# 项目文件：shelf_project/src/shelfweb/validation.py
# 先清理书名和标签，再把表单的已读标记转换成数据库保存的整数。
import re
from dataclasses import dataclass


@dataclass(frozen=True)
class BookDraft:
    title: str
    finished: bool
    tags: list[str]


def read_book_form(form):
    values = {
        "title": form.get("title", ""),
        "finished": form.get("finished") == "1",
        "tags": form.get("tags", ""),
    }
    errors = {}
    for name in ["title", "finished", "tags"]:
        if len(form.getlist(name)) > 1:
            errors[name] = "同一字段请只提交一次"
    if set(form) - {"title", "finished", "tags", "csrf_token"}:
        errors["_form"] = "表单中有未识别的字段"
    title = values["title"].strip()
    if not 1 <= len(title) <= 100:
        errors["title"] = "书名请填写 1 至 100 个字符"
    if form.get("finished") not in {None, "1"}:
        errors["finished"] = "已读状态请使用表单中的勾选框"
    tags = list(
        dict.fromkeys(
            piece.strip() for piece in values["tags"].split(",") if piece.strip()
        )
    )
    if len(tags) > 10 or any(len(tag) > 30 for tag in tags):
        errors["tags"] = "最多填写 10 个标签，每个标签不超过 30 个字符"
    draft = None if errors else BookDraft(title, values["finished"], tags)
    return draft, values, errors

# 项目文件：demos/form_parse.py
# 表单字段按单值读取，保留用户填写内容供校验失败后重新渲染页面。
from werkzeug.datastructures import MultiDict

from shelfweb.validation import read_book_form

for data in [
    MultiDict(
        {"title": "  Python Web  ", "tags": " 网络, 网络, 基础 ", "finished": "1"}
    ),
    MultiDict({"title": "A", "tags": ""}),
    MultiDict([("title", "A"), ("title", "B")]),
]:
    draft, values, errors = read_book_form(data)
    print("表单值", values)
    print("处理结果", draft if not errors else errors)