HL7v2

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   |  _  | |__ / / \ V / / __/
   |_| |_|____|_/   \_/ |_____|

   Pure Elixir HL7 v2.x Toolkit
   Schema-driven parsing, building, and MLLP transport.

Pure Elixir HL7 v2.x toolkit — typed segment structs, programmatic message building, structural validation, and integrated MLLP transport.

What You Get

• Typed segments — every v2.5.1 segment is an Elixir struct with named fields, not string maps with integer keys
• Programmatic message building — Message.new/3 + add_segment/2 with auto-populated MSH
• Structural validation — positional order/group/cardinality checks for supported message structures, opt-in HL7 table validation
• Lossless raw mode — canonical round-trip parsing that preserves everything, including malformed input
• Integrated MLLP — Ranch 2.x listener, GenServer client, TLS/mTLS, telemetry
• ACK/NAK builder — HL7v2.ack/2 with sender/receiver swap
• Path access — get/2, fetch/2, ~h sigil with compile-time validation

# Typed structs with named fields
{:ok, msg} = HL7v2.parse(text, mode: :typed)
pid = Enum.find(msg.segments, &is_struct(&1, HL7v2.Segment.PID))
pid.patient_name  #=> [%XPN{family_name: %FN{surname: "Smith"}, given_name: "John"}]

# Build messages programmatically
msg = HL7v2.Message.new("ADT", "A01", sending_application: "PHAOS")
      |> HL7v2.Message.add_segment(%HL7v2.Segment.PID{
           patient_name: [%XPN{family_name: %FN{surname: "Smith"}, given_name: "John"}]
         })

Installation

def deps do
  [{:hl7v2, "~> 2.2"}]
end

Quick Start

Parse

# Raw mode — canonical round-trip, zero allocation overhead
{:ok, raw} = HL7v2.parse(text)
raw.type  #=> {"ADT", "A01"}

# Typed mode — segments become structs
{:ok, msg} = HL7v2.parse(text, mode: :typed)

# Access fields naturally
HL7v2.get(msg, "PID-5")   #=> %XPN{family_name: %FN{surname: "Smith"}, ...}
HL7v2.get(msg, "PID-3")   #=> %CX{id: "12345", identifier_type_code: "MR"}
HL7v2.get(msg, "PID-8")   #=> "M"
HL7v2.get(msg, "PID-3[2]") #=> second identifier (repetition)

Build

msg =
  HL7v2.Message.new("ADT", "A01",
    sending_application: "PHAOS",
    sending_facility: "HOSP"
  )
  |> HL7v2.Message.add_segment(%HL7v2.Segment.PID{
    set_id: 1,
    patient_identifier_list: [
      %HL7v2.Type.CX{id: "MRN001", identifier_type_code: "MR"}
    ],
    patient_name: [
      %HL7v2.Type.XPN{
        family_name: %HL7v2.Type.FN{surname: "Smith"},
        given_name: "John"
      }
    ],
    administrative_sex: "M"
  })

wire = HL7v2.encode(msg)
# => "MSH|^~\\&|PHAOS|HOSP|...\rPID|1||MRN001^^^^MR||Smith^John|||M\r"

Validate

{:ok, typed} = HL7v2.parse(text, mode: :typed)

case HL7v2.validate(typed) do
  :ok ->
    :good

  {:error, errors} ->
    # [%{level: :error, location: "PID", field: :patient_name,
    #    message: "Required field is missing"}]
    Enum.each(errors, &IO.inspect/1)
end

ACK/NAK

# Accept
{ack_msh, msa} = HL7v2.Ack.accept(original_msh)
wire = HL7v2.Ack.encode({ack_msh, msa})

# Reject with error details
{ack_msh, msa, err} = HL7v2.Ack.reject(original_msh,
  text: "Unknown patient",
  error_code: "204"
)

MLLP Transport

# Server
defmodule MyHandler do
  @behaviour HL7v2.MLLP.Handler

  @impl true
  def handle_message(message, _meta) do
    {:ok, typed} = HL7v2.parse(message, mode: :typed)
    msh = hd(typed.segments)
    {ack_msh, msa} = HL7v2.Ack.accept(msh)
    {:ok, HL7v2.Ack.encode({ack_msh, msa})}
  end
end

{:ok, _} = HL7v2.MLLP.Listener.start_link(port: 2575, handler: MyHandler)

# Client
{:ok, client} = HL7v2.MLLP.Client.start_link(host: "hl7.hospital.local", port: 2575)
{:ok, ack} = HL7v2.MLLP.Client.send_message(client, wire)

# TLS / mTLS
{:ok, _} = HL7v2.MLLP.Listener.start_link(
  port: 2576,
  handler: MyHandler,
  tls: HL7v2.MLLP.TLS.mutual_tls_options(certfile: "cert.pem", keyfile: "key.pem", cacertfile: "ca.pem")
)

Coverage

 Segments    152 standard + generic ZXX
              152 of 152 v2.5.1 segments (100%) + generic Z-segment pass-through
              115 fully typed, 37 with raw holes
              Run `mix hl7v2.coverage` for the full list

 Types       89 of 89 v2.5.1 data types (100%)

 Messages    ADT (A01-A04, A08, A12) ORM^O01 ORU^R01 SIU^S12 RDE^O11
              RDS^O13 MDM^T02 ACK — structural validation (order + groups + cardinality)

 Transport   MLLP framing, Ranch 2.x listener, GenServer client,
              TLS/mTLS, telemetry instrumentation

 Validation  structural (order/groups/cardinality) + opt-in table checking
              20 HL7 tables, 11 coded fields validated

 Speed       <1s full suite

Scope

HL7 v2.5.1 with permissive parsing of adjacent versions (v2.3 through v2.8.x).

• Every v2.5.1 segment and data type has a typed Elixir module
• Raw mode is lossless for all valid HL7v2 messages, including malformed input
• Typed mode preserves values it cannot parse (invalid dates, malformed numbers) in original fields for round-trip fidelity
• Extra fields beyond declared definitions are preserved in extra_fields
• Escape sequences are preserved literally in typed fields — call HL7v2.Escape.decode/2 when you need decoded text

Run mix hl7v2.coverage for detailed per-segment field completeness.

Handling Unknown Segments

Real-world HL7 is messy. Messages arrive with vendor-specific Z-segments, obsolete segments from older versions, and segments your system doesn't care about. The library handles all of them without crashing or losing data:

{:ok, msg} = HL7v2.parse(text, mode: :typed)

# Known segments → typed structs with named fields
%HL7v2.Segment.PID{patient_name: [%XPN{...}], ...}

# Z-segments → ZXX struct preserving segment ID and all raw fields
%HL7v2.Segment.ZXX{segment_id: "ZPD", raw_fields: ["custom", "data"]}

# Unknown segments from other versions → raw tuples, lossless
{"XYZ", ["1", "DATA001", ...]}

All three forms encode back to valid HL7 wire format. The typed API (get/2, fetch/2, ~h sigil) works across all forms — typed segments return struct fields with component and repetition selection, raw tuples return whole fields by position (component/repetition selectors are not applied to raw tuples).

This means you can parse any HL7 message from any source, work with the segments you understand, and forward the rest unchanged. No schema registration required.

Documentation

Full API docs: hexdocs.pm/hl7v2

Getting started guide included.

Part of the Balneario Healthcare Toolkit

Three pure-Elixir libraries covering the core protocol surface of healthcare IT. Zero NIFs. Built for production.

dicom parses and writes DICOM files. dimse moves them over the network via DIMSE-C/N services. hl7v2 handles the clinical messages (ADT, ORM, ORU) that trigger and contextualize imaging workflows.

Together they give Elixir the same healthcare protocol coverage that Java has with dcm4che + HAPI, or C++ with DCMTK — on the BEAM.

License

MIT — see LICENSE.