"""Title library use cases."""

from __future__ import annotations

import uuid
from typing import List, Optional

from packages.adapters.sqlalchemy_impl.title_library_repository import SQLAlchemyTitleLibraryRepository
from packages.application.title_library.commands import (
    CreateTitleLibraryCommand,
    IncrementTitleUsageCommand,
    PickTitleCommand,
    UpdateTitleLibraryCommand,
)
from packages.domain.quota import QuotaDimension, quota_checker
from packages.domain.title_library import TitleLibraryItem


class ListTitleLibraryUseCase:
    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(
        self,
        user_id: str,
        *,
        category: Optional[str] = None,
        skip: int = 0,
        limit: int = 50,
    ) -> List[TitleLibraryItem]:
        return self.repository.list_by_user(user_id, category=category, skip=skip, limit=limit)


class GetTitleLibraryUseCase:
    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, title_id: str, user_id: str) -> Optional[TitleLibraryItem]:
        return self.repository.get(title_id, user_id)


class CreateTitleLibraryUseCase:
    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, command: CreateTitleLibraryCommand, plan_name: str = "free") -> TitleLibraryItem:
        # Quota check
        current_count = self.repository.count_by_user(command.user_id)
        result = quota_checker.check(plan_name, QuotaDimension.MAX_TITLES.value, current_count)
        if not result.allowed:
            raise QuotaExceededError(
                dimension=QuotaDimension.MAX_TITLES.value,
                limit=result.limit,
                used=result.used,
            )

        item = TitleLibraryItem(
            id=uuid.uuid4().hex,
            user_id=command.user_id,
            name=command.name,
            text=command.text,
            category=command.category,
            description=command.description,
            tags=command.tags,
            metadata_=command.metadata_,
        )
        return self.repository.create(item)


class UpdateTitleLibraryUseCase:
    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, command: UpdateTitleLibraryCommand) -> TitleLibraryItem:
        existing = self.repository.get(command.title_id, command.user_id)
        if existing is None:
            raise NotFoundError(f"Title {command.title_id} not found")

        if command.name is not None:
            existing.name = command.name
        if command.text is not None:
            existing.text = command.text
        if command.category is not None:
            existing.category = command.category
        if command.description is not None:
            existing.description = command.description
        if command.tags is not None:
            existing.tags = command.tags
        if command.is_active is not None:
            existing.is_active = command.is_active
        if command.metadata_ is not None:
            existing.metadata_ = command.metadata_

        return self.repository.update(existing)


class DeleteTitleLibraryUseCase:
    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, title_id: str, user_id: str) -> bool:
        return self.repository.delete(title_id, user_id)


class IncrementTitleUsageUseCase:
    """递增标题使用次数。用于生成视频成功后，更新标题的使用统计。"""

    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, command: IncrementTitleUsageCommand) -> bool:
        if command.increment <= 0:
            return False
        return self.repository.increment_usage_count(
            command.title_id,
            command.user_id,
            increment=command.increment,
        )


class PickTitleUseCase:
    """智能选择一个标题。

    策略：
    1. 可选按 category 过滤
    2. 排除指定的 title_ids（如本轮已用过的）
    3. 按使用次数升序，取最少的前 5 个
    4. 从中随机选一个，增加多样性
    5. 无可用标题时返回 None
    """

    _CANDIDATE_POOL_SIZE = 5

    def __init__(self, repository: SQLAlchemyTitleLibraryRepository) -> None:
        self.repository = repository

    def execute(self, command: PickTitleCommand) -> TitleLibraryItem | None:
        import random

        # 取该用户所有活跃标题（或指定分类）
        all_titles = self.repository.list_by_user(
            command.user_id,
            category=command.category,
            is_active=True,
            skip=0,
            limit=500,  # 取足够多的候选
        )

        if not all_titles:
            return None

        # 排除已使用/指定排除的
        exclude_set = set(command.exclude_ids or [])
        candidates = [t for t in all_titles if t.id not in exclude_set]
        if not candidates:
            # 排除后没了，就从全部里选
            candidates = all_titles

        # 按使用次数升序，取最少的前 N 个
        candidates.sort(key=lambda t: t.usage_count)
        pool = candidates[: self._CANDIDATE_POOL_SIZE]

        # 随机选一个
        return random.choice(pool)


class QuotaExceededError(Exception):
    def __init__(self, dimension: str, limit: float, used: float) -> None:
        self.dimension = dimension
        self.limit = limit
        self.used = used
        super().__init__(f"Quota exceeded for {dimension}: {used}/{limit}")


class NotFoundError(Exception):
    pass