from __future__ import annotations

import json
from pathlib import Path


class ProjectService:
    def __init__(self, workspace_dir: Path) -> None:
        self.workspace_dir = workspace_dir
        self.projects_dir = workspace_dir / "projects"
        self.index_dir = workspace_dir / "library" / "index"

    def add_items(self, project_id: str, item_keys: list[str]) -> dict[str, object]:
        selected_items = self._read_selected_items(project_id)
        selected_items = sorted(set(selected_items + item_keys))
        self._write_json(self._project_dir(project_id) / "selected-items.json", selected_items)
        return self._rebuild_project_index(project_id, selected_items)

    def remove_item(self, project_id: str, item_key: str) -> dict[str, object]:
        selected_items = [key for key in self._read_selected_items(project_id) if key != item_key]
        self._write_json(self._project_dir(project_id) / "selected-items.json", selected_items)
        return self._rebuild_project_index(project_id, selected_items)

    def get_project_view(self, project_id: str) -> dict[str, object]:
        index_path = self._project_dir(project_id) / "project-index.json"
        if not index_path.exists():
            selected_items = self._read_selected_items(project_id)
            return self._rebuild_project_index(project_id, selected_items)
        return json.loads(index_path.read_text(encoding="utf-8"))

    def _rebuild_project_index(self, project_id: str, selected_items: list[str]) -> dict[str, object]:
        cards_index = self._read_json(self.index_dir / "cards.json")
        collections_index = self._read_json(self.index_dir / "collections.json")
        project_cards = [cards_index[item_key] for item_key in selected_items if item_key in cards_index]
        project_collections = [
            payload
            for payload in collections_index.values()
            if set(payload.get("item_keys", [])) & set(selected_items)
        ]
        payload = {
            "project_id": project_id,
            "selected_items": selected_items,
            "cards": project_cards,
            "collections": project_collections,
        }
        self._write_json(self._project_dir(project_id) / "project-index.json", payload)
        return payload

    def _read_selected_items(self, project_id: str) -> list[str]:
        path = self._project_dir(project_id) / "selected-items.json"
        if not path.exists():
            return []
        return [str(value) for value in json.loads(path.read_text(encoding="utf-8"))]

    def _project_dir(self, project_id: str) -> Path:
        return self.projects_dir / project_id

    @staticmethod
    def _read_json(path: Path) -> dict[str, object]:
        if not path.exists():
            return {}
        return json.loads(path.read_text(encoding="utf-8"))

    @staticmethod
    def _write_json(path: Path, payload: object) -> None:
        path.write_text(json.dumps(payload, indent=2, ensure_ascii=False) + "\n", encoding="utf-8")