/**
 * Reading `* n FETCH (...)` responses whole.
 *
 * This exists because the two ad hoc readers it replaces each searched a FETCH
 * response for one thing and made an assumption about everything else, and both
 * assumptions were wrong against a real server.
 *
 * What a real server actually sends
 * ─────────────────────────────────
 * A `BODY[...]` section arrives as a `{N}` literal, RFC 3501 §4.3, which is a
 * byte count on the end of the line followed by exactly that many bytes:
 *
 *     * 3 FETCH (UID 307 BODY[HEADER.FIELDS (FROM SUBJECT)] {58}
 *     From: a@b.test
 *     Subject: Hello
 *
 *     )
 *
 * `ImapSession` reads the count, takes the bytes, and hands the response up as
 * ONE string with the payload welded onto the line that announced it. That is
 * the correct thing to do, the payload is not lines, it is bytes, and it may
 * contain anything including a line that looks like a response. But it means
 * every reader downstream sees a `* 3 FETCH (` line with a whole header block
 * hanging off the end of it, and a reader that expected the payload on lines of
 * its own finds nothing.
 *
 * The old `parseFetchHeaders` did worse than find nothing: it tested whether
 * the text after `* n FETCH ` started with `(` and discarded it if so. Against
 * a folded literal that text is `(UID 307 BODY[...] From: a@b.test…`, so the
 * whole header block went out with the data items it was welded to, and the
 * client built envelopes with every field empty while reporting success.
 *
 * Where the UID is, is the server's choice
 * ────────────────────────────────────────
 * `UID FETCH` makes the server include a `UID` data item whether or not it was
 * asked for (§6.4.8), and the server chooses where in the list it goes. Both of
 * these are conformant and both are in the wild:
 *
 *     * 3 FETCH (UID 307 BODY[HEADER.FIELDS (…)] {58}…)
 *     * 3 FETCH (BODY[HEADER.FIELDS (…)] {58}… UID 307)
 *
 * In the second, the `UID` lands AFTER the literal, which means it is not on
 * the `* n FETCH` line at all, it is on the line that closes the response. The
 * old `parseFetchUids` searched `line.slice(0, line.indexOf('BODY'))` of the
 * start line only, found nothing, and returned an empty map; the client then
 * produced no envelopes and the caller could not tell that from an empty
 * mailbox.
 *
 * So this reads the response as a response
 * ────────────────────────────────────────
 * One pass over the lines, tracking parenthesis depth, quoted strings and
 * `[section]` brackets, collecting the data items at depth 1 as structural text
 * and every `BODY[...]` payload as opaque bytes. A `UID` is then read from the
 * structural text, from wherever in the response it appeared, and never from
 * inside a payload, because payload text is never structural text.
 *
 * A response that cannot be read says so
 * ──────────────────────────────────────
 * `parseError` is the field this module exists for as much as the payloads are.
 * A caller advancing a cursor has to distinguish "the server did not mention
 * this message" from "the server mentioned it and we could not read the answer",
 * and it can only do that if the second one is reported rather than silently
 * looking like the first.
 */
/** One `* n FETCH (...)` response, read whole. */
export interface ImapFetchResponse {
    /**
     * The response's own sequence number.
     *
     * NOT a UID, even under `UID FETCH`, the prefix is a sequence number in both
     * commands, which is exactly why `uid` is read separately and joined rather
     * than assumed equal.
     */
    readonly seq: number;
    /** The `UID` data item, from wherever in the response it appeared. */
    readonly uid: number | null;
    /**
     * `BODY[<spec>]` payloads, keyed by the section spec upper-cased with runs of
     * whitespace collapsed: `HEADER.FIELDS (FROM SUBJECT)`, `TEXT`, or `''` for
     * `BODY[]`. A `<partial>` suffix is not part of the key.
     */
    readonly sections: ReadonlyMap<string, string>;
    /**
     * Null when the response was read whole; a plain-language reason when it was
     * not.
     *
     * A response carrying this describes NOTHING about the message it named. A
     * caller must not read the resulting absence as the message being gone.
     */
    readonly parseError: string | null;
}
/**
 * Read every `* n FETCH (...)` response in a command's collected lines.
 *
 * Responses come back in the order the server sent them. Anything that is not
 * part of a FETCH response, the tagged completion, other untagged data, is
 * ignored rather than guessed at.
 */
export declare function parseFetchResponses(lines: readonly string[]): ImapFetchResponse[];
/** The first section payload whose normalized spec the predicate accepts. */
export declare function fetchSection(response: ImapFetchResponse, matches: (spec: string) => boolean): string | null;
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