import { ISigner } from './interface';

/**
 * HMAC签名器
 */
export class HMACSigner implements ISigner {
    private key: CryptoKey | null = null;

    constructor(keyString: string) {
        this.importKey(keyString);
    }

    /**
     * 导入密钥
     */
    private async importKey(keyString: string): Promise<void> {
        const encoder = new TextEncoder();
        const keyData = encoder.encode(keyString);

        this.key = await crypto.subtle.importKey(
            'raw',
            keyData,
            {
                name: 'HMAC',
                hash: 'SHA-256',
            },
            false,
            ['sign', 'verify']
        );
    }

    /**
     * 生成签名
     */
    async sign(data: Uint8Array): Promise<Uint8Array> {
        if (!this.key) {
            throw new Error('密钥未设置');
        }

        const signature = await crypto.subtle.sign('HMAC', this.key, data);
        return new Uint8Array(signature);
    }

    /**
     * 验证签名
     */
    async verify(data: Uint8Array, signature: Uint8Array): Promise<boolean> {
        if (!this.key) {
            throw new Error('密钥未设置');
        }

        return await crypto.subtle.verify('HMAC', this.key, signature, data);
    }
}