from fastapi import HTTPException
from sqlalchemy.ext.asyncio import AsyncSession

from inbox.enums import Candidate_application_Status
from inbox.models import Inbox
from job.candidate.models import ApplicationStageTransitions
from job.pipeline.serializers import serialize_stage_transition


class Pipeline:
    def __init__(self,session:AsyncSession):
        self.session=session

    async def get_transitions(self,inbox_id=None,transition_id=None):
        if transition_id:
            row=await ApplicationStageTransitions.get_by_id(self.session,transition_id)
            if not row:
                raise HTTPException(status_code=404,detail="Transition not found")
            return serialize_stage_transition(row)
        if inbox_id is None:
            raise HTTPException(status_code=400,detail="transition_id or inbox_id is required")
        rows=await ApplicationStageTransitions.fetch_by_inbox(self.session,int(inbox_id))
        return [serialize_stage_transition(r) for r in rows]

    async def change_stage(self,inbox_id,to_stage,current_user,change_reason=None):
        inbox=await Inbox.get_inbox_with_message(self.session,inbox_id)
        if not inbox:
            raise HTTPException(status_code=404,detail="Inbox not found")
        message=inbox.messages
        if not message:
            raise HTTPException(status_code=404,detail="Inbox message not found")
        try:
            stage=Candidate_application_Status(to_stage)
        except ValueError:
            raise HTTPException(status_code=422,detail="Invalid to_stage")
        current=message.application_status
        from_stage=current.value if isinstance(current,Candidate_application_Status) else str(current)
        if from_stage==stage.value:
            raise HTTPException(status_code=400,detail="already at stage")
        changed_by=None
        if isinstance(current_user,dict) and current_user.get("id"):
            changed_by=ApplicationStageTransitions._as_uuid(current_user.get("id"))
        await ApplicationStageTransitions.close_open(self.session,inbox.id,commit=False)
        transition_data={
                "inbox_id":inbox.id,
                "from_stage":from_stage,
                "to_stage":stage.value,
                "changed_by":changed_by,
                "actor_kind":"user",
                "change_reason":change_reason,
            }
        transition=await ApplicationStageTransitions.insert_transition(
            self.session,
            transition_data,
            commit=False,
        )
        message.application_status=stage
        self.session.add(message)
        await self.session.commit()
        return {
            "inbox_id":inbox.id,
            "application_status":stage.value,
            "transition":serialize_stage_transition(transition),
        }