from fastapi import APIRouter, Depends, HTTPException, UploadFile, File, Form
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.deps import ensure_class_access, ensure_class_permission, require_role, resolve_class_id_for_user
from app.db.database import get_db
from app.db.models import User
from app.schemas.resource import ResourceCreate, ResourceOut
from app.schemas.common import PageResponse
from app.services.resource_service import (
    create_resource,
    list_resources,
    get_resource_by_id,
    increment_download_count,
    delete_resource,
)
from app.services.cos_service import upload_file

router = APIRouter(prefix="/api/resources", tags=["resources"])

ALLOWED_FILE_TYPES = {
    "application/pdf",
    "application/msword",
    "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
    "application/vnd.ms-excel",
    "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    "application/vnd.ms-powerpoint",
    "application/vnd.openxmlformats-officedocument.presentationml.presentation",
    "application/zip",
    "text/plain",
    "image/jpeg",
    "image/png",
    "image/gif",
    "image/webp",
}


@router.get("/", response_model=PageResponse[ResourceOut])
async def get_resources(
    page: int = 1,
    page_size: int = 20,
    category: str | None = None,
    class_id: int | None = None,
    user: User = Depends(require_role("super_admin", "teacher", "student")),
    db: AsyncSession = Depends(get_db),
):
    effective_class_id = resolve_class_id_for_user(user, class_id)
    if effective_class_id is None:
        return PageResponse(items=[], total=0, page=page, page_size=page_size, total_pages=0)
    ensure_class_access(user, effective_class_id)

    resources, total = await list_resources(db, effective_class_id, category, page, page_size)
    total_pages = (total + page_size - 1) // page_size

    items = []
    for r in resources:
        items.append(
            ResourceOut(
                id=r.id,
                class_id=r.class_id,
                uploader_id=r.uploader_id,
                uploader_name=r.uploader.name if r.uploader else "Unknown",
                title=r.title,
                description=r.description,
                file_url=r.file_url,
                file_type=r.file_type,
                file_size=r.file_size,
                category=r.category,
                download_count=r.download_count,
                created_at=r.created_at,
            )
        )

    return PageResponse(
        items=items, total=total, page=page, page_size=page_size, total_pages=total_pages
    )


@router.post("/", response_model=ResourceOut)
async def upload_new_resource(
    file: UploadFile = File(...),
    title: str = Form(...),
    category: str = Form(...),
    description: str | None = Form(None),
    class_id: int | None = Form(None),
    user: User = Depends(require_role("super_admin", "teacher", "student")),
    db: AsyncSession = Depends(get_db),
):
    effective_class_id = resolve_class_id_for_user(user, class_id)
    if effective_class_id is None:
        raise HTTPException(status_code=400, detail="You are not assigned to a class")
    ensure_class_permission(user, "resource_manage", effective_class_id)

    contents = await file.read()
    if len(contents) > 50 * 1024 * 1024:  # 50MB limit
        raise HTTPException(status_code=400, detail="File too large (max 50MB)")

    if file.content_type not in ALLOWED_FILE_TYPES:
        raise HTTPException(status_code=400, detail=f"File type {file.content_type} not allowed")

    file_url = upload_file(
        f"resources/{effective_class_id}",
        file.filename or "file",
        contents,
        file.content_type,
    )

    data = ResourceCreate(title=title, description=description, category=category)
    resource = await create_resource(
        db, effective_class_id, user.id, data, file_url, file.content_type, len(contents)
    )

    return ResourceOut(
        id=resource.id,
        class_id=resource.class_id,
        uploader_id=resource.uploader_id,
        uploader_name=user.name,
        title=resource.title,
        description=resource.description,
        file_url=resource.file_url,
        file_type=resource.file_type,
        file_size=resource.file_size,
        category=resource.category,
        download_count=resource.download_count,
        created_at=resource.created_at,
    )


@router.post("/{resource_id}/download")
async def download_resource(
    resource_id: int,
    user: User = Depends(require_role("super_admin", "teacher", "student")),
    db: AsyncSession = Depends(get_db),
):
    resource = await get_resource_by_id(db, resource_id)
    if resource is None:
        raise HTTPException(status_code=404, detail="Resource not found")
    ensure_class_access(user, resource.class_id)

    await increment_download_count(db, resource)
    return {"file_url": resource.file_url}


@router.delete("/{resource_id}")
async def delete_existing_resource(
    resource_id: int,
    user: User = Depends(require_role("super_admin", "teacher", "student")),
    db: AsyncSession = Depends(get_db),
):
    resource = await get_resource_by_id(db, resource_id)
    if resource is None:
        raise HTTPException(status_code=404, detail="Resource not found")
    ensure_class_permission(user, "resource_manage", resource.class_id)

    await delete_resource(db, resource)
    return {"message": "Resource deleted"}