"""
Knowledge Service - 業務邏輯層
===============================
Knowledge Base Phase 1: CRUD + 狀態流轉 + 搜尋

建立時間: 2026-04-02 (台北時區)
建立者: Claude Code (Knowledge Base Phase 1)

遵循 leWOOOgo 積木化原則:
- Service 層封裝業務邏輯
- 依賴 IKnowledgeRepository Protocol
- Router 層禁止直接存取 DB
"""

import structlog

from src.db.base import get_db_context
from src.models.knowledge import (
    CategoryCount,
    EntryStatus,
    EntryType,
    KnowledgeEntry,
    KnowledgeEntryCreate,
    KnowledgeEntryUpdate,
    KnowledgeListResponse,
)
from src.repositories.interfaces import IKnowledgeRepository
from src.repositories.knowledge_repository import KnowledgeDBRepository

logger = structlog.get_logger(__name__)

# =============================================================================
# Singleton
# =============================================================================

_knowledge_service: "KnowledgeService | None" = None


def get_knowledge_service() -> "KnowledgeService":
    """取得 Knowledge Service 實例"""
    global _knowledge_service
    if _knowledge_service is None:
        _knowledge_service = KnowledgeService()
    return _knowledge_service


class KnowledgeService:
    """Knowledge Base 業務邏輯"""

    async def create_entry(self, data: KnowledgeEntryCreate) -> KnowledgeEntry:
        """建立知識條目"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            entry = await repo.create(data)
            logger.info(
                "knowledge_entry_created",
                entry_id=entry.id,
                entry_type=entry.entry_type,
                source=entry.source,
            )
            return entry

    async def get_entry(self, entry_id: str) -> KnowledgeEntry | None:
        """取得知識條目 (view_count +1)"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            entry = await repo.get_by_id(entry_id)
            if entry:
                await repo.increment_view_count(entry_id)
                entry.view_count += 1
            return entry

    async def update_entry(
        self, entry_id: str, data: KnowledgeEntryUpdate
    ) -> KnowledgeEntry | None:
        """更新知識條目"""
        update_data = data.model_dump(exclude_none=True)
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            if not update_data:
                return await repo.get_by_id(entry_id)
            return await repo.update(entry_id, update_data)

    async def approve_entry(self, entry_id: str) -> KnowledgeEntry | None:
        """審核通過 (draft/review → approved)"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            entry = await repo.get_by_id(entry_id)
            if not entry:
                return None
            if entry.status == EntryStatus.APPROVED:
                return entry
            return await repo.update(entry_id, {"status": EntryStatus.APPROVED})

    async def archive_entry(self, entry_id: str) -> bool:
        """封存 (軟刪除)"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            return await repo.delete(entry_id)

    async def list_entries(
        self,
        category: str | None = None,
        entry_type: EntryType | None = None,
        status: EntryStatus | None = None,
        tags: list[str] | None = None,
        q: str | None = None,
        limit: int = 20,
        offset: int = 0,
    ) -> KnowledgeListResponse:
        """列出知識條目 + 分類統計"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            items, total = await repo.list_entries(
                category=category,
                entry_type=entry_type,
                status=status,
                tags=tags,
                q=q,
                limit=limit,
                offset=offset,
            )
            categories_raw = await repo.get_categories()
            categories = [
                CategoryCount(category=cat, count=cnt) for cat, cnt in categories_raw
            ]
            return KnowledgeListResponse(
                items=items, total=total, categories=categories
            )

    async def get_categories(self) -> list[CategoryCount]:
        """取得分類統計（直接呼叫 repo，不走 list_entries）"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            categories_raw = await repo.get_categories()
            return [CategoryCount(category=cat, count=cnt) for cat, cnt in categories_raw]

    async def search(self, query: str, limit: int = 20) -> list[KnowledgeEntry]:
        """關鍵字搜尋"""
        async with get_db_context() as db:
            repo: IKnowledgeRepository = KnowledgeDBRepository(db)
            return await repo.search(query, limit)