import { downloadBlob } from './exportImport.js'

export { downloadBlob }

/**
 * Build a rocket design JSON Blob for download.
 * Schema version 1: inputs section is re-importable; results is reference-only.
 */
export function exportRocketJSON({ outerRadius, tankConfig, propDensities, payload, structure, engineData, geometry, noseConeShape }) {
  const payload_ = {
    version: 1,
    type: 'rocket_design',
    exportedAt: new Date().toISOString(),
    inputs: {
      outerRadius,
      tankConfig,
      propDensities,
      payload,
      structure,
      noseConeShape,
    },
    engineData: engineData ?? null,
    results: geometry ?? null,
  }
  return new Blob([JSON.stringify(payload_, null, 2)], { type: 'application/json' })
}

/**
 * Parse an imported rocket design JSON string and return the inputs section.
 * Throws a descriptive Error if the file is invalid.
 */
export function parseRocketImport(jsonString) {
  let data
  try {
    data = JSON.parse(jsonString)
  } catch {
    throw new Error('File is not valid JSON.')
  }

  if (data.type !== 'rocket_design') {
    throw new Error('This file is not a rocket design export.')
  }
  if (data.version !== 1) {
    throw new Error(`Unsupported export version: ${data.version}`)
  }

  const { outerRadius, tankConfig, propDensities, payload, structure, noseConeShape } = data.inputs ?? {}

  return {
    outerRadius: outerRadius ?? null,
    tankConfig:  tankConfig  ?? null,
    propDensities: propDensities ?? null,
    payload:     payload     ?? null,
    structure:   structure   ?? null,
    noseConeShape: noseConeShape ?? null,
    engineData:  data.engineData ?? null,
  }
}