"""Every bundled skill keeps the shape Agent Skills can load well (#4398).

WHY THIS EXISTS

Anthropic's skill authoring guidance
(platform.claude.com/docs/en/agents-and-tools/agent-skills/best-practices):
keep the SKILL.md body under 500 lines, split into reference files as it
nears that, and link each reference file ONE level deep from SKILL.md —
Claude may only preview a file reached through another reference file.

using-scribe reached 478 lines because every new practice lands there, the
same squeeze `_INSTRUCTIONS` was in before #4389. It was split: what matters
on most turns stays in SKILL.md, what matters at one moment (placing a rule,
a missed retrieval, starting a project) moved to files SKILL.md names with
the moment to open them. These tests keep that shape from quietly undoing
itself.

WHAT IT PINS

1. A BUDGET BELOW THE GUIDELINE. 500 is where loading degrades; the budget
   sits under it so the next addition is a choice about what moves out, not
   a squeeze past the line.
2. EVERY REFERENCE FILE IS LINKED FROM SKILL.md. A file nothing links is
   never read — it states guidance that reaches nobody.
3. NO REFERENCE FILE LINKS ANOTHER. One level deep, per the guidance.
4. A LONG REFERENCE FILE OPENS WITH ITS CONTENTS, so a partial read still
   shows what the file covers.
"""
from __future__ import annotations

import pathlib
import re

SKILLS = pathlib.Path(__file__).resolve().parents[1] / "plugin" / "skills"

SKILL_LINE_BUDGET = 350
TOC_AFTER_LINES = 100
_MD_LINK = re.compile(r"\]\(([^)#\s]+\.md)\)")


def _skill_dirs() -> list[pathlib.Path]:
    return sorted(p.parent for p in SKILLS.glob("*/SKILL.md"))


def _refs(folder: pathlib.Path) -> list[pathlib.Path]:
    return sorted(p for p in folder.glob("*.md") if p.name != "SKILL.md")


def over_budget(texts: dict[str, str], budget: int) -> list[str]:
    return [f"{k}: {len(t.splitlines())} lines" for k, t in texts.items()
            if len(t.splitlines()) > budget]


def unlinked(skill_md: str, ref_names: list[str]) -> list[str]:
    linked = set(_MD_LINK.findall(skill_md))
    return [n for n in ref_names if n not in linked]


def nested(refs: dict[str, str]) -> list[str]:
    return [f"{name} → {target}" for name, text in refs.items()
            for target in _MD_LINK.findall(text)]


def missing_contents(refs: dict[str, str], after: int) -> list[str]:
    return [name for name, text in refs.items()
            if len(text.splitlines()) > after and "## Contents" not in text]


def test_every_skill_md_fits_its_budget():
    found = over_budget({d.name: (d / "SKILL.md").read_text() for d in _skill_dirs()},
                        SKILL_LINE_BUDGET)
    assert not found, (
        f"SKILL.md over {SKILL_LINE_BUDGET} lines: {found}. Move what matters at "
        f"one moment into a reference file SKILL.md links with that moment "
        f"(#4398), rather than raising the budget toward 500."
    )


def test_every_reference_file_is_linked_from_skill_md():
    found = [f"{d.name}/{n}" for d in _skill_dirs()
             for n in unlinked((d / "SKILL.md").read_text(), [p.name for p in _refs(d)])]
    assert not found, (
        f"reference files no SKILL.md links: {found}. Nothing reads a file "
        f"nothing names — link it from SKILL.md with the moment to open it."
    )


def test_reference_files_are_one_level_deep():
    found = [f"{d.name}/{x}" for d in _skill_dirs()
             for x in nested({p.name: p.read_text() for p in _refs(d)})]
    assert not found, (
        f"reference files linking other files: {found}. Link each from SKILL.md "
        f"directly; a file reached through another may only be previewed."
    )


def test_long_reference_files_open_with_contents():
    found = [f"{d.name}/{n}" for d in _skill_dirs()
             for n in missing_contents({p.name: p.read_text() for p in _refs(d)},
                                       TOC_AFTER_LINES)]
    assert not found, f"reference files over {TOC_AFTER_LINES} lines with no '## Contents': {found}"


def test_the_guards_can_fail():
    """Rule 167: each guard bites on the failure it exists for."""
    assert over_budget({"s": "x\n" * 400}, SKILL_LINE_BUDGET) == ["s: 400 lines"]
    assert unlinked("see [a](a.md)", ["a.md", "b.md"]) == ["b.md"]
    assert nested({"a.md": "then [b](b.md)"}) == ["a.md → b.md"]
    assert missing_contents({"a.md": "x\n" * 150}, TOC_AFTER_LINES) == ["a.md"]