// Small SVG charts for the statistics page: a line/area chart with a
// crosshair tooltip, a weekday x hour heatmap, and bar lists. No library;
// colors come from CSS custom properties (--series-N, --heat-N) so light
// and dark themes are handled in style.css. All text is inserted as text,
// never as markup.
import { h } from "./ui.js";

const NS = "http://www.w3.org/2000/svg";

function svg(tag, attrs, ...children) {
  const el = document.createElementNS(NS, tag);
  for (const [k, v] of Object.entries(attrs || {})) {
    if (v !== undefined && v !== null && v !== false) el.setAttribute(k, v);
  }
  for (const c of children.flat(Infinity)) {
    if (c === null || c === undefined || c === false) continue;
    el.append(c instanceof Node ? c : document.createTextNode(String(c)));
  }
  return el;
}

// compact formats a count: 1,234 / 12.9K / 4.2M.
export function compact(n) {
  const a = Math.abs(n);
  if (a >= 1e9) return (n / 1e9).toFixed(a >= 1e10 ? 0 : 1).replace(/\.0$/, "") + "B";
  if (a >= 1e6) return (n / 1e6).toFixed(a >= 1e7 ? 0 : 1).replace(/\.0$/, "") + "M";
  if (a >= 1e4) return (n / 1e3).toFixed(a >= 1e5 ? 0 : 1).replace(/\.0$/, "") + "K";
  return Math.round(n).toLocaleString();
}

// niceTicks returns 0..max in clean steps (1, 2 or 5 x 10^k), at most n+1 ticks.
export function niceTicks(max, n = 4) {
  if (max <= 0) return [0, 1];
  const raw = max / n;
  const mag = Math.pow(10, Math.floor(Math.log10(raw)));
  const step = [1, 2, 5, 10].map((m) => m * mag).find((s) => s >= raw);
  const ticks = [];
  for (let v = 0; v < max + step * 0.999; v += step) ticks.push(Math.round(v * 1e6) / 1e6);
  return ticks;
}

const MIN = 60, HOUR = 3600, DAY = 86400;
const tickSteps = [5 * MIN, 10 * MIN, 15 * MIN, 30 * MIN, HOUR, 2 * HOUR, 3 * HOUR, 6 * HOUR, 12 * HOUR, DAY, 2 * DAY, 7 * DAY, 14 * DAY, 30 * DAY];

// timeTicks picks local-time-aligned ticks between t0 and t1 (Unix seconds).
function timeTicks(t0, t1, maxTicks) {
  const span = t1 - t0;
  const step = tickSteps.find((s) => span / s <= maxTicks) || 30 * DAY;
  const out = [];
  const d = new Date(t0 * 1000);
  if (step >= DAY) {
    d.setHours(0, 0, 0, 0);
  } else {
    d.setSeconds(0, 0);
    const mins = d.getHours() * 60 + d.getMinutes();
    const stepMin = step / 60;
    d.setHours(0, Math.floor(mins / stepMin) * stepMin, 0, 0);
  }
  for (let t = d.getTime() / 1000; t <= t1; ) {
    if (t >= t0) out.push(t);
    if (step >= DAY) {
      const nd = new Date(t * 1000);
      nd.setDate(nd.getDate() + step / DAY);
      t = nd.getTime() / 1000;
    } else t += step;
  }
  return { ticks: out, step };
}

const weekdays = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];
const months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
const pad = (n) => String(n).padStart(2, "0");

function tickLabel(t, step) {
  const d = new Date(t * 1000);
  if (step >= DAY) return step >= 7 * DAY ? months[d.getMonth()] + " " + d.getDate() : weekdays[d.getDay()] + " " + d.getDate();
  const hm = pad(d.getHours()) + ":" + pad(d.getMinutes());
  return d.getHours() === 0 && d.getMinutes() === 0 ? weekdays[d.getDay()] + " " + d.getDate() : hm;
}

// longTime describes a bucket for tooltips and tables.
export function bucketLabel(t, stepSecs) {
  const d = new Date(t * 1000);
  const day = weekdays[d.getDay()] + " " + d.getDate() + " " + months[d.getMonth()];
  if (stepSecs >= DAY) return day;
  const end = new Date((t + stepSecs) * 1000);
  const hm = (x) => pad(x.getHours()) + ":" + pad(x.getMinutes());
  return day + ", " + hm(d) + (stepSecs > MIN ? "–" + hm(end) : "");
}

export const stepSeconds = { "1m": MIN, "5m": 5 * MIN, "15m": 15 * MIN, "1h": HOUR, "6h": 6 * HOUR, "1d": DAY };

// tooltip is one floating readout per chart.
function tooltip() {
  const el = h("div", { class: "chart-tip", role: "status" });
  el.hidden = true;
  return el;
}

// chartCard wraps a chart with its title and a table-view toggle (the
// accessible twin of every chart).
export function chartCard(title, subtitle, chart, tableView, opts = {}) {
  const body = h("div", { class: "chart-body" }, chart);
  const tableBox = h("div", { class: "chart-table" }, tableView);
  tableBox.hidden = true;
  const toggle = h("button", { class: "small link", type: "button", "aria-pressed": "false" }, "Table");
  toggle.addEventListener("click", () => {
    const showTable = tableBox.hidden;
    tableBox.hidden = !showTable;
    body.hidden = showTable;
    toggle.textContent = showTable ? "Chart" : "Table";
    toggle.setAttribute("aria-pressed", String(showTable));
  });
  return h("figure", { class: "panel chart-card" + (opts.wide ? " wide" : "") },
    h("figcaption", { class: "chart-head" },
      h("div", { class: "grow" }, h("h2", null, title), subtitle ? h("div", { class: "muted small" }, subtitle) : null),
      opts.legend || null,
      tableView ? toggle : null),
    body, tableBox);
}

// legend lists series with a short line key (the mark the series uses).
export function legend(series) {
  return h("ul", { class: "chart-legend" }, series.map((s) =>
    h("li", null, h("span", { class: "key line s" + s.slot }), s.label)));
}

// lineChart draws series over time. series: [{label, values, slot}] (slot
// = categorical color 1..3); times: bucket starts (Unix seconds); step in
// seconds. With area, the first series gets a 10% wash under its line.
export function lineChart({ series, times, step, area = false, height = 220, endLabels = true }) {
  const root = h("div", { class: "chart", tabindex: "0", "aria-label": series.map((s) => s.label).join(", ") + " over time" });
  const tip = tooltip();
  root.append(tip);
  let width = 0, focusIdx = -1, geom = null;

  function draw() {
    const w = root.clientWidth;
    if (!w || w === width) return;
    width = w;
    root.querySelector("svg")?.remove();
    const max = Math.max(1, ...series.flatMap((s) => s.values));
    const yTicks = niceTicks(max, 4);
    const yMax = yTicks[yTicks.length - 1];
    const labelW = Math.max(...yTicks.map((t) => compact(t).length)) * 7 + 10;
    const endW = endLabels && series.length > 1 && series.length <= 4 ? Math.max(...series.map((s) => s.label.length)) * 7 + 12 : 8;
    const m = { top: 10, right: endW, bottom: 24, left: labelW };
    const pw = Math.max(40, w - m.left - m.right), ph = height - m.top - m.bottom;
    const t0 = times[0], t1 = times[times.length - 1] + step;
    const x = (t) => m.left + ((t - t0) / Math.max(1, t1 - t0)) * pw;
    const cx = (i) => x(times[i] + step / 2); // the middle of a bucket
    const y = (v) => m.top + ph - (v / yMax) * ph;
    const s = svg("svg", { width: w, height, viewBox: `0 0 ${w} ${height}`, role: "img", "aria-hidden": "true" });
    // Grid and axes.
    for (const t of yTicks) {
      s.append(svg("line", { class: t === 0 ? "axis" : "grid", x1: m.left, x2: m.left + pw, y1: y(t), y2: y(t) }));
      s.append(svg("text", { class: "tick", x: m.left - 6, y: y(t) + 4, "text-anchor": "end" }, compact(t)));
    }
    const { ticks, step: tstep } = timeTicks(t0, t1, Math.max(2, Math.floor(pw / 90)));
    for (const t of ticks) {
      s.append(svg("text", { class: "tick", x: x(t), y: height - 6, "text-anchor": "middle" }, tickLabel(t, tstep)));
    }
    // Series.
    series.forEach((sr, k) => {
      const pts = sr.values.map((v, i) => [cx(i), y(v)]);
      const d = pts.map((p, i) => (i ? "L" : "M") + p[0].toFixed(1) + " " + p[1].toFixed(1)).join("");
      if (area && k === 0 && pts.length) {
        s.append(svg("path", { class: "area s" + sr.slot, d: d + `L${pts[pts.length - 1][0].toFixed(1)} ${y(0)}L${pts[0][0].toFixed(1)} ${y(0)}Z` }));
      }
      s.append(svg("path", { class: "line s" + sr.slot, d }));
      if (pts.length === 1) s.append(svg("circle", { class: "dot s" + sr.slot, cx: pts[0][0], cy: pts[0][1], r: 4 }));
    });
    // Direct end labels when there is room and they don't collide.
    if (m.right > 8) {
      const ends = series.map((sr) => ({ label: sr.label, y: y(sr.values[sr.values.length - 1] || 0) })).sort((a, b) => a.y - b.y);
      if (ends.every((e, i) => i === 0 || e.y - ends[i - 1].y >= 13)) {
        for (const e of ends) s.append(svg("text", { class: "end-label", x: m.left + pw + 6, y: e.y + 4 }, e.label));
      }
    }
    // Crosshair (drawn on hover/focus).
    const cross = svg("line", { class: "crosshair", y1: m.top, y2: m.top + ph, visibility: "hidden" });
    const dots = series.map((sr) => svg("circle", { class: "dot s" + sr.slot, r: 4, visibility: "hidden" }));
    s.append(cross, ...dots);
    // The hit area is the whole plot: readers aim at a time, not a line.
    const hit = svg("rect", { class: "hit", x: m.left, y: m.top, width: pw, height: ph });
    s.append(hit);
    root.prepend(s);
    geom = { cx, y, m, pw, ph, cross, dots, hit };
    hit.addEventListener("pointermove", (e) => {
      const r = s.getBoundingClientRect();
      const px = e.clientX - r.left;
      const i = Math.round(((px - m.left) / pw) * (times.length) - 0.5);
      show(Math.max(0, Math.min(times.length - 1, i)));
    });
    hit.addEventListener("pointerleave", hide);
    if (focusIdx >= 0) show(focusIdx);
  }

  function show(i) {
    if (!geom) return;
    focusIdx = i;
    const xpos = geom.cx(i);
    geom.cross.setAttribute("x1", xpos);
    geom.cross.setAttribute("x2", xpos);
    geom.cross.setAttribute("visibility", "visible");
    series.forEach((sr, k) => {
      geom.dots[k].setAttribute("cx", xpos);
      geom.dots[k].setAttribute("cy", geom.y(sr.values[i]));
      geom.dots[k].setAttribute("visibility", "visible");
    });
    tip.replaceChildren(
      h("div", { class: "tip-head" }, bucketLabel(times[i], step)),
      ...series.map((sr) => h("div", { class: "tip-row" },
        h("span", { class: "key line s" + sr.slot }), h("strong", null, sr.values[i].toLocaleString()), " ", h("span", { class: "muted" }, sr.label))));
    tip.hidden = false;
    // Keep the readout inside the chart, on the far side of the pointer.
    const left = xpos > root.clientWidth / 2 ? xpos - tip.offsetWidth - 12 : xpos + 12;
    tip.style.left = Math.max(0, left) + "px";
    tip.style.top = geom.m.top + "px";
  }

  function hide() {
    if (!geom) return;
    geom.cross.setAttribute("visibility", "hidden");
    geom.dots.forEach((d) => d.setAttribute("visibility", "hidden"));
    tip.hidden = true;
    focusIdx = -1;
  }

  // Keyboard: arrows move the crosshair, as hover does.
  root.addEventListener("focus", () => show(focusIdx >= 0 ? focusIdx : times.length - 1));
  root.addEventListener("blur", hide);
  root.addEventListener("keydown", (e) => {
    if (e.key === "ArrowLeft" || e.key === "ArrowRight") {
      e.preventDefault();
      show(Math.max(0, Math.min(times.length - 1, (focusIdx < 0 ? times.length - 1 : focusIdx) + (e.key === "ArrowLeft" ? -1 : 1))));
    }
  });
  new ResizeObserver(draw).observe(root);
  return root;
}

// timeTable is the table view of a line chart (busiest buckets first is
// not useful here: keep time order, newest first).
export function timeTable(series, times, step) {
  const rows = times.map((t, i) => ({ t, i })).reverse();
  return h("div", { class: "table-wrap scroll" }, h("table", null,
    h("thead", null, h("tr", null, h("th", null, "Time"), series.map((s) => h("th", { class: "num" }, s.label)))),
    h("tbody", null, rows.map((r) => h("tr", null, h("td", null, bucketLabel(r.t, step)),
      series.map((s) => h("td", { class: "num" }, s.values[r.i].toLocaleString())))))));
}

// heatmap draws average activity by weekday (rows, Monday first) and hour
// (columns) with a sequential one-hue ramp; cells without data stay empty.
export function heatmap(hm, unit) {
  const days = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
  let peak = 0;
  hm.avg.forEach((row) => row.forEach((v) => { peak = Math.max(peak, v); }));
  const steps = 7;
  const level = (v) => (peak <= 0 ? 0 : Math.min(steps - 1, Math.floor((v / peak) * steps)));
  const tip = tooltip();
  const grid = h("div", { class: "heatmap", role: "grid", "aria-label": "Average " + unit + " per hour by weekday and hour of day" });
  grid.append(h("div", { class: "hm-corner" }));
  for (let hr = 0; hr < 24; hr++) grid.append(h("div", { class: "hm-col" }, hr % 3 === 0 ? pad(hr) : ""));
  days.forEach((day, d) => {
    grid.append(h("div", { class: "hm-row" }, day));
    for (let hr = 0; hr < 24; hr++) {
      const v = hm.avg[d][hr];
      const n = hm.samples[d][hr];
      const text = v < 0 ? day + " " + pad(hr) + ":00 – no data" :
        day + " " + pad(hr) + ":00 – " + Math.round(v).toLocaleString() + " " + unit + " per hour (average of " + n + (n === 1 ? " hour)" : " hours)");
      const cell = h("div", { class: "hm-cell " + (v < 0 ? "empty" : "heat-" + level(v)), tabindex: "-1", "aria-label": text });
      const showTip = () => {
        tip.textContent = text;
        tip.hidden = false;
        const r = cell.getBoundingClientRect(), pr = grid.getBoundingClientRect();
        tip.style.left = Math.max(0, Math.min(pr.width - tip.offsetWidth, r.left - pr.left - tip.offsetWidth / 2 + r.width / 2)) + "px";
        tip.style.top = (r.bottom - pr.top + 6) + "px";
      };
      cell.addEventListener("pointerenter", showTip);
      cell.addEventListener("focus", showTip);
      cell.addEventListener("pointerleave", () => { tip.hidden = true; });
      cell.addEventListener("blur", () => { tip.hidden = true; });
      grid.append(cell);
    }
  });
  // Arrow keys move between cells.
  grid.tabIndex = 0;
  let cur = -1;
  const cells = () => [...grid.querySelectorAll(".hm-cell")];
  grid.addEventListener("keydown", (e) => {
    const delta = { ArrowLeft: -1, ArrowRight: 1, ArrowUp: -24, ArrowDown: 24 }[e.key];
    if (delta === undefined) return;
    e.preventDefault();
    cur = Math.max(0, Math.min(7 * 24 - 1, (cur < 0 ? 0 : cur) + delta));
    cells()[cur].focus();
  });
  const scale = h("div", { class: "hm-scale" },
    h("span", { class: "muted small" }, "0"),
    Array.from({ length: steps }, (_, i) => h("span", { class: "hm-swatch heat-" + i })),
    h("span", { class: "muted small" }, compact(peak) + " " + unit + "/hour"),
    h("span", { class: "hm-swatch empty" }), h("span", { class: "muted small" }, "no data"));
  return h("div", { class: "heatmap-wrap" }, grid, tip, scale);
}

export function heatmapTable(hm, unit) {
  const days = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"];
  return h("div", { class: "table-wrap scroll" }, h("table", null,
    h("thead", null, h("tr", null, h("th", null, "Hour"), days.map((d) => h("th", { class: "num" }, d)))),
    h("tbody", null, Array.from({ length: 24 }, (_, hr) => h("tr", null, h("td", null, pad(hr) + ":00"),
      days.map((_, d) => h("td", { class: "num" }, hm.avg[d][hr] < 0 ? "–" : Math.round(hm.avg[d][hr]).toLocaleString())))))),
    h("div", { class: "muted small" }, "Average " + unit + " per hour."));
}

// barList shows ranked entries as labelled horizontal bars in one hue
// (one series: no legend, the title names it). Values are always printed,
// so the list is its own table view.
export function barList(entries, { total, label = (k) => k, empty = "No data yet.", href } = {}) {
  if (!entries.length) return h("div", { class: "empty" }, empty);
  // Entries may be in a natural order (e.g. latency buckets), not by size.
  const peak = Math.max(1, ...entries.map((e) => e.count));
  const sum = total || entries.reduce((a, e) => a + e.count, 0);
  return h("ol", { class: "bar-list" }, entries.map((e) => {
    const share = sum ? (e.count / sum) * 100 : 0;
    const name = label(e.key);
    const link = href ? href(e.key) : null;
    return h("li", { title: name + ": " + e.count.toLocaleString() + " (" + share.toFixed(1) + "%)" },
      h("div", { class: "bar-text" },
        link ? h("a", { href: link, class: "bar-label" }, name) : h("span", { class: "bar-label" }, name),
        h("span", { class: "bar-value" }, compact(e.count), h("span", { class: "muted" }, " · " + share.toFixed(share < 10 ? 1 : 0) + "%"))),
      h("div", { class: "bar-track" }, h("div", { class: "bar-fill", style: { width: Math.max(0.5, (e.count / peak) * 100) + "%" } })));
  }));
}