from pathlib import Path

from django import forms

from apps.scenarios.services import ScenarioNotFound, get_scenario
from apps.scenarios.services import list_scenarios

SUPPORTED_EXTENSIONS = {".txt", ".md", ".pdf", ".docx"}


class DocumentUploadForm(forms.Form):
    # 使用 ChoiceField 让表单自己维护场景选项，
    # 这样模板、校验和后续扩展都能围绕一个入口完成。
    scenario_id = forms.ChoiceField(label="场景", choices=())
    file = forms.FileField(label="文件")

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields["scenario_id"].choices = [
            (scenario["id"], scenario["name"])
            for scenario in list_scenarios()
        ]

    def clean_scenario_id(self):
        scenario_id = self.cleaned_data["scenario_id"]
        try:
            get_scenario(scenario_id)
        except ScenarioNotFound as exc:
            raise forms.ValidationError("场景不存在") from exc
        return scenario_id

    def clean_file(self):
        uploaded_file = self.cleaned_data["file"]
        extension = Path(uploaded_file.name).suffix.lower()
        if extension not in SUPPORTED_EXTENSIONS:
            raise forms.ValidationError("仅支持 .txt、.md、.pdf 和 .docx 文件")
        return uploaded_file