error.go

// Copyright 2026 Joshua Jones <joshua.jones.software@gmail.com>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package hl7

import (
	"errors"
	"fmt"
)

// Sentinel errors for HL7 message parsing failures.
var (
	ErrMessageTooShort    = errors.New("hl7: message too short")
	ErrNoMSHSegment       = errors.New("hl7: message must begin with MSH segment")
	ErrInvalidMSH         = errors.New("hl7: malformed MSH segment header")
	ErrInvalidDelimiter   = errors.New("hl7: invalid delimiter character")
	ErrDuplicateDelimiter = errors.New("hl7: duplicate delimiter characters")
	ErrSegmentNotFound    = errors.New("hl7: segment not found")
	ErrFieldOutOfRange    = errors.New("hl7: field index out of range")
	ErrInvalidLocation    = errors.New("hl7: invalid location string")
	ErrMLLPFraming        = errors.New("hl7: invalid MLLP framing")
	ErrMLLPMissingEnd     = errors.New("hl7: MLLP end block not found")
	ErrMLLPMissingStart   = errors.New("hl7: MLLP start block not found")
	ErrBatchStructure     = errors.New("hl7: invalid batch structure")
	ErrMSHDelimiterField  = errors.New("hl7: cannot modify MSH-1 or MSH-2 (delimiter fields)")
	ErrDelimiterMismatch  = errors.New("hl7: delimiter mismatch between messages")
	ErrCannotDeleteMSH          = errors.New("hl7: cannot delete MSH segment")
	ErrInvalidADDContinuation   = errors.New("hl7: ADD cannot continue segment")
	ErrFrameTooLarge            = errors.New("hl7: MLLP frame exceeds maximum size")
)

// ParseError provides detailed context about a parsing failure.
type ParseError struct {
	Err      error
	Position int
	Context  string
}

func (e *ParseError) Error() string {
	if e.Context != "" {
		return fmt.Sprintf("%s at position %d: %s", e.Err, e.Position, e.Context)
	}
	return fmt.Sprintf("%s at position %d", e.Err, e.Position)
}

func (e *ParseError) Unwrap() error {
	return e.Err
}

func newParseError(err error, pos int, ctx string) *ParseError {
	return &ParseError{Err: err, Position: pos, Context: ctx}
}