import React, { useMemo } from 'react';
import { SeasonalOverlayProps } from '../types';
import { animGust, animLeafFall, animLeafFlutter, animLeafSway, leafBlade } from './Autumn.css';

/**
 * AutumnOverlay — falling leaves over the app as it is.
 *
 * A full-screen, pointer-events:none ambient decoration. The parent supplies a
 * fixed inset:0 overflow:hidden pointer-events:none container at the correct
 * z-index, so this component only returns absolutely-positioned aria-hidden
 * children and never sets position:fixed / z-index / pointer-events.
 *
 * [#237] Deliberately no full-screen tint, light shafts or vignette: they
 * turned the user's theme beige (muddy brown on dark) and lowered contrast
 * everywhere. The leaves carry the season on their own.
 *
 * Composition:
 *   1. maple / oak / aspen leaves drifting down with sway and a soft flutter
 *   2. every ~42 s a gust: a small group of leaves blows across the screen
 * All motion is transform/opacity only. When `reduced` is true: a few leaves
 * at rest in empty parts of the layout, no animation, no gust. The settings
 * preview always passes reduced=true, so the still form stands alone.
 */

// [#237] A real autumn palette: [body, tip highlight, vein]. The previous
// muted tans read as beige smudges on the light theme.
const LEAF_TONES: [string, string, string][] = [
  ['oklch(0.56 0.19 30)', 'oklch(0.68 0.17 45)', 'oklch(0.38 0.12 28)'], // crimson
  ['oklch(0.68 0.17 52)', 'oklch(0.8 0.15 75)', 'oklch(0.45 0.12 45)'], // pumpkin orange
  ['oklch(0.76 0.15 80)', 'oklch(0.85 0.13 92)', 'oklch(0.52 0.1 65)'], // gold
  ['oklch(0.5 0.1 50)', 'oklch(0.62 0.11 60)', 'oklch(0.34 0.06 45)'], // russet brown
  ['oklch(0.62 0.18 40)', 'oklch(0.74 0.16 60)', 'oklch(0.42 0.12 35)'], // burnt orange
];

type LeafKind = 'maple' | 'oak' | 'aspen';

// Leaf silhouettes (viewBox 0 0 100 100, stem at the bottom). The maple is the
// flag-style silhouette on purpose: its bold lobes stay recognisable at 30 px,
// where the previous star-like outline read as a splat.
const LEAF_SHAPES: Record<LeafKind, { body: string; veins: string }> = {
  maple: {
    body:
      'M50 5 L54 20 L62 14 L60 30 L74 22 L70 36 L86 34 L78 46 L90 52 L74 56 L78 66 ' +
      'L60 62 L56 72 L52 64 L52 94 L48 94 L48 64 L44 72 L40 62 L22 66 L26 56 L10 52 ' +
      'L22 46 L14 34 L30 36 L26 22 L40 30 L38 14 L46 20 Z',
    veins: 'M50 66 L50 14 M50 58 L80 40 M50 58 L20 40 M50 64 L70 60 M50 64 L30 60',
  },
  oak: {
    body:
      'M50 4 C58 14 56 22 64 24 C74 22 74 32 68 36 C78 38 76 48 68 50 ' +
      'C78 54 74 64 66 64 C70 74 60 78 54 72 C54 80 52 86 52 96 L48 96 ' +
      'C48 86 46 80 46 72 C40 78 30 74 34 64 C26 64 22 54 32 50 ' +
      'C24 48 22 38 32 36 C26 32 26 22 36 24 C44 22 42 14 50 4 Z',
    veins:
      'M50 76 L50 12 M50 34 L64 28 M50 34 L36 28 M50 50 L66 44 M50 50 L34 44 M50 64 L62 60 M50 64 L38 60',
  },
  aspen: {
    body: 'M50 8 C74 22 80 54 52 84 L52 96 L48 96 L48 84 C20 54 26 22 50 8 Z',
    veins: 'M50 84 L50 16 M50 40 L64 32 M50 40 L36 32 M50 58 L66 50 M50 58 L34 50',
  },
};

/** Build a CSS-ready data-URI of one leaf: gradient body, darker veins. */
function leafDataUri(kind: LeafKind, [body, tip, vein]: [string, string, string]): string {
  const shape = LEAF_SHAPES[kind];
  const svg =
    `<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'>` +
    `<defs><linearGradient id='g' x1='0' y1='1' x2='0.4' y2='0'>` +
    `<stop offset='0' stop-color='${body}'/><stop offset='1' stop-color='${tip}'/>` +
    `</linearGradient></defs>` +
    `<path d='${shape.body}' fill='url(#g)'/>` +
    `<path d='${shape.veins}' stroke='${vein}' stroke-opacity='0.7' stroke-width='2' ` +
    `fill='none' stroke-linecap='round'/>` +
    `</svg>`;
  return `url("data:image/svg+xml,${encodeURIComponent(svg)}")`;
}

type Leaf = {
  uri: string;
  left: number;
  size: number;
  duration: number; // s — fall time
  delay: number; // s
  swayDuration: number;
  flutterDuration: number;
  opacity: number;
};

type GustLeaf = {
  uri: string;
  top: number; // % of height where it enters
  size: number;
  delay: number; // s within the gust
  opacity: number;
};

/** Seconds between gusts, and when the first one comes after load. */
const GUST_PERIOD = 42;
const GUST_FIRST = 8;

// Leaves at rest for the reduced/static scene, in areas that are empty in the
// layout (middle of the left icon rail, the space under the member list),
// partly off-edge — never on the sidebar, members, composer or controls.
const RESTING_LEAVES: ReadonlyArray<{
  kind: LeafKind;
  left: number;
  top: number;
  size: number;
  tilt: number;
  tone: number;
  opacity: number;
}> = [
  { kind: 'maple', left: 0.5, top: 44, size: 60, tilt: 24, tone: 0, opacity: 0.62 },
  { kind: 'aspen', left: 1.5, top: 54, size: 44, tilt: -30, tone: 2, opacity: 0.6 },
  { kind: 'oak', left: 99, top: 62, size: 54, tilt: 160, tone: 3, opacity: 0.6 },
  { kind: 'maple', left: 97.5, top: 72, size: 46, tilt: 200, tone: 4, opacity: 0.6 },
];

// Composition for the Settings swatch (sizes are % of the tile width).
const PREVIEW_LEAVES: ReadonlyArray<{
  kind: LeafKind;
  left: number;
  top: number;
  size: number;
  tilt: number;
  tone: number;
}> = [
  { kind: 'maple', left: 30, top: 38, size: 42, tilt: -18, tone: 0 },
  { kind: 'oak', left: 70, top: 30, size: 30, tilt: 34, tone: 3 },
  { kind: 'aspen', left: 62, top: 70, size: 30, tilt: -60, tone: 2 },
  { kind: 'maple', left: 86, top: 80, size: 24, tilt: 20, tone: 1 },
  { kind: 'maple', left: 12, top: 82, size: 20, tilt: 40, tone: 4 },
];

export function AutumnOverlay({ reduced, preview }: SeasonalOverlayProps) {
  // Deterministic field, computed ONCE. No per-frame state.
  const { leaves, gust } = useMemo(() => {
    const kinds = ['maple', 'oak', 'maple', 'aspen'] as const;
    const builtLeaves: Leaf[] = Array.from({ length: 12 }, (_, i) => {
      const depth = i % 4; // 0..3 → parallax bucket
      return {
        uri: leafDataUri(kinds[i % 4], LEAF_TONES[i % LEAF_TONES.length]),
        left: (i * 8.3 + 4) % 100,
        size: 28 + depth * 8, // 28..52 px
        // Nearer leaves fall a touch faster; all slow and calm.
        duration: 16 - depth * 1.6 + (i % 3) * 1.3,
        delay: -((i * 1.37) % 16), // negative → already mid-fall on load
        swayDuration: 5 + (i % 5) * 0.8,
        flutterDuration: 2 + (i % 4) * 0.5,
        // Nearer → bolder. Small, moving and semi-transparent, so text under a
        // passing leaf stays readable.
        opacity: 0.58 + depth * 0.05,
      };
    });
    const builtGust: GustLeaf[] = Array.from({ length: 5 }, (_, i) => ({
      uri: leafDataUri(kinds[(i + 1) % 4], LEAF_TONES[(i * 2) % LEAF_TONES.length]),
      top: 30 + ((i * 13) % 40),
      size: 30 + (i % 3) * 10,
      delay: GUST_FIRST + i * 0.35,
      opacity: 0.7,
    }));
    return { leaves: builtLeaves, gust: builtGust };
  }, []);

  if (preview) {
    // The Settings swatch: a warm backdrop (fine inside the tile, unlike over
    // the app) with a few leaves arranged across it.
    return (
      <>
        <div
          aria-hidden="true"
          style={{
            position: 'absolute',
            inset: 0,
            background:
              'linear-gradient(160deg, oklch(0.42 0.09 55) 0%, oklch(0.32 0.08 40) 60%, oklch(0.24 0.06 35) 100%)',
          }}
        />
        {PREVIEW_LEAVES.map((leaf, i) => (
          <div
            key={`pv-${i}`}
            aria-hidden="true"
            style={{
              position: 'absolute',
              left: `${leaf.left}%`,
              top: `${leaf.top}%`,
              width: `${leaf.size}%`,
              aspectRatio: '1',
              backgroundImage: leafDataUri(leaf.kind, LEAF_TONES[leaf.tone]),
              backgroundSize: 'contain',
              backgroundRepeat: 'no-repeat',
              transform: `translate(-50%, -50%) rotate(${leaf.tilt}deg)`,
              filter: 'brightness(1.25)',
            }}
          />
        ))}
      </>
    );
  }

  if (reduced) {
    // Phones have no icon rail and the timeline runs edge to edge, so the
    // resting leaves tuck further off-edge and smaller there.
    const narrow = typeof window !== 'undefined' && window.matchMedia('(max-width: 750px)').matches;
    return (
      <>
        {RESTING_LEAVES.map((leaf, i) => (
          <div
            key={`rest-${i}`}
            aria-hidden="true"
            className={leafBlade}
            style={{
              position: 'absolute',
              left: narrow ? `${leaf.left < 50 ? -2 : 102}%` : `${leaf.left}%`,
              top: `${leaf.top}%`,
              width: `${narrow ? leaf.size * 0.8 : leaf.size}px`,
              height: `${narrow ? leaf.size * 0.8 : leaf.size}px`,
              backgroundImage: leafDataUri(leaf.kind, LEAF_TONES[leaf.tone]),
              backgroundSize: 'contain',
              backgroundRepeat: 'no-repeat',
              transform: `translate(-50%, -50%) rotate(${leaf.tilt}deg)`,
              opacity: leaf.opacity,
            }}
          />
        ))}
      </>
    );
  }

  return (
    <>
      {leaves.map((leaf, i) => (
        // Sway wrapper: horizontal wind, decoupled from the fall. No `paint`
        // containment: it would clip the leaf to this box at the top of the
        // screen, so it would never be drawn once falling (#237).
        <div
          key={`leaf-${i}`}
          aria-hidden="true"
          style={{
            position: 'absolute',
            top: 0,
            left: `${leaf.left}%`,
            width: `${leaf.size}px`,
            height: `${leaf.size}px`,
            willChange: 'transform',
            animation: `${animLeafSway} ${leaf.swayDuration}s ease-in-out ${leaf.delay}s infinite`,
          }}
        >
          {/* Fall wrapper: vertical descent + tumble. */}
          <div
            style={{
              width: '100%',
              height: '100%',
              willChange: 'transform, opacity',
              animation: `${animLeafFall} ${leaf.duration}s linear ${leaf.delay}s infinite`,
            }}
          >
            {/* The leaf itself, with a soft flutter. */}
            <div
              className={leafBlade}
              style={{
                width: '100%',
                height: '100%',
                backgroundImage: leaf.uri,
                backgroundSize: 'contain',
                backgroundRepeat: 'no-repeat',
                opacity: leaf.opacity,
                animation: `${animLeafFlutter} ${leaf.flutterDuration}s ease-in-out infinite`,
              }}
            />
          </div>
        </div>
      ))}

      {/* Gust: a handful of leaves blown across the screen together, then a
          long calm. Off-screen (and invisible) the rest of the cycle. */}
      {gust.map((leaf, i) => (
        <div
          key={`gust-${i}`}
          aria-hidden="true"
          style={{
            position: 'absolute',
            top: `${leaf.top}%`,
            left: 0,
            width: `${leaf.size}px`,
            height: `${leaf.size}px`,
            opacity: 0,
            willChange: 'transform, opacity',
            animation: `${animGust} ${GUST_PERIOD}s linear ${leaf.delay}s infinite`,
          }}
        >
          <div
            className={leafBlade}
            style={{
              width: '100%',
              height: '100%',
              backgroundImage: leaf.uri,
              backgroundSize: 'contain',
              backgroundRepeat: 'no-repeat',
              opacity: leaf.opacity,
            }}
          />
        </div>
      ))}
    </>
  );
}