stack:
+                parts.append("bg:" + bg_stack[-1])
+            return " ".join(parts)
+
+        def process_node(node: Any) -> None:
+            "Process node recursively."
+            for child in node.childNodes:
+                if child.nodeType == child.TEXT_NODE:
+                    result.append((get_current_style(), child.data))
+                else:
+                    add_to_name_stack = child.nodeName not in (
+                        "#document",
+                        "html-root",
+                        "style",
+                    )
+                    fg = bg = ""
+
+                    for k, v in child.attributes.items():
+                        if k == "fg":
+                            fg = v
+                        if k == "bg":
+                            bg = v
+                        if k == "color":
+                            fg = v  # Alias for 'fg'.
+
+                    # Check for spaces in attributes. This would result in
+                    # invalid style strings otherwise.
+                    if " " in fg:
+                        raise ValueError('"fg" attribute contains a space.')
+                    if " " in bg:
+                        raise ValueError('"bg" attribute contains a space.')
+
+                    if add_to_name_stack:
+                        name_stack.append(child.nodeName)
+                    if fg:
+                        fg_stack.append(fg)
+                    if bg:
+                        bg_stack.append(bg)
+
+                    process_node(child)
+
+                    if add_to_name_stack:
+                        name_stack.pop()
+                    if fg:
+                        fg_stack.pop()
+                    if bg:
+                        bg_stack.pop()
+
+        process_node(document)
+
+        self.formatted_text = FormattedText(result)
+
+    def __repr__(self) -> str:
+        return f"HTML({self.value!r})"
+
+    def __pt_formatted_text__(self) -> StyleAndTextTuples:
+        return self.formatted_text
+
+    def format(self, *args: object, **kwargs: object) -> HTML:
+        """
+        Like `str.format`, but make sure that the arguments are properly
+        escaped.
+        """
+        return HTML(FORMATTER.vformat(self.value, args, kwargs))
+
+    def __mod__(self, value: object) -> HTML:
+        """
+        HTML('<b>%s</b>') % value
+        """
+        if not isinstance(value, tuple):
+            value = (value,)
+
+        value = tuple(html_escape(i) for i in value)
+        return HTML(self.value % value)
+
+
+class HTMLFormatter(Formatter):
+    def format_field(self, value: object, format_spec: str) -> str:
+        return html_escape(format(value, format_spec))
+
+
+def html_escape(text: object) -> str:
+    # The string interpolation functions also take integers and other types.
+    # Convert to string first.
+    if not isinstance(text, str):
+        text = f"{text}"
+
+    return (
+        text.replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace('"', "&quot;")
+    )
+
+
+FORMATTER = HTMLFormatter()