"""Strip ANSI escape sequences from subprocess output.

Used by terminal_tool, code_execution_tool, and process_registry to clean
command output before returning it to the model.  This prevents ANSI codes
from entering the model's context — which is the root cause of models
copying escape sequences into file writes.

Covers the full ECMA-48 spec: CSI (including private-mode ``?`` prefix,
colon-separated params, intermediate bytes), OSC (BEL and ST terminators),
DCS/SOS/PM/APC string sequences, nF multi-byte escapes, Fp/Fe/Fs
single-byte escapes, and 8-bit C1 control characters.
"""

import re

_ANSI_ESCAPE_RE = re.compile(
    r"\x1b"
    r"(?:"
        r"\[[\x30-\x3f]*[\x20-\x2f]*[\x40-\x7e]"     # CSI sequence
        r"|\][\s\S]*?(?:\x07|\x1b\\)"                  # OSC (BEL or ST terminator)
        r"|[PX^_][\s\S]*?(?:\x1b\\)"                   # DCS/SOS/PM/APC strings
        r"|[\x20-\x2f]+[\x30-\x7e]"                    # nF escape sequences
        r"|[\x30-\x7e]"                                 # Fp/Fe/Fs single-byte
    r")"
    r"|\x9b[\x30-\x3f]*[\x20-\x2f]*[\x40-\x7e]"       # 8-bit CSI
    r"|\x9d[\s\S]*?(?:\x07|\x9c)"                       # 8-bit OSC
    r"|[\x80-\x9f]",                                    # Other 8-bit C1 controls
    re.DOTALL,
)

# Fast-path check — skip full regex when no escape-like bytes are present.
_HAS_ESCAPE = re.compile(r"[\x1b\x80-\x9f]")

# C0 control characters (minus tab/newline/carriage-return, handled
# separately) plus DEL. These survive strip_ansi() — it only removes
# well-formed escape *sequences* — but are still dangerous or garbled
# when echoed back to a terminal (BEL rings, backspace/DEL overwrite,
# NUL truncates in some terminals).
_CONTROL_CHARS_RE = re.compile(r"[\x00-\x08\x0b\x0c\x0e-\x1f\x7f]")

# Fast-path check for sanitize_display_text — any C0 control (except
# tab/newline), CR, DEL, ESC, or C1 byte triggers the slow path.
_HAS_CONTROL = re.compile(r"[\x00-\x08\x0b-\x1f\x7f-\x9f]")

# Unicode TAG characters (U+E0000–U+E007F).  Deprecated as language tags,
# these render as nothing in every terminal and chat UI but are perfectly
# visible to an LLM tokenizer — the classic "ASCII smuggling" prompt-injection
# channel (hide `\u{E0069}\u{E0067}\u{E006E}...` = invisible instructions
# inside otherwise benign tool output).  Ported from block/goose#10746.
#
# The ONLY legitimate modern use is emoji tag sequences (Unicode TR51):
# a U+1F3F4 black-flag base followed by tag spec characters and the
# U+E007F CANCEL TAG terminator (e.g. the flags of Scotland/Wales/England).
# goose strips those too; we preserve them — same rationale as keeping ZWJ
# inside emoji sequences.
_UNICODE_TAG_SUB_RE = re.compile(
    r"(\U0001F3F4[\U000E0020-\U000E007E]+\U000E007F)"  # valid emoji tag seq (kept)
    r"|[\U000E0000-\U000E007F]"                        # any other tag char (stripped)
)

# Fast-path check — plane-14 tag chars only.
_HAS_UNICODE_TAG = re.compile(r"[\U000E0000-\U000E007F]")


def strip_ansi(text: str) -> str:
    """Remove ANSI escape sequences from text.

    Returns the input unchanged (fast path) when no ESC or C1 bytes are
    present.  Safe to call on any string — clean text passes through
    with negligible overhead.
    """
    if not text or not _HAS_ESCAPE.search(text):
        return text
    return _ANSI_ESCAPE_RE.sub("", text)


def sanitize_display_text(text: str) -> str:
    """Sanitize stored/untrusted text before echoing it to a terminal.

    Removes ANSI/ECMA-48 escape sequences AND bare control characters,
    preserving only newlines and tabs (carriage returns are normalized
    to newlines so ``\\r``-overwrite spoofing can't hide content).

    Use this when re-rendering conversation history or other persisted
    text in a terminal UI (e.g. the ``/resume`` recap): a message that
    arrived with embedded escapes — pasted content, gateway-origin
    text, or model output echoing injected tool results — must not be
    able to clear the screen, retitle the window, move the cursor, or
    restyle adjacent UI when replayed. Rich's ``Text()`` does NOT
    neutralize raw escape bytes, so sanitization has to happen before
    display. Mirrors openai/codex#31494 (``sanitize_user_text``).
    """
    if not text or not _HAS_CONTROL.search(text):
        return text
    text = strip_ansi(text)
    if "\r" in text:
        text = text.replace("\r\n", "\n").replace("\r", "\n")
    return _CONTROL_CHARS_RE.sub("", text)


def strip_unicode_tags(text: str) -> str:
    """Remove invisible Unicode TAG characters (U+E0000–U+E007F) from text.

    Tag characters are invisible in terminals and chat UIs but fully visible
    to LLM tokenizers, making them a prompt-injection smuggling channel for
    untrusted tool output (MCP servers, web content).  Valid emoji tag
    sequences (U+1F3F4 base + tag spec + U+E007F CANCEL TAG — regional
    flags like Scotland/Wales) are preserved.

    Returns the input unchanged (fast path) when no plane-14 tag characters
    are present.  Ported from block/goose#10746.
    """
    if not text or not _HAS_UNICODE_TAG.search(text):
        return text
    return _UNICODE_TAG_SUB_RE.sub(lambda m: m.group(1) or "", text)