import { Expression, Instruction, InstructionType, Jump, Scope, Tag, XmlError, xmlFormat, parseXML } from "@cyklang/core";
import loglevel from 'loglevel'
const logger = loglevel.getLogger('LocalStorage')
logger.setLevel('debug')

export class LocalStorageInstructionType extends InstructionType {
    constructor() {
        super('localstorage')
    }
    async parseInstruction(tag: Tag, scope: Scope): Promise<Instruction> {
        return new LocalStorageInstruction(tag)
    }
}

class LocalStorageInstruction extends Instruction {

    constructor(tag: Tag) {
        super(tag)
    }

    async execute(scope: Scope): Promise<Jump> {
        try {
            if (this.tag.attributes.READ_INTO) {
                await getItem(scope, this.tag.attributes.NAME, this.tag.attributes.READ_INTO)
            }
            else if (this.tag.attributes.WRITE_FROM) {
                await setItem(scope, this.tag.attributes.NAME, this.tag.attributes.WRITE_FROM)
            }
            else {
                throw 'one of read_into or write_from attribute is mandatory'
            }
        }
        catch (err) {
            if (err instanceof XmlError) throw err
            throw new XmlError(String(err), this.tag)
        }
    }
}

/**
 * 
 * @param scope 
 * @param name 
 * @param read_into 
 */
async function getItem(scope: Scope, name: string, read_into: string) {
    try {
        const express = new Expression(scope)
        const varinto = await express.LValue(read_into)
        if (!varinto) throw 'READ_INTO variable ' + read_into + ' not found '
        const item = localStorage.getItem(name)
        if (item === null) return
        const tagItem = parseXML('READ_INTO', item)
        const data = await varinto.dataType.parseData(tagItem, scope)
        varinto.data = data
    }
    catch (err) {
        logger.error(err)
    }
}

/**
 * 
 * @param scope 
 * @param name 
 * @param write_from 
 */
async function setItem(scope: Scope, name: string, write_from: string) {
    const express = new Expression(scope)
    const data = await express.evaluate(write_from)
    if (data === undefined || data === null) {
        localStorage.removeItem(name)
    }
    else {
        const xml = xmlFormat(data)
        localStorage.setItem(name, xml)
    }
    
}