#Detailed explanation of django Form form processing

# app/forms.py
from django import forms

class ContactForm(forms.Form):
    name = forms.CharField(max_length=100, label="你的昵称")
    email = forms.EmailField(label="常用邮箱")
    subject = forms.CharField(max_length=200, label="留言主题")
    message = forms.CharField(widget=forms.Textarea, label="详细内容")
    # required=False默认不勾选，也不会校验必填
    subscribe = forms.BooleanField(required=False, label="订阅我们的更新")

# app/views.py
from django.shortcuts import render, redirect
from django.contrib import messages
from .forms import ContactForm

def contact_view(request):
    if request.method == "POST":
        # 用POST数据实例化表单（绑定数据）
        form = ContactForm(request.POST)
        # 先做全链路验证
        if form.is_valid():
            # 验证通过后，取cleaned_data（已转成Python对应类型的安全数据）
            name = form.cleaned_data["name"]
            email = form.cleaned_data["email"]
            # 处理数据：比如发邮件、存数据库
            # send_contact_mail(name, email, ...)
            messages.success(request, "留言发送成功！")
            return redirect("contact")  # 成功后重定向避免重复提交
    else:
        # GET请求返回空表单（未绑定数据）
        form = ContactForm()
    # 不管POST/GET失败，都把当前表单（空的或带错误的）传给模板
    return render(request, "contact.html", {"form": form})

# app/forms.py
from django import forms

class UserProfileForm(forms.Form):
    # 带长度限制和提示的用户名
    username = forms.CharField(
        max_length=150, min_length=3,
        label="用户名", help_text="3-150个字符，支持字母数字下划线"
    )
    # 密码输入框（隐藏内容）
    password = forms.CharField(widget=forms.PasswordInput, min_length=8)
    # 单选下拉框
    gender = forms.ChoiceField(
        choices=[("M", "男"), ("F", "女"), ("O", "其他")],
        label="性别"
    )
    # 多选复选框（默认是列表，用CheckboxSelectMultiple转成复选）
    hobbies = forms.MultipleChoiceField(
        choices=[("reading", "阅读"), ("sports", "运动"), ("music", "音乐")],
        widget=forms.CheckboxSelectMultiple, label="兴趣爱好"
    )
    # HTML5原生日期选择器
    birth_date = forms.DateField(
        widget=forms.DateInput(attrs={"type": "date"}), label="出生日期"
    )

# app/forms.py
from django import forms

class SearchForm(forms.Form):
    query = forms.CharField(
        max_length=200,
        widget=forms.TextInput(attrs={
            "class": "form-control",  # 适配Bootstrap
            "placeholder": "搜索你感兴趣的内容...",
            "id": "global-search"
        }),
        label=""  # 隐藏标签
    )

# app/forms.py
from django import forms
from .models import Article  # 假设你有Article模型

class ArticleForm(forms.Form):
    title = forms.CharField(max_length=200, label="文章标题")
    content = forms.CharField(widget=forms.Textarea, label="正文")

    def clean_title(self):
        title = self.cleaned_data["title"]
        # 规则1：至少5个字符
        if len(title) < 5:
            raise forms.ValidationError("标题太短啦，至少5个字符")
        # 规则2：不能和已有的重复
        if Article.objects.filter(title=title).exists():
            raise forms.ValidationError("这个标题已经被用过了")
        return title  # 必须返回！

class ArticleForm(forms.Form):
    # ... 上面的字段 ...

    def clean(self):
        # 先调用父类的clean，获取所有清洗后的字段
        cleaned_data = super().clean()
        title = cleaned_data.get("title")
        content = cleaned_data.get("content")
        
        # 规则：标题不能完全出现在正文开头
        if title and content and content.startswith(title):
            raise forms.ValidationError("正文开头不能直接复制标题")
        
        return cleaned_data

# app/forms.py
from django import forms
from .models import Article

class ArticleModelForm(forms.ModelForm):
    class Meta:  # 必须用这个内部类配置
        model = Article  # 绑定的Model
        fields = ["title", "content", "category", "status"]  # 要显示的字段（推荐显式写）
        # 或者 exclude = ["author", "created_at"]  # 排除某些字段
        
        # 覆盖Model默认的Widget
        widgets = {
            "content": forms.Textarea(attrs={"class": "form-control", "rows": 10}),
            "status": forms.Select(attrs={"class": "form-select"}),
        }
        
        # 覆盖默认的标签
        labels = {
            "category": "文章分类",
        }

# app/views.py
from django.contrib.auth.decorators import login_required

@login_required
def create_article(request):
    if request.method == "POST":
        form = ArticleModelForm(request.POST)
        if form.is_valid():
            # commit=False：先不存数据库，用来补充Model里没在表单显示的字段
            article = form.save(commit=False)
            article.author = request.user  # 补充当前登录用户
            article.save()  # 真正存数据库
            messages.success(request, "文章发布成功！")
            return redirect("article_detail", pk=article.pk)
    else:
        form = ArticleModelForm()
    return render(request, "create_article.html", {"form": form})

@login_required
def edit_article(request, pk):
    # 先获取要编辑的文章，找不到404
    article = get_object_or_404(Article, pk=pk)
    # 检查权限
    if article.author != request.user:
        messages.error(request, "您没有权限编辑这篇文章")
        return redirect("article_list")
    
    if request.method == "POST":
        # 绑定数据+实例，这样save()就是更新而不是新增
        form = ArticleModelForm(request.POST, instance=article)
        if form.is_valid():
            form.save()
            messages.success(request, "文章更新成功！")
            return redirect("article_detail", pk=article.pk)
    else:
        # GET请求绑定实例，自动填充已有内容
        form = ArticleModelForm(instance=article)
    return render(request, "edit_article.html", {"form": form, "article": article})