/**
 * InvestigationSummaryPanel — Phase 4
 * Displays key investigation metrics in a compact card.
 * Some fields are currently mocked; TODO comments identify what the
 * reasoning engine must eventually provide.
 */

/* ── Helpers ──────────────────────────────────────────────── */

import React from "react";

function formatTimestamp(iso) {
  if (!iso) return "—";
  try {
    const d = new Date(iso);
    if (isNaN(d)) return iso;
    const pad = (n) => String(n).padStart(2, "0");
    return `${d.getFullYear()}-${pad(d.getMonth()+1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}`;
  } catch {
    return iso;
  }
}

function humaniseDuration(seconds) {
  if (!seconds || seconds < 0) return "—";
  const mins = Math.floor(seconds / 60);
  const secs = seconds % 60;
  if (mins === 0) return `${secs}s`;
  return `${mins}m ${secs}s`;
}

/* ── Component ────────────────────────────────────────────── */

function InvestigationSummaryPanel({ graph, selectedQuestion, result, updateStatus }) {
  // ── Current status ────────────────────────────────────────────
  // TODO: reasoning should emit an explicit status field such as
  //   "investigating", "evidence_limit_reached", "resolution_achieved".
  // Currently derived heuristically from graph state.
  const isInvestigating = Boolean(selectedQuestion);
  const hasGraph = Boolean(graph);

  let currentStatus;
  if (updateStatus === "loading") {
    currentStatus = { label: "Reasoning", level: "investigating" };
  } else if (!hasGraph) {
    currentStatus = { label: "Not started", level: "idle" };
  } else if (isInvestigating) {
    currentStatus = { label: "Investigation in progress", level: "investigating" };
  } else if (graph.resolvedNodeIds?.length > 0 && graph.nodes) {
    const unresolvedUnknowns = graph.nodes.filter(
      (n) => n.kind === "unknown" && !graph.resolvedNodeIds.includes(n.id)
    );
    if (unresolvedUnknowns.length === 0) {
      currentStatus = { label: "Investigation complete", level: "complete" };
    } else {
      // TODO: reasoning should emit a terminal "evidence_limit_reached"
      // status when it stops selecting questions because no unknown has
      // sufficient upstream evidence. Currently we infer this from the
      // absence of an active question combined with unresolved unknowns.
      currentStatus = { label: "Current evidence limit reached", level: "limit" };
    }
  } else {
    currentStatus = { label: "Analysis complete", level: "complete" };
  }

  const statusColors = {
    idle:        { border: "border-gray-200/60",   bg: "bg-gray-50/40",    text: "text-gray-400" },
    investigating: { border: "border-blue-200/60",  bg: "bg-blue-50/30",   text: "text-blue-600" },
    complete:    { border: "border-green-200/60",   bg: "bg-green-50/30",  text: "text-green-600" },
    limit:       { border: "border-gray-200",    bg: "bg-gray-50/40",  text: "text-gray-400" },
  };

  const colors = statusColors[currentStatus.level] || statusColors.idle;

  // ── Current understanding ────────────────────────────────
  // TODO: reasoning should provide a durable summary field that is
  // guaranteed to be the latest plain-language synthesis.
  // Currently falls back to graph.currentSummary which may not exist
  // in all mock scenarios.
  const currentUnderstanding =
    result?.summary ||
    result?.updatedSituationGraph?.currentSummary ||
    graph?.currentSummary ||
    null;

  // ── Questions answered / remaining ───────────────────────
  // TODO: reasoning should emit a list of resolved unknown node IDs
  // and the total set of unknown nodes it identified at start.
  // Currently we count from the graph snapshot: every unknown whose
  // status is "resolved" (or whose ID appears in resolvedNodeIds).
  let questionsAnswered = 0;
  let questionsRemaining = 0;

  if (graph?.nodes) {
    const allUnknowns = graph.nodes.filter((n) => n.kind === "unknown");
    const resolvedCount = allUnknowns.filter(
      (n) => n.status === "resolved" || (graph.resolvedNodeIds && graph.resolvedNodeIds.includes(n.id))
    ).length;
    questionsAnswered = resolvedCount;
    // TODO: this is a rough heuristic — the reasoning engine should
    // explicitly track which unknowns were proposed for questioning.
    questionsRemaining = allUnknowns.length - resolvedCount;
  }

  // ── Timestamps ───────────────────────────────────────────
  // TODO: reasoning should provide investigationStartedAt and
  // lastUpdatedAt as part of the start/update contract.
  // Currently we use the session updatedAt timestamp (persisted by
  // the UI layer) as a best-effort approximation.
  const investigationStartTime = result?.updatedAt || null;
  const lastUpdatedAt = result?.updatedAt || null;

  // Derive elapsed time since last update
  let elapsedSeconds = 0;
  if (lastUpdatedAt) {
    elapsedSeconds = Math.floor((Date.now() - new Date(lastUpdatedAt).getTime()) / 1000);
  }

  return (
    <div className={`rounded-lg border ${colors.border} ${colors.bg} p-5 space-y-4`}>
      {/* Status */}
      <div className="flex items-center gap-2">
        <span className={`inline-block h-2.5 w-2.5 rounded-full bg-current ${colors.text}`} />
        <span className={`text-sm font-medium ${colors.text}`}>{currentStatus.label}</span>
      </div>

      {/* Current understanding */}
      {currentUnderstanding && (
        <div>
          <h3 className="mb-1 text-[11px] font-semibold tracking-widest uppercase text-gray-500">
            What we understand so far
          </h3>
          <p className="text-sm leading-relaxed text-gray-600">{currentUnderstanding}</p>
        </div>
      )}

      {/* Questions — hidden when no meaningful value to show */}
      {isInvestigating && questionsRemaining > 0 && (
        <div className="grid grid-cols-2 gap-4">
          <div>
            <span className="block text-xs text-gray-400">Questions answered</span>
            <span className={`text-lg font-semibold ${colors.text}`}>{questionsAnswered}</span>
          </div>
          <div>
            <span className="block text-xs text-gray-400">Still working on</span>
            <span className={`text-lg font-semibold ${colors.text}`}>{questionsRemaining + " items"}</span>
          </div>
        </div>
      )}
    </div>
  );
}

export default InvestigationSummaryPanel;