from fastapi import APIRouter, HTTPException
from fastapi.responses import FileResponse

from app.schemas.composition import CheckpointUpdate, CompositionSpec, MolecularPanelSpec, RuntimeCheckpoint
from app.schemas.visual_lesson import LessonPayload, NucleicAcidSpec, ProteinLessonSpec
from app.services.visual_lesson_service import VisualLessonService
from app.services.visual_lesson_store import CheckpointConflictError, LessonNotFoundError, LessonVersionError


router = APIRouter(prefix="/api/visual-lessons", tags=["visual-lessons"])
_service: VisualLessonService | None = None


def get_visual_lesson_service() -> VisualLessonService:
    global _service
    if _service is None:
        _service = VisualLessonService()
    return _service


@router.get("/{project_id}/{lesson_id}", response_model=LessonPayload)
def get_visual_lesson(project_id: str, lesson_id: str) -> LessonPayload:
    try:
        return get_visual_lesson_service().load_payload(project_id, lesson_id)
    except LessonNotFoundError as exc:
        raise HTTPException(status_code=404, detail=str(exc)) from exc
    except LessonVersionError as exc:
        raise HTTPException(status_code=409, detail=str(exc)) from exc


@router.put("/{project_id}/{lesson_id}/checkpoint", response_model=RuntimeCheckpoint)
def put_visual_lesson_checkpoint(project_id: str, lesson_id: str, update: CheckpointUpdate) -> RuntimeCheckpoint:
    service = get_visual_lesson_service()
    try:
        return service.save_checkpoint(project_id, lesson_id, update)
    except LessonNotFoundError as exc:
        raise HTTPException(status_code=404, detail=str(exc)) from exc
    except CheckpointConflictError as exc:
        raise HTTPException(status_code=409, detail=str(exc)) from exc
    except (LessonVersionError, ValueError) as exc:
        raise HTTPException(status_code=422, detail=str(exc)) from exc


@router.get("/{project_id}/{lesson_id}/assets/{asset_id}")
def get_visual_lesson_asset(project_id: str, lesson_id: str, asset_id: str) -> FileResponse:
    service = get_visual_lesson_service()
    try:
        spec = service.store.load(project_id, lesson_id)
        structure = spec.structure if isinstance(spec, (ProteinLessonSpec, NucleicAcidSpec)) else None
        if isinstance(spec, CompositionSpec):
            molecular = next((panel for panel in spec.panels if isinstance(panel, MolecularPanelSpec) and panel.asset_id == asset_id), None)
            if molecular is None:
                raise LessonNotFoundError("Molecular structure asset not found")
            coordinate_format = molecular.coordinate_format
            path = service.store.asset_path(project_id, asset_id, coordinate_format)
            media_type = "application/octet-stream" if coordinate_format == "bcif" else "chemical/x-mmcif"
            return FileResponse(path, media_type=media_type, filename=f"{asset_id}.{coordinate_format}")
        if structure is None or structure.coordinate_asset_id != asset_id:
            raise LessonNotFoundError("Molecular structure asset not found")
        coordinate_format = structure.coordinate_format
        path = service.store.asset_path(project_id, asset_id, coordinate_format)
        media_type = "application/octet-stream" if coordinate_format == "bcif" else "chemical/x-mmcif"
        return FileResponse(path, media_type=media_type, filename=f"{asset_id}.{coordinate_format}")
    except LessonNotFoundError as exc:
        raise HTTPException(status_code=404, detail=str(exc)) from exc