from __future__ import annotations

from app.core.ids import new_id
from app.models.entities import PreviewArtifact
from app.repositories.file_repository import FileRepository
from app.repositories.preview_artifact_repository import PreviewArtifactRepository


class PreviewService:
    def __init__(self, session) -> None:
        self.session = session
        self.file_repository = FileRepository(session)
        self.preview_artifact_repository = PreviewArtifactRepository(session)

    async def get_preview_artifacts_for_file(self, file_id: str) -> list[PreviewArtifact]:
        file_entry = await self.file_repository.get_by_id(file_id)
        if file_entry is None or file_entry.current_version_id is None:
            return []
        return await self.preview_artifact_repository.list_by_file_version(file_entry.current_version_id)

    async def generate_preview_artifacts_for_file(self, file_id: str) -> int:
        file_entry = await self.file_repository.get_by_id(file_id)
        if file_entry is None or file_entry.current_version_id is None:
            raise ValueError("File is unavailable.")
        blob = await self.file_repository.get_primary_blob_for_file(file_id)
        if blob is None:
            raise ValueError("Primary blob does not exist.")

        artifact_types = self._select_artifact_types(file_entry.mime_type)
        created = 0
        for artifact_type in artifact_types:
            existing = await self.preview_artifact_repository.get_by_version_and_type(
                file_entry.current_version_id,
                artifact_type,
            )
            if existing is not None:
                if existing.status != "ready":
                    existing.status = "ready"
                    existing.blob_id = blob.id
                    await self.preview_artifact_repository.save(existing)
                continue

            artifact = PreviewArtifact(
                id=new_id("prv"),
                file_version_id=file_entry.current_version_id,
                artifact_type=artifact_type,
                blob_id=blob.id,
                status="ready",
            )
            await self.preview_artifact_repository.create(artifact)
            created += 1
        await self.session.commit()
        return created

    @staticmethod
    def _select_artifact_types(mime_type: str | None) -> list[str]:
        if mime_type is None:
            return []
        if mime_type.startswith("image/"):
            return ["inline_preview", "thumbnail"]
        if mime_type == "application/pdf":
            return ["inline_preview", "poster"]
        if mime_type.startswith("video/"):
            return ["poster"]
        return []