// GODSEED — the god's gaze. A spherical camera rig with two modes:
//   TOWN  (default): sits LOW and close over townCenter, framing a ~28° cap so
//                    buildings read large — like standing over a model town.
//   WORLD (the reveal): eases out to the full-planet orbit (the wide shot) and
//                    back, via rig.beholdWorld()/rig.setMode().
// On each tool_call / world_delta it eases over to look at where the world is
// about to change — within the town zoom in TOWN mode, never flying to the far
// limb. Drag to orbit; wheel to approach. On a granted wish (or a Genesis Log
// replay) it can also descend — a slow liturgical swoop to the surface over the
// target, a glide arc, then a rise back. Every motion is sim-time deterministic
// (driven only by update(dt)); no Date/random.
import * as THREE from "three";
import { PLANET_R, clamp, lerp, easeInOutCubic, townCenter } from "./util.js";

const WIDE_DIST = PLANET_R * 3.3;
const GAZE_DIST = PLANET_R * 2.35;
const MIN_DIST = PLANET_R * 1.45;
const MAX_DIST = PLANET_R * 7.0;

// TOWN view: a low, close vantage that frames a ~28° cap around the town heart.
// The eye rides just above the surface; the look target floats over the town so
// buildings stand up into the frame. Tuned (with shot.mjs) so one district reads
// large yet the whole neighbourhood stays in view.
const TOWN_CAP = 0.49;               // ~28°, the framed cap half-angle (the spec)
// Eye distance so the cap roughly fills the 42° FOV from a low oblique. Derived
// from the cap so the framing follows the spec; the small factor is the visual
// tune (a hair tighter than the geometric fit so buildings read large).
const TOWN_DIST = PLANET_R * (1 + Math.sin(TOWN_CAP) * 1.27); // ≈ 1.6 R
const TOWN_TILT = TOWN_CAP * 0.62;   // eye sits this far "south" of the town for a low oblique look
const TOWN_LOOK_R = PLANET_R * 1.04; // look target floats just above the ground
// While granting in TOWN mode the gaze nudges a touch closer to the new feature.
const TOWN_GAZE_DIST = TOWN_DIST * 0.93;

// Descent geometry. We ride just above the surface and glide a short arc.
const DESCENT_DIST = PLANET_R * 1.18;  // eye distance from planet center at low point
const DESCENT_CLEAR = PLANET_R * 1.06; // the look target floats here, above terrain
const GLIDE_ARC = 0.42;                // radians swept over the target (~24°)
const PHI_FLOOR = 0.26;
const PHI_CEIL = Math.PI - 0.26;

export class CameraRig {
  constructor(camera, dom) {
    this.camera = camera;
    this.theta = 0.7;
    this.phi = 1.18;
    this.dist = WIDE_DIST;
    this.thetaT = this.theta;
    this.phiT = this.phi;
    this.distT = this.dist;
    this.look = new THREE.Vector3();
    this.lookT = new THREE.Vector3();
    this.idleSpeed = 0.05;
    this.userHold = 0;   // seconds left of user-control override
    this.gazeHold = 0;   // seconds left of god's-gaze hold
    this.descent = null; // active descent state, or null
    this._terrain = null; // optional terrain for analytic ground clearance
    // --- town/world mode ---
    this.mode = "town";              // "town" (default, close) | "world" (the reveal)
    this.townDir = new THREE.Vector3(); // current town heart (unit dir)
    townCenter([], this.townDir);    // seed at the genesis monolith
    this._bind(dom);
  }

  /** Let the rig clear terrain analytically during descents (set by the app). */
  setTerrain(terrain) { this._terrain = terrain; }

  /**
   * Re-anchor the town heart from the live feature list and, if we're resting in
   * TOWN mode, re-frame to follow it (the town centroid drifts as it grows). No
   * effect while granting (gazeHold), under the hand (userHold), or mid-descent.
   */
  setTownCenter(features) {
    const { dir } = townCenter(features);
    this.townDir.copy(dir);
    if (this.mode === "town" && !this.descent && this.userHold <= 0 && this.gazeHold <= 0) {
      this._frameTown();
    }
  }

  /** Switch modes with an eased transition (sim-time deterministic). */
  setMode(mode) {
    const next = mode === "world" ? "world" : "town";
    if (next === this.mode) return;
    this.mode = next;
    if (this.descent) this.cancelDescent();
    this.userHold = 0;
    this.gazeHold = 0;
    if (next === "town") this._frameTown();
    else this._frameWorld();
  }

  /** Toggle between beholding the whole world and returning to the town. */
  beholdWorld() {
    this.setMode(this.mode === "world" ? "town" : "world");
    return this.mode;
  }

  /** Spherical angles + distance that frame the close TOWN view over townDir. */
  _frameTown() {
    const { th, ph } = this._townAngles(this.townDir);
    this.thetaT = th;
    this.phiT = ph;
    this.distT = TOWN_DIST;
    this.lookT.copy(this.townDir).multiplyScalar(TOWN_LOOK_R);
  }

  /** The wide full-planet orbit (the reveal). */
  _frameWorld() {
    this.distT = WIDE_DIST;
    this.lookT.set(0, 0, 0);
    // keep the town roughly framed in the wide shot so the reveal reads as "this
    // patch is one town on a whole world", not a jump-cut to nowhere.
    const { th, ph } = this._anglesFor(this.townDir);
    this.thetaT = th;
    this.phiT = ph;
  }

  /**
   * Spherical (theta, phi) for the LOW oblique town look: the eye sits a little
   * "south" (toward higher phi) of the town heart so buildings stand up into the
   * frame, and the look target is the town itself.
   */
  _townAngles(dir) {
    const tau = Math.PI * 2;
    let th = Math.atan2(dir.z, dir.x);
    // drop the eye below the town's own latitude for the oblique, model-town read
    const base = Math.acos(clamp(dir.y, -1, 1));
    const ph = clamp(base + TOWN_TILT, PHI_FLOOR, PHI_CEIL);
    while (th - this.theta > Math.PI) th -= tau;
    while (th - this.theta < -Math.PI) th += tau;
    return { th, ph };
  }

  _bind(dom) {
    if (!dom) return;
    let dragging = false, px = 0, py = 0;
    dom.addEventListener("pointerdown", (e) => {
      // a deliberate click during a descent is the "take me back" gesture
      if (this.descent && !dragging) this.cancelDescent();
      dragging = true; px = e.clientX; py = e.clientY;
      dom.setPointerCapture?.(e.pointerId);
      this.userHold = 6;
    });
    dom.addEventListener("pointermove", (e) => {
      if (!dragging) return;
      const dx = e.clientX - px, dy = e.clientY - py;
      px = e.clientX; py = e.clientY;
      this.thetaT -= dx * 0.0052;
      this.phiT = clamp(this.phiT - dy * 0.0042, 0.28, Math.PI - 0.28);
      this.userHold = 6;
    });
    const end = () => { dragging = false; };
    dom.addEventListener("pointerup", end);
    dom.addEventListener("pointercancel", end);
    dom.addEventListener("wheel", (e) => {
      e.preventDefault();
      if (this.descent) this.cancelDescent();
      this.distT = clamp(this.distT * (1 + e.deltaY * 0.0011), MIN_DIST, MAX_DIST);
      this.userHold = 6;
    }, { passive: false });
    // ESC returns to orbit (camera liturgy, not a trap)
    this._onKey = (e) => { if (e.key === "Escape" && this.descent) this.cancelDescent(); };
    window.addEventListener("keydown", this._onKey);
  }

  /** Spherical angles (theta, phi) that frame a unit direction off-center. */
  _anglesFor(dir) {
    let th = Math.atan2(dir.z, dir.x) + 0.32; // feature sits just off-center
    const ph = clamp(Math.acos(clamp(dir.y, -1, 1)) - 0.14, 0.3, Math.PI - 0.3);
    const tau = Math.PI * 2;
    while (th - this.theta > Math.PI) th -= tau;
    while (th - this.theta < -Math.PI) th += tau;
    return { th, ph };
  }

  /**
   * Ease toward a world point — the demo money-shot. In TOWN mode this frames
   * the new feature WITHIN the close town zoom (never flying to the far limb);
   * in WORLD mode it eases over the planet to the spot. `point` null ⇒ the
   * mode's resting frame (town heart / wide shot).
   */
  gaze(point, { hold = 4.5 } = {}) {
    if (this.userHold > 0 || this.descent) return; // hand on the camera / mid-descent
    if (this.mode === "town") {
      // a new feature is always near the town; keep the low, close framing and
      // just lean the look toward it so it reads big without leaving the town.
      const dir = point ? point.clone().normalize() : this.townDir;
      // blend the look between the town heart and the new feature so the whole
      // block stays in the cap — don't snap the eye to a stray far-flung build.
      const lookDir = this.townDir.clone().lerp(dir, point ? 0.55 : 0).normalize();
      const { th, ph } = this._townAngles(lookDir);
      this.thetaT = th;
      this.phiT = ph;
      this.distT = point ? TOWN_GAZE_DIST : TOWN_DIST;
      this.lookT.copy(lookDir).multiplyScalar(TOWN_LOOK_R);
    } else if (point) {
      const dir = point.clone().normalize();
      const { th, ph } = this._anglesFor(dir);
      this.thetaT = th;
      this.phiT = ph;
      this.distT = GAZE_DIST;
      this.lookT.copy(dir).multiplyScalar(PLANET_R * 0.55);
    } else {
      this.distT = WIDE_DIST;
      this.lookT.set(0, 0, 0);
    }
    this.gazeHold = hold;
  }

  /** Drift back to the mode's resting frame (town heart in TOWN, wide in WORLD). */
  release() {
    if (this.descent) return; // a descent owns the camera until it finishes/cancels
    this.gazeHold = 0;
    if (this.mode === "town") this._frameTown();
    else { this.distT = WIDE_DIST; this.lookT.set(0, 0, 0); }
  }

  /**
   * Cinematic descent: swoop from orbit down to just above the surface over
   * `targetDir`, glide a slow arc with gentle look-ahead, then rise back to the
   * orbit framing. `targetDir` is a (not necessarily unit) world direction —
   * typically a granted wish's last landed feature. Sim-time deterministic.
   */
  descend(targetDir, { duration = 13 } = {}) {
    if (!targetDir) return;
    const dir = targetDir.clone().normalize();
    // a tangent basis around the target so the glide sweeps along the surface
    const up = Math.abs(dir.y) > 0.93 ? new THREE.Vector3(1, 0, 0) : new THREE.Vector3(0, 1, 0);
    const east = new THREE.Vector3().crossVectors(up, dir).normalize();
    const north = new THREE.Vector3().crossVectors(dir, east).normalize();
    // approach from a little "south & up" of the target, glide toward "north"
    const start = dir.clone()
      .multiplyScalar(Math.cos(GLIDE_ARC * 0.9))
      .addScaledVector(north, -Math.sin(GLIDE_ARC * 0.9))
      .normalize();
    const end = dir.clone()
      .multiplyScalar(Math.cos(GLIDE_ARC * 1.1))
      .addScaledVector(north, Math.sin(GLIDE_ARC * 1.1))
      .normalize();
    this.descent = {
      dir, north, start, end,
      t: 0,
      duration,
      // the orbit framing to dive from / rise back to — the town zoom in TOWN
      // mode, the wide shot in WORLD mode
      orbitDist: this.mode === "town" ? TOWN_DIST : WIDE_DIST,
      townMode: this.mode === "town",
      // phase fractions: dive → glide → rise
      dive: 0.34, glide: 0.40,
    };
    this.gazeHold = 0;
    this.userHold = 0;
  }

  cancelDescent() {
    if (!this.descent) return;
    this.descent = null;
    // hand control back to the mode's resting frame (back over the town in TOWN
    // mode, a gentle wide pull in WORLD mode)
    if (this.mode === "town") {
      this._frameTown();
    } else {
      this.distT = WIDE_DIST;
      this.lookT.set(0, 0, 0);
      this.thetaT = this.theta;
      this.phiT = this.phi;
    }
    this.gazeHold = 0.6;
  }

  get descending() { return !!this.descent; }

  /** Eye distance that keeps us safely above any terrain along the descent dir. */
  _groundClear(dir) {
    let h = 0;
    if (this._terrain?.heightAt) {
      try { h = this._terrain.heightAt(dir) || 0; } catch { h = 0; }
    }
    // ride a hair above the highest plausible relief beneath us
    return Math.max(DESCENT_DIST, PLANET_R + h + 0.10 * PLANET_R);
  }

  _updateDescent(dt) {
    const d = this.descent;
    d.t += dt;
    const u = clamp(d.t / d.duration, 0, 1);
    // three eased phases sharing one progress value
    let dist, lookDir, lookR;
    const orbitLookR = d.townMode ? TOWN_LOOK_R : PLANET_R * 0.5;
    if (u < d.dive) {
      // orbit → low point over the start of the glide
      const k = easeInOutCubic(u / d.dive);
      dist = lerp(d.orbitDist, this._groundClear(d.start), k);
      lookDir = d.start.clone();
      lookR = lerp(orbitLookR, DESCENT_CLEAR, k);
    } else if (u < d.dive + d.glide) {
      // glide arc: sweep eye + a forward look-ahead along the surface
      const k = (u - d.dive) / d.glide;
      const dir = slerp(d.start, d.end, k);
      dist = this._groundClear(dir);
      const ahead = slerp(d.start, d.end, Math.min(1, k + 0.16)); // gentle look-ahead
      lookDir = ahead;
      lookR = DESCENT_CLEAR;
    } else {
      // rise back to the resting frame. In TOWN mode re-acquire the close town
      // look (stay over the town); in WORLD mode pull up to the wide framing.
      const k = easeInOutCubic((u - d.dive - d.glide) / Math.max(1e-3, 1 - d.dive - d.glide));
      const dir = d.townMode ? slerp(d.end, this.townDir, k) : slerpToOrbit(d.end, k);
      dist = lerp(this._groundClear(d.end), d.orbitDist, k);
      lookDir = dir;
      // TOWN: settle the look just above the town; WORLD: ease the look to center
      lookR = lerp(DESCENT_CLEAR, d.townMode ? orbitLookR : 0, k);
    }
    // place the eye directly (no spherical-lerp; the descent is the authority)
    const eye = lookDir.clone();
    // keep the eye slightly behind the look target so we look forward/down
    const phi = clamp(Math.acos(clamp(eye.y, -1, 1)), PHI_FLOOR, PHI_CEIL);
    const theta = Math.atan2(eye.z, eye.x);
    this.theta = theta; this.thetaT = theta;
    this.phi = phi; this.phiT = phi;
    this.dist = dist; this.distT = dist;
    const sp = Math.sin(phi);
    this.camera.position.set(
      dist * sp * Math.cos(theta),
      dist * Math.cos(phi),
      dist * sp * Math.sin(theta)
    );
    this.look.copy(lookDir).multiplyScalar(lookR);
    this.lookT.copy(this.look);
    this.camera.lookAt(this.look);
    if (u >= 1) this.cancelDescent();
  }

  update(dt) {
    if (this.descent) { this._updateDescent(dt); return; }

    if (this.userHold > 0) this.userHold -= dt;
    if (this.gazeHold > 0) {
      this.gazeHold -= dt;
      if (this.gazeHold <= 0) {
        // a held gaze expires back to the mode's resting frame
        if (this.mode === "town") this._frameTown();
        else { this.distT = WIDE_DIST; this.lookT.set(0, 0, 0); }
      }
    } else if (this.userHold <= 0 && this.mode === "world") {
      this.thetaT += this.idleSpeed * dt; // eternal slow orbit (WORLD only)
    }
    // TOWN mode holds steady over the town — the town's own life is the motion.
    const k = 1 - Math.exp(-dt * 2.4);
    this.theta = lerp(this.theta, this.thetaT, k);
    this.phi = lerp(this.phi, this.phiT, k);
    this.dist = lerp(this.dist, this.distT, k * 0.8);
    this.look.lerp(this.lookT, k * 0.9);
    const sp = Math.sin(this.phi);
    this.camera.position.set(
      this.dist * sp * Math.cos(this.theta),
      this.dist * Math.cos(this.phi),
      this.dist * sp * Math.sin(this.theta)
    );
    this.camera.lookAt(this.look);
  }
}

// --- local helpers (sim-time pure) ------------------------------------------

/** Spherical interpolation between two unit vectors (short way). */
function slerp(a, b, t) {
  const dot = clamp(a.dot(b), -1, 1);
  const omega = Math.acos(dot);
  if (omega < 1e-4) return a.clone();
  const so = Math.sin(omega);
  return a.clone().multiplyScalar(Math.sin((1 - t) * omega) / so)
    .addScaledVector(b, Math.sin(t * omega) / so)
    .normalize();
}

/**
 * On the rise, pull the eye up and away from the surface dir toward a higher
 * latitude so we re-frame the whole planet, not the ground we just skimmed.
 */
function slerpToOrbit(surfaceDir, k) {
  const up = new THREE.Vector3(0, 1, 0);
  // a vantage offset from the surface dir, lifted toward the pole for the wide
  const high = surfaceDir.clone().lerp(up, 0.34).normalize();
  return slerp(surfaceDir, high, easeInOutCubic(k));
}