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// https://github.com/msgpack/msgpack/blob/master/spec.md#timestamp-extension-type

import { DecodeError } from "./DecodeError.ts";

import { getInt64, setInt64 } from "./utils/int.ts";

export const EXT_TIMESTAMP = -1;

export type TimeSpec = {

sec: number;

nsec: number;

};

const TIMESTAMP32_MAX_SEC = 0x100000000 - 1; // 32-bit unsigned int

const TIMESTAMP64_MAX_SEC = 0x400000000 - 1; // 34-bit unsigned int

export function encodeTimeSpecToTimestamp({ sec, nsec }: TimeSpec): Uint8Array {

if (sec >= 0 && nsec >= 0 && sec <= TIMESTAMP64_MAX_SEC) {

// Here sec >= 0 && nsec >= 0

if (nsec === 0 && sec <= TIMESTAMP32_MAX_SEC) {

// timestamp 32 = { sec32 (unsigned) }

const rv = new Uint8Array(4);

const view = new DataView(rv.buffer);

view.setUint32(0, sec);

return rv;

} else {

// timestamp 64 = { nsec30 (unsigned), sec34 (unsigned) }

const secHigh = sec / 0x100000000;

const secLow = sec & 0xffffffff;

const rv = new Uint8Array(8);

const view = new DataView(rv.buffer);

// nsec30 | secHigh2

view.setUint32(0, (nsec << 2) | (secHigh & 0x3));

// secLow32

view.setUint32(4, secLow);

return rv;

}

} else {

// timestamp 96 = { nsec32 (unsigned), sec64 (signed) }

const rv = new Uint8Array(12);

const view = new DataView(rv.buffer);

view.setUint32(0, nsec);

setInt64(view, 4, sec);

return rv;

}

export function encodeDateToTimeSpec(date: Date): TimeSpec {

const msec = date.getTime();

const sec = Math.floor(msec / 1e3);

const nsec = (msec - sec * 1e3) * 1e6;

// Normalizes { sec, nsec } to ensure nsec is unsigned.

const nsecInSec = Math.floor(nsec / 1e9);

return {

sec: sec + nsecInSec,

nsec: nsec - nsecInSec * 1e9,

};

}

export function encodeTimestampExtension(object: unknown): Uint8Array | null {

if (object instanceof Date) {

const timeSpec = encodeDateToTimeSpec(object);

return encodeTimeSpecToTimestamp(timeSpec);

} else {

return null;

}

export function decodeTimestampToTimeSpec(data: Uint8Array): TimeSpec {

const view = new DataView(data.buffer, data.byteOffset, data.byteLength);

// data may be 32, 64, or 96 bits

switch (data.byteLength) {

case 4: {

// timestamp 32 = { sec32 }

const sec = view.getUint32(0);

const nsec = 0;

return { sec, nsec };

}

case 8: {

// timestamp 64 = { nsec30, sec34 }

const nsec30AndSecHigh2 = view.getUint32(0);

const secLow32 = view.getUint32(4);

const sec = (nsec30AndSecHigh2 & 0x3) * 0x100000000 + secLow32;

const nsec = nsec30AndSecHigh2 >>> 2;

return { sec, nsec };

}

case 12: {

// timestamp 96 = { nsec32 (unsigned), sec64 (signed) }

const sec = getInt64(view, 4);

const nsec = view.getUint32(0);

return { sec, nsec };

}

default:

throw new DecodeError(`Unrecognized data size for timestamp (expected 4, 8, or 12): ${data.length}`);

}

export function decodeTimestampExtension(data: Uint8Array): Date {

const timeSpec = decodeTimestampToTimeSpec(data);

return new Date(timeSpec.sec * 1e3 + timeSpec.nsec / 1e6);

}

export const timestampExtension = {

type: EXT_TIMESTAMP,

encode: encodeTimestampExtension,

decode: decodeTimestampExtension,

};