builazoo/web/js/biome-rules.js

/**
 * Biomes: Meadow, Freshwater, Ocean, Forest, Mountain.
 * Each cell has a biome and a temperature; display uses optional interpolation for smooth transitions.
 */

export const BIOMES = ["Meadow", "Freshwater", "Ocean", "Forest", "Mountain"];

/**
 * Base biome from grid position (5 zones by column).
 * @param {number} width
 * @param {number} height
 * @param {number} x 1-based column
 * @param {number} y 1-based row
 * @returns {string}
 */
export function getCellBiome(width, height, x, y) {
  const w = Math.max(1, width);
  const h = Math.max(1, height);
  const col = Math.max(1, Math.min(w, Math.floor(x)));
  const _row = Math.max(1, Math.min(h, Math.floor(y)));
  const t = Math.floor((col - 1) / (w / 5));
  const index = Math.min(4, Math.max(0, t));
  return BIOMES[index] ?? "Meadow";
}

/**
 * Backward-compat: getCellBiome with 2 args (width, x) returns Meadow/Ocean/Mountain by column thirds.
 * @param {number} width
 * @param {number} x
 * @returns {string}
 */
export function getCellBiomeLegacy(width, x) {
  const third = Math.max(1, Math.floor(width / 3));
  if (x <= third) return "Meadow";
  if (x <= third * 2) return "Ocean";
  return "Mountain";
}

/**
 * Base temperature at cell (smooth gradient by position). Range about 10–28.
 * @param {number} width
 * @param {number} height
 * @param {number} x 1-based
 * @param {number} y 1-based
 * @returns {number}
 */
export function getCellTemperature(width, height, x, y) {
  const w = Math.max(1, width);
  const h = Math.max(1, height);
  const nx = (Math.max(1, Math.min(w, Math.floor(x))) - 0.5) / w;
  const ny = (Math.max(1, Math.min(h, Math.floor(y))) - 0.5) / h;
  return 10 + ny * 14 + nx * 4;
}

/**
 * Display biome at (x, y) — for now the cell's own biome (no string interpolation).
 * @param {number} x 1-based
 * @param {number} y 1-based
 * @param {{ width: number, height: number }} grid
 * @returns {string}
 */
export function getDisplayBiome(x, y, grid) {
  return getCellBiome(grid.width, grid.height, x, y);
}

/**
 * Display temperature at (x, y) with smooth interpolation from neighbours.
 * @param {number} x 1-based
 * @param {number} y 1-based
 * @param {{ width: number, height: number }} grid
 * @returns {number}
 */
export function getDisplayTemperature(x, y, grid) {
  const w = grid.width;
  const h = grid.height;
  let sum = 0;
  let count = 0;
  for (let dy = -1; dy <= 1; dy++) {
    for (let dx = -1; dx <= 1; dx++) {
      const nx = x + dx;
      const ny = y + dy;
      if (nx >= 1 && nx <= w && ny >= 1 && ny <= h) {
        sum += getCellTemperature(w, h, nx, ny);
        count += 1;
      }
    }
  }
  return count > 0 ? sum / count : getCellTemperature(w, h, x, y);
}

/**
 * Temperature band for CSS class: low (< 16), mid (16–22), high (> 22).
 * @param {number} temp
 * @returns {"low"|"mid"|"high"}
 */
export function getTemperatureBand(temp) {
  if (temp < 16) return "low";
  if (temp <= 22) return "mid";
  return "high";
}

/**
 * @param {string} animalBiome
 * @param {string} cellBiome
 * @returns {boolean}
 */
export function isAnimalAllowedOnBiome(animalBiome, cellBiome) {
  if (animalBiome === cellBiome) return true;
  if (animalBiome === "Meadow" && cellBiome === "Forest") return true;
  if (animalBiome === "Ocean" && cellBiome === "Freshwater") return true;
  return false;
}

/**
 * Biomes that are compatible with this cell for loot/placement (cell biome + compatible animal biomes).
 * @param {string} cellBiome
 * @returns {string[]}
 */
export function getBiomesCompatibleWithCell(cellBiome) {
  const set = [cellBiome];
  if (cellBiome === "Forest") set.push("Meadow");
  if (cellBiome === "Freshwater") set.push("Ocean");
  return set;
}