/**
 * Seedance VFX register — a PURE, deterministic physical-effects vocabulary.
 * No I/O, no Date, no Math.random.
 *
 * VFX prompts need material behavior, source, timing, and consequence: every
 * effect starts somewhere, interacts with light and objects, changes over time,
 * and ends in a visible state. Generic words (magical/explosive/cinematic)
 * become noisy overlays. Each effect here carries a PHYSICAL prompt-ready phrase
 * + a stability constraint; `vfxEffectLine` wraps it with the integration rules
 * (one hero effect, anchored to its source, respecting physics, resolving
 * forms -> travels -> dissipates to a visible endpoint).
 *
 * Core five harvested verbatim from the MIT `Emily2040/seedance-2.0` seedance-vfx
 * Effects Contract (@63b32dc); fire/water/explosion authored in the same register.
 */

export interface VfxEffect {
  id: string;
  label: string;
  /** The physical, prompt-ready phrase (source -> behavior -> endpoint). */
  phrase: string;
  /** The stability constraint that keeps the effect from corrupting the subject. */
  stability: string;
}

const EFFECTS: VfxEffect[] = [
  {
    id: 'particle',
    label: 'Particles',
    phrase: 'fine gold dust particles spiral up from behind the subject, catch the backlight, then settle on the surface',
    stability: 'keep the anchored object rigid',
  },
  {
    id: 'energy',
    label: 'Energy',
    phrase: 'thin blue electrical arcs crawl along the conductor, briefly illuminating the texture they pass',
    stability: 'keep the arcs attached to their source',
  },
  {
    id: 'smoke',
    label: 'Smoke / vapor',
    phrase: 'cold white vapor rolls over the rim, sinks down the side, and thins near the surface',
    stability: 'describe density and direction, never a uniform haze',
  },
  {
    id: 'transformation',
    label: 'Transformation',
    phrase: 'the edge chars inward from one corner, flakes curl and fall away, and the core identity is left untouched',
    stability: 'protect the identity anchor through the change',
  },
  {
    id: 'weather',
    label: 'Weather',
    phrase: 'wind pushes rain diagonally across the frame and puddles ripple outward from each footstep',
    stability: 'tie the weather to real surfaces',
  },
  {
    id: 'fire',
    label: 'Fire',
    phrase: 'flame climbs from its fuel source, licks upward through a rising heat shimmer, then drops to glowing embers and a thin trail of smoke',
    stability: 'anchor the flame to a clear fuel source',
  },
  {
    id: 'water',
    label: 'Water',
    phrase: 'water sheets off the surface, beads along the lowest edge, then drips and pools below',
    stability: 'tie the flow to gravity and the surface it runs on',
  },
  {
    id: 'explosion',
    label: 'Explosion',
    phrase: 'a bright core flashes from a single origin, a shockwave throws debris outward, and rolling smoke billows up and curls back inward',
    stability: 'one origin point; keep foreground subjects intact',
  },
];

export const VFX_EFFECTS: Record<string, VfxEffect> = Object.fromEntries(
  EFFECTS.map((effect) => [effect.id, effect]),
);

export const VFX_EFFECT_IDS: string[] = EFFECTS.map((effect) => effect.id);

/**
 * The effect contract line for `id`: the physical phrase + its stability
 * constraint + the standing integration rules. Throws on an unknown id (no
 * silent fallback).
 */
export function vfxEffectLine(id: string): string {
  const effect = VFX_EFFECTS[id];
  if (!effect) {
    throw new Error(`unknown vfx effect: ${id}. Expected one of ${VFX_EFFECT_IDS.join(', ')}.`);
  }
  return (
    `${effect.phrase}. ${capitalize(effect.stability)}. `
    + 'One hero effect only; anchor it to its source and let it respect gravity, wind, collision, reflection, and occlusion, '
    + 'resolving forms → travels → dissipates to a visible endpoint.'
  );
}

function capitalize(text: string): string {
  return text.length === 0 ? text : `${text[0]!.toUpperCase()}${text.slice(1)}`;
}