#!/usr/bin/env node
/*
 * build-mini-graph.mjs — builds the committed mini-graph.bin fixture.
 * ----------------------------------------------------------------------
 * A MAINTAINER-TIME REPO TOOL: regenerates routing/test/fixtures/
 * mini-graph.bin — the A* correctness ground truth (plan 06-01) and the
 * snap/astar suites' shared fixture. NOT a runtime dependency; nothing in
 * bot/src/, web/src/, or routing/src/ imports it. Tests consume the
 * COMMITTED binary; only a deliberate fixture redesign re-runs this.
 *
 * Usage:   node routing/test/fixtures/build-mini-graph.mjs
 * Exit:    0 on write; throws on any invariant violation (never writes).
 *
 * Design (pinned by 06-01): a hand-built 5x5 grid in a ~0.002 deg x 0.002 deg
 * bbox near KL center (lat 3.1500–3.1520, lng 101.6900–101.6920):
 *   - 25 nodes, 80 directed edge entries (20 H + 20 V segments, both ways)
 *   - three named streets: "Jalan Mini 1" (interior E-W rows),
 *     "Jalan Mini 2" (interior N-S columns), "Jalan Persiaran Mini" (perimeter)
 *   - exactly ONE oneway pair: 2 -> 3 traversable, 3 -> 2 flagged bit0
 *   - two speed classes: perimeter 60 km/h, interior 30 km/h
 *     (weights = segment meters / (kmh / 3.6), meters via haversineM)
 */
import { writeFileSync } from "node:fs";
import { encodeGraph } from "../../src/graph.ts";
import { haversineM } from "../../src/geo.ts";

const GRID = 5;
const LAT0 = 3.15;
const LNG0 = 101.69;
const STEP_DEG = 0.0005;
/** The single oneway pair (grid ids: row 0, cols 2->3). */
const ONEWAY_U = 2;
const ONEWAY_V = 3;

const NAME_MINI_1 = 0; // interior E-W rows
const NAME_MINI_2 = 1; // interior N-S columns
const NAME_PERIMETER = 2;
const names = ["Jalan Mini 1", "Jalan Mini 2", "Jalan Persiaran Mini"];

const SPEED_PERIMETER_KMH = 60;
const SPEED_INTERIOR_KMH = 30;

const lat = [];
const lng = [];
for (let r = 0; r < GRID; r++) {
  for (let c = 0; c < GRID; c++) {
    // 1e-6 integer grid then divide — exact decimal coordinates (the codec's
    // grid law); naive `3.15 + r * 0.0005` accumulates float error.
    lat.push((3150000 + r * 500) / 1e6);
    lng.push((101690000 + c * 500) / 1e6);
  }
}
const id = (r, c) => r * GRID + c;

const edges = [];
function addEdge(u, v, nameId) {
  const kmh = nameId === NAME_PERIMETER ? SPEED_PERIMETER_KMH : SPEED_INTERIOR_KMH;
  const meters = haversineM({ lat: lat[u], lng: lng[u] }, { lat: lat[v], lng: lng[v] });
  edges.push({ from: u, to: v, seconds: meters / (kmh / 3.6), nameId });
}
for (let r = 0; r < GRID; r++) {
  for (let c = 0; c < GRID - 1; c++) {
    const nameId = r === 0 || r === GRID - 1 ? NAME_PERIMETER : NAME_MINI_1;
    addEdge(id(r, c), id(r, c + 1), nameId);
    addEdge(id(r, c + 1), id(r, c), nameId);
  }
}
for (let c = 0; c < GRID; c++) {
  for (let r = 0; r < GRID - 1; r++) {
    const nameId = c === 0 || c === GRID - 1 ? NAME_PERIMETER : NAME_MINI_2;
    addEdge(id(r, c), id(r + 1, c), nameId);
    addEdge(id(r + 1, c), id(r, c), nameId);
  }
}

// Exactly ONE oneway: the reverse mirror of U->V carries flags bit0.
const reverse = edges.find((e) => e.from === ONEWAY_V && e.to === ONEWAY_U);
if (!reverse) throw new Error("oneway reverse edge not found — grid invariant broken");
reverse.flags = 1;

if (edges.length !== 80) throw new Error(`expected 80 directed edges, built ${edges.length}`);

const bin = encodeGraph({ lat, lng, edges, names, maxSpeedKmh: SPEED_PERIMETER_KMH });
writeFileSync(new URL("./mini-graph.bin", import.meta.url), Buffer.from(bin));
console.log(`mini-graph.bin: ${GRID * GRID} nodes, ${edges.length} edges, 3 names, ${bin.byteLength} B`);