Zazama / node-id3

import { FrameBuilder } from "../FrameBuilder"

import { FrameReader } from "../FrameReader"

import { getTags } from '../frames-reader'

import { buildFramesBuffer } from "../frames-builder"

import type { Chapter } from "../types/TagFrames"

import type { Tags, WriteTags } from "../types/Tags"

export const CHAP = {

    create: (chap: Chapter<WriteTags>): Buffer => {

        if (chap.elementID == undefined

            || chap.startTimeMs == undefined

            || chap.endTimeMs == undefined

        ) {

            throw new TypeError(

                "elementID, startTimeMs, endTimeMs must all be provided"

            )

        }

        const getOffset = (offset?: number) => offset ?? 0xFFFFFFFF

        return new FrameBuilder("CHAP")

            .appendTerminatedText(chap.elementID)

            .appendNumber(chap.startTimeMs, {size: 4})

            .appendNumber(chap.endTimeMs, {size: 4})

            .appendNumber(getOffset(chap.startOffsetBytes), {size: 4})

            .appendNumber(getOffset(chap.endOffsetBytes), {size: 4})

            .appendBuffer(buildFramesBuffer(chap.tags))

            .getBufferWithPartialHeader()

    },

    read: (buffer: Buffer, version: number): Chapter<Tags> => {

        const reader = new FrameReader(buffer)

        // Returns a spreadable object to insert an optional offset property

        // when the consumed offset is valid.

        const consumeOffset= <Key extends keyof Chapter<never>>(key: Key) => {

            const offset = reader.consumeNumber({size: 4})

            return offset === 0xFFFFFFFF ? {} : {[key]: offset}

        }

        return {

            elementID: reader.consumeTerminatedText(),

            startTimeMs: reader.consumeNumber({size: 4}),

            endTimeMs: reader.consumeNumber({size: 4}),

            ...consumeOffset("startOffsetBytes"),

            ...consumeOffset("endOffsetBytes"),

            tags: getTags(

                { buffer: reader.consumePossiblyEmptyBuffer(), version }

            ) as Tags

        }

    }

}