| 1 | import type { Nullable } from '../utils';
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| 2 | /**
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| 3 | * Transforms a domain name into a canonical domain name. The canonical domain name is a domain name
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| 4 | * that has been trimmed, lowercased, stripped of leading dot, and optionally punycode-encoded
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| 5 | * ({@link https://www.rfc-editor.org/rfc/rfc6265.html#section-5.1.2 | Section 5.1.2 of RFC 6265}). For
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| 6 | * the most part, this function is idempotent (calling the function with the output from a previous call
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| 7 | * returns the same output).
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| 8 | *
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| 9 | * @remarks
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| 10 | * A canonicalized host name is the string generated by the following
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| 11 | * algorithm:
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| 12 | *
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| 13 | * 1. Convert the host name to a sequence of individual domain name
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| 14 | * labels.
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| 15 | *
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| 16 | * 2. Convert each label that is not a Non-Reserved LDH (NR-LDH) label,
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| 17 | * to an A-label (see Section 2.3.2.1 of [RFC5890] for the former
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| 18 | * and latter), or to a "punycode label" (a label resulting from the
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| 19 | * "ToASCII" conversion in Section 4 of [RFC3490]), as appropriate
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| 20 | * (see Section 6.3 of this specification).
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| 21 | *
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| 22 | * 3. Concatenate the resulting labels, separated by a %x2E (".")
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| 23 | * character.
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| 24 | *
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| 25 | * @example
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| 26 | * ```
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| 27 | * canonicalDomain('.EXAMPLE.com') === 'example.com'
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| 28 | * ```
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| 29 | *
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| 30 | * @param domainName - the domain name to generate the canonical domain from
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| 31 | * @public
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| 32 | */
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| 33 | export declare function canonicalDomain(domainName: Nullable<string>): string | undefined;
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