/*
Copyright 2023 New Vector Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import {
  column,
  cycleTileSize,
  fillGaps,
  forEachCellInArea,
  Grid,
  row,
} from "../../src/video-grid/model";
import { TileDescriptor } from "../../src/video-grid/TileDescriptor";

/**
 * Builds a grid from a string specifying the contents of each cell as a letter.
 */
function mkGrid(spec: string): Grid {
  const secondNewline = spec.indexOf("\n", 1);
  const columns = secondNewline === -1 ? spec.length : secondNewline - 1;
  const cells = spec.match(/[a-z ]/g) ?? [];
  const areas = new Set(cells);
  areas.delete(" "); // Space represents an empty cell, not an area
  const grid: Grid = { columns, cells: new Array(cells.length) };

  for (const area of areas) {
    const start = cells.indexOf(area);
    const end = cells.lastIndexOf(area);
    const rows = row(end, grid) - row(start, grid) + 1;
    const columns = column(end, grid) - column(start, grid) + 1;

    forEachCellInArea(start, end, grid, (_c, i) => {
      grid.cells[i] = {
        item: { id: area } as unknown as TileDescriptor,
        origin: i === start,
        rows,
        columns,
      };
    });
  }

  return grid;
}

/**
 * Turns a grid into a string showing the contents of each cell as a letter.
 */
function showGrid(g: Grid): string {
  let result = "\n";
  g.cells.forEach((c, i) => {
    if (i > 0 && i % g.columns == 0) result += "\n";
    result += c?.item.id ?? " ";
  });
  return result;
}

function testFillGaps(title: string, input: string, output: string): void {
  test(`fillGaps ${title}`, () => {
    expect(showGrid(fillGaps(mkGrid(input)))).toBe(output);
  });
}

testFillGaps(
  "fills a gap",
  `
a b
cde
f`,
  `
cab
fde`
);

testFillGaps(
  "fills multiple gaps",
  `
a bc 
defgh
 ijkl
mno`,
  `
aebch
difgl
monjk`
);

testFillGaps(
  "fills a big gap",
  `
abcd
e  f
g  h
ijkl`,
  `
abcd
elhf
gkji`
);

testFillGaps(
  "only moves 1×1 tiles",
  `
  
aa
bc`,
  `
bc
aa`
);

testFillGaps(
  "prefers moving around large tiles",
  `
a bc
ddde
dddf
ghij
k`,
  `
abce
dddf
dddj
kghi`
);

testFillGaps(
  "moves through large tiles if necessary",
  `
a bc
dddd
efgh
i`,
  `
afbc
dddd
iegh`
);

function testCycleTileSize(
  title: string,
  tileId: string,
  input: string,
  output: string
): void {
  test(`cycleTileSize ${title}`, () => {
    expect(showGrid(cycleTileSize(tileId, mkGrid(input)))).toBe(output);
  });
}

testCycleTileSize(
  "does nothing if the tile is not present",
  "z",
  `
abcd
efgh`,
  `
abcd
efgh`
);

testCycleTileSize(
  "expands a tile to 2×2 in a 3 column layout",
  "c",
  `
abc
def
ghi`,
  `
acc
bcc
def
ghi`
);

testCycleTileSize(
  "expands a tile to 3×3 in a 4 column layout",
  "g",
  `
abcd
efgh`,
  `
abcd
eggg
fggg
h`
);

testCycleTileSize(
  "restores a tile to 1×1",
  "b",
  `
abbc
dbbe
fghi
jk`,
  `
abhc
djge
fik`
);

testCycleTileSize(
  "expands a tile even in a crowded grid",
  "c",
  `
abb
cbb
dde
ddf
ghi
klm`,
  `
abb
gbb
dde
ddf
cci
cch
klm`
);

testCycleTileSize(
  "does nothing if the tile has no room to expand",
  "c",
  `
abb
cbb
dde
ddf`,
  `
abb
cbb
dde
ddf`
);