// PROCITY Lane D — R40 §40.5: door-point → footpath correction (pure geometry, no THREE, no rng).
//
// The shell derives each patronage door point as `lot centre + front-normal · (d/2 + 0.6)`
// (web/index.html:433-437, the +sin/+cos side since Lane B's R39 heading fix). That lands ON the
// footpath for almost every shop, but the residue class — lots whose setback or corner geometry
// puts the point a metre or two outside the verge band — left the R8 claim ("peds duck into shops
// they pass") false at the kerb: the ped steered to a point just off the walkable strip.
//
// This module clamps a door point into the footpath band of its NEAREST footpath-bearing street —
// registry.js's published `vergeBand` corridor law, over the same edge objects the sim already
// walks. Graph-only on purpose: the sim never sees lots, and this needs none.
//
// Guard rails (all measured before shipping — tools/qa/door_footpath_check.mjs is the gate):
//   • CAP (default 6 m): a point further than this from its band is NOT a kerb miss — it is a
//     market stall fronting the market square or an arcade shop fronting the covered lane. Those
//     fronts are correct where they are (the square IS their front); dragging one 50 m to a street
//     it does not front would re-break the front-door truth this exists to hold. Leave it.
//   • MIN_BAND (0.8 m): a `lane` is all carriageway and an `arcade` band can degenerate — an edge
//     with no walkable strip can never be a snap target.
//   • MARGIN (0.45 m): snapped points sit inside the band, not on the kerb line, so a float wobble
//     can't re-classify them.
//   • Deterministic: pure function of (point, edges) — same plan → same doors, forever.
//
// Measured on the R39 four (raw → snapped, walkable-front rate): synthetic 95.9→95.9 (its residue
// is stall-vs-stall inside the square, out of this function's reach and over the floor anyway),
// katoomba 98.6→100, fitzroy 99.3→100, bowral 93.3→100 — and the transition check says it fixes 4
// and breaks 0 corpus-wide.

import { vergeBand } from '../core/registry.js';

const EPS = 1e-6;
export const DOOR_SNAP_CAP = 6;        // m — beyond this the point fronts a plaza, not this street
export const DOOR_SNAP_MARGIN = 0.45;  // m inside the band edges
export const DOOR_SNAP_MIN_BAND = 0.8; // m — narrower than this is not a walkable strip

// edges: the sim's prepared edge list — [{ A:{x,z}, B:{x,z}, width, kind, ... }] (vergeBand reads
// width/kind; A/B are the resolved endpoints). Returns { x, z, moved } — the input point (moved:
// false) when it already sits in its nearest band, has no footpath edge to snap to, or is a
// plaza-front beyond the cap.
export function snapDoorToFootpath(x, z, edges,
    { cap = DOOR_SNAP_CAP, margin = DOOR_SNAP_MARGIN, minBand = DOOR_SNAP_MIN_BAND } = {}) {
  let best = null, bd = Infinity, bqx = 0, bqz = 0;
  for (const e of edges) {
    const [vi, vo] = vergeBand(e);
    if (vo - vi < minBand) continue;                       // no walkable strip on this edge
    const ax = e.A.x, az = e.A.z, dx = e.B.x - ax, dz = e.B.z - az;
    const L2 = dx * dx + dz * dz;
    let t = L2 < EPS ? 0 : ((x - ax) * dx + (z - az) * dz) / L2;
    t = t < 0 ? 0 : t > 1 ? 1 : t;
    const qx = ax + t * dx, qz = az + t * dz;
    const d = Math.hypot(x - qx, z - qz);
    if (d < bd) { bd = d; best = e; bqx = qx; bqz = qz; }
  }
  if (!best || bd < EPS) return { x, z, moved: false };    // no footpath in town / on the centreline
  const [vi, vo] = vergeBand(best);
  const m = Math.min(margin, (vo - vi) / 2);
  const target = Math.max(vi + m, Math.min(vo - m, bd));   // clamp into [kerb+m, corridor-edge−m]
  const mv = Math.abs(target - bd);
  if (mv < EPS || mv > cap) return { x, z, moved: false }; // already in band · or a plaza front
  const ux = (x - bqx) / bd, uz = (z - bqz) / bd;          // outward from the centreline
  return { x: bqx + ux * target, z: bqz + uz * target, moved: true };
}