/**
 * @file EventTimeline.tsx
 * @description A session's events as a flat, expandable list — one row per
 * event (age, status badge, origin · title, tool), opening into EventDetail.
 * Used by the session analysis page's Timeline tab and the read-only snapshot
 * page.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import { useMemo, useState } from "react";
import { useTranslation } from "react-i18next";
import { AgentStatusBadge } from "./StatusBadge";
import { EventDetail } from "./EventDetail";
import {
  agentOriginLabel,
  buildEventTitle,
  buildOriginLabel,
  projectFromCwd,
  projectFromEvent,
  statusFromEventType,
} from "../lib/event-grouping";
import type { AgentInfo } from "../lib/event-grouping";
import { timeAgo } from "../lib/format";
import type { DashboardEvent } from "../lib/types";

export function EventTimeline({
  events,
  agentInfoById,
  sessionNameById,
  fallbackCwd,
}: {
  events: DashboardEvent[];
  agentInfoById: Map<string, AgentInfo>;
  sessionNameById: Map<string, string>;
  /** The session's cwd, for events that carry none of their own. */
  fallbackCwd?: string | null;
}) {
  const { t } = useTranslation("sessions");
  const [expandedEvents, setExpandedEvents] = useState<Set<number>>(() => new Set());

  function toggleEvent(id: number) {
    setExpandedEvents((prev) => {
      const next = new Set(prev);
      if (next.has(id)) next.delete(id);
      else next.add(id);
      return next;
    });
  }

  // Precompute project per event so flat-row rendering doesn't re-parse JSON.
  const projectByEventId = useMemo(() => {
    const map = new Map<number, string | null>();
    for (const e of events) map.set(e.id, projectFromEvent(e));
    return map;
  }, [events]);

  return (
    <div className="card overflow-hidden">
      <div className="divide-y divide-border max-h-[600px] overflow-y-auto overflow-x-auto">
        {events.map((event, i) => {
          const key = event.id ?? i;
          const isOpen = event.id != null && expandedEvents.has(event.id);
          return (
            // Off-screen rows skip layout/paint (a long timeline is not virtualized).
            <div
              key={key}
              style={
                isOpen
                  ? undefined
                  : { contentVisibility: "auto", containIntrinsicSize: "auto 45px" }
              }
            >
              <button
                type="button"
                onClick={() => event.id != null && toggleEvent(event.id)}
                aria-expanded={isOpen}
                aria-label={
                  isOpen ? t("common:eventDetail.collapse") : t("common:eventDetail.expand")
                }
                className="w-full text-left px-5 py-3 flex items-center gap-4 hover:bg-surface-4 transition-colors min-w-0 cursor-pointer"
              >
                <span
                  className={`text-fg-muted text-[10px] w-3 flex-shrink-0 transition-transform ${isOpen ? "rotate-90" : ""}`}
                  aria-hidden="true"
                >
                  ▶
                </span>
                <div className="w-16 text-[11px] text-fg-muted font-mono flex-shrink-0">
                  {timeAgo(event.created_at)}
                </div>
                <AgentStatusBadge status={statusFromEventType(event.event_type)} />
                {(() => {
                  // Session is implicit on this page - project is
                  // still shown so the row identifies the working
                  // directory when you share / search. Events without
                  // their own cwd (e.g. TurnDuration) fall back to the
                  // session's cwd so every row carries the dir prefix.
                  const project =
                    projectByEventId.get(event.id) ?? projectFromCwd(fallbackCwd) ?? null;
                  const origin = buildOriginLabel(
                    project,
                    null,
                    agentOriginLabel(event.agent_id, agentInfoById)
                  );
                  return (
                    <span className="text-sm text-fg-secondary flex-1 truncate">
                      {origin && (
                        <span className="text-fg-muted mr-1" title={event.agent_id ?? undefined}>
                          {origin} ·
                        </span>
                      )}
                      {buildEventTitle(event)}
                    </span>
                  );
                })()}
                {event.tool_name && (
                  <span className="text-[11px] px-2 py-0.5 bg-surface-2 rounded text-fg-muted font-mono">
                    {event.tool_name}
                  </span>
                )}
              </button>
              {isOpen && (
                <EventDetail
                  event={event}
                  agentInfoById={agentInfoById}
                  sessionNameById={sessionNameById}
                />
              )}
            </div>
          );
        })}
      </div>
    </div>
  );
}