exposalud-data

Compact guest data encoding for ExpoSalud health fair events. Encodes a full guest profile into ~133 bytes (vs ~600+ bytes JSON). QR code compatible.

Install

npm install exposalud-data

Protocol — Encode/Decode Guest Data

const { encode, decode, toBase64, fromBase64 } = require('exposalud-data/protocol')

// Encode a guest profile to binary
const buf = encode({
  code: 'FE689B8A',
  name: 'John Doe',
  age: 38,
  sex: 'M',
  height: 175,
  weight: 80,
  bmi: 26.12,
  bmiCat: 'overweight',
  glucose: 95,
  sbp: 120,
  dbp: 80,
  habits: { breakfast: 1, snacks: 0.5, exercise: 1 /* ... */ },
  survey: {
    discovery: ['social'],
    interests: ['nutrition', 'healthy-food'],
    needs: ['health'],
  },
  // ... all other fields
})

console.log(buf.length) // ~133 bytes

// Decode back to object
const guest = decode(buf)
console.log(guest.name) // 'John Doe'
console.log(guest.bmi)  // 26.12

// For QR codes — convert to/from base64
const qr = toBase64(buf)   // 180 chars, fits QR v10
const restored = decode(fromBase64(qr))

Schema Versioning

The protocol is version-aware. Adding new fields is safe:

1. Add the field to FIXED_FIELDS or STRING_FIELDS at the end
2. Bump SCHEMA_VERSION
3. Add the new count to VERSION_FIELD_COUNTS

Old decoders skip unknown fields. New decoders fill defaults for missing fields.

// Example: adding a 'bloodType' field in v2

// In FIXED_FIELDS, append:
['bloodType', cenc.uint8, or0, identity],

// Bump version:
const SCHEMA_VERSION = 2

// Update counts:
const VERSION_FIELD_COUNTS = {
  1: { fixed: 32, strings: 6 },
  2: { fixed: 33, strings: 6 },  // one more fixed field
}

Size Comparison

| Format | Typical Guest | 1000 Guests | |--------|--------------|-------------| | JSON | ~600 bytes | ~600 KB | | Protocol | ~133 bytes | ~133 KB | | Reduction | 78% | 78% |

QR Code Compatibility

| Guest Type | Binary | Base64 | QR Version | |-----------|--------|--------|------------| | Empty | 53 bytes | 72 chars | v3 | | Typical | 133 bytes | 180 chars | v10 | | Long strings | 373 bytes | 500 chars | v20 |

All fit within standard QR code capacity.

Performance

1000 guests: 5ms encode, 5ms decode (Node.js)

License

MIT