function createCSVScanner(onRow, cols) {
  let buffer = '';

  return function scanChunk(chunk) {
    buffer += chunk;
    const lines = buffer.split('\n');
    buffer = lines.pop(); // Save incomplete line

    for (const line of lines)
    {
      const fields = [];
      let start = 0;
      let col = 0;
      for (let i = 0; i < line.length; i++) {
        if (line[i] === ',' && col < cols-1) {
          fields.push(line.slice(start, i));
          start = i + 1;
          col++;
        }
      }
      fields.push(line.slice(start, line.length-1));
      onRow(...fields);
    }

  };
}

async function DB(url, cols, onRow) {
    const response = await fetch(url);

    if (!response.ok) {
        throw new Error(`HTTP error! status: ${response.status}`);
    }

    const reader = response.body.getReader();
    const decoder = new TextDecoder("utf-8");

    const scanner = createCSVScanner(onRow, cols);

    while (true)
    {
        const { done, value } = await reader.read();
        if (done) break;
        const chunk = decoder.decode(value, { stream: true });
        scanner(chunk);
    }
}


const instances = {};
/** @import DBTypes from "./types.d.ts" */
/** @type {DBTypes.Builder} */
export default function(params)
{
    const obj = {
        list:{},
        load(){
            let index = 0;
            this.list = {};
            return DB(import.meta.resolve(params.path), params.cols, (...args)=>{
                const [id, data] = params.load(index, ...args);
                id && (this.list[id] = data);
                index++;
            });
        },
        find(id){return this.list[id];},
        save(){},
    };

    return obj;
}