import type { ReactNode } from "react";
import {
  aqiLabel, compass, formatClock, formatDistance, formatDuration, formatPrecip, formatPressure, formatTemp,
  formatWind, moonPhase, uvLabel, type Units,
} from "@/lib/display";
import { pixelLabel, sectionHeading } from "@/lib/styles";
import type { WeatherReport } from "@/lib/weather/types";
import { Slot } from "./Slot";

/**
 * Every current reading the provider gives us, one tile each.
 * Tiles for readings the provider doesn't offer are simply left out.
 */
export function ConditionsGrid({ report, units }: { report: WeatherReport; units: Units }) {
  const { current: c, airQuality: aq, timeZone } = report;
  const today = report.daily[0];
  const moon = moonPhase();

  return (
    <section aria-labelledby="conditions-heading" className="flex flex-col gap-3">
      <div className="flex items-center gap-3">
        <h2 id="conditions-heading" className={sectionHeading}>
          Current conditions
        </h2>
        <span className="h-px flex-1 bg-linear-to-r from-gold-dim/70 to-transparent" aria-hidden="true" />
      </div>
      <div className="grid grid-cols-2 gap-3 sm:grid-cols-4">
        <Tile label="Feels like" value={formatTemp(c.feelsLikeC, units)} note={c.dewPointC !== null ? `Dew point ${formatTemp(c.dewPointC, units)}` : undefined} />

        <Tile label="Humidity" value={`${c.humidity}%`} meter={<Segments total={10} lit={Math.round(c.humidity / 10)} />} />

        <Tile
          label="Wind"
          value={formatWind(c.windKph, units)}
          note={[c.windDeg !== null && `From ${compass(c.windDeg)}`, c.gustKph && `gusts ${formatWind(c.gustKph, units)}`].filter(Boolean).join(", ") || undefined}
          icon={c.windDeg !== null ? <WindArrow fromDegrees={c.windDeg} /> : undefined}
        />

        {c.uvIndex !== null && (
          <Tile
            label="UV index"
            value={String(Math.round(c.uvIndex))}
            note={uvLabel(c.uvIndex)}
            meter={<Segments total={11} lit={Math.min(11, Math.round(c.uvIndex))} />}
          />
        )}

        {aq && (
          <Tile label="Air quality" value={`${aq.usAqi} AQI`} note={`${aqiLabel(aq.usAqi)}${aq.pm25 !== null ? ` · PM2.5 ${Math.round(aq.pm25)} µg/m³` : ""}`} />
        )}

        {c.pressureHpa !== null && <Tile label="Pressure" value={formatPressure(c.pressureHpa, units)} />}
        {c.visibilityKm !== null && <Tile label="Visibility" value={formatDistance(c.visibilityKm, units)} />}
        {c.cloudCover !== null && <Tile label="Cloud cover" value={`${Math.round(c.cloudCover)}%`} />}
        {c.precipMm !== null && <Tile label="Precipitation" value={formatPrecip(c.precipMm, units)} note="In the last hour" />}

        {today?.sunrise && today.sunset && (
          <Tile
            label="Sun"
            value={`${formatClock(today.sunrise, timeZone)} – ${formatClock(today.sunset, timeZone)}`}
            note={`${formatDuration(today.sunrise, today.sunset)} of daylight`}
          />
        )}

        <Tile label="Moon" value={moon.name} note={`${moon.illumination}% lit`} icon={<MoonIcon fraction={moon.fraction} />} />
      </div>
    </section>
  );
}

/**
 * One reading.  `icon` sits beside the value; `meter` sits underneath it.
 */
function Tile({ label, value, note, icon, meter }: { label: string; value: string; note?: string; icon?: ReactNode; meter?: ReactNode }) {
  return (
    <Slot className="[--cut:10px]" innerClassName="flex flex-col gap-1 p-3 sm:px-4">
      <p className={pixelLabel}>{label}</p>
      <div className="flex items-center justify-between gap-2">
        <p className="font-display text-lg font-medium sm:text-xl">{value}</p>
        {icon}
      </div>
      {note && <p className="text-xs text-stone first-letter:uppercase">{note}</p>}
      {meter}
    </Slot>
  );
}

/** A row of lit/unlit segments, like a stamina gauge. */
function Segments({ total, lit }: { total: number; lit: number }) {
  return (
    <span className="mt-1 flex gap-[3px]" aria-hidden="true">
      {Array.from({ length: total }, (_, i) => (
        <span key={i} className={`h-1.5 flex-1 ${i < lit ? "bg-teal" : "bg-teal-off"}`} />
      ))}
    </span>
  );
}

/** An arrow pointing where the wind is blowing TO (opposite of where it comes from). */
function WindArrow({ fromDegrees }: { fromDegrees: number }) {
  return (
    <svg width={28} height={28} viewBox="-10 -10 20 20" aria-hidden="true" style={{ transform: `rotate(${fromDegrees + 180}deg)` }}>
      <path d="M0,-8 L5,4 L0,1 L-5,4 Z" fill="var(--color-gold-bright)" />
    </svg>
  );
}

/**
 * The moon drawn from its phase: a dark disc, with the lit part outlined by
 * an outer half-circle and a terminator ellipse whose width follows the phase.
 */
function MoonIcon({ fraction }: { fraction: number }) {
  const r = 9;
  const waxing = fraction < 0.5;
  const terminatorWidth = r * Math.abs(Math.cos(fraction * 2 * Math.PI));
  // The terminator bulges toward the lit side for crescents and away from it for gibbous moons.
  const isCrescent = fraction < 0.25 || fraction > 0.75;
  const outerSweep = waxing ? 1 : 0;
  const innerSweep = isCrescent === waxing ? 0 : 1;
  const lit = `M0,${-r} A${r},${r} 0 0 ${outerSweep} 0,${r} A${terminatorWidth},${r} 0 0 ${innerSweep} 0,${-r} Z`;

  return (
    <svg width={28} height={28} viewBox="-10 -10 20 20" aria-hidden="true">
      <circle r={r} fill="var(--color-teal-off)" />
      <path d={lit} fill="var(--color-ink)" />
    </svg>
  );
}