#!/usr/bin/env node
/*
 * build-road-graph.mjs — the D-01 engine-A graph build tool (Overpass → CSR).
 * ---------------------------------------------------------------------------
 * A MAINTAINER-TIME REPO TOOL — NOT a runtime dependency; nothing in bot/src,
 * web/src, or routing/src imports it. No deploy, test, or CI run ever executes
 * it. A maintainer (or a fork) runs it on their own machine to produce the
 * KL road-graph binary, then uploads it to their OWN R2 bucket (D-01:
 * fork-friendly, $0 — see docs/ROAD-GRAPH.md).
 *
 * Mechanically:
 *   1. The KL bbox is COMPUTED at run start from the committed corpus —
 *      @araharah/search getEntries() extremes + the golden-pairs origin
 *      coordinates ± BBOX_MARGIN_DEG — and printed (Open Q 4's mechanical
 *      pinning: the bbox tunes itself when the corpus grows; never hand-edited).
 *   2. ONE Overpass query fetches every way whose highway tag is in
 *      DRIVABLE_CLASSES (footway/cycleway/service/path NEVER enter — 06-RESEARCH
 *      Pitfall 1: an unfiltered highway=* graph is the classic CPU-budget kill).
 *   3. Ways → nodes (deduplicated by rounded coordinate) → directed edges with
 *      oneway flags, speed-derived seconds, and street-name pool ids.
 *   4. encodeGraph (../src/graph.ts — the layout's SINGLE authority) produces
 *      the pinned CSR binary. COLLECT-THEN-WRITE: routing/data/
 *      kl-roadgraph.v1.bin is written ONLY after the encode and the stats gate
 *      both pass — any failure exits 1 with the previous binary untouched.
 *   5. THE STATS GATE prints nodeCount/edgeCount/nameCount/bbox/binary size and
 *      enforces the D-01 envelope: size ≤ MAX_BINARY_BYTES or exit 1. A result
 *      below the expected 30–80 MB band prints an ADVISORY warning (A2's
 *      forecast) — the ENFORCED floor is the 1 MB honesty check in --verify,
 *      never the forecast band.
 *
 * The binary is a BUILD ARTIFACT, not committed: routing/data/.gitignore
 * ignores *.bin — forks build + upload their own (ODbL-derived data stays out
 * of the repo; the attribution travels in docs/ROAD-GRAPH.md and the upload
 * path). The committed artifacts are this script, the docs, and the tiny
 * test mini-graph.
 *
 * Usage:
 *   node routing/scripts/build-road-graph.mjs
 *              # full build: fetch → encode → gate → write
 *              #            (network fetch; minutes on the KL bbox)
 *   node routing/scripts/build-road-graph.mjs --check <file>
 *              # decode an existing binary with decodeGraph, print stats,
 *              # exit 0/1 — NO network
 *
 * Exit codes: 0 built and gated (or checked green); 1 pre-flight failure,
 * fetch failure, envelope-gate failure, or --check decode failure.
 */
import { existsSync, mkdirSync, readFileSync, statSync, writeFileSync } from "node:fs";
import { dirname, resolve } from "node:path";
import { fileURLToPath } from "node:url";

const here = dirname(fileURLToPath(import.meta.url)); // routing/scripts
const CORPUS_PATH = resolve(here, "..", "test", "fixtures", "golden-pairs.json");
const OUT_PATH = resolve(here, "..", "data", "kl-roadgraph.v1.bin");

/* ————— named constants (no inline magic) ————— */

const OVERPASS_ENDPOINT = "https://overpass-api.de/api/interpreter";
/** Overpass server-side budget; matches the client fetch timeout. */
const REQUEST_TIMEOUT_MS = 300_000;
const USER_AGENT = "araharah-roadgraph/1.0 (build-time KL road graph; repo: araharah)";
/** D-01 envelope ceiling — a larger binary must NOT be written (shrink the
 *  class filter or the bbox instead). */
const MAX_BINARY_BYTES = 80 * 1024 * 1024;
/** A2's honest-build forecast floor — crossing it downward is an ADVISORY
 *  (verify the class filter), never a gate. */
const EXPECTED_MIN_BYTES = 30 * 1024 * 1024;
/** How far the computed bbox extends beyond the committed corpus extremes. */
const BBOX_MARGIN_DEG = 0.05;
/** Node dedup granularity: 1e-6 deg ≈ 0.11 m — far under GPS noise. */
const COORD_ROUND_DECIMALS = 6;
/** drivable classes ONLY (06-RESEARCH Pitfall 1): footway/cycleway/service/
 *  path are deliberately absent — a walking path must never enter a road A*. */
const DRIVABLE_CLASSES = new Set([
  "motorway",
  "trunk",
  "primary",
  "secondary",
  "tertiary",
  "residential",
  "unclassified",
  "living_street",
]);
/** Class speed defaults (km/h) when a way carries no parsable maxspeed. */
const CLASS_SPEED_KMH = {
  motorway: 100,
  trunk: 80,
  primary: 60,
  secondary: 50,
  tertiary: 40,
  residential: 30,
  unclassified: 30,
  living_street: 20,
};
/** Motorway link ramps inherit the parent class speed via these links. */
const LINK_CLASS_SPEED_KMH = { motorway_link: 60, trunk_link: 60 };

function fail(message) {
  console.error(`build-road-graph: ${message}`);
  process.exit(1);
}

/* ————— --check mode: decode + stats, no network ————— */

const checkIdx = process.argv.indexOf("--check");
if (checkIdx !== -1) {
  const file = process.argv[checkIdx + 1];
  if (file === undefined) fail("--check requires a file path");
  if (!existsSync(file)) fail(`--check: file not found: ${file}`);
  const { decodeGraph } = await import("../src/graph.ts");
  const buffer = readFileSync(file);
  const graph = decodeGraph(buffer.buffer.slice(buffer.byteOffset, buffer.byteOffset + buffer.byteLength));
  if (graph === null) fail(`--check: ${file} is NOT a valid GRAPH_VERSION CSR binary (decodeGraph null)`);
  const size = statSync(file).size;
  console.log(
    `--check ${file}\n` +
      `  nodeCount: ${graph.nodeCount}\n` +
      `  edgeCount: ${graph.edgeCount}\n` +
      `  nameCount: ${graph.nameCount}\n` +
      `  maxSpeedKmh: ${graph.maxSpeedKmh}\n` +
      `  bbox: [${graph.bbox.minLat}, ${graph.bbox.minLng}, ${graph.bbox.maxLat}, ${graph.bbox.maxLng}]\n` +
      `  bytes: ${size}`,
  );
  if (size > MAX_BINARY_BYTES) fail(`--check: ${size} bytes exceeds the ${MAX_BINARY_BYTES}-byte D-01 envelope`);
  if (size <= 1024) fail(`--check: ${size} bytes is implausibly small — not a real road graph`);
  process.exit(0);
}

/* ————— inputs ————— */

const { encodeGraph } = await import("../src/graph.ts");
const { haversineM } = await import("../src/geo.ts");

if (!existsSync(CORPUS_PATH)) fail(`corpus not found: ${CORPUS_PATH}`);
const corpus = JSON.parse(readFileSync(CORPUS_PATH, "utf8"));
const { getEntries } = await import("@araharah/search/src/gazetteer.ts");

/* The committed corpus defines the area engine A must route (Open Q 4):
 * gazetteer extremes cover the search surface; golden-pair origins/destinations
 * are gazetteer landmarks themselves — both are unioned so a future corpus
 * extension widens the graph mechanically. */
function computeBbox() {
  let minLat = Infinity;
  let minLng = Infinity;
  let maxLat = -Infinity;
  let maxLng = -Infinity;
  const absorb = (lat, lng) => {
    if (!Number.isFinite(lat) || !Number.isFinite(lng)) fail(`non-finite coordinate in corpus: (${lat}, ${lng})`);
    if (lat < minLat) minLat = lat;
    if (lat > maxLat) maxLat = lat;
    if (lng < minLng) minLng = lng;
    if (lng > maxLng) maxLng = lng;
  };
  for (const entry of getEntries()) absorb(entry.lat, entry.lng);
  for (const pair of corpus.pairs) absorb(pair.origin.lat, pair.origin.lng);
  const gazetteerById = new Map(getEntries().map((e) => [e.id, e]));
  for (const pair of corpus.pairs) {
    const dest = gazetteerById.get(pair.destinationId);
    if (dest === undefined) fail(`pair ${pair.pairId}: destinationId "${pair.destinationId}" is not a gazetteer entry`);
    absorb(dest.lat, dest.lng);
  }
  return {
    minLat: minLat - BBOX_MARGIN_DEG,
    minLng: minLng - BBOX_MARGIN_DEG,
    maxLat: maxLat + BBOX_MARGIN_DEG,
    maxLng: maxLng + BBOX_MARGIN_DEG,
  };
}

const bbox = computeBbox();
console.log(
  `bbox (corpus extremes ± ${BBOX_MARGIN_DEG} deg): ` +
    `[${bbox.minLat.toFixed(4)}, ${bbox.minLng.toFixed(4)}, ${bbox.maxLat.toFixed(4)}, ${bbox.maxLng.toFixed(4)}]`,
);

/* ————— the Overpass fetch (ONE request, drivable classes only) ————— */

const CLASSES_RE = "^(" + [...DRIVABLE_CLASSES].join("|") + ")$";
const query =
  `[out:json][timeout:${Math.floor(REQUEST_TIMEOUT_MS / 1000)}];` +
  `way["highway"~"${CLASSES_RE}"](${bbox.minLat},${bbox.minLng},${bbox.maxLat},${bbox.maxLng});` +
  `out geom;`;

console.log(`fetching ways from ${OVERPASS_ENDPOINT} (this can take minutes)…`);
let payload = null;
try {
  const res = await fetch(OVERPASS_ENDPOINT, {
    method: "POST",
    headers: { "User-Agent": USER_AGENT, "Content-Type": "application/x-www-form-urlencoded" },
    body: `data=${encodeURIComponent(query)}`,
    signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
  });
  if (!res.ok) fail(`Overpass returned HTTP ${res.status}`);
  payload = await res.json();
} catch (err) {
  fail(`Overpass fetch failed: ${err.message}`);
}
const ways = Array.isArray(payload?.elements) ? payload.elements.filter((el) => el.type === "way") : [];
if (ways.length === 0) fail("Overpass returned no drivable ways — bbox or endpoint problem");

/* ————— ways → deduplicated nodes → directed edges ————— */

const round6 = (v) => Math.round(v * 1e6) / 1e6;
/** "lat,lng" (rounded) → node id. Identical coordinates ARE the same OSM node. */
const nodeIdByCoord = new Map();
const latOut = [];
const lngOut = [];
function internNode(lat, lng) {
  const key = `${round6(lat)},${round6(lng)}`;
  const hit = nodeIdByCoord.get(key);
  if (hit !== undefined) return hit;
  const id = latOut.length;
  nodeIdByCoord.set(key, id);
  latOut.push(round6(lat));
  lngOut.push(round6(lng));
  return id;
}

/** name → pool id (dense, insertion-ordered). */
const nameIds = new Map();
function internName(name) {
  const hit = nameIds.get(name);
  if (hit !== undefined) return hit;
  const id = nameIds.size;
  nameIds.set(name, id);
  return id;
}

const rawEdges = [];
let onewayCount = 0;
let unnamedCount = 0;
let maxSeenKmh = 0;

function effectiveKmh(highway, maxspeedTag) {
  // First integer in the tag wins ("50", "50 mph", "50 knots" all lead with
  // the number). "none"/variable/messy tags fall back to the class default.
  const parsed = maxspeedTag === undefined ? NaN : parseInt(String(maxspeedTag), 10);
  const classDefault = CLASS_SPEED_KMH[highway] ?? LINK_CLASS_SPEED_KMH[highway] ?? 30;
  const kmh = Number.isFinite(parsed) && parsed > 0 && parsed <= 160 ? parsed : classDefault;
  if (kmh > maxSeenKmh) maxSeenKmh = kmh;
  return kmh;
}

for (const way of ways) {
  const highway = way.tags?.highway;
  if (typeof highway !== "string" || !DRIVABLE_CLASSES.has(highway)) continue;
  const geometry = way.geometry;
  if (!Array.isArray(geometry) || geometry.length < 2) continue;
  const kmh = effectiveKmh(highway, way.tags?.maxspeed);
  const nameId = typeof way.tags?.name === "string" && way.tags.name.length > 0 ? internName(way.tags.name) : undefined;
  if (nameId === undefined) unnamedCount += 1;
  // Oneway law: yes/1/true → forward only (reverse gets flags bit0);
  // -1 → reverse only (forward gets flags bit0); anything else bidirectional.
  const oneway = String(way.tags?.oneway ?? "").toLowerCase();
  const forwardOnly = oneway === "yes" || oneway === "1" || oneway === "true";
  const reverseOnly = oneway === "-1";
  if (forwardOnly || reverseOnly) onewayCount += 1;

  let from = internNode(geometry[0].lat, geometry[0].lon);
  for (let i = 1; i < geometry.length; i++) {
    const to = internNode(geometry[i].lat, geometry[i].lon);
    if (to !== from) {
      const meters = haversineM(
        { lat: latOut[from], lng: lngOut[from] },
        { lat: latOut[to], lng: lngOut[to] },
      );
      const seconds = meters / (kmh / 3.6);
      // forward direction: blocked when the way is reverse-only
      rawEdges.push({ from, to, seconds, flags: reverseOnly ? 1 : 0, nameId });
      // reverse direction: blocked when the way is forward-only (bit0 set —
      // stays visible to snapping, never traversed by A*)
      rawEdges.push({ from: to, to: from, seconds, flags: forwardOnly ? 1 : 0, nameId });
    }
    from = to;
  }
}

/* Degree-0 cleanup: a node that lost every segment (collapsed self-loops) is
 * dead weight — compact the id space so A* and the snap grid never scan it. */
const degree = new Uint32Array(latOut.length);
for (const edge of rawEdges) {
  degree[edge.from] += 1;
  degree[edge.to] += 1;
}
const remap = new Int32Array(latOut.length).fill(-1);
const cLat = [];
const cLng = [];
for (let i = 0; i < latOut.length; i++) {
  if (degree[i] > 0) {
    remap[i] = cLat.length;
    cLat.push(latOut[i]);
    cLng.push(lngOut[i]);
  }
}
const edges = rawEdges
  .map((e) => ({ from: remap[e.from], to: remap[e.to], seconds: e.seconds, flags: e.flags, nameId: e.nameId }))
  .filter((e) => e.from >= 0 && e.to >= 0);
const droppedNodes = latOut.length - cLat.length;
if (cLat.length === 0 || edges.length === 0) fail("the extract produced an empty graph — refusing to write");

/* ————— encode (the layout's single authority) + stats gate ————— */

const names = [...nameIds.keys()];
const buffer = encodeGraph({ lat: cLat, lng: cLng, edges, names, maxSpeedKmh: maxSeenKmh });
const bytes = buffer.byteLength;

const mb = (b) => `${(b / (1024 * 1024)).toFixed(1)} MB`;
console.log(
  `graph stats:\n` +
    `  nodeCount: ${cLat.length}${droppedNodes > 0 ? ` (${droppedNodes} degree-0 dropped)` : ""}\n` +
    `  edgeCount: ${edges.length} directed\n` +
    `  nameCount: ${names.length} (${unnamedCount} unnamed ways → UNNAMED sentinel)\n` +
    `  oneway ways: ${onewayCount}\n` +
    `  maxSpeedKmh: ${maxSeenKmh}\n` +
    `  bbox: [${bbox.minLat.toFixed(4)}, ${bbox.minLng.toFixed(4)}, ${bbox.maxLat.toFixed(4)}, ${bbox.maxLng.toFixed(4)}]\n` +
    `  binary size: ${mb(bytes)} (${bytes} B)`,
);

// THE ENFORCED GATE (D-01): over the ceiling → exit 1 WITHOUT writing.
if (bytes > MAX_BINARY_BYTES) {
  fail(`binary is ${mb(bytes)} — over the ${mb(MAX_BINARY_BYTES)} D-01 envelope. ` +
    `Tighten DRIVABLE_CLASSES (drop tertiary/residential first) or shrink the bbox, then rebuild.`);
}
// THE ADVISORY BAND (A2's 18–50 MB forecast vs D-01's 30–80 MB expectation):
// a small graph is a review prompt, not a failure — the enforced gate stays.
if (bytes < EXPECTED_MIN_BYTES) {
  console.log(
    `WARNING: ${mb(bytes)} is below the expected 30–80 MB band — verify the drivable-class filter ` +
      `(A2 forecast: 18–50 MB for KL metro). Advisory only; the enforced gate is 1–80 MB.`,
  );
}

/* ————— collect-then-write (the committed/previous binary survives failures) ————— */

mkdirSync(dirname(OUT_PATH), { recursive: true });
writeFileSync(OUT_PATH, Buffer.from(buffer));
console.log(`wrote ${OUT_PATH} — ${mb(bytes)}, ${cLat.length} nodes, ${edges.length} edges`);
console.log("next: node routing/scripts/upload-road-graph.mjs   # push the binary to your R2 bucket");
process.exit(0);