#!/usr/bin/env python3
"""Check required lesson sections and local Markdown links."""

from __future__ import annotations

import ast
import re
import sys
from pathlib import Path


REQUIRED = (
    "本节目标",
    "前置知识",
    "问题动机",
    "核心",
    "实现指南",
    "扩展与联系",
    "精选例题",
    "总结与自检",
    "课后训练建议",
)

# 「课前零食」不是缩短版的正式课：它没有 OJ 例题或 C++ 附件，
# 但必须有从直觉到算法的引导、可运行的小实验和可读的图示。
SNACK_REQUIRED = (
    "本节目标",
    "前置知识",
    "互动规则",
    "从零搭框架",
    "问题动机",
    "步步式引导",
    "核心知识",
    "实现指南",
    "纸上模拟",
    "互动小实验室",
    "扩展与联系",
    "总结与自检",
    "一周预热安排",
)


def main() -> int:
    root = Path(sys.argv[1] if len(sys.argv) > 1 else "课程")
    errors: list[str] = []
    all_documents = sorted(root.rglob("*.md"))
    lessons = [
        path
        for path in all_documents
        if path.name != "README.md" and not path.name.startswith("00-")
    ]
    snacks = [
        path for path in all_documents if path.name.startswith("00-课前零食-")
    ]
    for path in lessons + snacks:
        text = path.read_text(encoding="utf-8")
        headings = "\n".join(re.findall(r"^#{1,6}\s+(.+)$", text, flags=re.MULTILINE))
        required_sections = SNACK_REQUIRED if path in snacks else REQUIRED
        for required in required_sections:
            if required not in headings:
                errors.append(f"{path}: missing section containing {required!r}")
        if "<details>" not in text:
            errors.append(f"{path}: no folded hints/self-check content")
        if re.search(r"```(?:cpp|c\+\+)\n.*?\bint\s+main\s*\(", text, flags=re.DOTALL):
            errors.append(f"{path}: standalone C++ implementation must be an attachment")
        if re.search(r"^\\\[\s*$|^\\\]\s*$", text, flags=re.MULTILINE):
            errors.append(f"{path}: display LaTeX must use $$ delimiters, not \\[ or \\]")

        if path in snacks:
            if len(text) < 4500:
                errors.append(f"{path}: snack is too short for an interactive scaffold")
            pauses = len(re.findall(r"^>\s*停顿", text, flags=re.MULTILINE))
            if pauses < 3:
                errors.append(f"{path}: snack needs at least three prediction pauses")
            if text.count("<details>") < 5:
                errors.append(f"{path}: snack needs several staged feedback blocks")
            svg_links = re.findall(r"!\[[^]]*\]\(([^)]+\.svg)\)", text)
            if len(svg_links) < 2:
                errors.append(f"{path}: snack needs at least two SVG illustrations")
            python_links = re.findall(r"\]\(([^)]*互动程序/[^)]*\.py)\)", text)
            if not python_links:
                errors.append(f"{path}: snack needs a linked Python mini-lab")
            for target in python_links:
                lab = (path.parent / target).resolve()
                if not lab.exists():
                    continue  # The generic local-link pass below reports this too.
                try:
                    ast.parse(lab.read_text(encoding="utf-8"), filename=str(lab))
                except SyntaxError as error:
                    errors.append(f"{path}: Python mini-lab has syntax error: {error}")
            if "精选例题" in headings:
                errors.append(f"{path}: snack must not contain formal OJ examples")

    for path in sorted(root.rglob("*.md")):
        text = path.read_text(encoding="utf-8")
        prose = re.sub(r"```.*?```", "", text, flags=re.DOTALL)
        for target in re.findall(r"\[[^]]*\]\(([^)]+)\)", prose):
            target = target.split("#", 1)[0]
            if not target or re.match(r"(?:https?|mailto):", target):
                continue
            resolved = (path.parent / target).resolve()
            if not resolved.exists():
                errors.append(f"{path}: broken local link {target}")

    for error in errors:
        print(error, file=sys.stderr)
    print(f"lessons={len(lessons)} snacks={len(snacks)} errors={len(errors)}")
    return 1 if errors else 0


if __name__ == "__main__":
    raise SystemExit(main())