"use client";

import Link from "next/link";
import { useRouter } from "next/navigation";
import { useCallback, useEffect, useRef, useState } from "react";
import type { Assessment, AssessmentSummary } from "@/lib/types";
import { dateLabel, money } from "@/lib/format";
import { Empty } from "@/components/charts";
import LoadError from "@/components/LoadError";
import { errorMessage, getJson, sendJson } from "@/lib/client";

export default function Home() {
  const router = useRouter();
  const [rows, setRows] = useState<AssessmentSummary[] | null>(null);
  const [name, setName] = useState("");
  const [busy, setBusy] = useState(false);
  const [err, setErr] = useState("");
  const [loadError, setLoadError] = useState("");
  const fileRef = useRef<HTMLInputElement>(null);

  const load = useCallback(async () => {
    setLoadError("");
    try {
      setRows(await getJson<AssessmentSummary[]>("/api/assessments"));
    } catch (e) {
      setLoadError(errorMessage(e));
    }
  }, []);
  useEffect(() => { load(); }, [load]);

  /** Only navigate once the server has confirmed the new id. */
  async function open(created: Assessment) {
    if (!created?.id) throw new Error("The server did not return an assessment id.");
    router.push(`/assessments/${created.id}`);
  }

  async function create(e: React.FormEvent) {
    e.preventDefault();
    if (!name.trim() || busy) return;
    setBusy(true); setErr("");
    try {
      await open(await sendJson<Assessment>("/api/assessments", "POST", { customerName: name.trim() }));
    } catch (e) {
      setErr(errorMessage(e));
      setBusy(false);
    }
  }

  async function importFile(f: File) {
    setBusy(true); setErr("");
    try {
      const parsed = JSON.parse(await f.text());
      await open(await sendJson<Assessment>("/api/assessments", "POST", { import: parsed }));
    } catch (e) {
      setErr(f.name.endsWith(".json") ? errorMessage(e) : `${f.name} is not a JSON assessment file.`);
      setBusy(false);
    }
  }

  async function remove(id: string, label: string) {
    if (!confirm(`Delete the assessment for ${label}? The JSON file is removed from data/assessments.`)) return;
    try {
      await sendJson(`/api/assessments/${id}`, "DELETE");
      load();
    } catch (e) {
      setErr(errorMessage(e));
    }
  }

  const totalSavings = (rows ?? []).reduce((s, r) => s + r.annualSavings, 0);

  return (
    <div className="fade-up">
      <div className="mb-7 flex flex-wrap items-end gap-6">
        <div>
          <h1 className="text-[28px] font-semibold tracking-tight">Assessments</h1>
          <p className="mt-1 max-w-2xl text-[13.5px] text-[var(--text-secondary)]">
            Capture a customer&rsquo;s incumbent tool landscape, map it onto our portfolio, and build the consolidation
            business case. Every assessment is a portable JSON file under <code className="rounded bg-[var(--surface-2)] px-1 py-0.5 text-[12px]">data/assessments/</code>.
          </p>
        </div>
        {rows && rows.length > 0 && (
          <div className="ml-auto text-right">
            <div className="text-[11px] font-semibold uppercase tracking-[.05em] text-[var(--text-muted)]">Pipeline savings identified</div>
            <div className="tabnum text-[22px] font-semibold" style={{ color: "var(--success-text)" }}>{money(totalSavings)}/yr</div>
          </div>
        )}
      </div>

      <div className="mb-6 flex flex-wrap items-end gap-3">
        <form onSubmit={create} className="flex items-end gap-2">
          <div className="w-[260px]">
            <label className="label" htmlFor="new-customer">New assessment</label>
            <input id="new-customer" className="field" placeholder="Customer name" value={name} onChange={(e) => setName(e.target.value)} />
          </div>
          <button className="btn btn-primary" disabled={!name.trim() || busy}>{busy ? "Working…" : "Create"}</button>
        </form>
        <button className="btn" onClick={() => fileRef.current?.click()} disabled={busy}>Import JSON</button>
        <input
          ref={fileRef} type="file" accept="application/json" className="hidden"
          onChange={(e) => { const f = e.target.files?.[0]; if (f) importFile(f); e.target.value = ""; }}
        />
      </div>

      {err && (
        <div className="mb-4 rounded-xl border px-4 py-3 text-[13px]" style={{ borderColor: "var(--critical)", color: "var(--critical)" }}>
          {err}
        </div>
      )}

      {loadError ? (
        <LoadError message={loadError} onRetry={load} />
      ) : rows === null ? (
        <div className="card p-10 text-center text-[13px] text-[var(--text-muted)]">Loading…</div>
      ) : rows.length === 0 ? (
        <Empty>No assessments yet — name a customer above to start one.</Empty>
      ) : (
        <div className="grid gap-3 sm:grid-cols-2 xl:grid-cols-3">
          {rows.map((r) => (
            <div key={r.id} className="card group relative p-5 transition-shadow hover:border-[var(--text-muted)]">
              <Link href={`/assessments/${r.id}`} className="block">
                <div className="flex items-start gap-3">
                  <h2 className="truncate text-[15.5px] font-semibold tracking-tight">{r.customerName}</h2>
                  <span className="chip ml-auto shrink-0">{r.candidateCount} tools</span>
                </div>
                <div className="mt-4 grid grid-cols-2 gap-3">
                  <div>
                    <div className="text-[10.5px] font-semibold uppercase tracking-[.05em] text-[var(--text-muted)]">Spend assessed</div>
                    <div className="tabnum text-[16px] font-semibold">{money(r.annualSpend, true)}</div>
                  </div>
                  <div>
                    <div className="text-[10.5px] font-semibold uppercase tracking-[.05em] text-[var(--text-muted)]">Annual saving</div>
                    <div className="tabnum text-[16px] font-semibold" style={{ color: "var(--success-text)" }}>{money(r.annualSavings, true)}</div>
                  </div>
                </div>
                <div className="mt-4 text-[11.5px] text-[var(--text-muted)]">
                  {r.preparedBy ? `${r.preparedBy} · ` : ""}Updated {dateLabel(r.updatedAt)}
                </div>
              </Link>
              <div className="absolute right-3 top-3 flex gap-1 opacity-0 transition-opacity group-hover:opacity-100 focus-within:opacity-100">
                <Link className="btn btn-ghost btn-sm" href={`/assessments/${r.id}/report`}>Report</Link>
                <button className="btn btn-ghost btn-sm btn-danger" onClick={() => remove(r.id, r.customerName)} aria-label={`Delete ${r.customerName}`}>×</button>
              </div>
            </div>
          ))}
        </div>
      )}
    </div>
  );
}