import { describe, expect, test } from "bun:test";
import {
  GRID_COLUMNS,
  clampH,
  clampW,
  placeWidgets,
  type WidgetPlacementInput,
} from "./dashboard-grid";

// Regression suite for m/paliad#70 (t-paliad-228): the post-#69 edit
// mode produced overlapping widgets when a 2-col widget sat next to a
// 1-col widget on the same row, when a drag swapped widgets of
// different widths, and when a resize grew a widget into a sibling. The
// fix moved the placement math into ./dashboard-grid + made it
// collision-aware. These tests pin the no-overlap invariant.

function spec(
  key: string,
  x: number | undefined,
  y: number | undefined,
  w: number,
  h = 1,
  visible = true,
): WidgetPlacementInput {
  return { key, visible, x, y, w, h };
}

// hasOverlap returns true if any placed pair shares a cell. O(n²) is
// fine — layouts cap at 32 widgets and the tests stay tiny.
function hasOverlap(rects: Map<string, { x: number; y: number; w: number; h: number }>): string | null {
  const list = Array.from(rects.entries());
  for (let i = 0; i < list.length; i++) {
    const [ka, a] = list[i];
    for (let j = i + 1; j < list.length; j++) {
      const [kb, b] = list[j];
      const xOverlap = a.x < b.x + b.w && b.x < a.x + a.w;
      const yOverlap = a.y < b.y + b.h && b.y < a.y + a.h;
      if (xOverlap && yOverlap) return `${ka} ↔ ${kb} at (${a.x},${a.y},${a.w}x${a.h}) vs (${b.x},${b.y},${b.w}x${b.h})`;
    }
  }
  return null;
}

describe("placeWidgets — basic auto-flow", () => {
  test("places two 6-wide widgets side by side on row 0", () => {
    const out = placeWidgets([
      spec("a", undefined, undefined, 6),
      spec("b", undefined, undefined, 6),
    ]);
    expect(out.get("a")).toEqual({ x: 0, y: 0, w: 6, h: 1 });
    expect(out.get("b")).toEqual({ x: 6, y: 0, w: 6, h: 1 });
    expect(hasOverlap(out)).toBeNull();
  });

  test("wraps when row doesn't fit", () => {
    const out = placeWidgets([
      spec("a", undefined, undefined, 8),
      spec("b", undefined, undefined, 8),
    ]);
    expect(out.get("a")!.y).toBe(0);
    expect(out.get("b")!.y).toBeGreaterThan(0);
    expect(hasOverlap(out)).toBeNull();
  });

  test("hidden widgets are skipped and reserve no cells", () => {
    const out = placeWidgets([
      spec("hidden", 0, 0, 12, 1, false),
      spec("visible", undefined, undefined, 6),
    ]);
    expect(out.has("hidden")).toBe(false);
    expect(out.get("visible")).toEqual({ x: 0, y: 0, w: 6, h: 1 });
  });
});

describe("placeWidgets — explicit positions, no collision", () => {
  test("trusts non-colliding explicit positions exactly", () => {
    const out = placeWidgets([
      spec("a", 0, 0, 6),
      spec("b", 6, 0, 6),
      spec("c", 0, 1, 12),
    ]);
    expect(out.get("a")).toEqual({ x: 0, y: 0, w: 6, h: 1 });
    expect(out.get("b")).toEqual({ x: 6, y: 0, w: 6, h: 1 });
    expect(out.get("c")).toEqual({ x: 0, y: 1, w: 12, h: 1 });
    expect(hasOverlap(out)).toBeNull();
  });
});

describe("placeWidgets — mixed-width collision (m/paliad#70 regression)", () => {
  test("1-col + 2-col on same row do not overlap when both explicit", () => {
    // Half-width left + half-width right is the canonical 'two widgets per
    // row' layout; pre-fix this was fine but the next regression below
    // exercises the actual bug.
    const out = placeWidgets([
      spec("left", 0, 0, 6),
      spec("right", 6, 0, 6),
    ]);
    expect(hasOverlap(out)).toBeNull();
  });

  test("4-col + 8-col both claiming (0,0) end up non-overlapping", () => {
    // Simulates a post-#69 layout where a 4-wide widget sits at (0, 0)
    // and an 8-wide widget got accidentally placed at (0, 0) too (e.g.
    // a buggy reset path or a stale spec from before #70). Placer must
    // honour the first one's position and fit the second somewhere
    // free — landing it on the same row at x=4 is acceptable (better
    // density) as long as nothing overlaps.
    const out = placeWidgets([
      spec("first", 0, 0, 4),
      spec("colliding", 0, 0, 8),
    ]);
    expect(out.get("first")).toEqual({ x: 0, y: 0, w: 4, h: 1 });
    expect(out.get("colliding")!.w).toBe(8);
    expect(hasOverlap(out)).toBeNull();
  });

  test("drag-drop swap of 12-wide onto 6-wide does not overlap", () => {
    // Setup before swap:
    //   A at (0, 0, w=12) — full width row 0
    //   B at (0, 1, w=6)  — half row 1 left
    //   C at (6, 1, w=6)  — half row 1 right
    // User drags A onto B. reorderViaDnd swaps (x, y):
    //   A.x=0, A.y=1
    //   B.x=0, B.y=0
    // Result must not overlap C.
    const out = placeWidgets([
      spec("a", 0, 1, 12),
      spec("b", 0, 0, 6),
      spec("c", 6, 1, 6),
    ]);
    expect(hasOverlap(out)).toBeNull();
  });

  test("auto-flow widget steps past explicit blocker on same row", () => {
    // Explicit widget at (6, 0, w=6); auto-flow widget would pack into
    // (0, 0, w=6) which is fine — but the next auto-flow widget at w=6
    // would want (6, 0) which is taken. Placer must wrap it.
    const out = placeWidgets([
      spec("flow-a", undefined, undefined, 6),
      spec("anchored", 6, 0, 6),
      spec("flow-b", undefined, undefined, 6),
    ]);
    expect(out.get("flow-a")).toEqual({ x: 0, y: 0, w: 6, h: 1 });
    expect(out.get("anchored")).toEqual({ x: 6, y: 0, w: 6, h: 1 });
    expect(out.get("flow-b")!.y).toBeGreaterThan(0);
    expect(hasOverlap(out)).toBeNull();
  });
});

describe("placeWidgets — resize-grow shifts siblings", () => {
  test("growing a 6-wide to 12-wide bumps the sibling on the same row", () => {
    // Pre-resize state:
    //   A at (0, 0, w=6)
    //   B at (6, 0, w=6)
    // User resizes A to w=12. resizeWidget() updates A.w but leaves B
    // at (6, 0). Placer must shift B down.
    const out = placeWidgets([
      spec("a", 0, 0, 12),
      spec("b", 6, 0, 6),
    ]);
    expect(out.get("a")).toEqual({ x: 0, y: 0, w: 12, h: 1 });
    expect(out.get("b")!.y).toBeGreaterThan(0);
    expect(hasOverlap(out)).toBeNull();
  });

  test("growing widget pushes only the first colliding sibling", () => {
    // A grows to 12-wide; B and C on row 0 are both colliding. Both must
    // move; their relative order on row 0 is preserved (B at x=0, C at
    // x=6) on row 1.
    const out = placeWidgets([
      spec("a", 0, 0, 12),
      spec("b", 0, 0, 4),
      spec("c", 4, 0, 4),
    ]);
    expect(hasOverlap(out)).toBeNull();
    expect(out.get("a")!.y).toBe(0);
    expect(out.get("b")!.y).toBeGreaterThan(0);
    expect(out.get("c")!.y).toBeGreaterThan(0);
  });
});

describe("placeWidgets — explicit position overflow clamp", () => {
  test("x+w > GRID_COLUMNS is clamped not rejected", () => {
    // A 12-wide widget with x=6 would extend past col 11. Placer must
    // clamp x to 0 (or wherever fits) so the widget renders inside the
    // grid.
    const out = placeWidgets([
      spec("wide", 6, 0, 12),
    ]);
    const r = out.get("wide")!;
    expect(r.x + r.w).toBeLessThanOrEqual(GRID_COLUMNS);
    expect(r.w).toBe(12);
  });
});

describe("placeWidgets — vertical (multi-row) widgets", () => {
  test("a 2-row-tall widget reserves both rows", () => {
    const out = placeWidgets([
      spec("tall", 0, 0, 6, 2),
      spec("collides-on-row-1", 0, 1, 6, 1),
    ]);
    expect(out.get("tall")).toEqual({ x: 0, y: 0, w: 6, h: 2 });
    // The colliding widget must move because tall covers cols 0..5
    // on both row 0 and row 1. The placer may shift it to the right
    // half of row 1 (cols 6..11) or to a later row — either is fine
    // as long as nothing overlaps.
    const other = out.get("collides-on-row-1")!;
    expect(other.x >= 6 || other.y >= 2).toBe(true);
    expect(hasOverlap(out)).toBeNull();
  });
});

describe("clamp helpers", () => {
  test("clampW respects min/max bounds", () => {
    expect(clampW(2, { min_w: 4, max_w: 12 })).toBe(4);
    expect(clampW(20, { min_w: 4, max_w: 12 })).toBe(12);
    expect(clampW(0, { default_w: 6 })).toBe(6);
    expect(clampW(NaN, { default_w: 8 })).toBe(8);
  });

  test("clampH respects min/max bounds and MAX_ROW_SPAN", () => {
    expect(clampH(0, { default_h: 2 })).toBe(2);
    expect(clampH(99, undefined)).toBe(5); // MAX_ROW_SPAN
    expect(clampH(1, { min_h: 3 })).toBe(3);
  });
});