/* RestockIQ dashboard — plain-English, decision-first. */

const $ = (id) => document.getElementById(id);
let chart = null;

async function getJSON(url) {
  const r = await fetch(url);
  if (!r.ok) throw new Error(`${url} -> ${r.status}`);
  return r.json();
}

function params() {
  return new URLSearchParams({
    current_inventory: $("inventory").value || "0",
    service_level: $("service").value,
    lead_time_days: $("leadtime").value || "7",
  });
}

async function loadSkus() {
  const { stores, items } = await getJSON("/api/skus");
  $("store").innerHTML = stores.map((s) => `<option>${s}</option>`).join("");
  $("item").innerHTML = items.map((i) => `<option>${i}</option>`).join("");
  if (items.includes("FOODS_3_090")) $("item").value = "FOODS_3_090";
}

/* ---------- chart ---------- */

// draws a vertical divider + labels where history ends and the forecast begins
const forecastDivider = {
  id: "forecastDivider",
  afterDraw(c, _args, opts) {
    const i = opts.splitIndex;
    if (!i) return;
    const x = c.scales.x.getPixelForValue(i - 0.5);
    const { top, bottom } = c.chartArea;
    const g = c.ctx;
    g.save();
    g.strokeStyle = "rgba(245,166,35,0.55)";
    g.setLineDash([4, 4]);
    g.beginPath(); g.moveTo(x, top); g.lineTo(x, bottom); g.stroke();
    g.setLineDash([]);
    g.font = "600 11px 'IBM Plex Sans', sans-serif";
    g.fillStyle = "rgba(163,148,111,0.9)";
    g.textAlign = "right";
    g.fillText("the past", x - 8, top + 14);
    g.textAlign = "left";
    g.fillStyle = "rgba(245,166,35,0.95)";
    g.fillText("our forecast →", x + 8, top + 14);
    g.restore();
  },
};
Chart.register(forecastDivider);

function renderChart(fc) {
  const histDates = fc.history_dates || [];
  const labels = histDates.concat(fc.dates).map((d) => d.slice(5)); // MM-DD
  const pad = new Array(histDates.length).fill(null);

  const css = getComputedStyle(document.documentElement);
  const ink = css.getPropertyValue("--ink").trim();
  const amber = css.getPropertyValue("--amber").trim();
  const muted = css.getPropertyValue("--muted").trim();

  if (chart) chart.destroy();
  chart = new Chart($("chart"), {
    type: "line",
    data: {
      labels,
      datasets: [
        { label: "what actually sold", data: (fc.history_actual || []).concat(fc.actual),
          borderColor: ink, borderWidth: 1.5, pointRadius: 0, tension: 0.25 },
        { label: "what we predicted", data: pad.concat(fc.p50),
          borderColor: amber, borderWidth: 2, borderDash: [6, 4], pointRadius: 0, tension: 0.25 },
        { label: "low", data: pad.concat(fc.p10),
          borderColor: "rgba(245,166,35,0.25)", borderWidth: 1, pointRadius: 0, tension: 0.25 },
        { label: "likely range", data: pad.concat(fc.p90),
          borderColor: "rgba(245,166,35,0.25)", backgroundColor: "rgba(245,166,35,0.16)",
          borderWidth: 1, pointRadius: 0, tension: 0.25, fill: "-1" },
      ],
    },
    options: {
      responsive: true, maintainAspectRatio: false,
      interaction: { mode: "index", intersect: false },
      scales: {
        x: { ticks: { color: muted, maxTicksLimit: 9, font: { size: 11 } }, grid: { display: false } },
        y: { beginAtZero: true, ticks: { color: muted, font: { size: 11 } },
             grid: { color: "rgba(53,44,24,0.5)" },
             title: { display: true, text: "units sold per day", color: muted } },
      },
      plugins: {
        legend: { display: false },
        tooltip: { filter: (i) => i.dataset.label !== "low" },
        forecastDivider: { splitIndex: histDates.length },
      },
    },
  });
}

/* ---------- answer card ---------- */

function setChip(status) {
  const chip = $("status-chip");
  const map = {
    order_now: ["red", "Order today"],
    order_soon: ["amber", "Order soon"],
    ok: ["green", "You're covered"],
  };
  const [cls, text] = map[status];
  chip.className = `chip ${cls}`;
  chip.textContent = text;
}

function verdictText(status, lead) {
  if (status === "ok")
    return `No order needed. Your current stock comfortably covers the next ${lead} days.`;
  if (status === "order_soon")
    return `You're below the safe level. Order in the next day or two to stay ahead.`;
  return `Your stock will likely run out before a new delivery could arrive (${lead} days). Order now.`;
}

async function refreshSeries() {
  const store = $("store").value, item = $("item").value;
  if (!store || !item) return;
  const lead = parseInt($("leadtime").value || "7", 10);
  const inv = parseFloat($("inventory").value || "0");

  const [fc, rec] = await Promise.all([
    getJSON(`/api/forecast/${store}/${item}`),
    getJSON(`/api/recommendation/${store}/${item}?${params()}`),
  ]);

  renderChart(fc);

  const leadDemand = rec.avg_daily_demand * lead;
  let status = "ok";
  if (rec.suggested_order_qty > 0) status = inv <= leadDemand ? "order_now" : "order_soon";
  setChip(status);

  $("order-qty").textContent = Math.ceil(rec.suggested_order_qty);
  $("verdict").textContent = verdictText(status, lead);
  $("r-sell").textContent = Math.round(leadDemand);
  $("r-cushion").textContent = Math.round(rec.safety_stock);
  $("r-have").textContent = Math.round(inv);

  $("n-rop").textContent = rec.reorder_point.toFixed(1);
  $("n-ss").textContent = rec.safety_stock.toFixed(1);
  $("n-std").textContent = rec.demand_std.toFixed(2);
  $("n-sl").textContent = `${Math.round(rec.service_level * 100)}%`;
}

/* ---------- store-wide action list ---------- */

async function refreshActionList() {
  const store = $("store").value;
  if (!store) return;
  const al = await getJSON(`/api/action_list/${store}?${params()}&limit=25`);

  $("al-store").textContent = store;
  $("al-inv").textContent = al.assumptions.current_inventory_per_item;

  const c = al.counts;
  $("al-counts").innerHTML = [
    ["red", "order_now", "need ordering today"],
    ["amber", "order_soon", "order soon"],
    ["green", "ok", "covered"],
  ].map(([cls, k, label]) =>
    `<span class="countpill ${cls}"><b>${(c[k] || 0).toLocaleString()}</b> ${label}</span>`
  ).join("") + `<span class="countpill">of <b>${al.total_items.toLocaleString()}</b> products</span>`;

  const dot = { order_now: "red", order_soon: "amber", ok: "green" };
  const word = { order_now: "today", order_soon: "soon", ok: "covered" };
  $("al-body").innerHTML = al.items.map((r) => `
    <tr data-item="${r.item_id}">
      <td>${r.item_id}</td>
      <td><span class="dot ${dot[r.status]}"></span>${word[r.status]}</td>
      <td class="num">${Math.ceil(r.suggested_order_qty)}</td>
      <td class="num">${Number(r.expected_daily_sales).toFixed(1)}</td>
      <td class="num">${Math.round(r.safety_cushion)}</td>
    </tr>`).join("");

  $("al-body").querySelectorAll("tr").forEach((tr) =>
    tr.addEventListener("click", () => {
      $("item").value = tr.dataset.item;
      refreshSeries();
      window.scrollTo({ top: 0, behavior: "smooth" });
    })
  );
}

/* ---------- proof ---------- */

async function loadProof() {
  let bt;
  try { bt = await getJSON("/api/backtest_summary"); }
  catch { $("proof-note").textContent = "Backtest results not available."; return; }

  const n = bt.policies.naive, r = bt.policies.recommended;
  const drop = ((n.stockout_rate_pct - r.stockout_rate_pct) / n.stockout_rate_pct * 100).toFixed(0);
  $("proofgrid").innerHTML = `
    <div class="prooftile">
      <h3>Gut-feel manager — empty-shelf days</h3>
      <div class="val">${n.stockout_rate_pct.toFixed(1)}%</div>
      <div class="sub">holding ${n.avg_holding_units.toFixed(1)} units on average</div>
    </div>
    <div class="prooftile winner">
      <h3>RestockIQ manager — empty-shelf days</h3>
      <div class="val good">${r.stockout_rate_pct.toFixed(1)}%</div>
      <div class="sub">holding ${r.avg_holding_units.toFixed(1)} units on average</div>
    </div>
    <div class="prooftile winner">
      <h3>Result</h3>
      <div class="val good">−${drop}%</div>
      <div class="sub">fewer empty-shelf days, for ~${(r.avg_holding_units - n.avg_holding_units).toFixed(1)} extra units held</div>
    </div>`;
  $("proof-note").textContent =
    `Replayed over ${bt.n_series.toLocaleString()} products × ${bt.horizon_days} days (${bt.holdout}), ` +
    `${bt.lead_time_days}-day delivery gap, ${Math.round(bt.service_level * 100)}% protection target. ` +
    `Identical simulation rules for both sides; only the reorder logic differs.`;
}

/* ---------- init ---------- */

function wireSteppers() {
  document.querySelectorAll(".stepper button").forEach((b) =>
    b.addEventListener("click", () => {
      const input = $(b.dataset.for);
      const v = (parseFloat(input.value) || 0) + parseInt(b.dataset.step, 10);
      const min = input.min !== "" ? parseFloat(input.min) : -Infinity;
      const max = input.max !== "" ? parseFloat(input.max) : Infinity;
      input.value = Math.min(max, Math.max(min, v));
      input.dispatchEvent(new Event("change"));
    })
  );
}

async function init() {
  wireSteppers();
  await loadSkus();
  await Promise.all([refreshSeries(), refreshActionList(), loadProof()]);
  $("store").addEventListener("change", () => { refreshSeries(); refreshActionList(); });
  $("item").addEventListener("change", refreshSeries);
  for (const id of ["inventory", "service", "leadtime"]) {
    $(id).addEventListener("change", () => { refreshSeries(); refreshActionList(); });
  }
}

init().catch((e) => {
  document.querySelector("main").insertAdjacentHTML(
    "afterbegin",
    `<div class="card" style="border-color:#ff7a5c;color:#ff7a5c">Failed to load: ${e.message}</div>`
  );
});