import { CSSProperties } from 'react';
import { ChatBgVariants } from './types';
import { auroraFlow } from './animAurora.css';

// Aurora Flow — a premium ANIMATED aurora: soft ribbons of northern-lights color
// slowly drifting and curling over a deep, calm base.
//
// CONCEPT
// Broad, heavily-feathered gradient bands stacked over a deep midnight base, with
// a gentle vignette that darkens the edges and keeps the reading center calm.
// The distinct STATIC 'aurora' is a favorite still; this one earns its own slot
// by MOVING — see animAurora.css.ts, which slowly pans each ribbon along its own
// path via `background-position` so the curtains appear to fold and cross.
//
// LAYER ORDER (must stay in lockstep with auroraFlow's per-layer position list):
//   1. green ribbon    2. teal ribbon    3. violet ribbon    4. sky highlight
//   5. calm reading core (static)        6. vignette (static)
//
// READABILITY
// Every ribbon is a wide ellipse fading fully to transparent well before its
// edge, at low alpha (~0.05–0.13), so no band ever concentrates enough contrast
// under the message column to threaten WCAG-AA. Layer 5 lifts a soft, even wash
// through the vertical center — the reading zone — so text always sits on a calm,
// low-variance field. oklch() keeps every hue perceptually smooth and low-chroma.
//
// MOTION / SEAMLESS LOOP
// backgroundSize is >100% per animated layer, giving room to drift; the keyframe
// returns every band to its start over one long, ease-in-out period, so the loop
// is seamless and the motion barely-perceptible. willChange/animation are added
// (and stripped for reduced-motion) by getChatBg; the static positions below are
// the finished still that shows when motion is off.

const dark: CSSProperties = {
  // Deep midnight blue — the polar night sky the aurora glows over.
  backgroundColor: 'oklch(0.17 0.045 255)',
  backgroundImage: [
    // 1. Green ribbon — the signature aurora band.
    'radial-gradient(ellipse 70% 45% at 50% 50%, oklch(0.7 0.14 160 / 0.13) 0%, oklch(0.7 0.14 160 / 0.05) 45%, transparent 72%)',
    // 2. Teal ribbon — cool counterpart, offset.
    'radial-gradient(ellipse 80% 40% at 50% 50%, oklch(0.65 0.12 200 / 0.12) 0%, oklch(0.65 0.12 200 / 0.04) 48%, transparent 74%)',
    // 3. Violet ribbon — the high curtain fold.
    'radial-gradient(ellipse 65% 55% at 50% 50%, oklch(0.55 0.13 300 / 0.11) 0%, oklch(0.55 0.13 300 / 0.04) 46%, transparent 70%)',
    // 4. Sky/aqua highlight — subtle shimmer that counter-drifts.
    'radial-gradient(ellipse 55% 35% at 50% 50%, oklch(0.72 0.1 220 / 0.09) 0%, transparent 65%)',
    // 5. Calm reading core (static) — a soft even wash down the center column so
    //    message text always rests on a low-variance field.
    'radial-gradient(ellipse 120% 60% at 50% 50%, oklch(0.2 0.04 255 / 0.5) 0%, transparent 70%)',
    // 6. Vignette (static) — gently darkens the edges for luminous depth.
    'radial-gradient(ellipse 130% 120% at 50% 50%, transparent 55%, oklch(0.12 0.04 260 / 0.55) 100%)',
  ].join(','),
  backgroundSize: '260% 240%, 300% 260%, 240% 280%, 220% 200%, 100% 100%, 100% 100%',
  backgroundPosition: '0% 30%, 100% 70%, 50% 0%, 20% 80%, 50% 50%, 50% 50%',
  backgroundRepeat: 'no-repeat',
  animation: `${auroraFlow} 60s ease-in-out infinite`,
};

const light: CSSProperties = {
  // Pale cool base — a soft pre-dawn sky the pastel aurora dreams over.
  backgroundColor: 'oklch(0.97 0.012 240)',
  backgroundImage: [
    // 1. Mint ribbon.
    'radial-gradient(ellipse 70% 45% at 50% 50%, oklch(0.85 0.08 160 / 0.5) 0%, oklch(0.85 0.08 160 / 0.16) 45%, transparent 72%)',
    // 2. Sky ribbon.
    'radial-gradient(ellipse 80% 40% at 50% 50%, oklch(0.83 0.07 220 / 0.48) 0%, oklch(0.83 0.07 220 / 0.14) 48%, transparent 74%)',
    // 3. Lilac ribbon — the high curtain fold.
    'radial-gradient(ellipse 65% 55% at 50% 50%, oklch(0.82 0.07 300 / 0.42) 0%, oklch(0.82 0.07 300 / 0.12) 46%, transparent 70%)',
    // 4. Aqua highlight — subtle shimmer that counter-drifts.
    'radial-gradient(ellipse 55% 35% at 50% 50%, oklch(0.88 0.06 200 / 0.34) 0%, transparent 65%)',
    // 5. Calm reading core (static) — a bright even wash down the center column
    //    so dark message text always rests on a light, low-variance field.
    'radial-gradient(ellipse 120% 60% at 50% 50%, oklch(0.99 0.005 240 / 0.6) 0%, transparent 70%)',
    // 6. Vignette (static) — a whisper of cool shade at the edges for depth.
    'radial-gradient(ellipse 130% 120% at 50% 50%, transparent 55%, oklch(0.9 0.02 250 / 0.45) 100%)',
  ].join(','),
  backgroundSize: '260% 240%, 300% 260%, 240% 280%, 220% 200%, 100% 100%, 100% 100%',
  backgroundPosition: '0% 30%, 100% 70%, 50% 0%, 20% 80%, 50% 50%, 50% 50%',
  backgroundRepeat: 'no-repeat',
  animation: `${auroraFlow} 60s ease-in-out infinite`,
};

export const animAurora: ChatBgVariants = { dark, light };
