第5章: カリー化と部分適用¶

// 通常の関数
function add(a: number, b: number): number {
    return a + b;
}

// カリー化された関数
function addCurried(a: number): (b: number) => number {
    return (b: number) => a + b;
}

// 使用例
const add5 = addCurried(5);
console.log(add5(3)); // 8
console.log(add5(7)); // 12

// 直接呼び出し
console.log(addCurried(5)(3)); // 8

// 3引数の関数をカリー化
function multiply(a: number): (b: number) => (c: number) => number {
    return (b: number) => (c: number) => a * b * c;
}

const result = multiply(2)(3)(4); // 24

// 段階的な適用
const multiplyBy2 = multiply(2);
const multiplyBy2And3 = multiplyBy2(3);
const final = multiplyBy2And3(4); // 24

// 2引数関数用のcurry
function curry2<A, B, C>(
    fn: (a: A, b: B) => C
): (a: A) => (b: B) => C {
    return (a: A) => (b: B) => fn(a, b);
}

// 使用例
const add = (a: number, b: number) => a + b;
const curriedAdd = curry2(add);

console.log(curriedAdd(5)(3)); // 8

// より柔軟なcurry実装
function curry<T extends (...args: any[]) => any>(
    fn: T,
    ...args: any[]
): any {
    if (args.length >= fn.length) {
        return fn(...args);
    }
    return (...nextArgs: any[]) => 
        curry(fn, ...args, ...nextArgs);
}

// 使用例
const sum = (a: number, b: number, c: number) => a + b + c;
const curriedSum = curry(sum);

console.log(curriedSum(1)(2)(3)); // 6
console.log(curriedSum(1, 2)(3)); // 6
console.log(curriedSum(1)(2, 3)); // 6

// 部分適用
function partial<T extends any[], U extends any[], R>(
    fn: (...args: [...T, ...U]) => R,
    ...fixedArgs: T
): (...remainingArgs: U) => R {
    return (...remainingArgs: U) => 
        fn(...fixedArgs, ...remainingArgs);
}

// 使用例
const greet = (greeting: string, name: string, punctuation: string) => 
    `${greeting}, ${name}${punctuation}`;

const sayHello = partial(greet, "Hello");
console.log(sayHello("Alice", "!")); // "Hello, Alice!"

const sayHelloAlice = partial(greet, "Hello", "Alice");
console.log(sayHelloAlice(".")); // "Hello, Alice."

// ログ出力関数
const log = curry(
    (level: string, timestamp: Date, message: string) => {
        console.log(`[${level}] ${timestamp.toISOString()}: ${message}`);
    }
);

// 特定のログレベルの関数を作成
const info = log("INFO");
const error = log("ERROR");
const debug = log("DEBUG");

// 現在時刻でログ出力
const now = new Date();
info(now)("Application started");
error(now)("Connection failed");

// フィルタリング関数
const filter = curry(
    <T>(predicate: (item: T) => boolean, array: T[]) => 
        array.filter(predicate)
);

// マッピング関数
const map = curry(
    <T, U>(fn: (item: T) => U, array: T[]) => 
        array.map(fn)
);

// 特定の条件でフィルタリング
const filterActive = filter((user: User) => user.isActive);
const filterAdults = filter((user: User) => user.age >= 18);

// 変換関数
const getName = map((user: User) => user.name);
const toUpperCase = map((name: string) => name.toUpperCase());

// パイプラインの構築
const getActiveAdultNames = pipe(
    filterActive,
    filterAdults,
    getName,
    toUpperCase
);

// イベントハンドラー生成関数
const createHandler = curry(
    (eventType: string, selector: string, callback: Function) => {
        document.querySelectorAll(selector).forEach(element => {
            element.addEventListener(eventType, callback as EventListener);
        });
    }
);

// 特定のイベントタイプのハンドラー
const onClick = createHandler("click");
const onHover = createHandler("mouseenter");

// 使用例
onClick(".button")(() => console.log("Button clicked"));
onClick(".link")(() => console.log("Link clicked"));
onHover(".card")(() => console.log("Card hovered"));

// バリデーション関数
const minLength = curry(
    (min: number, value: string) => 
        value.length >= min || `Must be at least ${min} characters`
);

const maxLength = curry(
    (max: number, value: string) => 
        value.length <= max || `Must be at most ${max} characters`
);

const matches = curry(
    (pattern: RegExp, value: string) => 
        pattern.test(value) || `Does not match required pattern`
);

// 特定のバリデーションルール
const minLength8 = minLength(8);
const maxLength20 = maxLength(20);
const hasNumber = matches(/\d/);
const hasUpperCase = matches(/[A-Z]/);

// パスワードバリデーション
const validatePassword = (password: string) => {
    const validators = [minLength8, maxLength20, hasNumber, hasUpperCase];

    for (const validate of validators) {
        const result = validate(password);
        if (result !== true) {
            return { valid: false, error: result };
        }
    }

    return { valid: true };
};

function calculate(operation: string, a: number, b: number): number {
    switch (operation) {
        case "+": return a + b;
        case "-": return a - b;
        case "*": return a * b;
        case "/": return a / b;
        default: throw new Error("Unknown operation");
    }
}

// カリー化バージョンを実装
function calculateCurried(/* ... */) {
    // 実装
}

type Product = {
    name: string;
    price: number;
    category: string;
};

// 以下の機能を実装
// 1. カテゴリーでフィルタリング
// 2. 価格に税金を追加
// 3. 価格でソート