/**
 * Proof of concept of “magic” repeated field.
 * 
 * message Test {
 *   uint32 id = 1;
 *   repeated string tags = 2;
 *   string last = 3;
 * }
 */

interface Test {
    id: number;
    tags: string[];
    last: string;
}

const TestBase: Test = {
    id:  0,
    tags: null as unknown as string[],
    last: '',
};

Object.defineProperty(TestBase, 'tags', {
    configurable: false,
    get() {
        const value: string[] = [];
        if (this === TestBase) return value;
        Object.defineProperty(this, 'tags', {
            enumerable: true,
            configurable: true,
            writable: true,
            value
        });
        return value;
    },
    set(value: string[]) {
        Object.defineProperty(this, 'tags', {
            enumerable: true,
            configurable: true,
            writable: true,
            value
        });
    }
});

console.log('TestBase', TestBase);
const message = Object.create(TestBase) as Test;

console.log('Empty message', message);
console.log('Empty message keys', Object.keys(message));

message.id = 42;
// tags is populated automatically
message.tags.push('test', 'my', 'tags');
message.last = 'Final';
console.log('Filled message', message);
console.log('TestBase', TestBase);

/**
 * Proof of concept of “magic” repeated field.
 * 
 * message Test {
 *   uint32 id = 1;
 *   repeated string tags = 2;
 *   repeated uint32 children = 3;
 * }
 * 
 * message Second {
 *   repeated Test tests = 1;
 * }
 */

interface Test {
    id: number;
    tags: string[];
    children: number[];
}

interface Second {
    tests: Test[];
}

function materialize<Base>(obj: Base, field: keyof Base, value: unknown[]) {
    Object.defineProperty(obj, field, {
        enumerable: true,
        configurable: true,
        writable: true,
        value
    });
    return value;
};

function createRepeatedFields<Base>(Base: Base, ...fields: Array<keyof Base>) {
    fields.forEach(field => {
        Object.defineProperty(Base, field, {
            enumerable: true,
            get() {
                const value: unknown[] = [];
                if (this === Base) return value;
                return materialize(this, field, value);
            },
            set(value: unknown[]) {
                materialize(this, field, value);
            }
        });
    });

    return Base;
}

const TestBase: Test = createRepeatedFields({ id:  0 } as Test, 'tags', 'children');
const SecondBase: Second = createRepeatedFields({} as Second, 'tests');

console.log('TestBase', TestBase);
console.log('SecondBase', SecondBase);

const test = Object.create(TestBase) as Test;
const second: Second = Object.create(SecondBase);

console.log('Fresh test and keys', test, Object.keys(test));
console.log('Fresh second and keys', second, Object.keys(second));

test.id = 42;
// tags is populated automatically
test.tags.push('test', 'my', 'tags');
// one could assign array directly
test.children = [ 1, 3 ];
console.log('Filled test and keys', test, Object.keys(test));

second.tests.push(test, test);
console.log('Filled second and keys', second, Object.keys(second));

console.log('TestBase still empty', TestBase);
console.log('SecondBase still empty', SecondBase);