"use client";

import { useState, useEffect, useCallback, type FormEvent } from "react";
import Link from "next/link";
import { TextField } from "@nexarch/shl";
import { search, facets, ApiError, type SearchHit, type AppliedFilter, type FacetsResponse } from "../lib/api";
import { splitHighlighted } from "../lib/highlight";
import { HIGHLIGHT_BG_LIGHT, HIGHLIGHT_FG_LIGHT } from "../lib/highlightColors";
import { ActiveFilterChips, FacetPanel } from "./FacetPanel";
import { addFilter, removeFilter } from "../lib/filterState";

function tenantSlug(): string {
  return process.env.NEXT_PUBLIC_MAIL_TENANT_SLUG ?? "";
}

function Snippet({ text }: { text: string }) {
  if (!text) {
    return null;
  }
  return (
    <span>
      {splitHighlighted(text).map((segment, idx) =>
        segment.matched ? (
          <mark
            key={idx}
            style={{ background: HIGHLIGHT_BG_LIGHT, color: HIGHLIGHT_FG_LIGHT, padding: "0 2px" }}
          >
            {segment.text}
          </mark>
        ) : (
          <span key={idx}>{segment.text}</span>
        )
      )}
    </span>
  );
}

function resultHref(hit: SearchHit): string {
  const params = new URLSearchParams({
    subject: hit.subjectSnippet,
    snippet: hit.bodySnippet,
  });
  return `/mail/${encodeURIComponent(hit.messageId)}?${params.toString()}#fundstelle`;
}

export default function SearchPage() {
  const [query, setQuery] = useState("");
  const [appliedFilters, setAppliedFilters] = useState<AppliedFilter[]>([]);
  const [hits, setHits] = useState<SearchHit[] | null>(null);
  const [facetsData, setFacetsData] = useState<FacetsResponse | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [loading, setLoading] = useState(false);

  const runSearch = useCallback(
    async (q: string, filters: AppliedFilter[]) => {
      if (!q.trim() && filters.length === 0) {
        setHits(null);
        setFacetsData(null);
        setError(null);
        return;
      }
      setLoading(true);
      setError(null);
      try {
        const [searchResult, facetsResult] = await Promise.all([
          search(tenantSlug(), q, filters),
          facets(tenantSlug(), q, filters),
        ]);
        setHits(searchResult.hits);
        setFacetsData(facetsResult);
      } catch (err) {
        // Akzeptanzkriterium 3 (SRC-04, sinngemäß auf Fehlerfall
        // übertragen): auch ein Suchfehler zeigt einen verständlichen
        // Hinweis statt einer leeren Fläche.
        setHits([]);
        setFacetsData(null);
        setError(err instanceof ApiError ? err.message : "Suche konnte nicht ausgeführt werden.");
      } finally {
        setLoading(false);
      }
    },
    []
  );

  function onSubmit(e: FormEvent) {
    e.preventDefault();
    void runSearch(query, appliedFilters);
  }

  // SRC-06 Akzeptanzkriterium 2: Trefferzahl je Facettenwert live
  // aktualisiert — jede Filteränderung löst Such- UND Facettenabfrage
  // erneut aus.
  useEffect(() => {
    void runSearch(query, appliedFilters);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [appliedFilters]);

  function onAddFilter(filter: AppliedFilter) {
    setAppliedFilters((prev) => addFilter(prev, filter));
  }
  function onRemoveFilter(filter: AppliedFilter) {
    setAppliedFilters((prev) => removeFilter(prev, filter));
  }
  function onClearFilters() {
    setAppliedFilters([]);
  }

  return (
    <main style={{ maxWidth: 720, margin: "40px auto", padding: "0 16px" }}>
      <h1>Mail-Suche</h1>
      <form onSubmit={onSubmit}>
        <TextField
          label="Suchbegriff"
          value={query}
          onChange={(e) => setQuery(e.target.value)}
          placeholder='z. B. "Quartalsbericht" oder Umsatz -Verlust'
        />
        <button type="submit" disabled={loading} style={{ marginTop: 8 }}>
          Suchen
        </button>
      </form>

      <ActiveFilterChips
        facetsData={facetsData}
        appliedFilters={appliedFilters}
        onAddFilter={onAddFilter}
        onRemoveFilter={onRemoveFilter}
        onClearFilters={onClearFilters}
      />

      {error && (
        <p role="alert" style={{ marginTop: 16 }}>
          {error}
        </p>
      )}

      {hits !== null && hits.length === 0 && !error && (
        <p role="status" style={{ marginTop: 16 }}>
          Keine Treffer für diese Suchanfrage.
        </p>
      )}

      <FacetPanel
        facetsData={facetsData}
        appliedFilters={appliedFilters}
        onAddFilter={onAddFilter}
        onRemoveFilter={onRemoveFilter}
        onClearFilters={onClearFilters}
      />

      {hits !== null && hits.length > 0 && (
        <ul style={{ listStyle: "none", padding: 0, marginTop: 16 }}>
          {hits.map((hit) => (
            <li key={hit.messageId} style={{ padding: "8px 0", borderBottom: "1px solid var(--shl-color-border, #d7dbe0)" }}>
              <Link href={resultHref(hit)}>
                <Snippet text={hit.subjectSnippet} />
                <div>
                  <Snippet text={hit.bodySnippet} />
                </div>
              </Link>
            </li>
          ))}
        </ul>
      )}
    </main>
  );
}