A Golang module to specify edifact document formats and to read from io.Reader into user-defined data structures. Inspired by json.Unmarshal and xml.Unmarshal.

Install with go get

go get github.com/shogg/edifact

Document specifications are written as go source code: Msg defines a message, S a segment and SG a segment group (a loop). "UNA" is a segment tag. C and M stand for conditional or mandatory. The last number specifies maximal repetitions.

The notation is derived from here (example): https://service.unece.org/trade/untdid/d96a/trmd/desadv_s.htm

import "github.com/shogg/edifact/spec"

var desadv = spec.Msg("DESADV",
	spec.S("UNA", spec.C, 1),
	spec.S("UNB", spec.C, 1),
	spec.S("UNH", spec.M, 1),
	spec.S("BGM", spec.M, 1),
	spec.S("DTM", spec.C, 10),
	spec.S("ALI", spec.C, 5),
	spec.S("MEA", spec.C, 5),
	spec.S("MOA", spec.C, 5),
	spec.SG("SG1", spec.C, 10,
		spec.S("RFF", spec.M, 1),
		spec.S("DTM", spec.C, 1),
	),
[..]

A specification must be registered. This can be done anywhere. For instance in the main function or in an init function:

func init() {
	spec.Add(desadv)
}

Currently only struct is supported (and array, slice and pointer of struct). The tag of a struct field specifies where data is located in an edifact document. All annotated information must match to make segment data suitable (segment groups, segment tag, fixed data in elements). A question mark ? annotates the relevant data element separated by :. The type of the target value decides how to parse. Simple data types are implemented, more complex ones need to implement edifact.Marshaller. A star * annotates a composite of elements, an edifact.Marshaller is needed to parse. If no ? or * is present, the edifact.Marshaller will receive the full segment with tag and terminator.

Arrays and slices in a struct can specify a segment group path like this edifact:"SG10/SG17". Each time a segment group repeats in the edifact data a new array/slice element is inserted.

type Message struct {
	Date       time.Time `edifact:"DTM+17|18"`
	DeliveryNr string    `edifact:"SG1/RFF+VN|DQ+?"`
	OrderNr    int       `edifact:"SG1/RFF+ON+?"`
	Items      []Item    `edifact:"SG10/SG17"`
}
type Item struct {
	ItemNr      int    `edifact:"SG10/SG17/LIN+?"`
	Description string `edifact:"SG10/SG17/LIN+++?"`
	Quantity    int    `edifact:"SG10/SG17/QTY+12:?"`
}

Out of the box only simple data types (string, int, bool ... ) and time.Time are parseable. A user defined type can implement edifact.Unmarshaller to provide its own parsing.

// Unmarshaller interface for custom data type parsing.
type Unmarshaller interface {
	UnmarshalEdifact(data []byte) error
}

The top level API is edifact.Unmarshal. You provide an io.Reader and a pointer to your data structure to be filled. Here is a complete example. It uses the built-in document specification "DESADV" so no doc spec here:

package main

import (
	"fmt"
	"strings"
	"time"

	"github.com/shogg/edifact"
)

var ediMessage = `
UNA:+.? '
UNB+UNOC:3+sender+receiver+060620:0931+1++1234567'
UNH+1+DESADV:D:96A:UN'
BGM+220+B10001'
DTM+17:20060620:102'
RFF+ON+1'
RFF+DQ+2'
NAD+BY+++name+street+city++23436+xx'
CPS+'
LIN+1++product A:SA'
QTY+12:10'
LIN+2++product B:SA'
QTY+12:20'
CNT+2:1'
UNT+9+1'`

type Message struct {
	Date       time.Time `edifact:"DTM+17|18"`
	DeliveryNr string    `edifact:"SG1/RFF+VN|DQ+?"`
	OrderNr    int       `edifact:"SG1/RFF+ON+?"`
	Items      []Item    `edifact:"SG10/SG17"`
}
type Item struct {
	ItemNr      int    `edifact:"SG10/SG17/LIN+?"`
	Description string `edifact:"SG10/SG17/LIN+++?"`
	Quantity    int    `edifact:"SG10/SG17/QTY+12:?"`
}

func main() {
	document := strings.NewReader(ediMessage)
	var messages []*Message
	if err := edifact.Unmarshal(document, &messages); err != nil {
		panic(err)
	}
	fmt.Println("number of messages", len(messages))
}

• meta characters are fixed to UNA:+.? '
• UNA, UNB don't get evaluated
• time.Time can only parse DTM formats 101, 102, 201-204
• only ORDERS and DESADV are included atm but you can register your own specs
• multiple message format versions are not supported atm
• max. segment repetitions is part of the spec but is ignored atm

Contributions are welcome.