from __future__ import annotations

import json
from datetime import datetime, timedelta, timezone

from sqlalchemy import select

from app.modules.documents.models import ERPWorkstationAgent


ONLINE_WINDOW = timedelta(minutes=5)


def workstation_companies(workstation) -> list[dict]:
    try:
        rows = json.loads(workstation.tally_companies_json or "[]")
    except Exception:
        rows = []
    if not isinstance(rows, list):
        return []

    result = []
    seen = set()
    for row in rows:
        if not isinstance(row, dict):
            continue
        guid = str(row.get("guid") or "").strip()
        name = str(row.get("name") or "").strip()
        if not guid or guid in seen:
            continue
        seen.add(guid)
        result.append(
            {
                "guid": guid,
                "name": name,
                "gstin": str(row.get("gstin") or "").strip(),
                "gstins": list(row.get("gstins") or []),
            }
        )
    return result


def workstation_is_recent(workstation) -> bool:
    seen = getattr(workstation, "last_seen_at_utc", None)
    if not seen:
        return False
    if seen.tzinfo is None:
        seen = seen.replace(tzinfo=timezone.utc)
    return datetime.now(timezone.utc) - seen <= ONLINE_WINDOW


def eligible_tally_workstations(db, tenant_id: int, branch_id: int | None = None):
    stmt = select(ERPWorkstationAgent).where(
        ERPWorkstationAgent.tenant_id == int(tenant_id),
        ERPWorkstationAgent.is_active.is_(True),
        ERPWorkstationAgent.tally_connected.is_(True),
    )
    if branch_id is not None:
        stmt = stmt.where(ERPWorkstationAgent.branch_id == int(branch_id))

    rows = list(
        db.execute(
            stmt.order_by(
                ERPWorkstationAgent.last_seen_at_utc.desc(),
                ERPWorkstationAgent.machine_name.asc(),
            )
        ).scalars().all()
    )
    return [
        row
        for row in rows
        if workstation_is_recent(row) and workstation_companies(row)
    ]


def resolve_workstation_company(
    db,
    *,
    workstation_id: int,
    tenant_id: int,
    branch_id: int | None,
    tally_guid: str,
):
    workstation = db.get(ERPWorkstationAgent, int(workstation_id))
    if (
        not workstation
        or int(workstation.tenant_id) != int(tenant_id)
        or not workstation.is_active
        or not workstation.tally_connected
        or not workstation_is_recent(workstation)
        or (
            branch_id is not None
            and int(workstation.branch_id or 0) != int(branch_id)
        )
    ):
        raise ValueError(
            "Selected ERP Local Agent workstation is offline, stale, or not connected to Tally."
        )

    guid = str(tally_guid or "").strip()
    company = next(
        (
            row
            for row in workstation_companies(workstation)
            if str(row.get("guid") or "").strip() == guid
        ),
        None,
    )
    if not company:
        raise ValueError(
            "Selected Tally company is not currently advertised by this workstation. "
            "Open the company in TallyPrime and allow the Local Agent to refresh."
        )
    return workstation, company