import pytest

from genesis.inference.token import (
    _tiktoken_estimator,
    approximate_token_count,
    make_estimator,
)


def test_approximate_count_minimum():
    assert approximate_token_count("") >= 1
    assert approximate_token_count("a") == 1


def test_approximate_count_linear():
    # 每 4 字符约 1 token（向上取整）
    assert approximate_token_count("abcd") == 1
    assert approximate_token_count("abcdefgh") == 2
    assert approximate_token_count("abcdefghi") == 3


def test_tiktoken_estimator_missing_falls_back():
    # 未安装 tiktoken 或不可用时返回 None（由 make_estimator 回落 approximate）
    r = _tiktoken_estimator("hello")
    assert r is None or isinstance(r, int)


def test_make_estimator_approximate_backend():
    est = make_estimator("approximate")
    assert est("abcd") == 1


def test_make_estimator_default_without_tiktoken(monkeypatch):
    # 强制模拟 tiktoken 缺失：make_estimator 必须回落 approximate
    import builtins
    real_import = builtins.__import__

    def fake_import(name, *args, **kwargs):
        if name == "tiktoken":
            raise ImportError("no tiktoken")
        return real_import(name, *args, **kwargs)

    monkeypatch.setattr(builtins, "__import__", fake_import)
    est = make_estimator("tiktoken")
    assert est("abcd") == 1


def test_tiktoken_estimator_success_path(monkeypatch):
    # 注入假 tiktoken 模块：验证编码成功路径（len(encode(text))）
    import sys

    class _FakeEncoding:
        def encode(self, s: str):
            return ["t"] * len(s)

    class _FakeTiktoken:
        @staticmethod
        def get_encoding(name):
            assert name == "cl100k_base"
            return _FakeEncoding()

    monkeypatch.setitem(sys.modules, "tiktoken", _FakeTiktoken)
    assert _tiktoken_estimator("hello") == 5


def test_tiktoken_estimator_encoding_error(monkeypatch):
    # tiktoken 可用但编码抛异常：返回 None（由 make_estimator 回落 approximate）
    import sys

    class _FakeTiktoken:
        @staticmethod
        def get_encoding(name):
            raise RuntimeError("boom")

    monkeypatch.setitem(sys.modules, "tiktoken", _FakeTiktoken)
    assert _tiktoken_estimator("hello") is None