#!/usr/bin/env node
/*
 * astar.test.mjs — typed-array A* + turn classifier + step derivation (A1–A8).
 * -----------------------------------------------------------------------------
 * RED first (plan 06-01 task 3): behavior cases fail while
 * routing/src/astar.ts does not exist (lazy-import pattern).
 *
 * The correctness gate RESEARCH mandates: A* must equal brute-force
 * Dijkstra's optimal cost for EVERY (origin, goal) pair of the mini-graph —
 * the exhaustive 25x25 equivalence sweep (A1). The test-local Dijkstra uses
 * plain arrays (fine in tests) and the SAME traversal law as routeAstar:
 * oneway-reverse edges (edgeFlags bit0) are never relaxed.
 *
 *   A1  exhaustive equivalence — 625 pairs, cost equality + path endpoints
 *   A2  oneway respected       — the pair behind the flagged edge routes the
 *                                long way (matching Dijkstra); the open
 *                                direction is direct
 *   A3  unreachable -> null    — honest miss (synthetic disconnected graph)
 *   A4  deriveSteps L-path     — 90-deg bearing changes classify left/right;
 *                                steps carry name/distanceM/polyline6
 *   A5  depart + arrive always — straight paths still start "depart" and end
 *                                "arrive"
 *   A6  classifyTurn pins      — sign convention: compass bearings increase
 *                                clockwise, so negative delta = left
 *                                (NOTE: the plan's "classifyTurn(0, 40) ->
 *                                slight-left" contradicts its own
 *                                (0,-90)->left / (0,90)->right cases; the
 *                                compass-consistent reading is pinned here)
 *   A7  public surface         — index.ts exposes the engine-A exports;
 *                                createHttpRoutingSource is NOT here yet
 *                                (plan 04 adds it)
 *   A8  structural             — no `new Map(` in astar.ts (allocation-free
 *                                hot loop: typed arrays only)
 *
 * Run:  npm run routing:test   (exit 0 = all green)
 */
import { strict as assert } from "node:assert";
import { readFileSync } from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import { test } from "./harness.mjs";

const here = path.dirname(fileURLToPath(import.meta.url)); // routing/test

let astarPromise = null;
function loadAstar() {
  if (!astarPromise) astarPromise = import("../src/astar.ts");
  return astarPromise;
}
let graphPromise = null;
function loadGraph() {
  if (!graphPromise) graphPromise = import("../src/graph.ts");
  return graphPromise;
}

function toArrayBuffer(buf) {
  return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
}

async function loadMiniGraph() {
  const { decodeGraph } = await loadGraph();
  const g = decodeGraph(toArrayBuffer(readFileSync(path.join(here, "fixtures", "mini-graph.bin"))));
  assert.ok(g, "the committed mini-graph decodes");
  return g;
}

/** Brute-force O(n^2) Dijkstra — plain arrays, SAME traversal law as A*. */
function dijkstra(g, origin, goal) {
  const dist = new Array(g.nodeCount).fill(Infinity);
  const done = new Array(g.nodeCount).fill(false);
  dist[origin] = 0;
  for (;;) {
    let u = -1;
    let best = Infinity;
    for (let i = 0; i < g.nodeCount; i++) {
      if (!done[i] && dist[i] < best) {
        best = dist[i];
        u = i;
      }
    }
    if (u === -1 || u === goal) return dist[goal];
    done[u] = true;
    for (let e = g.edgeStart[u]; e < g.edgeStart[u + 1]; e++) {
      if ((g.edgeFlags[e] & 1) !== 0) continue; // oneway-reverse: never relaxed
      const v = g.edgeTarget[e];
      const nd = dist[u] + g.edgeSeconds[e];
      if (nd < dist[v]) dist[v] = nd;
    }
  }
}

/* ————— A1–A8 ————— */

test("A1 exhaustive equivalence — A* matches brute-force Dijkstra on EVERY 25x25 node pair", async () => {
  const { routeAstar } = await loadAstar();
  const g = await loadMiniGraph();
  let pairs = 0;
  let reachable = 0;
  for (let o = 0; o < g.nodeCount; o++) {
    for (let t = 0; t < g.nodeCount; t++) {
      pairs++;
      const optimal = dijkstra(g, o, t);
      const result = routeAstar(g, o, t);
      if (optimal === Infinity) {
        assert.equal(result, null, `pair ${o}->${t}: unreachable must resolve null, never a path`);
        continue;
      }
      reachable++;
      assert.ok(result, `pair ${o}->${t}: reachable must route`);
      assert.ok(
        Math.abs(result.seconds - optimal) < 1e-6,
        `pair ${o}->${t}: A* cost ${result.seconds} vs Dijkstra ${optimal}`,
      );
      assert.equal(result.nodes[0], o, `pair ${o}->${t}: path starts at origin`);
      assert.equal(result.nodes[result.nodes.length - 1], t, `pair ${o}->${t}: path ends at goal`);
      assert.ok(result.distanceM > 0 || o === t, `pair ${o}->${t}: distanceM summed over the path`);
    }
  }
  assert.equal(pairs, 625, "the full 25x25 sweep ran");
  assert.ok(reachable > 600, `the grid is densely connected (${reachable} reachable pairs)`);
});

test("A2 oneway respected — the flagged edge is never traversed; the open direction is direct", async () => {
  const { routeAstar } = await loadAstar();
  const g = await loadMiniGraph();
  // The fixture's single oneway-reverse edge is 3 -> 2 (perimeter, row 0).
  // Routing AGAINST it (3 -> 2) must take the long way around the block.
  const against = routeAstar(g, 3, 2);
  assert.ok(against, "3->2 routes via the detour");
  assert.equal(
    against.nodes.length > 2,
    true,
    `the flagged 1-edge path must NOT be used (path: ${against.nodes.join("->")})`,
  );
  assert.ok(
    Math.abs(against.seconds - dijkstra(g, 3, 2)) < 1e-6,
    "the detour cost matches Dijkstra",
  );
  // The open direction is the direct edge.
  const with_flow = routeAstar(g, 2, 3);
  assert.ok(with_flow, "2->3 routes");
  assert.equal(with_flow.nodes.length, 2, "2->3 is the direct single edge");
  assert.ok(Math.abs(with_flow.seconds - dijkstra(g, 2, 3)) < 1e-6);
});

test("A3 unreachable -> null — a disconnected pair resolves the honest miss", async () => {
  const { routeAstar } = await loadAstar();
  const { encodeGraph, decodeGraph } = await loadGraph();
  // Two disconnected components: 0<->1 and 2<->3.
  const g = decodeGraph(
    encodeGraph({
      lat: [3.15, 3.1505, 3.16, 3.1605],
      lng: [101.69, 101.6905, 101.69, 101.6905],
      edges: [
        { from: 0, to: 1, seconds: 4, nameId: 0 },
        { from: 1, to: 0, seconds: 4, nameId: 0 },
        { from: 2, to: 3, seconds: 4, nameId: 0 },
        { from: 3, to: 2, seconds: 4, nameId: 0 },
      ],
      names: ["Isolated Road"],
      maxSpeedKmh: 60,
    }),
  );
  assert.ok(g, "synthetic graph decodes");
  assert.equal(dijkstra(g, 0, 2), Infinity, "Dijkstra agrees: unreachable");
  assert.equal(routeAstar(g, 0, 2), null, "unreachable -> null (never a fabricated path)");
  const within = routeAstar(g, 0, 1);
  assert.ok(within, "the connected pair routes");
  assert.deepEqual(within.nodes, [0, 1]);
});

test("A4 deriveSteps L-path — 90-deg turns classify, steps carry name/distance/polyline6", async () => {
  const { routeAstar, deriveSteps } = await loadAstar();
  const { decodePolyline6 } = await import("../src/polyline.ts");
  const g = await loadMiniGraph();
  // 0=(r0,c0) -> 1=(r0,c1) -> 6=(r1,c1) -> 7=(r1,c2): east, then south, then east.
  const steps = deriveSteps(g, [0, 1, 6, 7]);
  const kinds = steps.map((s) => s.kind);
  assert.deepEqual(kinds, ["depart", "right", "left", "arrive"]);
  assert.equal(steps[0].name, "Jalan Persiaran Mini", "step 0 rides the perimeter");
  assert.equal(steps[1].name, "Jalan Mini 2", "the right turn turns onto Jalan Mini 2");
  assert.equal(steps[2].name, "Jalan Mini 1", "the left turn turns onto Jalan Mini 1");
  for (const step of steps) {
    if (step.kind === "arrive") continue;
    assert.ok(step.distanceM > 0, `${step.kind} step has positive distance`);
    const points = decodePolyline6(step.geometry);
    assert.equal(points.length, 2, `${step.kind} step geometry decodes to its two endpoints`);
  }
  const arrive = steps[steps.length - 1];
  assert.equal(decodePolyline6(arrive.geometry).length, 1, "the arrive step anchors the goal node");
  // round-trip: a full route's steps derive from A*'s own node path
  const routed = routeAstar(g, 0, 11);
  assert.ok(routed, "0->11 routes");
  const routeSteps = deriveSteps(g, routed.nodes);
  assert.equal(routeSteps[0].kind, "depart", "route-derived steps start with depart");
  assert.equal(routeSteps[routeSteps.length - 1].kind, "arrive", "and end with arrive");
  const total = routeSteps
    .filter((s) => s.kind !== "arrive")
    .reduce((sum, s) => sum + s.distanceM, 0);
  assert.ok(
    Math.abs(total - routed.distanceM) < 1e-6,
    `step distances sum to the route distance (${total} vs ${routed.distanceM})`,
  );
});

test("A5 depart + arrive always — a straight same-name path still yields [depart, arrive]", async () => {
  const { deriveSteps } = await loadAstar();
  const g = await loadMiniGraph();
  const steps = deriveSteps(g, [0, 1]);
  assert.deepEqual(
    steps.map((s) => s.kind),
    ["depart", "arrive"],
    "even the simplest path starts depart and ends arrive",
  );
  assert.equal(steps[0].name, "Jalan Persiaran Mini");
  assert.ok(steps[0].distanceM > 0);
  assert.equal(deriveSteps(g, []).length, 0, "an empty path derives no steps");
  assert.deepEqual(
    deriveSteps(g, [12]).map((s) => s.kind),
    ["arrive"],
    "a trivial single-node path is just the arrive step",
  );
});

test("A6 classifyTurn pins — compass convention: negative bearing delta = left", async () => {
  const { classifyTurn, TURN_STRAIGHT_MAX_DEG, TURN_SLIGHT_MAX_DEG, TURN_UTURN_MIN_DEG } = await loadAstar();
  assert.equal(TURN_STRAIGHT_MAX_DEG, 25);
  assert.equal(TURN_SLIGHT_MAX_DEG, 60);
  assert.equal(TURN_UTURN_MIN_DEG, 150);
  assert.equal(classifyTurn(0, -90), "left");
  assert.equal(classifyTurn(0, 90), "right");
  assert.equal(classifyTurn(0, 20), "straight");
  assert.equal(classifyTurn(0, -20), "straight");
  // The plan's "(0, 40) -> slight-left" contradicts its own (0,-90)->left /
  // (0,90)->right cases; the compass-consistent reading is pinned:
  assert.equal(classifyTurn(0, 40), "slight-right");
  assert.equal(classifyTurn(0, -40), "slight-left");
  assert.equal(classifyTurn(0, 175), "uturn");
  assert.equal(classifyTurn(0, -175), "uturn");
  assert.equal(classifyTurn(0, 180), "uturn");
  // boundaries: 25 stays straight, 61 is a full turn, 150 is uturn
  assert.equal(classifyTurn(0, 25), "straight");
  assert.equal(classifyTurn(0, 26), "slight-right");
  assert.equal(classifyTurn(0, 60), "slight-right");
  assert.equal(classifyTurn(0, 61), "right");
  assert.equal(classifyTurn(0, 149), "right");
  assert.equal(classifyTurn(0, 150), "uturn");
  // wrap-around normalization
  assert.equal(classifyTurn(350, 10), "straight", "20 deg across north is straight");
  assert.equal(classifyTurn(350, 80), "right", "90 deg across north is a right");
});

test("A7 public surface — index.ts exposes engine A; createHttpRoutingSource is NOT here yet", async () => {
  const mod = await import("../src/index.ts");
  for (const name of [
    "decodeGraph",
    "encodeGraph",
    "GRAPH_MAGIC",
    "GRAPH_VERSION",
    "snapToGraph",
    "SNAP_BBOX_MARGIN_DEG",
    "routeAstar",
    "deriveSteps",
    "classifyTurn",
    "TURN_STRAIGHT_MAX_DEG",
    "TURN_SLIGHT_MAX_DEG",
    "TURN_UTURN_MIN_DEG",
  ]) {
    assert.notEqual(mod[name], undefined, `index.ts must export ${name}`);
  }
  assert.equal(
    mod.createHttpRoutingSource,
    undefined,
    "createHttpRoutingSource belongs to plan 04 — NOT this plan",
  );
});

test("A8 structural — no `new Map(` in astar.ts (typed arrays only in the hot loop)", () => {
  const src = readFileSync(path.join(here, "..", "src", "astar.ts"), "utf8");
  const code = src
    .replace(/\/\*[\s\S]*?\*\//g, " ")
    .replace(/(^|[^:\\])\/\/[^\n]*/g, "$1");
  assert.ok(!code.includes("new Map("), "no Map allocation — the hot loop is typed arrays");
});