breach/src/game/Game.ts

export enum EndState {
    Won,
    Lost,
}

export enum SelectionMode {
    FreePick,
    RowPick,
    ColumnPick,
}

type FreeSelection = {
    selectionMode: SelectionMode.FreePick,
}

type RowSelection = {
    selectionMode: SelectionMode.RowPick,
    column: number;
}

type ColumnSelection = {
    selectionMode: SelectionMode.ColumnPick,
    row: number;
}

type SelectionState = FreeSelection | RowSelection | ColumnSelection;

type State = SelectionState | EndState.Won | EndState.Lost;

interface StateSpecificHandler<T> {
    Won(): T
    Lost(): T
    InProgress(selectionState: SelectionState): T
}

function matchState<T>(h: StateSpecificHandler<T>): (a: State) => T {
    return (a: State) => {
        switch (a) {
            case EndState.Won:
                return h.Won();
            case EndState.Lost:
                return h.Lost();
            default:
                return h.InProgress(a);
        }
    }
}

interface SelectionStateSpecificHandler<T> {
    Free(): T;
    Row(row: number): T;
    Column(column: number): T;
}

function matchSelectionState<T>(h: SelectionStateSpecificHandler<T>): (a: SelectionState) => T {
    return (a: SelectionState) => {
        switch (a.selectionMode) {
            case SelectionMode.FreePick:
                return h.Free();
            case SelectionMode.RowPick:
                return h.Row(a.column);
            case SelectionMode.ColumnPick:
                return h.Column(a.row);
        }
    }
}

class IllegalMoveError extends Error {
    constructor() {
        super("Illegal move!")
    }
}

export class Game {
    state: State = {selectionMode: SelectionMode.FreePick}
    public readonly size: number

    constructor(public readonly matrix: string[]) {
        this.size = Math.sqrt(matrix.length)
    }

    getCell(row: number, column: number) {
        return this.matrix[row + column * this.size]
    }

    pick(row: number, column: number): void {
        if (row < 0 || column < 0 || row >= this.size || column >= this.size) {
            throw new IllegalMoveError()
        }

        matchState({
            Won: () => {throw new IllegalMoveError()},
            Lost: () => {throw new IllegalMoveError()},
            InProgress: (selectionMode) =>
                matchSelectionState({
                    Free: () => {
                        this.state = {
                            selectionMode: SelectionMode.RowPick,
                            column: column,
                        };
                    },
                    Column: (r) => {
                        if (r === row) {
                            this.state = {
                                selectionMode: SelectionMode.RowPick,
                                column: column,
                            }
                        } else {
                            throw new IllegalMoveError()
                        }
                    },
                    Row: (c) => {
                        if (c === column) {
                            this.state = {
                                selectionMode: SelectionMode.ColumnPick,
                                row: row,
                            }
                        } else {
                            throw new IllegalMoveError()
                        }
                    },
                })(selectionMode),
        })(this.state)
    }
}