import { config } from '../config/Config.js';
import { Rng } from '../utils/Rng.js';
import { NameGenerator } from '../utils/NameGenerator.js';

const clamp = (v, lo, hi) => Math.min(hi, Math.max(lo, v));

/**
 * Turns a lightweight galaxy record (id, name, type, x, y, rNorm) into a
 * fully generated system: star, planets, moons, SETTLEMENTS, debris belt,
 * hazard flag.
 *
 * Deterministic contract:
 *   same galaxy seed + same record id ⇒ identical content, every time.
 * The draw stream is derived from (seed, 'system', id) — NOT from the
 * galaxy-level sequence — so a system generated when the player arrives
 * is byte-for-byte identical to one generated during an up-front
 * generateAll(). That's what makes lazy generation safe.
 *
 * What the system contains is steered by the TYPE'S ATTRIBUTES in
 * data/systems.json (`types.<id>.attributes`): star classes, binary
 * chance, planet count spread, planet class weights, moon/belt chances,
 * habitability, hazard, and — the lived-in layer — `settlements` (chance
 * + required planet class per settlement kind). Settlement kinds and their
 * population ranges live in data/settlements.json; the core→rim density
 * gradient in data/galaxy.json (`settlements.gradient`).
 *
 * The galaxy is ALREADY LIVED IN: it was settled long before the player.
 * Colonies on habitable worlds, mining stations over resource worlds,
 * cloud bases riding gas giants, stations adrift in open space — and a
 * fair number of charted-but-unclaimed systems. Nothing here is hostile
 * yet: `owner` on every settlement is a reserved seam for the factions
 * and pirates we'll introduce later.
 */
export function generateSystemContent(galaxy, record, typeDefs = null) {
  const defs = typeDefs ?? config.get('systems.types', {});
  const type = defs[record.type] ?? { label: record.type, attributes: {} };
  const attr = type.attributes ?? {};
  const rng = Rng.derive(galaxy.seed, 'system', record.id);

  // --- Star -------------------------------------------------------------
  const starClasses = attr.star?.classes ?? { G: 30, K: 35, M: 35 };
  const massTable = attr.star?.mass ?? {};
  const starClass = rng.weighted(starClasses, 'M');
  const mass = Array.isArray(massTable[starClass]) ? massTable[starClass] : [0.3, 1.2];
  const star = {
    name: NameGenerator.star(rng),
    class: starClass,
    mass: Number(rng.range(mass[0], mass[1]).toFixed(2)),
    binary: false,
  };
  if (rng.chance(attr.binaryChance ?? 0.05)) {
    star.binary = true;
    star.secondary = {
      name: NameGenerator.star(rng),
      class: rng.weighted(starClasses, starClass),
    };
  }

  // --- Planets ----------------------------------------------------------
  const pc = attr.planetCount ?? { min: 3, max: 8, mean: 5 };
  const count = Math.round(
    clamp(pc.mean + (rng.next() - 0.5) * (pc.max - pc.min), pc.min, pc.max),
  );
  const classWeights = attr.planetClasses ?? { rocky: 45, gas: 25, ice: 18, lava: 12 };
  // Planet names come from a curated bank (data/naming.json → banks.planet),
  // dealt out per-system without repeats (see NameGenerator.planetDeck).
  // A dedicated derived stream keeps this order-independent (lazy === eager).
  const planetDeck = NameGenerator.planetDeck(
    Rng.derive(galaxy.seed, 'system', record.id, 'names', 'planets')
  );
  // The player's home world sits at the origin of the STARTING system and is
  // not one of the generated planets. It takes the first name off that
  // system's deck so it can never clash with a planet; the planets then draw
  // from the rest of the deck (all distinct within the system).
  const isHome = record.id === galaxy?.currentSystemId;
  const homeName = isHome ? planetDeck[0] : null;
  const planets = [];
  for (let i = 1; i <= count; i++) {
    const pclass = rng.weighted(classWeights, 'rocky');
    let moons = 0;
    if (rng.chance(attr.moonChance ?? 0.3)) {
      // Jovian/ice worlds drag moon systems; terrestrials mostly don't.
      moons = pclass === 'gas' || pclass === 'ice' ? rng.int(1, 6) : rng.int(0, 2);
    }
    planets.push({
      name: planetDeck[(isHome ? i : i - 1) % planetDeck.length],
      ordinal: i,
      class: pclass,
      moons,
      habitable: pclass === 'rocky' && rng.chance(attr.habitability ?? 0.1),
    });
  }
  // --- Settlements (the lived-in layer) ---------------------------------
  const settlements = generateSettlements({
    rng,
    kindDefs: config.get('settlements.kinds', {}),
    spec: attr.settlements ?? {},
    planets,
    stationDeck: NameGenerator.stationDeck(
      Rng.derive(galaxy.seed, 'system', record.id, 'names', 'stations')
    ),
    density: settlementDensity(galaxy, record),
  });

  // --- Layout: orbits around the home world -----------------------------
  // Planets and free-space stations are the system's layout objects — each
  // gets an x/y (see layoutSystem for the spacing rules and the N=11 case).
  const freeSpace = settlements.filter((s) => s.anchor?.type === 'space');
  layoutSystem(galaxy.seed, record.id, planets, freeSpace);

  // --- Debris belt & system-level hazard --------------------------------
  const belt = {
    present: rng.chance(attr.beltChance ?? 0.35),
    kind: rng.pick(['asteroid', 'debris']) ?? 'asteroid',
  };
  const hazard = rng.chance(attr.hazard ?? 0.1);

  const content = {
    name: record.name,
    type: record.type,
    star,
    planets,
    settlements,
    belt,
    hazard,
  };
  if (isHome) content.homeName = homeName; // the player's home world (starting system only)
  return content;
}

/**
 * Top-down layout of a system's objects — its planets and its free-space
 * stations — as one or two ORBITS (rings) around the home world, which
 * always sits at the system origin (the game renders a solid world there;
 * see GameScene).
 *
 * Each object gains x, y (world position). Planets also gain scale (size
 * multiplier, data/planets.json → classScale — the spacing rules below are
 * center-to-center, but the rendered discs still scale by class).
 *
 * The hard spacing rules (data/planets.json → solarSystem):
 *   minSpacing  — no two objects (planets, space stations, the home world)
 *                 may be closer than this, center to center;
 *   maxNeighbor — whenever a system holds more than one object, every
 *                 object must be within this of at least one other.
 *
 * A ring of k objects at radius R around the origin satisfies both at once:
 *   - object ⇄ home-world distance is R, so R ∈ [minSpacing, maxNeighbor]
 *     takes care of the home world's own pair of constraints;
 *   - the closest object-object pair on a regular k-gon is an edge,
 *     2·R·sin(π/k) — an edge is the shortest chord (vertices further around
 *     are further), so edge ≥ minSpacing covers every pair;
 *   - every object's nearest neighbor is then the home world, at
 *     R ≤ maxNeighbor.
 * That radius range is non-empty for k ≤ 10 (k = 11 would need
 * R ≥ 10905, which already strands the home world beyond maxNeighbor). So
 * the 11-object maximum (9 planets + 2 stations — the most the current
 * data can produce) gets two orbits: an inner 3-ring and an outer 8-ring.
 * The outer ring's near neighbor is its ring-mate (edge stays in
 * [minSpacing, maxNeighbor]); the inner ring keeps the home world within
 * maxNeighbor; and any inner/outer pair is at least R_outer − R_inner ≥
 * minSpacing apart. Smaller N all share one orbit. (Defensively, beyond
 * 11 objects the orbits chain outward — rings of ≤ 10, and a lone world
 * always fits radially outside the previous orbit — so this terminates
 * for any N.)
 *
 * What counts as an object: planets (all of them) and free-space
 * settlements (anchor.type 'space' — deep-space stations, waypoints).
 * Planet-bound settlements are features OF their planet (a colony sits on
 * it) and so are not layout objects of their own.
 *
 * Determinism: draws come from the dedicated fork (seed, 'system', id,
 * 'layout') — layout never perturbs the star/planet/settlement draws
 * above, and lazy (on-arrival) === eager (generateAll) is preserved.
 */
function layoutSystem(seed, systemId, planets, freeSpace) {
  const band = config.get('planets.solarSystem', {});
  if (band.enabled === false) return;
  const MIN_SEP = band.minSpacing ?? 6144;
  const MAX_NBR = band.maxNeighbor ?? 10240;

  // Rendered size per class (visual only — the spacing rules are
  // center-to-center, not edge-to-edge).
  for (const p of planets) {
    p.scale = config.get(`planets.classScale.${p.class}`, 1) ?? 1;
  }

  // Slot assignment order: planets in orbital order, then free-space
  // stations in generation order (deep-space station, then waypoint) —
  // stable per system, so lazy === eager.
  const objects = [...planets, ...freeSpace];
  const N = objects.length;
  if (N === 0) return;

  const TAU = Math.PI * 2;
  const lay = Rng.derive(seed, 'system', systemId, 'layout');
  const edgeFactor = (k) => (k <= 1 ? 1 : 2 * Math.sin(Math.PI / k));
  const slots = [];
  let prevR = 0;
  let prevAngle = 0;

  const placeRing = (k, lo, hi) => {
    const R = lay.range(lo, hi);
    // A LONE object on an outer orbit sits radially outside an
    // already-placed one: its guaranteed neighbor is then exactly
    // R − prevR away, whereas a random angle could leave it more than
    // maxNeighbor from every inner object.
    const th0 = k === 1 && prevR > 0 ? prevAngle : lay.range(0, TAU);
    for (let i = 0; i < k; i++) {
      const th = th0 + (k === 1 ? 0 : (TAU * i) / k);
      slots.push({ x: R * Math.cos(th), y: R * Math.sin(th) });
    }
    prevR = R;
    prevAngle = th0;
  };

  if (N <= 10) {
    // One orbit around the home world (k = 1: a single object, whose only
    // neighbor is the home world — fine, it's still within [MIN_SEP, MAX_NBR]).
    const f = edgeFactor(N);
    placeRing(N, Math.max(MIN_SEP, MIN_SEP / f), MAX_NBR);
  } else if (N === 11) {
    // Inner 3-ring: the home world must stay within MAX_NBR of it (R1 ≤
    // MAX_NBR), and the outer 8-ring must sit at least MIN_SEP beyond it
    // at a radius where its edge is still ≤ MAX_NBR:
    //   R1 ≤ MAX_NBR / edgeFactor(8) − MIN_SEP.
    const f8 = edgeFactor(8);
    placeRing(
      3,
      Math.max(MIN_SEP, MIN_SEP / edgeFactor(3)),
      Math.min(MAX_NBR, MAX_NBR / f8 - MIN_SEP),
    );
    const R1 = prevR;
    // Outer 8-ring: ring-mates are its near neighbors (edge in
    // [MIN_SEP, MAX_NBR]); every inner object is ≥ R2 − R1 ≥ MIN_SEP away.
    placeRing(
      8,
      Math.max(MIN_SEP / f8, R1 + MIN_SEP),
      Math.min(MAX_NBR / f8, R1 + MAX_NBR),
    );
  } else {
    // Beyond the data maximum: chain orbits outward. A ring of ≤ 10
    // objects always has a valid radius as ring 1, a lone world always
    // fits on any outer orbit — the loop terminates for any N.
    let rem = N;
    while (rem > 0) {
      const k = Math.min(rem, 10);
      const f = edgeFactor(k);
      const lo = prevR === 0 ? Math.max(MIN_SEP, MIN_SEP / f) : Math.max(MIN_SEP / f, prevR + MIN_SEP);
      const hi = prevR === 0 ? MAX_NBR : Math.min(MAX_NBR / f, prevR + MAX_NBR);
      if (lo <= hi) {
        placeRing(k, lo, hi);
        rem -= k;
      } else {
        placeRing(1, prevR + MIN_SEP, prevR + MAX_NBR);
        rem -= 1;
      }
    }
  }

  for (let i = 0; i < objects.length; i++) {
    objects[i].x = slots[i].x;
    objects[i].y = slots[i].y;
  }
}

/**
 * Core→rim density: the settled heart of the galaxy has more activity per
 * system; the rim is thinner, lonelier. `factor` scales every settlement
 * chance (clamped to a floor so the rim isn't dead). 0 = no gradient.
 */
function settlementDensity(galaxy, record) {
  const g = galaxy?.params?.settlements?.gradient ?? {};
  const falloff = Math.max(0, g.falloff ?? 0.7);
  const floor = clamp(g.floor ?? 0.22, 0, 1);
  const rNorm = clamp(record?.rNorm ?? 0, 0, 1);
  return clamp(1 - rNorm * falloff, floor, 1);
}

/**
 * Draw settlements for one system. Stable draw order: planet-bound kinds in
 * orbital order (colony, mining, cloud), then free-floating (deep-space
 * station, waypoint). Every roll goes through the system's own stream.
 */
function generateSettlements({ rng, kindDefs, spec, planets, stationDeck, density }) {
  const out = [];
  let nameIndex = 0; // next station name from the system's deck (no repeats)

  const make = (kind, anchor) => {
    const def = kindDefs[kind] ?? {};
    out.push({
      kind,
      name: stationDeck[nameIndex++ % stationDeck.length],
      anchor,
      population: logPopulation(rng, def.population),
      owner: null, // reserved: factions / pirates claim settlements later
    });
  };

  // Planet-bound, in orbital order.
  for (const p of planets) {
    if (p.habitable && roll(rng, spec.colony?.chance ?? 0.3, density)) {
      make('colony', { type: 'planet', ordinal: p.ordinal });
    }
    if (needs(p, spec.miningStation?.needs, ['rocky', 'lava', 'ice']) &&
        roll(rng, spec.miningStation?.chance ?? 0.2, density)) {
      make('miningStation', { type: 'planet', ordinal: p.ordinal });
    }
    if (needs(p, spec.cloudBase?.needs, ['gas']) &&
        roll(rng, spec.cloudBase?.chance ?? 0.15, density)) {
      make('cloudBase', { type: 'planet', ordinal: p.ordinal });
    }
  }

  // Free-floating, out in the dark.
  if (roll(rng, spec.deepSpaceStation?.chance ?? 0.12, density)) {
    make('deepSpaceStation', { type: 'space' });
  }
  if (roll(rng, spec.waypoint?.chance ?? 0.2, density)) {
    make('waypoint', { type: 'space' });
  }

  return out;
}

/** One deterministic roll, scaled by the core→rim density factor. */
function roll(rng, chance, density) {
  return rng.chance(chance * density);
}

/** Does the planet satisfy the kind's requirements? */
function needs(planet, needsList, defaults) {
  const list = Array.isArray(needsList) && needsList.length ? needsList : defaults;
  return list.includes(planet.class);
}

/** Log-uniform population in [min, max] (a few towns to a few megacities). */
function logPopulation(rng, pop) {
  const min = pop?.min ?? 1;
  const max = Math.max(min, pop?.max ?? min);
  if (min <= 0 && rng.chance(0.5)) return 0; // e.g. unmanned waypoints
  return Math.round(Math.exp(rng.range(Math.log(Math.max(1, min)), Math.log(max))));
}