import {
  correspondingBoxPositionCells,
  littleKillerCells,
  orthogonalNeighbours,
  outsideLineCells,
} from "./geometry";
import type { CellId, VariantConstraint } from "./types";

export type ConstraintType = VariantConstraint["type"];
export type ConstraintCategory =
  "global" | "region" | "line" | "adjacency" | "outside" | "cell";

export type ConstraintFieldKind =
  | "discriminator"
  | "boolean"
  | "integer"
  | "enum"
  | "cell"
  | "cells"
  | "integers"
  | "outside-side";

export interface ConstraintFieldMetadata {
  readonly key: string;
  readonly kind: ConstraintFieldKind;
  readonly required: boolean;
}

export interface ConstraintRegistryEntry<
  Type extends ConstraintType = ConstraintType,
> {
  readonly type: Type;
  readonly label: string;
  readonly category: ConstraintCategory;
  readonly negatable: boolean;
  readonly fields: readonly ConstraintFieldMetadata[];
  readonly cells: (
    size: number,
    constraint: Extract<VariantConstraint, { readonly type: Type }>,
  ) => readonly CellId[];
}

type ConstraintRegistry = {
  readonly [Type in ConstraintType]: ConstraintRegistryEntry<Type>;
};

const typeField: ConstraintFieldMetadata = {
  key: "type",
  kind: "discriminator",
  required: true,
};
const negatedField: ConstraintFieldMetadata = {
  key: "negated",
  kind: "boolean",
  required: false,
};
const allCells = (size: number): CellId[] =>
  Array.from({ length: size * size }, (_, cell) => cell);
const cellField = (key = "cell"): ConstraintFieldMetadata => ({
  key,
  kind: "cell",
  required: true,
});
const cellsField = (key = "cells"): ConstraintFieldMetadata => ({
  key,
  kind: "cells",
  required: true,
});
const integerField = (key: string): ConstraintFieldMetadata => ({
  key,
  kind: "integer",
  required: true,
});
const enumField = (key: string): ConstraintFieldMetadata => ({
  key,
  kind: "enum",
  required: true,
});
const outsideFields = (
  valueField: string,
): readonly ConstraintFieldMetadata[] => [
  typeField,
  { key: "side", kind: "outside-side", required: true },
  integerField("index"),
  integerField(valueField),
  negatedField,
];

function entry<Type extends ConstraintType>(
  value: ConstraintRegistryEntry<Type>,
): ConstraintRegistryEntry<Type> {
  return value;
}

export const CONSTRAINT_REGISTRY = {
  diagonal: entry({
    type: "diagonal",
    label: "Diagonal",
    category: "global",
    negatable: false,
    fields: [typeField, enumField("direction")],
    cells: (size, constraint) =>
      Array.from({ length: size }, (_, index) =>
        constraint.direction === "main"
          ? index * size + index
          : index * size + size - index - 1,
      ),
  }),
  "anti-knight": entry({
    type: "anti-knight",
    label: "Anti-knight",
    category: "global",
    negatable: false,
    fields: [typeField],
    cells: (size) => allCells(size),
  }),
  "anti-king": entry({
    type: "anti-king",
    label: "Anti-king",
    category: "global",
    negatable: false,
    fields: [typeField],
    cells: (size) => allCells(size),
  }),
  "non-consecutive": entry({
    type: "non-consecutive",
    label: "Non-consecutive",
    category: "global",
    negatable: false,
    fields: [typeField],
    cells: (size) => allCells(size),
  }),
  "disjoint-groups": entry({
    type: "disjoint-groups",
    label: "Disjoint groups",
    category: "global",
    negatable: false,
    fields: [typeField],
    cells: (size) => allCells(size),
  }),
  "killer-cage": entry({
    type: "killer-cage",
    label: "Killer cage",
    category: "region",
    negatable: true,
    fields: [
      typeField,
      cellsField(),
      integerField("sum"),
      { key: "noRepeat", kind: "boolean", required: false },
      negatedField,
    ],
    cells: (_size, constraint) => constraint.cells,
  }),
  thermo: entry({
    type: "thermo",
    label: "Thermometer",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  arrow: entry({
    type: "arrow",
    label: "Arrow",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField("bulb"), cellsField("line"), negatedField],
    cells: (_size, constraint) => [...constraint.bulb, ...constraint.line],
  }),
  kropki: entry({
    type: "kropki",
    label: "Kropki dot",
    category: "adjacency",
    negatable: true,
    fields: [
      typeField,
      cellField("a"),
      cellField("b"),
      enumField("kind"),
      negatedField,
    ],
    cells: (_size, constraint) => [constraint.a, constraint.b],
  }),
  xv: entry({
    type: "xv",
    label: "XV pair",
    category: "adjacency",
    negatable: true,
    fields: [
      typeField,
      cellField("a"),
      cellField("b"),
      integerField("total"),
      negatedField,
    ],
    cells: (_size, constraint) => [constraint.a, constraint.b],
  }),
  inequality: entry({
    type: "inequality",
    label: "Inequality",
    category: "adjacency",
    negatable: true,
    fields: [
      typeField,
      cellField("lesser"),
      cellField("greater"),
      negatedField,
    ],
    cells: (_size, constraint) => [constraint.lesser, constraint.greater],
  }),
  renban: entry({
    type: "renban",
    label: "Renban line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  palindrome: entry({
    type: "palindrome",
    label: "Palindrome line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  "x-sum": entry({
    type: "x-sum",
    label: "X-sum",
    category: "outside",
    negatable: true,
    fields: outsideFields("sum"),
    cells: (size, constraint) =>
      outsideLineCells(size, constraint.side, constraint.index),
  }),
  skyscraper: entry({
    type: "skyscraper",
    label: "Skyscraper",
    category: "outside",
    negatable: true,
    fields: outsideFields("count"),
    cells: (size, constraint) =>
      outsideLineCells(size, constraint.side, constraint.index),
  }),
  quadruple: entry({
    type: "quadruple",
    label: "Quadruple",
    category: "cell",
    negatable: true,
    fields: [
      typeField,
      cellsField(),
      { key: "digits", kind: "integers", required: true },
      negatedField,
    ],
    cells: (_size, constraint) => constraint.cells,
  }),
  maximum: entry({
    type: "maximum",
    label: "Maximum cell",
    category: "cell",
    negatable: true,
    fields: [typeField, cellField(), negatedField],
    cells: (size, constraint) => [
      constraint.cell,
      ...orthogonalNeighbours(size, constraint.cell),
    ],
  }),
  minimum: entry({
    type: "minimum",
    label: "Minimum cell",
    category: "cell",
    negatable: true,
    fields: [typeField, cellField(), negatedField],
    cells: (size, constraint) => [
      constraint.cell,
      ...orthogonalNeighbours(size, constraint.cell),
    ],
  }),
  odd: entry({
    type: "odd",
    label: "Odd cell",
    category: "cell",
    negatable: true,
    fields: [typeField, cellField(), negatedField],
    cells: (_size, constraint) => [constraint.cell],
  }),
  even: entry({
    type: "even",
    label: "Even cell",
    category: "cell",
    negatable: true,
    fields: [typeField, cellField(), negatedField],
    cells: (_size, constraint) => [constraint.cell],
  }),
  "little-killer": entry({
    type: "little-killer",
    label: "Little killer",
    category: "outside",
    negatable: true,
    fields: [
      typeField,
      { key: "side", kind: "outside-side", required: true },
      integerField("index"),
      enumField("direction"),
      integerField("sum"),
      negatedField,
    ],
    cells: (size, constraint) =>
      littleKillerCells(
        size,
        constraint.side,
        constraint.index,
        constraint.direction,
      ),
  }),
  sandwich: entry({
    type: "sandwich",
    label: "Sandwich sum",
    category: "outside",
    negatable: true,
    fields: outsideFields("sum"),
    cells: (size, constraint) =>
      outsideLineCells(size, constraint.side, constraint.index),
  }),
  "between-line": entry({
    type: "between-line",
    label: "Between line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  "german-whisper": entry({
    type: "german-whisper",
    label: "German whisper",
    category: "line",
    negatable: true,
    fields: [
      typeField,
      cellsField(),
      { key: "minimumDifference", kind: "integer", required: false },
      negatedField,
    ],
    cells: (_size, constraint) => constraint.cells,
  }),
  "region-sum-line": entry({
    type: "region-sum-line",
    label: "Region-sum line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  clone: entry({
    type: "clone",
    label: "Clone regions",
    category: "region",
    negatable: true,
    fields: [typeField, cellsField(), cellsField("cloneCells"), negatedField],
    cells: (_size, constraint) => [
      ...constraint.cells,
      ...constraint.cloneCells,
    ],
  }),
  "extra-region": entry({
    type: "extra-region",
    label: "Extra region",
    category: "region",
    negatable: false,
    fields: [typeField, cellsField()],
    cells: (_size, constraint) => constraint.cells,
  }),
  "modular-line": entry({
    type: "modular-line",
    label: "Modular line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  "entropic-line": entry({
    type: "entropic-line",
    label: "Entropic line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  "zipper-line": entry({
    type: "zipper-line",
    label: "Zipper line",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  "double-arrow": entry({
    type: "double-arrow",
    label: "Double arrow",
    category: "line",
    negatable: true,
    fields: [typeField, cellsField(), negatedField],
    cells: (_size, constraint) => constraint.cells,
  }),
  indexer: entry({
    type: "indexer",
    label: "Indexer",
    category: "cell",
    negatable: true,
    fields: [typeField, enumField("kind"), cellField(), negatedField],
    cells: (size, constraint) => {
      const row = Math.floor(constraint.cell / size);
      const column = constraint.cell % size;
      if (constraint.kind === "row") {
        return Array.from(
          { length: size },
          (_, targetRow) => targetRow * size + column,
        );
      }
      if (constraint.kind === "column") {
        return Array.from(
          { length: size },
          (_, targetColumn) => row * size + targetColumn,
        );
      }
      return correspondingBoxPositionCells(size, constraint.cell);
    },
  }),
  fog: entry({
    type: "fog",
    label: "Fog of war",
    category: "global",
    negatable: false,
    fields: [
      typeField,
      cellsField("lights"),
      { key: "revealRadius", kind: "integer", required: false },
    ],
    cells: (_size, constraint) => constraint.lights,
  }),
} satisfies ConstraintRegistry;

export const CONSTRAINT_TYPES = Object.freeze(
  Object.keys(CONSTRAINT_REGISTRY) as ConstraintType[],
);

export function isConstraintType(value: string): value is ConstraintType {
  return Object.hasOwn(CONSTRAINT_REGISTRY, value);
}

export function constraintMetadata<Type extends ConstraintType>(
  type: Type,
): ConstraintRegistryEntry<Type> {
  return CONSTRAINT_REGISTRY[type] as unknown as ConstraintRegistryEntry<Type>;
}

export function constraintLabel(type: string): string {
  if (isConstraintType(type)) return CONSTRAINT_REGISTRY[type].label;
  return type
    .split("-")
    .map((part) => `${part.charAt(0).toUpperCase()}${part.slice(1)}`)
    .join(" ");
}

export function constraintAllowedFields(
  type: ConstraintType,
): ReadonlySet<string> {
  return new Set(CONSTRAINT_REGISTRY[type].fields.map(({ key }) => key));
}

export function constraintCells(
  size: number,
  constraint: VariantConstraint,
): readonly CellId[] {
  const resolver = CONSTRAINT_REGISTRY[constraint.type].cells as (
    size: number,
    constraint: never,
  ) => readonly CellId[];
  return [...new Set(resolver(size, constraint as never))];
}