import type { ModifierIR } from "./scene-ir";

function fnv1a(value: string): number {
  let hash = 0x811c9dc5;
  for (let index = 0; index < value.length; index++) {
    hash ^= value.charCodeAt(index);
    hash = Math.imul(hash, 0x01000193);
  }
  return hash >>> 0;
}

export type ModifierParameterMetadata = {
  key: string;
  value: unknown;
  kind: "boolean" | "number" | "string" | "enum" | "enum_set" | "object" | "collection" | "texture" | "cachefile" | "curve_mapping" | "profile";
  options?: string[];
  items?: Array<{ id: string; label: string }>;
  label?: string;
  description?: string;
  /** Native MOD_subsurf panel text for derived, read-only values. */
  display?: string;
  visible?: boolean;
  enabled?: boolean;
  editable?: boolean;
  nullable?: boolean;
  suggestionsOnly?: boolean;
  maxLength?: number;
  unit?: 'ANGLE';
  integer?: boolean;
  length?: number;
  minimum?: number;
  maximum?: number;
};

export type ModifierCurveProfile = {
  view: [number, number, number, number];
  clip: [number, number, number, number];
  points: Array<{ location: [number, number]; handle1: [number, number]; handle2: [number, number]; handleType: 'AUTO' | 'VECTOR' | 'FREE' | 'ALIGN' }>;
  samples: Array<[number, number]>;
  use_clip: boolean;
  use_sample_straight_edges: boolean;
  use_sample_even_lengths: boolean;
};

export function isModifierCurveProfile(value: unknown): value is ModifierCurveProfile {
  if (!value || typeof value !== 'object') return false;
  const profile = value as ModifierCurveProfile;
  const pair = (point: unknown) => Array.isArray(point) && point.length === 2 && point.every(n => typeof n === 'number' && Number.isFinite(n));
  const rect = (value: unknown) => Array.isArray(value) && value.length === 4 && value.every(n => typeof n === 'number' && Number.isFinite(n)) && value[2] > value[0] && value[3] > value[1];
  return rect(profile.view) && rect(profile.clip) && typeof profile.use_clip === 'boolean' && typeof profile.use_sample_straight_edges === 'boolean' &&
    typeof profile.use_sample_even_lengths === 'boolean' && Array.isArray(profile.points) &&
    profile.points.length >= 2 && profile.points.length <= 32767 && profile.points.every(point => point &&
      pair(point.location) && pair(point.handle1) && pair(point.handle2) && ['AUTO', 'VECTOR', 'FREE', 'ALIGN'].includes(point.handleType)) &&
    Array.isArray(profile.samples) && profile.samples.length <= 1048576 && profile.samples.every(pair);
}

/** Derives editable fields from the metadata carried by the authoritative modifier IR. */
export function modifierParameterMetadata(modifier: ModifierIR): ModifierParameterMetadata[] {
  return (modifier.editableParameters ?? []).map((field) => ({ ...field,
    options: field.items?.map((item) => item.id),
  }));
}

/** Hashes evaluated modifier identity/state, excluding display timestamps. */
export function modifierStackHash(stack: readonly ModifierIR[] | undefined): string {
  const canonical = (stack ?? []).map((modifier) => ({
    uuid: modifier.uuid,
    type: modifier.type,
    enabled: modifier.enabled,
    showViewport: modifier.showViewport,
    showRender: modifier.showRender,
    showEditMode: modifier.showEditMode,
    showOnCage: modifier.showOnCage,
    parameters: modifier.parameters,
    dependsOn: modifier.dependsOn,
    evaluationStatus: modifier.evaluationStatus,
  }));
  return `mod-${fnv1a(JSON.stringify(canonical)).toString(16).padStart(8, "0")}`;
}