// Invoice extractor frontend
(() => {
  const $ = (id) => document.getElementById(id);
  const sections = {
    upload: $("s-upload"),
    processing: $("s-processing"),
    result: $("s-result"),
  };
  const show = (name) => {
    for (const [k, el] of Object.entries(sections)) el.classList.toggle("hidden", k !== name);
  };

  let state = { jobId: null, data: null };

  // ── Upload ──
  const fileInput = $("file-input");
  const dropZone = $("drop-zone");
  $("browse-btn").addEventListener("click", () => fileInput.click());
  fileInput.addEventListener("change", (e) => e.target.files[0] && upload(e.target.files[0]));
  ["dragenter", "dragover"].forEach((ev) =>
    dropZone.addEventListener(ev, (e) => { e.preventDefault(); dropZone.classList.add("drag-over"); }));
  ["dragleave", "drop"].forEach((ev) =>
    dropZone.addEventListener(ev, (e) => { e.preventDefault(); dropZone.classList.remove("drag-over"); }));
  dropZone.addEventListener("drop", (e) => e.dataTransfer.files[0] && upload(e.dataTransfer.files[0]));

  async function upload(file) {
    show("processing");
    try {
      const fd = new FormData();
      fd.append("file", file);
      const r = await fetch("/api/upload", { method: "POST", body: fd });
      if (!r.ok) throw new Error((await r.json()).detail || r.statusText);
      const json = await r.json();
      state.jobId = json.job_id;
      state.data = json.data || {};
      renderForm();
      show("result");
    } catch (err) {
      alert("Chyba: " + err.message);
      show("upload");
    }
  }

  // ── Render editable form ──
  function field(key, label, value, opts = {}) {
    const isEmpty = value === null || value === undefined || value === "";
    const display = isEmpty ? "" : value;
    const cls = "inv-input" + (isEmpty ? " is-empty" : "");
    return `
      <div class="inv-field ${opts.wide ? "inv-field-wide" : ""}">
        <label class="inv-label">${escapeHtml(label)}</label>
        <input class="${cls}" data-key="${key}" type="${opts.type || "text"}"
               value="${escapeHtmlAttr(display)}"
               placeholder="${escapeHtmlAttr(opts.placeholder || "—")}">
      </div>`;
  }

  function nestedField(parent, key, label, value, opts = {}) {
    const isEmpty = value === null || value === undefined || value === "";
    const display = isEmpty ? "" : value;
    const cls = "inv-input" + (isEmpty ? " is-empty" : "");
    return `
      <div class="inv-field ${opts.wide ? "inv-field-wide" : ""}">
        <label class="inv-label">${escapeHtml(label)}</label>
        <input class="${cls}" data-parent="${parent}" data-key="${key}"
               type="${opts.type || "text"}"
               value="${escapeHtmlAttr(display)}"
               placeholder="${escapeHtmlAttr(opts.placeholder || "—")}">
      </div>`;
  }

  function renderForm() {
    const d = state.data;
    const sup = d.supplier || {};
    const cust = d.customer || {};
    const items = d.line_items || [];
    const vat = d.vat_breakdown || [];

    const html = `
      <!-- Identifikace -->
      <div class="inv-card">
        <div class="inv-card-title">Identifikace faktury</div>
        <div class="inv-grid-3">
          ${field("invoice_number", "Číslo faktury", d.invoice_number)}
          ${field("variable_symbol", "Variabilní symbol", d.variable_symbol)}
          ${field("currency", "Měna", d.currency || "CZK")}
          ${field("issue_date", "Datum vystavení", d.issue_date, {type: "date"})}
          ${field("due_date", "Datum splatnosti", d.due_date, {type: "date"})}
          ${field("taxable_date", "DUZP", d.taxable_date, {type: "date"})}
          ${field("constant_symbol", "Konstantní symbol", d.constant_symbol)}
          ${field("specific_symbol", "Specifický symbol", d.specific_symbol)}
          ${field("payment_method", "Způsob platby", d.payment_method)}
        </div>
      </div>

      <!-- Dodavatel -->
      <div class="inv-card">
        <div class="inv-card-title">Dodavatel</div>
        <div class="inv-grid">
          ${nestedField("supplier", "name", "Název", sup.name, {wide: true})}
          ${nestedField("supplier", "ico", "IČO", sup.ico)}
          ${nestedField("supplier", "dic", "DIČ", sup.dic)}
          ${nestedField("supplier", "address", "Adresa", sup.address, {wide: true})}
        </div>
      </div>

      <!-- Odběratel -->
      <div class="inv-card">
        <div class="inv-card-title">Odběratel</div>
        <div class="inv-grid">
          ${nestedField("customer", "name", "Název", cust.name, {wide: true})}
          ${nestedField("customer", "ico", "IČO", cust.ico)}
          ${nestedField("customer", "dic", "DIČ", cust.dic)}
          ${nestedField("customer", "address", "Adresa", cust.address, {wide: true})}
        </div>
      </div>

      <!-- Platba -->
      <div class="inv-card">
        <div class="inv-card-title">Platební údaje</div>
        <div class="inv-grid">
          ${field("bank_account", "Číslo účtu", d.bank_account)}
          ${field("iban", "IBAN", d.iban)}
        </div>
      </div>

      <!-- Položky -->
      <div class="inv-card">
        <div class="inv-card-title">Položky faktury</div>
        <div class="inv-table-wrap">
          <table class="inv-table" id="items-table">
            <thead>
              <tr>
                <th style="min-width:200px">Popis</th>
                <th style="width:80px">Množství</th>
                <th style="width:70px">Jednotka</th>
                <th style="width:110px">Cena/jed. bez DPH</th>
                <th style="width:70px">DPH %</th>
                <th style="width:110px">Bez DPH</th>
                <th style="width:110px">S DPH</th>
                <th class="inv-row-actions"></th>
              </tr>
            </thead>
            <tbody id="items-body">
              ${items.map((it, i) => renderItemRow(it, i)).join("")}
            </tbody>
          </table>
        </div>
        <div class="inv-table-foot">
          <button class="btn-add-row" type="button" id="add-item-btn">+ Přidat položku</button>
        </div>
      </div>

      ${vat.length ? `
      <!-- Rekapitulace DPH -->
      <div class="inv-card">
        <div class="inv-card-title">Rekapitulace DPH</div>
        <div class="inv-table-wrap">
          <table class="inv-table" id="vat-table">
            <thead>
              <tr>
                <th style="width:100px">Sazba (%)</th>
                <th>Základ</th>
                <th>DPH</th>
                <th>Celkem</th>
                <th class="inv-row-actions"></th>
              </tr>
            </thead>
            <tbody id="vat-body">
              ${vat.map((br, i) => renderVatRow(br, i)).join("")}
            </tbody>
          </table>
        </div>
      </div>` : ""}

      <!-- Totals -->
      <div class="inv-card">
        <div class="inv-card-title">Celkem</div>
        <div class="totals-row">
          <div class="total-cell">
            <span class="total-cell-label">Bez DPH</span>
            <input class="inv-input total-cell-input" data-key="total_excluding_vat"
                   type="text" value="${fmtNum(d.total_excluding_vat)}">
          </div>
          <div class="total-cell">
            <span class="total-cell-label">DPH</span>
            <input class="inv-input total-cell-input" data-key="total_vat"
                   type="text" value="${fmtNum(d.total_vat)}">
          </div>
          <div class="total-cell primary">
            <span class="total-cell-label">K úhradě</span>
            <input class="inv-input total-cell-input" data-key="total_including_vat"
                   type="text" value="${fmtNum(d.total_including_vat)}">
          </div>
        </div>
      </div>

      ${d.notes ? `
      <div class="inv-card">
        <div class="inv-card-title">Poznámka</div>
        <input class="inv-input" data-key="notes" type="text"
               value="${escapeHtmlAttr(d.notes)}">
      </div>` : ""}
    `;
    $("invoice-form").innerHTML = html;
    bindFieldHandlers();
  }

  function renderItemRow(item, i) {
    return `
      <tr data-row="${i}">
        <td><input data-field="description" type="text" value="${escapeHtmlAttr(item.description || "")}"></td>
        <td class="num"><input data-field="quantity" type="text" value="${fmtNum(item.quantity)}"></td>
        <td><input data-field="unit" type="text" value="${escapeHtmlAttr(item.unit || "")}"></td>
        <td class="num"><input data-field="unit_price_excluding_vat" type="text" value="${fmtNum(item.unit_price_excluding_vat)}"></td>
        <td class="num"><input data-field="vat_rate" type="text" value="${fmtNum(item.vat_rate)}"></td>
        <td class="num"><input data-field="total_excluding_vat" type="text" value="${fmtNum(item.total_excluding_vat)}"></td>
        <td class="num"><input data-field="total_including_vat" type="text" value="${fmtNum(item.total_including_vat)}"></td>
        <td class="inv-row-actions"><button class="inv-row-delete" type="button" data-action="delete-item" title="Smazat">×</button></td>
      </tr>`;
  }

  function renderVatRow(br, i) {
    return `
      <tr data-row="${i}">
        <td class="num"><input data-field="rate" type="text" value="${fmtNum(br.rate)}"></td>
        <td class="num"><input data-field="base" type="text" value="${fmtNum(br.base)}"></td>
        <td class="num"><input data-field="vat" type="text" value="${fmtNum(br.vat)}"></td>
        <td class="num"><input data-field="total" type="text" value="${fmtNum(br.total)}"></td>
        <td class="inv-row-actions"><button class="inv-row-delete" type="button" data-action="delete-vat" title="Smazat">×</button></td>
      </tr>`;
  }

  function bindFieldHandlers() {
    // Top-level + nested fields
    $("invoice-form").querySelectorAll("input[data-key]").forEach((el) => {
      el.addEventListener("input", () => {
        const key = el.dataset.key;
        const parent = el.dataset.parent;
        const val = parseFieldValue(key, el.value);
        if (parent) {
          if (!state.data[parent]) state.data[parent] = {};
          state.data[parent][key] = val;
        } else {
          state.data[key] = val;
        }
        el.classList.toggle("is-empty", el.value === "");
      });
    });

    // Item rows
    const itemsBody = $("items-body");
    if (itemsBody) {
      itemsBody.addEventListener("input", (e) => {
        const inp = e.target.closest("input");
        if (!inp) return;
        const tr = inp.closest("tr");
        const i = +tr.dataset.row;
        const field = inp.dataset.field;
        if (!state.data.line_items) state.data.line_items = [];
        if (!state.data.line_items[i]) state.data.line_items[i] = {};
        const numFields = ["quantity", "unit_price_excluding_vat", "vat_rate",
                           "total_excluding_vat", "total_including_vat"];
        state.data.line_items[i][field] =
          numFields.includes(field) ? parseNum(inp.value) : inp.value;
      });
      itemsBody.addEventListener("click", (e) => {
        const btn = e.target.closest('[data-action="delete-item"]');
        if (!btn) return;
        const tr = btn.closest("tr");
        const i = +tr.dataset.row;
        state.data.line_items.splice(i, 1);
        renderForm();
      });
    }
    const addItem = $("add-item-btn");
    if (addItem) {
      addItem.addEventListener("click", () => {
        if (!state.data.line_items) state.data.line_items = [];
        state.data.line_items.push({description: "", quantity: null, unit: "",
          unit_price_excluding_vat: null, vat_rate: null,
          total_excluding_vat: null, total_including_vat: null});
        renderForm();
      });
    }

    // VAT rows
    const vatBody = $("vat-body");
    if (vatBody) {
      vatBody.addEventListener("input", (e) => {
        const inp = e.target.closest("input");
        if (!inp) return;
        const tr = inp.closest("tr");
        const i = +tr.dataset.row;
        const field = inp.dataset.field;
        if (!state.data.vat_breakdown) state.data.vat_breakdown = [];
        if (!state.data.vat_breakdown[i]) state.data.vat_breakdown[i] = {};
        state.data.vat_breakdown[i][field] = parseNum(inp.value);
      });
      vatBody.addEventListener("click", (e) => {
        const btn = e.target.closest('[data-action="delete-vat"]');
        if (!btn) return;
        const tr = btn.closest("tr");
        const i = +tr.dataset.row;
        state.data.vat_breakdown.splice(i, 1);
        renderForm();
      });
    }
  }

  function parseFieldValue(key, str) {
    // Numeric top-level fields
    const num = ["total_excluding_vat", "total_vat", "total_including_vat"];
    if (num.includes(key)) return parseNum(str);
    return str;
  }
  function parseNum(s) {
    if (s === "" || s == null) return null;
    const n = parseFloat(String(s).replace(",", ".").replace(/\s/g, ""));
    return Number.isFinite(n) ? n : null;
  }
  function fmtNum(v) {
    if (v === null || v === undefined || v === "") return "";
    if (typeof v === "number") return String(v);
    return String(v);
  }

  // ── Export ──
  $("export-btn").addEventListener("click", async () => {
    if (!state.jobId) return;
    // Persist edits server-side before downloading
    await fetch(`/api/save/${state.jobId}`, {
      method: "POST",
      headers: {"Content-Type": "application/json"},
      body: JSON.stringify({data: state.data}),
    }).catch(() => {});
    window.location.href = `/api/export/${state.jobId}`;
  });

  $("restart-btn").addEventListener("click", () => {
    state = { jobId: null, data: null };
    fileInput.value = "";
    $("invoice-form").innerHTML = "";
    show("upload");
  });

  function escapeHtml(s) {
    return String(s ?? "").replace(/[&<>"']/g, (c) =>
      ({"&":"&amp;","<":"&lt;",">":"&gt;",'"':"&quot;","'":"&#39;"}[c]));
  }
  function escapeHtmlAttr(s) { return escapeHtml(s); }
})();