// The trend chart: a shared line-series renderer (percentile fan + median +
// value trace + labeled points) with per-metric wrappers, the site-matched
// palette, and the pointer-driven hover. Extracted from app.js so any page can
// plot a metric series; app.js keeps only its page orchestration (buildChart).
import { fmtTemp, toUnit, toWind, fmtPrecip, fmtWind, fmtHumid,
         windUnit, humidUnit } from "./units.js";
import { TIER_COLORS, drynessColor, pctOrd } from "./shared.js";

// #rrggbb -> rgba() with alpha, so band tints derive from the same site colors.
const hexA = (hex, a) => {
  let h = (hex || "").trim().replace("#", "");
  if (h.length === 3) h = h.split("").map((c) => c + c).join("");
  const n = parseInt(h || "888888", 16);
  return `rgba(${(n >> 16) & 255}, ${(n >> 8) & 255}, ${n & 255}, ${a})`;
};

export function chartPalette() {
  // Read straight from the site's CSS variables so the chart matches the rest of
  // the UI and follows the light/dark theme automatically. hiBand/loBand are
  // applied once per tier ring (p1-99, p10-90, p25-75, p40-60) and stack, so keep
  // each layer light — the center (Normal) darkens naturally.
  const css = getComputedStyle(document.documentElement);
  const v = (name, f) => (css.getPropertyValue(name).trim() || f);
  const dark = matchMedia("(prefers-color-scheme: dark)").matches;
  const hi = v("--very-hot", "#dd6b52");        // daily-high series = warm tier red
  const lo = v("--cold", "#4393c3");            // daily-low series = cool tier blue
  return {
    surface: v("--surface-2", dark ? "#1e242c" : "#eef1f5"),
    ink: v("--text", dark ? "#e7ecf2" : "#1a2029"),
    muted: v("--muted", dark ? "#9aa6b2" : "#5b6673"),
    grid: v("--border", dark ? "#2a323c" : "#dde3ea"),
    accent: v("--accent", "#f0803c"),
    hi, lo,
    // Distinct line/point accents for the three added series; the graded fan
    // behind them still uses the shared diverging tier colors (same as temps).
    feels: v("--accent", "#f0803c"),   // "feels like" = orange accent
    humid: "#2ea9bf",                  // humidity = cyan
    wind: "#5aa9a3",                   // wind speed = teal
    gust: "#8f86d8",                   // wind gust = periwinkle
    precip: v("--wet-6", "#2b8cbe"),
    hiBand: hexA(hi, dark ? 0.15 : 0.11),
    loBand: hexA(lo, dark ? 0.17 : 0.12),
  };
}

// W/PW are recomputed per build from the container width (setChartWidth), so a
// wide monitor gets a genuinely wider drawing — more room between days — instead
// of the same 720-unit canvas magnified. Live bindings: importers see updates.
export let W = 720;
export const H = 340;
export const PL = 46, PR = 62, plotTop = 48, plotBot = 288, xLabY = 308;
export let PW = W - PL - PR;

// Drawing width tracks the on-screen box at a steady ~1.5 CSS px per SVG unit,
// so text renders the same size everywhere while wide monitors gain plot room.
export function setChartWidth(clientWidth) {
  W = Math.max(720, Math.min(1400, Math.round((clientWidth || 720) / 1.5)));
  PW = W - PL - PR;
}

// Read a percentile from a normals object, falling back to nearby keys so an
// older/partial API response (missing p1/p30/p70/p99) still renders a chart.
const PCT_FALLBACK = {
  p1: ["p1", "p10", "min", "p50"], p10: ["p10", "p50"],
  p25: ["p25", "p30", "p50"], p40: ["p40", "p30", "p50"],
  p60: ["p60", "p70", "p50"], p75: ["p75", "p70", "p50"],
  p90: ["p90", "p50"], p95: ["p95", "p90", "p50"], p99: ["p99", "p90", "max", "p50"],
};
const pget = (o, k) => {
  for (const kk of (PCT_FALLBACK[k] || [k])) if (o && o[kk] != null) return o[kk];
  return null;
};


// Per-series display meta for the diverging-scale metrics. `sfx` is the unit
// appended to axis + point labels ("°"); wind carries its unit in the subtitle
// instead of on every point to keep the plot uncluttered.
// `kind` picks the formatter and says whether the value converts; the labels that
// name a unit are built per render so they follow the active unit system.
const SERIES = {
  tmax: (C) => ({ color: C.hi, label: "Daily high", sfx: "°", kind: "temp" }),
  tmin: (C) => ({ color: C.lo, label: "Daily low", sfx: "°", kind: "temp" }),
  feels: (C) => ({ color: C.feels, label: "Feels like", sfx: "°", kind: "temp" }),
  humid: (C) => ({ color: C.humid, label: `Absolute humidity (${humidUnit()})`, sfx: "", kind: "humid" }),
  wind: (C) => ({ color: C.wind, label: `Wind speed (${windUnit()})`, sfx: "", kind: "wind" }),
  gust: (C) => ({ color: C.gust, label: `Wind gust (${windUnit()})`, sfx: "", kind: "wind" }),
};

// Percentile "fan" tiers — bands between successive percentile marks, colored to
// match the calendar. Temperature is diverging (cold→green→hot); precipitation
// uses the sequential rain-intensity ramp.
const TEMP_FAN = [
  ["p90", "p99", "very-hot"], ["p75", "p90", "hot"], ["p60", "p75", "warm"],
  ["p40", "p60", "normal"], ["p25", "p40", "cool"], ["p10", "p25", "cold"], ["p1", "p10", "very-cold"],
];
// Eight rain-intensity tiers (post-split): Trace / Light / Brisk / Typical / Heavy
// (60-90) / Very Heavy (90-95) / Severe (95-99) / Extreme. Each band maps a rain-day
// percentile range to its calendar tier colour; the p75 vertex inside the single
// Heavy tier keeps the fan following the p75 contour.
const RAIN_FAN = [
  ["p95", "p99", "wet-8"], ["p90", "p95", "wet-7"], ["p75", "p90", "wet-6"], ["p60", "p75", "wet-6"],
  ["p40", "p60", "wet-5"], ["p25", "p40", "wet-4"], ["p10", "p25", "wet-3"], ["p1", "p10", "wet-2"],
];

// Shared line-series chart: an optional shaded percentile fan + dashed median, the
// value line with dots, and labeled points — so temperature, wind, humidity,
// precipitation and dry streak all read in one consistent style.
function lineChart(cfg) {
  const { days, n, xFor, C, key, color, fan, hasNormals, baseZero,
          getVal, getPct, dotColor, fmtAxis, fmtLabel, labelOn,
          subtitle, legend, aria } = cfg;

  // y-range: the plotted values plus the fan extremes (p1/p99) when present.
  const vals = [];
  days.forEach((d) => {
    const v = getVal(d); if (v != null && !isNaN(v)) vals.push(v);
    if (hasNormals && d.normals && d.normals[key]) {
      const u = pget(d.normals[key], "p99"), l = pget(d.normals[key], "p1");
      if (u != null) vals.push(u); if (l != null) vals.push(l);
    }
  });
  let finite = vals.filter((v) => v != null && !isNaN(v));
  if (!finite.length) finite = [0, 1];
  let lo = Math.min(...finite), hi = Math.max(...finite);
  if (baseZero) lo = Math.min(lo, 0);
  if (hi <= lo) hi = lo + 1;
  const pad = baseZero ? Math.max((hi - lo) * 0.12, 0.01) : Math.max((hi - lo) * 0.08, 3);
  hi += pad; if (!baseZero) lo -= pad;
  const yT = (v) => plotBot - ((v - lo) / (hi - lo)) * (plotBot - plotTop);

  let grid = "";
  for (let t = 0; t <= 4; t++) {
    const v = lo + ((hi - lo) * t) / 4, y = yT(v).toFixed(1);
    grid += `<line x1="${PL}" y1="${y}" x2="${W - PR}" y2="${y}" stroke="${C.grid}" stroke-width="1"/>`;
    grid += `<text x="${PL - 8}" y="${+y + 4}" text-anchor="end" font-size="11" fill="${C.muted}">${fmtAxis(v)}</text>`;
  }

  // Shaded fan bands between percentile marks (the "highlights"), same as the calendar tiers.
  const band = (dnKey, upKey, cls) => {
    let top = "", bot = "";
    days.forEach((d, i) => { const u = d.normals && pget(d.normals[key], upKey); if (u == null) return;
      top += (top ? "L" : "M") + xFor(i).toFixed(1) + " " + yT(u).toFixed(1) + " "; });
    for (let i = n - 1; i >= 0; i--) { const dd = days[i].normals && pget(days[i].normals[key], dnKey); if (dd == null) continue;
      bot += "L" + xFor(i).toFixed(1) + " " + yT(dd).toFixed(1) + " "; }
    return top ? `<path d="${top + bot}Z" fill="${hexA(TIER_COLORS[cls], 0.4)}"/>` : "";
  };
  const fanSvg = (hasNormals && fan) ? fan.map((t) => band(t[0], t[1], t[2])).join("") : "";

  const normTrace = (pctKey) => {
    let p = "", st = false;
    days.forEach((d, i) => { const v = d.normals && pget(d.normals[key], pctKey); if (v == null) return;
      p += (st ? "L" : "M") + xFor(i).toFixed(1) + " " + yT(v).toFixed(1) + " "; st = true; });
    return p;
  };
  const valTrace = () => {
    let p = "", st = false;
    days.forEach((d, i) => { const v = getVal(d); if (v == null || isNaN(v)) { st = false; return; }
      p += (st ? "L" : "M") + xFor(i).toFixed(1) + " " + yT(v).toFixed(1) + " "; st = true; });
    return p;
  };
  const medianSvg = hasNormals
    ? `<path d="${normTrace("p50")}" fill="none" stroke="${color}" stroke-width="1.2" stroke-dasharray="4 4" opacity="0.55"/>` : "";

  const dots = days.map((d, i) => {
    const v = getVal(d); if (v == null || isNaN(v)) return "";
    return `<circle cx="${xFor(i).toFixed(1)}" cy="${yT(v).toFixed(1)}" r="3.4" fill="${dotColor ? dotColor(d) : color}" stroke="${C.surface}" stroke-width="1.6"/>`;
  }).join("");
  const labels = days.map((d, i) => {
    const v = getVal(d); if (v == null || isNaN(v)) return "";
    if (labelOn && !labelOn(v, d)) return "";
    const x = xFor(i).toFixed(1), y = yT(v);
    const vy = (y - plotTop < 26 ? y + 15 : y - 15).toFixed(1);   // flip below near the top
    const pv = getPct ? getPct(d) : null;
    const pct = pv == null ? "" :
      `<tspan x="${x}" dy="9" font-size="7.5" font-weight="600" fill="${C.muted}">${pctOrd(pv)}</tspan>`;
    return `<text x="${x}" y="${vy}" text-anchor="middle" font-size="8.5" font-weight="700" fill="${C.ink}" stroke="${C.surface}" stroke-width="2.4" paint-order="stroke" stroke-linejoin="round">${fmtLabel(v)}${pct}</text>`;
  }).join("");

  const content = grid + fanSvg + medianSvg +
    `<path d="${valTrace()}" fill="none" stroke="${color}" stroke-width="2.2" stroke-linejoin="round" stroke-linecap="round"/>` +
    dots + labels;

  return { content, legend, color, subtitle, aria };
}

// One temperature-scale series (High/Low/Feels/Wind/Gust).
export function tempChart(key, days, n, xFor, C) {
  const s = SERIES[key](C);
  // Labels show the active unit; the plot keeps its imperial domain — only the
  // labels convert — so point positions and the fan geometry hold.
  const fmtV = (v) => (s.kind === "temp"
    ? `${Math.round(toUnit(v))}${s.sfx}`
    : s.kind === "wind" ? `${Math.round(toWind(v))}` : `${Math.round(v)}`);
  return lineChart({
    days, n, xFor, C, key, color: s.color, fan: TEMP_FAN, hasNormals: true, baseZero: false,
    getVal: (d) => (d[key] ? d[key].value : null),
    getPct: (d) => (d[key] ? d[key].percentile : null),
    fmtAxis: fmtV,
    fmtLabel: fmtV,
    legend:
      `<span><i style="background:${s.color}"></i>${s.label} (dashed = median)</span>` +
      `<span><i class="swatch-band" style="background:${hexA(TIER_COLORS.normal, 0.5)};border-color:${TIER_COLORS.normal}"></i>Band shaded by grade tier</span>` +
      `<span class="legend-note">Points labeled value · percentile; grade from the band tier (scale below)</span>`,
    subtitle: `${s.label}: recent trend vs normal`,
    aria: `Recent ${s.label.toLowerCase()} versus the normal range.`,
  });
}

// Precipitation as a line vs its normal range — same fan/median/labels style as
// temperature, so the metrics read consistently. Rain days are labeled; dry days
// sit on the baseline. The fan is the rain-intensity tier ramp.
export function precipChart(days, n, xFor, C) {
  return lineChart({
    days, n, xFor, C, key: "precip", color: C.precip, fan: RAIN_FAN, hasNormals: true, baseZero: true,
    getVal: (d) => (d.precip ? d.precip.value : null),
    getPct: (d) => (d.precip ? d.precip.percentile : null),
    // Rain days take their intensity-tier color; no-rain days warm with the dry
    // streak (tan→red) so a dry spell reads as dry, matching the Dry chart.
    dotColor: (d) => (d.precip && d.precip.class && d.precip.class !== "dry" ? (TIER_COLORS[d.precip.class] || C.precip) : (drynessColor(d.dsr) || C.precip)),
    fmtAxis: (v) => fmtPrecip(v, false),
    fmtLabel: (v) => fmtPrecip(v, false),
    labelOn: (v) => v > 0,   // only label rain days; dry days rest on the baseline
    legend:
      `<span><i style="background:${C.precip}"></i>Precipitation (dashed = median)</span>` +
      `<span><i class="swatch-band" style="background:${hexA(TIER_COLORS["wet-6"], 0.5)};border-color:${TIER_COLORS["wet-6"]}"></i>Band shaded by rain-intensity tier</span>` +
      `<span class="legend-note">Rain days labeled amount · percentile (rain scale below)</span>`,
    subtitle: "Precipitation: daily totals vs normal",
    aria: "Daily precipitation totals versus the normal range.",
  });
}

// Dry streak as a line: days since last rain, dots warming with the streak; a rain
// day drops the line to 0 with a blue dot. (No climatology fan — it's not graded.)
export function dryChart(days, n, xFor, C) {
  return lineChart({
    days, n, xFor, C, key: "dry", color: drynessColor(9), fan: null, hasNormals: false, baseZero: true,
    getVal: (d) => (d.dsr == null ? null : d.dsr),
    getPct: () => null,
    dotColor: (d) => drynessColor(d.dsr),
    fmtAxis: (v) => `${Math.round(v)}d`,
    fmtLabel: (v) => `${Math.round(v)}`,
    labelOn: (v) => v > 0,   // label the streak length; rain days (0) just show the dot
    legend:
      `<span><i style="background:${drynessColor(9)}"></i>Days since last rain: dry streak</span>` +
      `<span><i style="background:${drynessColor(0)}"></i>Rain that day (streak = 0)</span>`,
    subtitle: "Dry streak: days since last measurable rain",
    aria: "Days since last measurable rain, as a line.",
  });
}

export function attachChartHover(wrap, days) {
  const svg = wrap.querySelector("svg");
  const tip = wrap.querySelector("#chart-tip");
  const cross = wrap.querySelector("#crosshair");
  const C = chartPalette();
  // Every measurable line converts to the active unit system; `kind` picks how.
  const TIP_FMT = {
    temp: (v) => `${Math.round(toUnit(v))}°`,
    humid: (v) => fmtHumid(v),
    wind: (v) => fmtWind(v),
    precip: (v) => fmtPrecip(v),
  };
  const pctLine = (label, g, kind, color) => {
    if (!g) return `<div><b style="color:${color}">${label}</b> —</div>`;
    const pct = g.percentile == null ? "" : ` · ${pctOrd(g.percentile)} pct`;
    const gc = TIER_COLORS[g.class] || "";
    return `<div><b style="color:${color}">${label}</b> ${TIP_FMT[kind](g.value)}${pct} <span class="tt-grade" style="color:${gc}">${g.grade}</span></div>`;
  };

  // Pointer events cover mouse, touch and pen with one path, so tapping/dragging
  // the chart works on phones (mousemove never fires on touchscreens).
  const showTip = (r, e) => {
    const d = days[+r.dataset.i];
    const x = +r.getAttribute("x") + +r.getAttribute("width") / 2;
    cross.setAttribute("x1", x); cross.setAttribute("x2", x); cross.setAttribute("opacity", "0.7");
    const dt = new Date(d.date + "T00:00:00");
    const nt = d.normals.tmax, ni = d.normals.tmin;
    tip.innerHTML = `<div class="tt-date">${dt.toLocaleDateString(undefined, { weekday: "short", month: "short", day: "numeric" })}</div>
      ${pctLine("High", d.tmax, "temp", C.hi)}
      ${pctLine("Low", d.tmin, "temp", C.lo)}
      ${pctLine("Feels", d.feels, "temp", C.feels)}
      ${pctLine("Humidity", d.humid, "humid", C.humid)}
      ${pctLine("Wind", d.wind, "wind", C.wind)}
      ${pctLine("Gust", d.gust, "wind", C.gust)}
      ${pctLine("Precip", d.precip, "precip", C.precip)}
      <div><b>Dry</b> ${d.dsr == null ? "—" : d.dsr === 0 ? "rain today" : `${d.dsr} d since rain`}</div>
      <div class="tt-norm">normal ${nt ? fmtTemp(nt.p50) : "—"} / ${ni ? fmtTemp(ni.p50) : "—"}</div>`;
    tip.hidden = false;
    const box = wrap.getBoundingClientRect();
    let px = e.clientX - box.left + 12;
    if (px > box.width - 160) px = e.clientX - box.left - 160;
    tip.style.left = Math.max(4, px) + "px";
    tip.style.top = Math.max(8, e.clientY - box.top - 10) + "px";
  };

  wrap.querySelectorAll("rect.hit").forEach((r) => {
    r.addEventListener("pointermove", (e) => showTip(r, e));
    r.addEventListener("pointerdown", (e) => showTip(r, e));
  });
  const hide = () => { tip.hidden = true; cross.setAttribute("opacity", "0"); };
  svg.addEventListener("pointerleave", hide);
  svg.addEventListener("pointerup", hide);
}
