risuai/src/ts/storage/risuSave.ts

import { Packr, Unpackr, decode } from "msgpackr";
import * as fflate from "fflate";
import { AppendableBuffer, isTauri } from "../globalApi.svelte";

const packr = new Packr({
    useRecords:false
});

const unpackr = new Unpackr({
    int64AsType: 'number',
    useRecords:false
})

const magicHeader = new Uint8Array([0, 82, 73, 83, 85, 83, 65, 86, 69, 0, 7]); 
const magicCompressedHeader = new Uint8Array([0, 82, 73, 83, 85, 83, 65, 86, 69, 0, 8]);
const magicStreamCompressedHeader = new Uint8Array([0, 82, 73, 83, 85, 83, 65, 86, 69, 0, 9]);


async function checkCompressionStreams(){
    if(!CompressionStream){
        const {makeCompressionStream} = await import('compression-streams-polyfill/ponyfill');
        globalThis.CompressionStream = makeCompressionStream(TransformStream);
    }
    if(!DecompressionStream){
        const {makeDecompressionStream} = await import('compression-streams-polyfill/ponyfill');
        globalThis.DecompressionStream = makeDecompressionStream(TransformStream);
    }
}

export function encodeRisuSaveLegacy(data:any, compression:'noCompression'|'compression' = 'noCompression'){
    let encoded:Uint8Array = packr.encode(data)
    if(compression === 'compression'){
        encoded = fflate.compressSync(encoded)
        const result = new Uint8Array(encoded.length + magicCompressedHeader.length);
        result.set(magicCompressedHeader, 0)
        result.set(encoded, magicCompressedHeader.length)
        return result
    }
    else{
        const result = new Uint8Array(encoded.length + magicHeader.length);
        result.set(magicHeader, 0)
        result.set(encoded, magicHeader.length)
        return result
    }
}

export async function encodeRisuSave(data:any) {
    await checkCompressionStreams()
    let encoded:Uint8Array = packr.encode(data)
    const cs = new CompressionStream('gzip');
    const writer = cs.writable.getWriter();
    writer.write(encoded);
    writer.close();
    const buf = await new Response(cs.readable).arrayBuffer()
    const result = new Uint8Array(new Uint8Array(buf).length + magicStreamCompressedHeader.length);
    result.set(magicStreamCompressedHeader, 0)
    result.set(new Uint8Array(buf), magicStreamCompressedHeader.length)
    return result
}

export async function decodeRisuSave(data:Uint8Array){
    try {
        switch(checkHeader(data)){
            case "compressed":
                data = data.slice(magicCompressedHeader.length)
                return decode(fflate.decompressSync(data))
            case "raw":
                data = data.slice(magicHeader.length)
                return unpackr.decode(data)
            case "stream":{
                await checkCompressionStreams()
                data = data.slice(magicStreamCompressedHeader.length)
                const cs = new DecompressionStream('gzip');
                const writer = cs.writable.getWriter();
                writer.write(data);
                writer.close();
                const buf = await new Response(cs.readable).arrayBuffer()
                return unpackr.decode(new Uint8Array(buf))
            }
        }
        return unpackr.decode(data)
    }
    catch (error) {
        try {
            console.log('risudecode')
            const risuSaveHeader = new Uint8Array(Buffer.from("\u0000\u0000RISU",'utf-8'))
            const realData = data.subarray(risuSaveHeader.length)
            const dec = unpackr.decode(realData)
            return dec   
        } catch (error) {
            const buf = Buffer.from(fflate.decompressSync(Buffer.from(data)))
            try {
                return JSON.parse(buf.toString('utf-8'))                            
            } catch (error) {
                return unpackr.decode(buf)
            }
        }
    }
}

function checkHeader(data: Uint8Array) {

    let header:'none'|'compressed'|'raw'|'stream' = 'raw'

    if (data.length < magicHeader.length) {
      return false;
    }
  
    for (let i = 0; i < magicHeader.length; i++) {
      if (data[i] !== magicHeader[i]) {
        header = 'none'
        break
      }
    }

    if(header === 'none'){
        header = 'compressed'
        for (let i = 0; i < magicCompressedHeader.length; i++) {
            if (data[i] !== magicCompressedHeader[i]) {
                header = 'none'
                break
            }
        }
    }

    if(header === 'none'){
        header = 'stream'
        for (let i = 0; i < magicStreamCompressedHeader.length; i++) {
            if (data[i] !== magicStreamCompressedHeader[i]) {
                header = 'none'
                break
            }
        }
    }

    // All bytes matched
    return header;
  }