"""Prompt-cache prefix discipline (架构文档 §7.2 缓存前缀纪律, TD-04).

A volatile token in the fixed prefix cannot be caught by functional tests: the
answer still looks right, the bill just quietly multiplies. So it gets its own
mechanical check.
"""

from __future__ import annotations

from pathlib import Path

import pytest

from packages.llm.errors import CachePrefixViolationError, PromptNotFoundError
from packages.llm.prompts import (
    PromptRegistry,
    find_volatile_tokens,
    parse_prompt_file,
    validate_cache_prefix,
)

CLEAN_PREFIX = "你是「美搭」的穿搭顾问助手。只回答穿搭、色彩与风格相关的问题。"


def test_clean_prefix_has_no_violations() -> None:
    assert find_volatile_tokens(CLEAN_PREFIX) == []
    assert validate_cache_prefix(CLEAN_PREFIX, mode="strict") == []


@pytest.mark.parametrize(
    ("prefix", "expected_kind"),
    [
        ("今天是 2026-08-13，请为用户搭配。", "iso-date"),
        ("当前时间 09:31:00，请回答。", "iso-time"),
        ("现在是 2026 年 8 月。", "cn-date"),
        ("时间戳 1755012345 供参考。", "epoch-seconds"),
        ("会话 550e8400-e29b-41d4-a716-446655440000 开始。", "uuid"),
        ("追踪号 9f8c1d2e3b4a5f6071829304 记录在案。", "long-hex-id"),
        ("你好 {nickname}，我来帮你搭配。", "volatile-placeholder"),
        ("用户编号 {user_id} 的偏好如下。", "volatile-placeholder"),
        ("当前时刻 {now}。", "volatile-placeholder"),
    ],
)
def test_volatile_tokens_are_detected(prefix: str, expected_kind: str) -> None:
    kinds = {v.kind for v in find_volatile_tokens(prefix)}
    assert expected_kind in kinds


def test_strict_mode_raises_with_the_offending_samples() -> None:
    with pytest.raises(CachePrefixViolationError) as excinfo:
        validate_cache_prefix("生成于 2026-08-13 的提示词", mode="strict", ref="p@v1")
    assert "p@v1" in str(excinfo.value)
    assert excinfo.value.violations


def test_warn_mode_reports_without_raising() -> None:
    violations = validate_cache_prefix("生成于 2026-08-13", mode="warn")
    assert [v.kind for v in violations] == ["iso-date"]


def test_off_mode_skips_the_check() -> None:
    assert validate_cache_prefix("生成于 2026-08-13", mode="off") == []


def test_registry_rejects_a_bad_prompt_at_load_time(tmp_path: Path) -> None:
    bad = tmp_path / "bad" / "v1.txt"
    bad.parent.mkdir(parents=True)
    bad.write_text("[system]\n你好 {nickname}\n\n[user]\n{user_input}\n", encoding="utf-8")

    registry = PromptRegistry(tmp_path, cache_prefix_mode="strict")
    with pytest.raises(CachePrefixViolationError):
        registry.get("bad", "v1")


def test_shipped_prompts_all_satisfy_the_discipline(repo_root: Path) -> None:
    """Regression guard: every prompt in the repo keeps a cacheable prefix."""
    prompts_root = repo_root / "prompts"
    files = sorted(prompts_root.glob("*/*.txt"))
    assert files, "no prompt templates found"
    for path in files:
        template = parse_prompt_file(
            path.read_text(encoding="utf-8"), prompt_id=path.parent.name, version=path.stem
        )
        assert find_volatile_tokens(template.system_prefix) == [], f"{path} has a volatile prefix"


def test_prompt_file_without_system_section_is_rejected() -> None:
    with pytest.raises(PromptNotFoundError):
        parse_prompt_file("[user]\nhello\n", prompt_id="x", version="v1")