// Factual Java 26.2 block-state metadata, generated by scripts/measure_lighting.py.
// The catalog's minecraft_id is distinct from Shacraft's material registry id.
let loading;
const decoded = new WeakMap();

export function loadLightProperties() {
  loading ??= fetch(new URL("./light-properties.json", import.meta.url))
    .then((response) => {
      if (!response.ok) throw new Error(`Light properties HTTP ${response.status}`);
      return response.json();
    })
    .then((properties) => {
      if (!Array.isArray(properties.codes) || !Array.isArray(properties.shapes) ||
          !Array.isArray(properties.schemas) || !properties.blocks) {
        throw new Error("Invalid block light properties");
      }
      return properties;
    })
    .catch((error) => { loading = undefined; throw error; });
  return loading;
}

function stateId(state, properties) {
  if (typeof state !== "string") return undefined;
  const match = /^([a-z0-9_]+:[a-z0-9_/.]+)(?:\[([^\]]*)\])?$/.exec(state);
  if (!match) return undefined;
  const definition = properties.blocks?.[match[1]];
  if (!definition) return undefined;
  const [first, defaultId, schemaId] = definition;
  if (match[2] === undefined || match[2] === "") return defaultId;
  const schema = properties.schemas[schemaId];
  const requested = new Map();
  for (const pair of match[2].split(",")) {
    const parts = pair.split("=");
    if (parts.length !== 2 || requested.has(parts[0])) return undefined;
    requested.set(parts[0], parts[1]);
  }
  const defaults = [];
  let remaining = defaultId - first;
  for (let index = schema.length - 1; index >= 0; index--) {
    const values = schema[index][1];
    defaults[index] = remaining % values.length;
    remaining = Math.floor(remaining / values.length);
  }
  let offset = 0;
  for (let index = 0; index < schema.length; index++) {
    const [name, values] = schema[index];
    const selected = requested.has(name) ? values.indexOf(requested.get(name)) : defaults[index];
    if (selected < 0) return undefined;
    requested.delete(name);
    offset = offset * values.length + selected;
  }
  return requested.size ? undefined : first + offset;
}

/** Enrich a copy; explicit Minecraft IDs take priority over the state fallback. */
export function applyLightProperties(material, properties) {
  if (!material || !properties?.codes) return { ...material };
  let id = material.minecraft_id;
  if (!Number.isInteger(id) || id < 0 || id >= properties.codes.length) id = stateId(material.state, properties);
  if (id === undefined) return { ...material };
  const code = properties.codes[id];
  let cache = decoded.get(properties);
  if (!cache) { cache = new Map(); decoded.set(properties, cache); }
  let lighting = cache.get(code);
  if (!lighting) {
    const boxes = properties.shapes[Math.floor(code / 16)];
    if (!boxes) return { ...material };
    lighting = {
      light_dampening: code % 16,
      light_occlusion: Object.freeze(boxes.map((box) => Object.freeze({
        min: Object.freeze(box.slice(0, 3)), max: Object.freeze(box.slice(3, 6)),
      }))),
    };
    cache.set(code, lighting);
  }
  return { ...material, ...lighting };
}