#!/usr/bin/env python3
import argparse

from common import (
    DEFAULT_CHROME_PROFILE,
    discover_grafana_dashboard,
    grafana_query,
    grafana_query_range,
    grafana_session,
    series_last_values,
    write_json,
)


def find_panel_expr(discovery: dict, panel_title: str, expression_index: int) -> str:
    want = str(panel_title or "").strip()
    for panel in discovery.get("panels") or []:
        if str(panel.get("title") or "").strip() != want:
            continue
        targets = panel.get("targets") or []
        if expression_index < 0 or expression_index >= len(targets):
            raise ValueError(f"expression_index out of range for panel {panel_title!r}: {expression_index}")
        expr = str((targets[expression_index] or {}).get("expr") or "").strip()
        if not expr:
            raise ValueError(f"empty expr for panel {panel_title!r} expression_index={expression_index}")
        return expr
    raise ValueError(f"panel not found: {panel_title!r}")


def main() -> int:
    parser = argparse.ArgumentParser(
        description="Fetch metric values from an online Grafana dashboard through the Prometheus datasource proxy"
    )
    parser.add_argument("link", help="Grafana dashboard link, or Grafana base URL when --dashboard-uid is provided")
    parser.add_argument("--dashboard-uid", default="", help="Grafana dashboard uid when link is only the Grafana base URL")
    parser.add_argument(
        "--profile",
        default=DEFAULT_CHROME_PROFILE,
        help="Chrome profile name for reusing an existing Grafana browser login session (default: auto).",
    )
    parser.add_argument("--datasource-id", default="1", help="Grafana datasource proxy id, for example 1")
    parser.add_argument("--panel-title", required=True, help="Grafana panel title")
    parser.add_argument("--expression-index", type=int, default=0, help="Expression index within the selected panel")
    parser.add_argument("--step", default="60s", help="Query step for range queries")
    parser.add_argument(
        "--instant",
        action="store_true",
        help="Use the /query endpoint with the dashboard to/from end timestamp instead of /query_range",
    )
    args = parser.parse_args()

    discovery = discover_grafana_dashboard(args.link, dashboard_uid=args.dashboard_uid or None, profile_name=args.profile)
    grafana_context = discovery.get("grafana_context") or {}
    expr = find_panel_expr(discovery, args.panel_title, args.expression_index)
    session = grafana_session(
        grafana_context.get("base_url") or "",
        profile_name=args.profile,
        path_prefix=str(grafana_context.get("path_prefix") or ""),
    )

    if args.instant:
        payload = grafana_query(
            session,
            args.datasource_id,
            expr,
            time_ts=grafana_context.get("to") or grafana_context.get("from"),
        )
    else:
        start_ts = grafana_context.get("from")
        end_ts = grafana_context.get("to")
        if start_ts is None or end_ts is None:
            raise ValueError("grafana link must include from/to when using range query mode")
        payload = grafana_query_range(
            session,
            args.datasource_id,
            expr,
            start_ts=int(start_ts),
            end_ts=int(end_ts),
            step=args.step,
        )

    write_json(
        {
            "grafana_context": grafana_context,
            "dashboard": discovery.get("dashboard") or {},
            "panel_title": args.panel_title,
            "expression_index": args.expression_index,
            "datasource_id": str(args.datasource_id),
            "final_promql": expr,
            "raw_series": payload,
            "last_values": series_last_values(payload),
        }
    )
    return 0


if __name__ == "__main__":
    raise SystemExit(main())