Source code for pythainlp.morpheme.word_formation

# SPDX-FileCopyrightText: 2016-2026 PyThaiNLP Project
# SPDX-FileType: SOURCE
# SPDX-License-Identifier: Apache-2.0
from __future__ import annotations

from pythainlp import thai_consonants




def nighit(w1: str, w2: str) -> str:
    """Create a new word using Nighit (นิคหิต or ํ).

    Nighit is the niggahita in Thai, used to form new words
    from Pali roots. This function applies a simple rule to
    combine two Thai words derived from Pali.

    Reference: https://www.trueplookpanya.com/learning/detail/1180

    :param str w1: a Thai word ending with a nighit (ํ)
    :param str w2: a Thai word
    :return: combined Thai word
    :rtype: str
    :Example:

        >>> from pythainlp.morpheme import nighit
        >>> nighit("สํ", "คีต")
        'สังคีต'
        >>> nighit("สํ", "จร")
        'สัญจร'
        >>> nighit("สํ", "ฐาน")
        'สัณฐาน'
        >>> nighit("สํ", "นิษฐาน")
        'สันนิษฐาน'
        >>> nighit("สํ", "ปทา")
        'สัมปทา'
        >>> nighit("สํ", "โยค")
        'สังโยค'
    """
    if not isinstance(w1, str) or not isinstance(w2, str):
        raise TypeError("Both w1 and w2 must be strings.")
    w1 = w1.strip()
    w2 = w2.strip()
    if not w1:
        return w2
    if not w2:
        return w1
    if not str(w1).endswith("ํ") and len(w1) != 2:
        raise NotImplementedError(f"The function doesn't support {w1}.")
    list_w1 = list(w1)
    list_w2 = list(w2)
    newword = []
    newword.append(list_w1[0])
    newword.append("ั")
    _consonants = set(thai_consonants)
    consonants_in_w2 = [i for i in list_w2 if i in _consonants]
    if not consonants_in_w2:
        raise ValueError(
            f"w2 {w2!r} contains no Thai consonants."
        )
    consonant_start = consonants_in_w2[0]
    if consonant_start in ["ก", "ช", "ค", "ข", "ง"]:
        newword.append("ง")
    elif consonant_start in ["จ", "ฉ", "ช", "ฌ"]:
        newword.append("ญ")
    elif consonant_start in ["ฎ", "ฐ", "ฑ", "ณ"]:
        newword.append("ณ")
    elif consonant_start in ["ด", "ถ", "ท", "ธ", "น"]:
        newword.append("น")
    elif consonant_start in ["ป", "ผ", "พ", "ภ"]:
        newword.append("ม")
    elif consonant_start in ["ย", "ร", "ล", "ฬ", "ว", "ศ", "ษ", "ส", "ห"]:
        newword.append("ง")
    else:
        raise NotImplementedError(f"""
        The function doesn't support {w1} and {w2}.
        """)
    newword.extend(list_w2)
    return "".join(newword)