from __future__ import annotations

import json
from uuid import uuid4

from sqlalchemy.orm import Session

from app.core.constants import (
    APPROVAL_STATUS_APPROVED,
    APPROVAL_STATUS_PENDING,
    APPROVAL_STATUS_REJECTED,
    DECISION_APPROVED,
    DECISION_REJECTED,
    ERROR_CODE_CONFLICT,
    ERROR_CODE_NOT_FOUND,
    TASK_STATUS_CANCELLED,
    TASK_STATUS_PENDING_APPROVAL,
    TASK_STATUS_RUNNING,
)
from app.core.time import format_now
from app.models.audit_log import AuditLog
from app.models.approval import ApprovalRequest
from app.repositories.audit_repository import AuditRepository
from app.repositories.approval_repository import ApprovalRepository
from app.repositories.task_repository import TaskRepository
from app.schemas.approval import ApprovalDecisionRequest, CreateApprovalRequest


class ApprovalConflictError(Exception):
    code = ERROR_CODE_CONFLICT


class ApprovalNotFoundError(Exception):
    code = ERROR_CODE_NOT_FOUND


class ApprovalService:
    def __init__(self, db: Session, timezone_name: str) -> None:
        self.db = db
        self.timezone_name = timezone_name
        self.repository = ApprovalRepository(db)
        self.audit_repository = AuditRepository(db)
        self.task_repository = TaskRepository(db)

    def create_request(self, payload: CreateApprovalRequest) -> ApprovalRequest:
        current_time = format_now(self.timezone_name)
        approval = ApprovalRequest(
            approval_id=f"ap-{uuid4().hex[:12]}",
            task_id=payload.task_id,
            approval_status=APPROVAL_STATUS_PENDING,
            risk_level=payload.risk_level,
            operator_user_id=payload.operator.user_id,
            operator_user_name=payload.operator.user_name,
            approver_user_ids_json=json.dumps(payload.approvers, ensure_ascii=False),
            reason=payload.reason,
            created_at=current_time,
            updated_at=current_time,
        )
        created_approval = self.repository.add(approval)
        self._write_audit_log(
            task_id=payload.task_id,
            request_id=None,
            action="APPROVAL_REQUEST_CREATED",
            result="PENDING",
            target=payload.target.app_code,
            operator_user_id=payload.operator.user_id,
            operator_user_name=payload.operator.user_name,
            detail={
                "approval_id": created_approval.approval_id,
                "approvers": payload.approvers,
                "reason": payload.reason,
            },
        )
        return created_approval

    def get_request(self, approval_id: str) -> ApprovalRequest:
        approval = self.repository.get_by_approval_id(approval_id)
        if not approval:
            raise ApprovalNotFoundError()
        return approval

    def list_pending(self, approver_user_id: str | None = None) -> list[ApprovalRequest]:
        return self.repository.list_pending(approver_user_id)

    def decide(self, approval_id: str, payload: ApprovalDecisionRequest, request_id: str | None = None) -> ApprovalRequest:
        approval = self.repository.get_by_approval_id(approval_id)
        if not approval:
            raise ApprovalNotFoundError()
        if approval.approval_status != APPROVAL_STATUS_PENDING:
            raise ApprovalConflictError("当前审批单状态不允许重复决策。")

        task = self.task_repository.get_by_task_id(approval.task_id)
        if not task:
            raise ApprovalConflictError("审批关联任务不存在，无法继续决策。")
        if task.task_status != TASK_STATUS_PENDING_APPROVAL or task.approval_status != APPROVAL_STATUS_PENDING:
            raise ApprovalConflictError("审批关联任务已不处于待审批状态。")

        current_time = format_now(self.timezone_name)
        if payload.decision == DECISION_APPROVED:
            approval.approval_status = APPROVAL_STATUS_APPROVED
            self._update_task_after_decision(approval.task_id, TASK_STATUS_RUNNING, APPROVAL_STATUS_APPROVED, request_id=request_id)
        elif payload.decision == DECISION_REJECTED:
            approval.approval_status = APPROVAL_STATUS_REJECTED
            self._update_task_after_decision(approval.task_id, TASK_STATUS_CANCELLED, APPROVAL_STATUS_REJECTED, request_id=request_id)
        else:
            raise ApprovalConflictError("decision 仅支持 APPROVED 或 REJECTED。")

        approval.updated_at = current_time
        updated_approval = self.repository.update(approval)
        self._write_audit_log(
            task_id=updated_approval.task_id,
            request_id=request_id,
            action="APPROVAL_DECISION",
            result=updated_approval.approval_status,
            target=payload.operator.user_name,
            operator_user_id=payload.operator.user_id,
            operator_user_name=payload.operator.user_name,
            detail={"approval_id": updated_approval.approval_id, "comment": payload.comment},
        )
        return updated_approval

    def _update_task_after_decision(self, task_id: str, task_status: str, approval_status: str, request_id: str | None = None) -> None:
        task = self.task_repository.get_by_task_id(task_id)
        if not task:
            raise ApprovalConflictError("审批关联任务不存在，无法更新任务状态。")
        if task.task_status != TASK_STATUS_PENDING_APPROVAL or task.approval_status != APPROVAL_STATUS_PENDING:
            raise ApprovalConflictError("审批关联任务已不处于待审批状态。")
        task.task_status = task_status
        task.approval_status = approval_status
        task.updated_at = format_now(self.timezone_name)
        if approval_status == APPROVAL_STATUS_APPROVED:
            task.summary = "审批已通过,准备调用 software-a 最小能力实现执行。"
            self.task_repository.update(task)
            from app.services.task_service import TaskService

            TaskService(self.db, self.timezone_name).execute_task(task_id, request_id=request_id)
        else:
            task.summary = "审批已驳回,任务已取消。"
            self.task_repository.update(task)

    def _write_audit_log(
        self,
        task_id: str,
        request_id: str | None,
        action: str,
        result: str,
        target: str | None,
        operator_user_id: str | None,
        operator_user_name: str | None,
        detail: dict,
    ) -> AuditLog:
        audit_log = AuditLog(
            audit_id=f"audit-{uuid4().hex[:12]}",
            task_id=task_id,
            request_id=request_id,
            action=action,
            operator_user_id=operator_user_id,
            operator_user_name=operator_user_name,
            target=target,
            result=result,
            detail_json=json.dumps(detail, ensure_ascii=False),
            timestamp=format_now(self.timezone_name),
        )
        return self.audit_repository.add(audit_log)