"""Augmentations to prompt_toolkit's input-parsing tables.

Imported once at CLI startup. Each helper installs a small mapping into
prompt_toolkit's `ANSI_SEQUENCES` so byte sequences emitted by modern
keyboard protocols (Kitty / xterm `modifyOtherKeys`) decode to existing
key tuples Hermes already binds.

Kept in a standalone module — separate from `cli.py` — so the registrations
can be unit-tested without importing the whole CLI runtime.
"""

from __future__ import annotations


def install_shift_enter_alias() -> int:
    """Map Shift+Enter byte sequences to the (Escape, ControlM) key tuple
    that Alt+Enter produces, so the existing Alt+Enter newline handler
    fires for terminals that emit a distinct Shift+Enter.

    Sequences mapped:
      - "\\x1b[13;2u"     — Kitty keyboard protocol / CSI-u, modifier=2 (Shift)
      - "\\x1b[27;2;13~"  — xterm modifyOtherKeys=2, modifier=2 (Shift)
      - "\\x1b[27;2;13u"  — alternate ordering some emitters use

    The CSI-u sequence is not in stock prompt_toolkit. The modifyOtherKeys
    variant `\\x1b[27;2;13~` IS in stock prompt_toolkit but mapped to plain
    `Keys.ControlM` — i.e. Shift+Enter behaves identically to Enter, which
    is the very bug this helper exists to fix. We therefore overwrite
    those two specific keys (and `\\x1b[27;2;13u`) unconditionally; other
    `\\x1b[27;...;13~` sequences (Ctrl+Enter, Alt+Enter via modifyOtherKeys
    variants 5/6/etc.) are left untouched.

    Default macOS Terminal and stock Windows Terminal still send the same
    byte for Enter and Shift+Enter, so there is no fix for those terminals
    at the application layer — the sequences above never reach Hermes.

    Returns the number of sequences whose mapping was changed.
    """
    try:
        from prompt_toolkit.input.ansi_escape_sequences import ANSI_SEQUENCES
        from prompt_toolkit.keys import Keys
    except Exception:
        return 0

    alt_enter = (Keys.Escape, Keys.ControlM)
    changed = 0
    for seq in ("\x1b[13;2u", "\x1b[27;2;13~", "\x1b[27;2;13u"):
        if ANSI_SEQUENCES.get(seq) != alt_enter:
            ANSI_SEQUENCES[seq] = alt_enter
            changed += 1
    return changed