"use strict";

const fs = require("fs");

const EARTH_RADIUS = 6371008.8;
const CURB_OFFSET_METERS = 5.2;
const MAST_REACH_METERS = 4.5;

function buildTrafficSignals(stopLines, intersections) {
  const centers = (intersections.features || []).map((feature, index) => {
    const point = polygonCenter(feature.geometry);
    return { id: `intersection-${index + 1}`, point, radius: polygonRadius(feature.geometry, point) };
  }).filter((entry) => entry.point);
  const signals = [];
  for (const feature of stopLines.features || []) {
    const center = polygonCenter(feature.geometry);
    if (!center) continue;
    const intersection = nearestCenter(center, centers);
    if (!intersection || metersBetween(center, intersection.point) > 32) continue;
    const axis = roadAxis(feature.geometry, center, intersection.point);
    if (!axis) continue;
    // A vehicle signal belongs beyond the junction, facing back toward the
    // approaching stop line. Use the far edge of the intersection, never the
    // near-side stop-line area where it would read as a pedestrian signal.
    const right = [axis[1], -axis[0]];
    const farSide = moveMeters(intersection.point, axis, intersection.radius + 3.2);
    // The pole is on the far-side sidewalk, not at the stop line or inside
    // the intersection. Its mast then reaches back above the approach lanes.
    const point = moveMeters(farSide, right, CURB_OFFSET_METERS);
    signals.push({
      id: `signal-${signals.length + 1}`,
      intersectionId: intersection.id,
      phaseGroup: signals.length % 2,
      longitude: point[0],
      latitude: point[1],
      stopLongitude: center[0],
      stopLatitude: center[1],
      headingDegrees: Math.atan2(axis[0], axis[1]) * 180 / Math.PI,
      mastReachMeters: MAST_REACH_METERS,
    });
  }
  return { version: 1, signals };
}

function readTrafficSignals(stopLinePath, intersectionPath) {
  return buildTrafficSignals(JSON.parse(fs.readFileSync(stopLinePath, "utf8")), JSON.parse(fs.readFileSync(intersectionPath, "utf8")));
}

function polygonCenter(geometry) {
  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
  if (!ring || ring.length < 4) return null;
  const points = ring.slice(0, -1);
  return [points.reduce((sum, point) => sum + point[0], 0) / points.length, points.reduce((sum, point) => sum + point[1], 0) / points.length];
}

function polygonRadius(geometry, center) {
  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
  if (!ring || !center) return 0;
  return Math.max(...ring.slice(0, -1).map((point) => metersBetween(center, point)), 0);
}

function roadAxis(geometry, center, target) {
  const ring = geometry?.coordinates?.[0];
  if (!ring || ring.length < 3) return null;
  let longest = null;
  for (let i = 0; i < ring.length - 1; i += 1) {
    const dx = (ring[i + 1][0] - ring[i][0]) * Math.cos(center[1] * Math.PI / 180);
    const dy = ring[i + 1][1] - ring[i][1];
    const length = Math.hypot(dx, dy);
    if (!longest || length > longest.length) longest = { dx, dy, length };
  }
  if (!longest?.length) return null;
  let axis = [-longest.dy / longest.length, longest.dx / longest.length];
  const toward = [(target[0] - center[0]) * Math.cos(center[1] * Math.PI / 180), target[1] - center[1]];
  if (axis[0] * toward[0] + axis[1] * toward[1] < 0) axis = [-axis[0], -axis[1]];
  return axis;
}

function nearestCenter(point, centers) {
  return centers.map((entry) => ({ ...entry, distance: metersBetween(point, entry.point) })).sort((a, b) => a.distance - b.distance)[0] || null;
}

function metersBetween(a, b) {
  const lat = (a[1] + b[1]) / 2 * Math.PI / 180;
  return Math.hypot((a[0] - b[0]) * Math.cos(lat), a[1] - b[1]) * Math.PI / 180 * EARTH_RADIUS;
}

function moveMeters(point, vector, meters) {
  const scale = 180 / Math.PI / EARTH_RADIUS;
  return [point[0] + vector[0] * meters * scale / Math.cos(point[1] * Math.PI / 180), point[1] + vector[1] * meters * scale];
}

module.exports = { buildTrafficSignals, readTrafficSignals };