bison

BSON encoder and decoder for Gleam

Quick start

gleam test  # Run the tests
gleam shell # Run an Erlang shell

Installation

gleam add bison

Roadmap

• support encoding and decoding basic bson types (null, string, int32, int64, double, boolean, objectId, array, document).
• support encoding and decoding min, max, timestamp, datetime, javascript and regex bson types.
• support encoding and decoding the generic, md5, uuid and user-defined binary subtypes.
• support generating new object-ids
• support encoding and decoding decimal128 bson type.
• support encoding and decoding encrypted binary subtype.
• support encoding and decoding relaxed EJSON.

Usage

Encoding

import gleam/dict
import gleam/list
import gleam/result
import bison
import bison/md5
import bison/bson
import bison/object_id

fn calf_to_bson(calf: Calf) -> Result(BitArray, Nil) {
  use id <- result.then(object_id.from_string(calf.id))
  use checksum <- result.then(md5.from_string(calf.checksum))

  [
    #("id", bson.ObjectId(id)),
    #("age", bson.Int32(calf.age)),
    #("name", bson.String(calf.name)),
    #("weight", bson.Double(calf.weight)),
    #("birthdate", bson.DateTime(calf.birthdate)),
    #("is_healthy", bson.Boolean(calf.is_healthy)),
    #("checksum", bson.Binary(bson.MD5(checksum))),
    #("nicknames", bson.Array(list.map(calf.nicknames, bson.String))),
  ]
  |> dict.from_list
  |> bison.encode
  |> Ok
}

Decoding

import gleam/dict
import gleam/result
import gleam/dynamic
import bison
import bison/bson
import bison/decoders

pub type Habitat {
  Habitat(kind: String, location: String)
}

pub type Species {
  Species(alternative_name: String, weight_range: List(Int), habitat: Habitat)
}

pub type ExtantBisons {
  ExtantBisons(buffalo: Species, wisent: Species)
}

pub fn extant_bisons_from_bson(
  binary: BitArray,
) -> Result(ExtantBisons, List(dynamic.DecodeError)) {
  let habitat_decoder =
    dynamic.decode2(
      Habitat,
      dynamic.field("kind", decoders.string),
      dynamic.field("location", decoders.string),
    )

  let species_decoder =
    dynamic.decode3(
      Species,
      dynamic.field("alternative name", decoders.string),
      dynamic.field("weight range", decoders.list(decoders.int)),
      dynamic.field("habitat", decoders.wrap(habitat_decoder)),
    )

  let decoder =
    dynamic.decode2(
      ExtantBisons,
      dynamic.field("Buffalo", decoders.wrap(species_decoder)),
      dynamic.field("Wisent", decoders.wrap(species_decoder)),
    )

  use doc <- result.then(
    bison.decode(binary)
    |> result.replace_error([dynamic.DecodeError("BSON", "bit array", [])]),
  )

  bison.to_custom_type(doc, decoder)
}