import { describe, expect, it } from "vitest";
import {
  candidatesForCell,
  classicRegions,
  compilePuzzle,
  constraintIsFeasible,
  normalizePuzzle,
  validatePuzzle,
  type PuzzleDefinition,
  type VariantConstraint,
} from "../../src/domain";
import { solveExact } from "../../src/solver";

const solved4 = [1, 2, 3, 4, 3, 4, 1, 2, 4, 3, 2, 1, 2, 1, 4, 3] as const;

function puzzle4(overrides: Partial<PuzzleDefinition> = {}): PuzzleDefinition {
  return {
    version: 1,
    size: 4,
    givens: new Array<number>(16).fill(0),
    regions: classicRegions(4),
    constraints: [],
    ...overrides,
  };
}

const packTwoConstraints: readonly VariantConstraint[] = [
  { type: "between-line", cells: [0, 1, 2] },
  { type: "german-whisper", cells: [0, 3, 1] },
  { type: "region-sum-line", cells: [0, 1, 2] },
  { type: "clone", cells: [0, 1], cloneCells: [6, 7] },
  { type: "extra-region", cells: [0, 7, 9, 14] },
];

describe("Pack 2 constraint validation", () => {
  it("accepts and clones every production shape", () => {
    const source = puzzle4({ constraints: packTwoConstraints });
    expect(validatePuzzle(source)).toEqual({ valid: true, issues: [] });
    const normalized = normalizePuzzle(source);
    expect(normalized.constraints).toEqual(packTwoConstraints);
    expect(normalized.constraints).not.toBe(packTwoConstraints);
  });

  it.each([
    { type: "between-line", cells: [0, 1] },
    { type: "between-line", cells: [0, 1, 0] },
    { type: "german-whisper", cells: [0] },
    { type: "german-whisper", cells: [0, 1], minimumDifference: 0 },
    { type: "german-whisper", cells: [0, 1], minimumDifference: 4 },
    { type: "region-sum-line", cells: [0, 1] },
    { type: "clone", cells: [0, 1], cloneCells: [8] },
    { type: "clone", cells: [0, 1], cloneCells: [8, 8] },
    { type: "extra-region", cells: [0, 1, 2] },
    { type: "extra-region", cells: [0, 1, 2, 3], negated: true },
  ] as const)("rejects malformed constraint $type", (constraint) => {
    const result = validatePuzzle({ ...puzzle4(), constraints: [constraint] });
    expect(result.valid).toBe(false);
    expect(
      result.issues.some(({ path }) => path.startsWith("constraints[0]")),
    ).toBe(true);
  });

  it("uses the puzzle's actual regions when checking region-sum crossings", () => {
    expect(
      validatePuzzle(
        puzzle4({ constraints: [{ type: "region-sum-line", cells: [0, 1] }] }),
      ).issues,
    ).toContainEqual({
      path: "constraints[0].cells",
      message: "region-sum line must cross at least one region boundary",
    });
    expect(
      validatePuzzle(
        puzzle4({ constraints: [{ type: "region-sum-line", cells: [1, 2] }] }),
      ).valid,
    ).toBe(true);
  });
});

describe("Pack 2 partial and completed semantics", () => {
  it("enforces between-line interiors and its negated truth", () => {
    const constraint = { type: "between-line", cells: [0, 1, 2] } as const;
    const partial = new Array<number>(16).fill(0);
    partial[0] = 1;
    partial[2] = 4;
    expect(
      candidatesForCell(puzzle4({ constraints: [constraint] }), partial, 1),
    ).toEqual([2, 3]);
    expect(
      constraintIsFeasible(
        constraint,
        [2, 0, 3, ...new Array<number>(13).fill(0)],
        4,
      ),
    ).toBe(false);
    expect(constraintIsFeasible(constraint, solved4, 4)).toBe(true);
    expect(
      constraintIsFeasible({ ...constraint, negated: true }, solved4, 4),
    ).toBe(false);
    expect(
      constraintIsFeasible(
        { ...constraint, negated: true },
        [1, 4, 3, ...new Array<number>(13).fill(0)],
        4,
      ),
    ).toBe(true);
  });

  it("runs exact dynamic feasibility for default and explicit German whispers", () => {
    const constraint = {
      type: "german-whisper",
      cells: [0, 5, 10],
    } as const;
    const partial = new Array<number>(16).fill(0);
    partial[0] = 2;
    expect(
      candidatesForCell(puzzle4({ constraints: [constraint] }), partial, 5),
    ).toEqual([4]);
    const impossible = new Array<number>(16).fill(0);
    impossible[5] = 2;
    expect(
      constraintIsFeasible(
        { ...constraint, minimumDifference: 3 },
        impossible,
        4,
      ),
    ).toBe(false);

    const complete = [1, 4, 2, ...new Array<number>(13).fill(0)];
    const short = { type: "german-whisper", cells: [0, 1, 2] } as const;
    expect(constraintIsFeasible(short, complete, 4)).toBe(true);
    expect(constraintIsFeasible({ ...short, negated: true }, complete, 4)).toBe(
      false,
    );
    complete[1] = 2;
    expect(constraintIsFeasible({ ...short, negated: true }, complete, 4)).toBe(
      true,
    );
  });

  it("balances contiguous region sums using the supplied region map", () => {
    const constraint = {
      type: "region-sum-line",
      cells: [0, 1, 2],
    } as const;
    const partial = new Array<number>(16).fill(0);
    partial[0] = 1;
    partial[2] = 3;
    expect(
      candidatesForCell(puzzle4({ constraints: [constraint] }), partial, 1),
    ).toEqual([2]);
    expect(constraintIsFeasible(constraint, solved4, 4)).toBe(true);
    expect(
      constraintIsFeasible({ ...constraint, negated: true }, solved4, 4),
    ).toBe(false);
    const unequal = [...solved4];
    unequal[2] = 4;
    expect(
      constraintIsFeasible({ ...constraint, negated: true }, unequal, 4),
    ).toBe(true);
  });

  it("enforces ordered clone equality and exact negated state", () => {
    const constraint = {
      type: "clone",
      cells: [0, 1],
      cloneCells: [6, 7],
    } as const;
    const partial = new Array<number>(16).fill(0);
    partial[0] = 1;
    partial[1] = 2;
    partial[6] = 1;
    expect(
      candidatesForCell(puzzle4({ constraints: [constraint] }), partial, 7),
    ).toEqual([2]);
    expect(constraintIsFeasible(constraint, solved4, 4)).toBe(true);
    expect(
      constraintIsFeasible({ ...constraint, negated: true }, solved4, 4),
    ).toBe(false);
    const mismatch = [...solved4];
    mismatch[7] = 3;
    expect(constraintIsFeasible(constraint, mismatch, 4)).toBe(false);
    expect(
      constraintIsFeasible({ ...constraint, negated: true }, mismatch, 4),
    ).toBe(true);
  });

  it("compiles extra regions as all-different units and remote peers", () => {
    const constraint = {
      type: "extra-region",
      cells: [0, 7, 9, 14],
    } as const;
    const compiled = compilePuzzle(
      normalizePuzzle(puzzle4({ constraints: [constraint] })),
    );
    expect(
      compiled.units.filter(({ kind }) => kind === "extra-region"),
    ).toEqual([{ kind: "extra-region", index: 0, cells: constraint.cells }]);
    const partial = new Array<number>(16).fill(0);
    partial[0] = 1;
    expect(candidatesForCell(compiled, partial, 7)).not.toContain(1);
    expect(compilePuzzle(normalizePuzzle(puzzle4())).peers[7]?.has(0)).toBe(
      false,
    );
  });
});

describe("Pack 2 exact solving", () => {
  it.each(
    packTwoConstraints.map(
      (constraint) => [constraint.type, constraint] as const,
    ),
  )("solves a puzzle containing %s", (_type, constraint) => {
    const givens: number[] = [...solved4];
    givens[5] = 0;
    givens[10] = 0;
    const result = solveExact(puzzle4({ givens, constraints: [constraint] }));
    expect(result.count).toBe(1);
    expect(result.truncated).toBe(false);
    expect(result.solutions[0]).toEqual(solved4);
  });
});