import Schema from './schema.js';

export default class Serializer {

  constructor(schema) {
    this.schema = schema instanceof Schema ? schema : new Schema(schema);
  }

  decode(view, destination, offset = 0) {
    let cursor = offset;
    for (const [key, {type}] of this.schema) {
      const viewGetMethod = Schema.viewGetMethods[type];
      let value;
      if (viewGetMethod) {
        value = view[viewGetMethod](cursor, true);
        cursor += Schema.sizeOfType(type);
      }
      else {
        switch (type) {
          case 'string': {
            const length = view.getUint32(cursor, true);
            cursor += 4;
            const {buffer, byteOffset} = view;
            const decoder = new TextDecoder();
            value = decoder.decode(new DataView(buffer, byteOffset + cursor, length));
            cursor += length;
            break;
          }
        }
      }
      destination[key] = value;
    }
  }

  encode(source, view, offset = 0) {
    let cursor = offset;
    for (const [key, {type}] of this.schema) {
      const viewSetMethod = Schema.viewSetMethods[type];
      if (viewSetMethod) {
        view[viewSetMethod](cursor, source[key], true);
        cursor += Schema.sizeOfType(type);
      }
      else {
        switch (type) {
          case 'string': {
            const lengthOffset = cursor;
            cursor += 4;
            const encoder = new TextEncoder();
            const bytes = encoder.encode(source[key]);
            for (let i = 0; i < bytes.length; ++i) {
              view.setUint8(cursor++, bytes[i]);
            }
            view.setUint32(lengthOffset, bytes.length, true);
            break;
          }
        }
      }
    }
  }

}