import { useEffect, useState } from "react";
import { useApp } from "../state/store";
import { api, type WorkItem, type RuntimeTransaction } from "../lib/api";
import { Branch, Layers, Pulse } from "../components/icons";

interface DecoratedWorkItem extends WorkItem {
  age_label: string;
}

const HUB_LABELS: Record<string, string> = {
  procurement: "Procurement",
  hr: "People",
  it: "IT",
  manufacturing: "Manufacturing",
  finance: "Finance",
};

function ageLabel(item: WorkItem): string {
  const days = item.age_days ?? 0;
  if (days === 0) return "today";
  if (days === 1) return "1 day";
  if (days < 14) return `${days} days`;
  if (days < 60) return `${Math.floor(days / 7)} wk`;
  return `${Math.floor(days / 30)} mo`;
}

export default function Approvals() {
  const userEmail = useApp((s) => s.userEmail);
  const actor = useApp((s) => s.actor);
  const pushToast = useApp((s) => s.pushToast);
  const setScene = useApp((s) => s.setScene);
  const [items, setItems] = useState<DecoratedWorkItem[] | null>(null);
  const [hubFilter, setHubFilter] = useState<string>("all");
  const [activeKey, setActiveKey] = useState<string | null>(null);
  const [tx, setTx] = useState<RuntimeTransaction | null>(null);
  const [busy, setBusy] = useState<string | null>(null);

  const tenantId = useApp((s) => s.tenantId);
  const loadQueue = async () => {
    if (!tenantId) {
      setItems([]);
      return;
    }
    try {
      const rows = await api.workItems();
      const scoped = rows.filter((it) => (it as any).tenant_id === tenantId);
      setItems(scoped.map((it) => ({ ...it, age_label: ageLabel(it) })));
    } catch (err: any) {
      pushToast("err", `Queue failed: ${err.message}`);
    }
  };

  useEffect(() => { void loadQueue(); }, [tenantId]);

  useEffect(() => {
    if (!activeKey) return;
    let cancelled = false;
    api.transaction(activeKey).then((r) => { if (!cancelled) setTx(r); });
    return () => { cancelled = true; };
  }, [activeKey]);

  const hubs = Array.from(new Set((items || []).map((it) => it.hub).filter((h): h is string => !!h)));
  const visible = (items || []).filter((it) => hubFilter === "all" || it.hub === hubFilter).slice(0, 50);
  const counts = { running: 0, waiting: 0, blocked: 0 };
  for (const it of items || []) {
    if (it.status === "running") counts.running++;
    else if (it.status === "waiting") counts.waiting++;
    else if (it.status === "blocked" || it.status === "stuck") counts.blocked++;
  }

  const handleAction = async (actionId: string) => {
    if (!tx?.transaction_id || !actor) return;
    setBusy(actionId);
    try {
      const res = await api.executeAction(tx.transaction_id, actionId, actor, {});
      pushToast("ok", `Action recorded · ${res.status || "ok"}`);
      const fresh = await api.transaction(tx.transaction_id);
      setTx(fresh);
      await loadQueue();
    } catch (err: any) {
      const msg = err.message || "";
      if (/runtime-values|action_execution_failed/i.test(msg)) {
        pushToast("err", "Backend can't accept this action yet — runtime-values isn't reachable. The frontend sent the right shape.");
      } else {
        pushToast("err", `Action failed: ${msg.slice(0, 100)}`);
      }
    } finally {
      setBusy(null);
    }
  };

  return (
    <div className="approvals-scene">
      <header className="approvals-head">
        <div className="mc-hero-eyebrow"><Layers size={12} /> Approvals · {userEmail.split("@")[0]}</div>
        <h2 className="mc-hero-title">Work that needs you</h2>
        <p className="approvals-intro">
          Every running process instance for your tenant. Pick a row to see the active step and the actions available right now. Acting on a row writes the decision back to EA2.
        </p>
        <div className="approvals-stats">
          <span className="approvals-stat approvals-stat-running">{counts.running} running</span>
          <span className="approvals-stat approvals-stat-waiting">{counts.waiting} waiting</span>
          {counts.blocked > 0 && <span className="approvals-stat approvals-stat-blocked">{counts.blocked} blocked</span>}
        </div>
        <div className="approvals-filter-row">
          <button className={`hub-chip ${hubFilter === "all" ? "active" : ""}`} onClick={() => setHubFilter("all")}>All hubs</button>
          {hubs.map((h) => (
            <button key={h} className={`hub-chip ${hubFilter === h ? "active" : ""}`} onClick={() => setHubFilter(h)}>{HUB_LABELS[h] || h}</button>
          ))}
        </div>
      </header>

      <div className="approvals-split">
        <section className="approvals-queue">
          <div className="hub-section-label">QUEUE · {visible.length}</div>
          {items === null && <div className="hub-empty">Loading…</div>}
          {items !== null && visible.length === 0 && (
            <div className="hub-empty">
              Nothing waiting in this hub. Open the <button className="link-inline" onClick={() => setScene("studio")}>Process Studio</button> to publish a new flow, or check back later.
            </div>
          )}
          <ul className="approvals-list">
            {visible.map((it) => (
              <li key={it.transaction_id}>
                <button
                  className={`approvals-row ${it.transaction_id === activeKey ? "active" : ""}`}
                  onClick={() => setActiveKey(it.transaction_id)}
                >
                  <div className="approvals-row-head">
                    <span className="approvals-row-title">{(it as any).display_name || it.business_subject || "Untitled case"}</span>
                    <span className="approvals-row-age">{it.age_label}</span>
                  </div>
                  <div className="approvals-row-meta">
                    <span className="approvals-row-step">{it.active_step_display_name || it.next_action || "—"}</span>
                    {it.hub && <span className="approvals-row-hub">{HUB_LABELS[it.hub] || it.hub}</span>}
                    {(it as any).requester_display_name && <span className="approvals-row-by">by {(it as any).requester_display_name}</span>}
                  </div>
                </button>
              </li>
            ))}
          </ul>
        </section>

        <section className="approvals-detail">
          <div className="hub-section-label">ACTIVE STEP</div>
          {!activeKey && <div className="hub-empty">Select a case on the left to see its current step and actions.</div>}
          {activeKey && tx && (
            <div className="approvals-card">
              <div className="approvals-card-title">
                <Branch size={11} /> {tx.active_step?.display_name || "Active step"}
              </div>
              {tx.business_subject && <div className="approvals-card-meta">Subject · {tx.business_subject}</div>}
              {(tx.active_step as any)?.dispatch_kind && (
                <div className="approvals-card-meta">Dispatch · {(tx.active_step as any).dispatch_kind}</div>
              )}
              {(tx.active_step as any)?.form_fields && (tx.active_step as any).form_fields.length > 0 && (
                <div className="approvals-fields">
                  <div className="approvals-fields-label">Form fields</div>
                  <ul>
                    {(tx.active_step as any).form_fields.slice(0, 6).map((f: any) => (
                      <li key={f.name}>{f.label || f.name} <span className="approvals-field-type">· {f.type}</span></li>
                    ))}
                  </ul>
                </div>
              )}
              <div className="approvals-actions">
                {(tx.available_actions || []).map((a: any) => (
                  <button
                    key={a.id}
                    className={`btn ${a.kind === "approve" || a.kind === "submit" ? "btn-primary" : "btn-secondary"}`}
                    disabled={!a.enabled || busy === a.id}
                    onClick={() => handleAction(a.id)}
                  >
                    <Pulse size={11} /> {busy === a.id ? "Sending…" : a.display_label || a.id}
                  </button>
                ))}
                {(!tx.available_actions || tx.available_actions.length === 0) && (
                  <div className="hub-empty">No actions available on this step.</div>
                )}
              </div>
            </div>
          )}
          {activeKey && !tx && <div className="hub-empty">Loading case…</div>}
        </section>
      </div>
    </div>
  );
}