@softvisio/core/lib/data-structures/list.js

Softisio core

import ListEntry from "#lib/data-structures/list/entry";

export default class List {
    #length = 0;
    #firstEntry = null;
    #lastEntry = null;

    // properties
    get length () {
        return this.#length;
    }

    get firstEntry () {
        return this.#firstEntry;
    }

    get lastEntry () {
        return this.#lastEntry;
    }

    // public
    push ( value ) {
        var entry;

        if ( value instanceof ListEntry ) {
            entry = value;

            entry.delete();
        }
        else {
            entry = new ListEntry( value );
        }

        entry.list = this;

        if ( this.#lastEntry ) {
            entry.previousEntry = this.#lastEntry;
            this.#lastEntry.nextEntry = entry;
        }

        this.#lastEntry = entry;
        this.#firstEntry ||= entry;

        this.#length++;

        return entry;
    }

    pop () {
        if ( !this.#lastEntry ) return;

        const entry = this.#lastEntry;

        this.#lastEntry = entry.previousEntry;

        if ( this.#lastEntry ) {
            this.#lastEntry.nextEntry = null;
        }
        else {
            this.#firstEntry = null;
        }

        this.#length--;

        return entry;
    }

    unshift ( value ) {
        var entry;

        if ( value instanceof ListEntry ) {
            entry = value;

            entry.delete();
        }
        else {
            entry = new ListEntry( value );
        }

        entry.list = this;

        if ( this.#firstEntry ) {
            entry.nextEntry = this.#firstEntry;
            this.#firstEntry.previousEntry = entry;
        }

        this.#firstEntry = entry;
        this.#lastEntry ||= entry;

        this.#length++;

        return entry;
    }

    shift () {
        if ( !this.#firstEntry ) return;

        const entry = this.#firstEntry;

        this.#firstEntry = entry.nextEntry;

        if ( this.#firstEntry ) {
            this.#firstEntry.previousEntry = null;
        }
        else {
            this.#lastEntry = null;
        }

        this.#length--;

        return entry;
    }

    delete ( entry ) {
        if ( !entry.list ) return;

        if ( entry.list !== this ) throw new Error( "Unable to delete entry" );

        const previousEntry = entry.previousEntry,
            nextEntry = entry.nextEntry;

        if ( previousEntry ) {
            previousEntry.nextEntry = nextEntry;
        }

        if ( nextEntry ) {
            nextEntry.previousEntry = previousEntry;
        }

        if ( entry === this.#firstEntry ) this.#firstEntry = nextEntry;

        if ( entry === this.#lastEntry ) this.#lastEntry = previousEntry;

        entry.list = null;
        entry.previousEntry = null;
        entry.nextEntry = null;

        this.#length--;

        return this;
    }

    clear () {
        this.#length = 0;
        this.#firstEntry = null;
        this.#lastEntry = null;
    }

    * [ Symbol.iterator ] () {
        var entry = this.#firstEntry;

        while ( entry ) {
            const nextEntry = entry.nextEntry;

            yield entry;

            entry = nextEntry;
        }
    }

    * reverse () {
        var entry = this.#lastEntry;

        while ( entry ) {
            const previousEntry = entry.previousEntry;

            yield entry;

            entry = previousEntry;
        }
    }
}