add kerio format support

internal/csvimport/csvimport.go

@@ -1,9 +1,11 @@
 package csvimport
 
 import (
+	"bufio"
 	"encoding/csv"
 	"fmt"
 	"io"
+	"regexp"
 	"strings"
 )
 
@@ -52,3 +54,110 @@ func Parse(r io.Reader) ([]Row, error) {
 	}
 	return rows, nil
 }
+
+// Kerio Connect exports users as a semicolon-separated file whose first line is
+// a header. Only these columns matter; the rest (quotas, last login, …) is
+// ignored. The file carries no domain — the caller supplies it.
+const (
+	kerioColName        = 0 // login without the domain part
+	kerioColDescription = 2 // Kerio keeps the plaintext password here
+	kerioColEnable      = 3 // "Yes" / "No"
+	kerioMinColumns     = 4
+)
+
+// domainRe accepts a bare DNS domain: labels of alphanumerics/hyphens with at
+// least one dot and no scheme, user part, or whitespace.
+var domainRe = regexp.MustCompile(`^[a-z0-9]([a-z0-9-]*[a-z0-9])?(\.[a-z0-9]([a-z0-9-]*[a-z0-9])?)+$`)
+
+func normalizeDomain(domain string) (string, error) {
+	d := strings.ToLower(strings.TrimSpace(domain))
+	if d == "" {
+		return "", fmt.Errorf("domain is required")
+	}
+	if !domainRe.MatchString(d) {
+		return "", fmt.Errorf("invalid domain %q", domain)
+	}
+	return d, nil
+}
+
+// skipBOM consumes a leading UTF-8 byte-order mark, which Kerio writes into its
+// exports and encoding/csv would otherwise glue onto the first header field.
+func skipBOM(br *bufio.Reader) error {
+	b, err := br.Peek(3)
+	if err != nil && err != io.EOF {
+		return err
+	}
+	if len(b) == 3 && b[0] == 0xEF && b[1] == 0xBB && b[2] == 0xBF {
+		_, _ = br.Discard(3)
+	}
+	return nil
+}
+
+// ParseKerio reads a Kerio Connect user export and maps every enabled, non-admin
+// account onto both sides of a migration: the login and password are identical
+// on source and destination, only the server differs. Rows for disabled accounts
+// and the built-in admin are skipped.
+func ParseKerio(r io.Reader, domain string) ([]Row, error) {
+	d, err := normalizeDomain(domain)
+	if err != nil {
+		return nil, err
+	}
+
+	br := bufio.NewReader(r)
+	if err := skipBOM(br); err != nil {
+		return nil, err
+	}
+
+	cr := csv.NewReader(br)
+	cr.Comma = ';'
+	cr.FieldsPerRecord = -1 // проверяем сами
+	cr.LazyQuotes = true    // FullName нередко содержит одиночную кавычку
+
+	header, err := cr.Read()
+	if err != nil {
+		return nil, fmt.Errorf("cannot read header: %w", err)
+	}
+	if len(header) < kerioMinColumns || !strings.EqualFold(strings.TrimSpace(header[kerioColName]), "Name") {
+		return nil, fmt.Errorf("not a Kerio export: expected a header starting with Name;FullName;Description;Enable")
+	}
+
+	var rows []Row
+	seen := map[string]bool{}
+	for {
+		rec, err := cr.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		line, _ := cr.FieldPos(0)
+		if len(rec) == 1 && strings.TrimSpace(rec[0]) == "" {
+			continue
+		}
+		if len(rec) < kerioMinColumns {
+			return nil, fmt.Errorf("line %d: expected at least %d columns, got %d", line, kerioMinColumns, len(rec))
+		}
+		name := strings.ToLower(strings.TrimSpace(rec[kerioColName]))
+		if name == "" {
+			return nil, fmt.Errorf("line %d: Name is empty", line)
+		}
+		if !strings.EqualFold(strings.TrimSpace(rec[kerioColEnable]), "Yes") || name == "admin" {
+			continue
+		}
+		pass := strings.TrimSpace(rec[kerioColDescription])
+		if pass == "" {
+			return nil, fmt.Errorf("line %d: no password in the Description column for %q", line, name)
+		}
+		if seen[name] {
+			return nil, fmt.Errorf("line %d: duplicate Name %q", line, name)
+		}
+		seen[name] = true
+		login := name + "@" + d
+		rows = append(rows, Row{SrcLogin: login, SrcPass: pass, DstLogin: login, DstPass: pass})
+	}
+	if len(rows) == 0 {
+		return nil, fmt.Errorf("no enabled accounts found in the export")
+	}
+	return rows, nil
+}