index.ts

export interface S3Params {
    Bucket: string | undefined;
    Key: string | undefined;
}

export interface S3Permutations {
    S3: string;
    BucketInPath: string;
    BucketInHost: string;
}

export default class S3URLs {
    static fromUrl(url: string): S3Params {
        const uri = new URL(url);
        uri.pathname = decodeURIComponent(uri.pathname || '');

        const style = (function(uri) {
            if (uri.protocol === 's3:') return 'S3';
            if (/^s3[.-](\w{2}-(gov-)?\w{4,9}-\d\.)?amazonaws\.com/.test(uri.hostname)) return 'BucketInPath';
            if (/\.s3[.-](\w{2}-(gov-)?\w{4,9}-\d\.)?amazonaws\.com/.test(uri.hostname)) return 'BucketInHost';
        })(uri);

        let bucket, key;
        if (style === 'S3') {
            bucket = uri.hostname;
            key = uri.pathname.slice(1);
        } else if (style === 'BucketInPath') {
            bucket = uri.pathname.split('/')[1];
            key = uri.pathname.split('/').slice(2).join('/');
        } else if (style === 'BucketInHost') {
            const match = uri.hostname.replace(/\.s3[.-](\w{2}-(gov-)?\w{4,9}-\d\.)?amazonaws\.com(\.cn)?/, '');
            if (match.length) {
                bucket = match;
            } else {
                bucket =  uri.hostname.split('.')[0];
            }
            key = uri.pathname.slice(1);
        }

        return {
            Bucket: bucket,
            Key: key
        };
    }

    static toUrl(bucket: string, key: string): S3Permutations {
        return {
            'S3': ['s3:/', bucket, key].join('/'),
            'BucketInPath': ['https://s3.amazonaws.com', bucket, key].join('/'),
            'BucketInHost': ['https:/', bucket + '.s3.amazonaws.com', key].join('/')
        };
    }

    static valid(url: string): boolean {
        const params = this.fromUrl(url);
        return !!(params.Bucket && params.Key)
    }
}