/**
 * The renderer, run for real against a canvas that writes down what it was
 * asked to draw. No browser, but every line of the draw path is executed —
 * which is what catches a typo in a frame nobody can see from a unit test.
 *
 * This is the engine's half: walls, bodies, marks, arrivals. What a game puts
 * on the floor besides is drawn through hooks and tested with the game.
 */

import { expect, test } from "bun:test";
import { GHOST, ghosts, makePresence, shown, sighted } from "../../static/engine/presence.js";
import { drawScene, makeScene } from "../../static/engine/scene.js";

type Op = { op: string; args: unknown[]; alpha: number; fill: string; stroke: string };

/** A canvas that records. Every call the renderer makes has to exist here. */
function fakeContext() {
  const ops: Op[] = [];
  const note =
    (op: string) =>
    (...args: unknown[]) => {
      // The opacity in force when the call was made: how faded a body
      // arriving into sight is, and how far a last-seen mark has dimmed.
      ops.push({ op, args, alpha: ctx.globalAlpha, fill: ctx.fillStyle, stroke: ctx.strokeStyle });
    };
  const ctx = {
    ops,
    fillStyle: "",
    strokeStyle: "",
    lineWidth: 1,
    font: "",
    textAlign: "left",
    globalAlpha: 1,
    clearRect: note("clearRect"),
    fillRect: note("fillRect"),
    strokeRect: note("strokeRect"),
    beginPath: note("beginPath"),
    closePath: note("closePath"),
    moveTo: note("moveTo"),
    lineTo: note("lineTo"),
    arc: note("arc"),
    ellipse: note("ellipse"),
    fill: note("fill"),
    stroke: note("stroke"),
    clip: note("clip"),
    rect: note("rect"),
    save: note("save"),
    restore: note("restore"),
    translate: note("translate"),
    rotate: note("rotate"),
    fillText: note("fillText"),
    measureText: (text: string) => ({ width: text.length * 6 }),
    createLinearGradient: () => ({ addColorStop() {} }),
  };
  return ctx;
}

// A room three tiles deep running east, with a pillar standing in it at
// column 5 — enough geometry for a body to hide behind.
const room = (col: number, row: number): boolean =>
  col < 1 || col > 12 || row < 1 || row > 3 || col === 5;
const TILE = 80;
const world = { solid: room, tile: TILE };

// What the engine's renderer needs of a snapshot: you, who you can see,
// and the shots you were let see. Nothing of the game.
const snapshot = (players: unknown[]) => ({
  me: { id: "me", x: 120, y: 200, angle: 0, alive: true, hp: 100 },
  players,
  shots: [],
});

const body = (over: Record<string, unknown> = {}) => ({
  id: "them",
  name: "Sable",
  x: 280,
  y: 200,
  angle: 3.1,
  hp: 100,
  alive: true,
  mate: false,
  ...over,
});

const view = { width: 900, height: 570, look: (p: { x: number; y: number; angle: number }) => p };
const eye = { x: 120, y: 200, angle: 0 };

test("a frame draws walls in runs: the whole width covered, far fewer fills", () => {
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([]), view);
  const rects = ctx.ops.filter((o) => o.op === "fillRect");
  // The bands are the full width; the rest are wall runs.
  const walls = rects
    .map((o) => ({ x: Number(o.args[0]), w: Number(o.args[2]) }))
    .filter((r) => r.w < view.width)
    .sort((a, b) => a.x - b.x);
  // This room is closed, so every column of the picture is wall: the runs
  // start at the left edge, meet end to end and reach the right one. That is
  // the same picture the old one-fill-a-column loop drew.
  expect(walls[0]!.x).toBe(0);
  let reach = 0;
  for (const rect of walls) {
    expect(rect.x).toBeLessThanOrEqual(reach);
    reach = Math.max(reach, rect.x + rect.w);
  }
  expect(reach).toBeGreaterThanOrEqual(view.width);
  // And it costs a fraction of the fills: one a column would be 900.
  expect(walls.length).toBeLessThan(view.width / 2);
});

test("a body in the open is drawn; the same body behind the pillar is not", () => {
  const open = fakeContext();
  drawScene(open as never, makeScene(), world, eye, snapshot([body()]), view);
  // The head is the only arc in this scene, so it stands for the body.
  expect(open.ops.some((o) => o.op === "arc")).toBe(true);

  const hidden = fakeContext();
  drawScene(hidden as never, makeScene(), world, eye, snapshot([body({ x: 700 })]), view);
  expect(hidden.ops.some((o) => o.op === "arc")).toBe(false);
});

test("a team mate gets a name tag and an enemy never does", () => {
  const mate = fakeContext();
  drawScene(mate as never, makeScene(), world, eye, snapshot([body({ mate: true })]), view);
  expect(mate.ops.some((o) => o.op === "fillText" && o.args[0] === "Sable")).toBe(true);

  const enemy = fakeContext();
  drawScene(enemy as never, makeScene(), world, eye, snapshot([body()]), view);
  expect(enemy.ops.some((o) => o.op === "fillText")).toBe(false);
});

test("the dead lie on the floor and wear no markers at all", () => {
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([body({ mate: true, alive: false, hp: 0 })]), view);
  // Flat on the ground: an ellipse, not an upright body with a head.
  expect(ctx.ops.some((o) => o.op === "ellipse")).toBe(true);
  // No name tag, and no chevron — the chevron is the only closed path here.
  expect(ctx.ops.some((o) => o.op === "fillText")).toBe(false);
  expect(ctx.ops.some((o) => o.op === "closePath")).toBe(false);
});

test("an enemy wears a chevron and a team mate does not", () => {
  const enemy = fakeContext();
  drawScene(enemy as never, makeScene(), world, eye, snapshot([body()]), view);
  expect(enemy.ops.some((o) => o.op === "closePath")).toBe(true);

  const mate = fakeContext();
  drawScene(mate as never, makeScene(), world, eye, snapshot([body({ mate: true })]), view);
  expect(mate.ops.some((o) => o.op === "closePath")).toBe(false);
  expect(mate.ops.some((o) => o.op === "fillText")).toBe(true);
});

test("a body has a hard dark edge, whichever side it is on", () => {
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([body()]), view);
  expect(ctx.ops.some((o) => o.op === "strokeRect")).toBe(true);
});

// ------------------------------------------- coming into sight, and leaving

test("a body arriving is drawn faded and small, and solid once it is in", () => {
  const edgeOf = (ctx: ReturnType<typeof fakeContext>) => ctx.ops.find((o) => o.op === "strokeRect")!;

  const arriving = fakeContext();
  drawScene(arriving as never, makeScene(), world, eye, snapshot([body()]), { ...view, shown: () => 0.4 });
  const solid = fakeContext();
  drawScene(solid as never, makeScene(), world, eye, snapshot([body()]), { ...view, shown: () => 1 });

  expect(edgeOf(arriving).alpha).toBeCloseTo(0.4, 5);
  expect(edgeOf(solid).alpha).toBe(1);
  // And smaller: it grows from its feet as it comes in.
  expect(Number(edgeOf(arriving).args[2])).toBeLessThan(Number(edgeOf(solid).args[2]));
  expect(Number(edgeOf(arriving).args[2])).toBeGreaterThan(Number(edgeOf(solid).args[2]) * 0.7);
});

test("a body the presence store has only just seen is the one being faded", () => {
  const seen = makePresence();
  const them = body();
  sighted(seen, [them], 100);
  const draw = (at: number) => {
    const ctx = fakeContext();
    drawScene(ctx as never, makeScene(), world, eye, snapshot([them]), {
      ...view,
      shown: (p: { id: string }) => shown(seen, p.id, at),
    });
    return ctx.ops.find((o) => o.op === "strokeRect")!;
  };
  expect(draw(100.03).alpha).toBeGreaterThan(0);
  expect(draw(100.03).alpha).toBeLessThan(1);
  expect(draw(100.5).alpha).toBe(1);
});

test("a last-seen mark is an outline, dimming, and never a body", () => {
  const marks = [{ id: "them", x: 280, y: 200, angle: 0, mate: false, fade: 0.6 }];
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([]), { ...view, marks });
  const edge = ctx.ops.find((o) => o.op === "strokeRect");
  expect(edge).toBeDefined();
  expect(edge!.alpha).toBeCloseTo(0.6, 5);
  // No head, no chevron, no name: a memory of a sighting, not a sighting.
  expect(ctx.ops.some((o) => o.op === "arc")).toBe(false);
  expect(ctx.ops.some((o) => o.op === "closePath")).toBe(false);
  expect(ctx.ops.some((o) => o.op === "fillText")).toBe(false);
  expect(GHOST).toBeGreaterThan(0);
});

test("a body that steps out of sight leaves the outline the store hands over", () => {
  const seen = makePresence();
  const them = body();
  sighted(seen, [them], 100); // in sight, in the open
  sighted(seen, [], 100.1); // and gone behind the corner
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([]), {
    ...view,
    marks: ghosts(seen, 100.1),
  });
  // Nobody is in the snapshot at all, and there is still something there.
  const edge = ctx.ops.find((o) => o.op === "strokeRect");
  expect(edge).toBeDefined();
  expect(edge!.alpha).toBeCloseTo(1, 2);

  // A second later the store hands over nothing, and nothing is drawn.
  const after = fakeContext();
  drawScene(after as never, makeScene(), world, eye, snapshot([]), {
    ...view,
    marks: ghosts(seen, 100.1 + GHOST),
  });
  expect(after.ops.some((o) => o.op === "strokeRect")).toBe(false);
});

test("a mark where the wall now stands between you and it is not drawn", () => {
  const marks = [{ id: "them", x: 700, y: 200, angle: 0, mate: false, fade: 1 }];
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([]), { ...view, marks });
  expect(ctx.ops.some((o) => o.op === "strokeRect")).toBe(false);
});

// ------------------------------------------------------- colour, by side

/** The fill of each upright body, left to right: the rect its edge is drawn round. */
function skins(ctx: ReturnType<typeof fakeContext>): string[] {
  const out: { x: number; fill: string }[] = [];
  ctx.ops.forEach((o, i) => {
    if (o.op !== "strokeRect") return;
    const body = ctx.ops[i - 1]!;
    if (body.op === "fillRect") out.push({ x: Number(body.args[0]), fill: body.fill });
  });
  return out.sort((a, b) => a.x - b.x).map((b) => b.fill);
}

test("without `side`, a mate and an enemy wear exactly today's colours", () => {
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([body({ id: "m", mate: true, y: 150 }), body({ id: "e", y: 250 })]), view);
  // Looking east, the smaller y is on the left.
  expect(skins(ctx)).toEqual(["#3f9fd6", "#d8483f"]);
  // And a last-seen enemy is outlined in today's colour too.
  const marked = fakeContext();
  drawScene(marked as never, makeScene(), world, eye, snapshot([]), {
    ...view,
    marks: [{ id: "e", x: 280, y: 200, angle: 0, mate: false, fade: 1 }],
  });
  expect(marked.ops.find((o) => o.op === "strokeRect")!.stroke).toBe("rgba(235,150,120,0.9)");
});

test("three enemy sides draw in three colours, and each keeps its colour next frame", () => {
  const three = [
    body({ id: "a", side: "scene-north", y: 130 }),
    body({ id: "b", side: "scene-east", y: 200 }),
    body({ id: "c", side: "scene-west", y: 270 }),
  ];
  const first = fakeContext();
  drawScene(first as never, makeScene(), world, eye, snapshot(three), view);
  const colours = skins(first);
  expect(colours).toHaveLength(3);
  expect(new Set(colours).size).toBe(3);
  // None of them is the mate's blue.
  expect(colours).not.toContain("#3f9fd6");

  // Next frame the server lists them the other way round: same colours.
  const second = fakeContext();
  drawScene(second as never, makeScene(), world, eye, snapshot([...three].reverse()), view);
  expect(skins(second)).toEqual(colours);

  // And a side alone on screen still wears its own, not the first slot's.
  const alone = fakeContext();
  drawScene(alone as never, makeScene(), world, eye, snapshot([three[2]]), view);
  expect(skins(alone)).toEqual([colours[2]!]);
});

test("a mate with a side is still the mate's colour, and the dead are still grey", () => {
  const ctx = fakeContext();
  drawScene(ctx as never, makeScene(), world, eye, snapshot([body({ mate: true, side: "scene-mine" })]), view);
  expect(skins(ctx)).toEqual(["#3f9fd6"]);

  const dead = fakeContext();
  drawScene(dead as never, makeScene(), world, eye, snapshot([body({ side: "scene-dead", alive: false, hp: 0 })]), view);
  expect(dead.ops.find((o) => o.op === "fill")!.fill).toBe("#4a4e57");
});