Add text parser implementation for IP extraction from plain text files

parser/text.go

@@ -0,0 +1,160 @@
+package parser
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// TextExtract defines the function signature for extracting IP addresses from a text item.
+type TextExtract interface {
+	// Extract extracts an IP address from the given text line.
+	Extract(line string) (string, bool)
+}
+
+// defaultTextExtract is a default implementation of TextExtract.
+type defaultTextExtract struct {
+	// fieldIndexOne is the index of the field that contains the IP address.
+	fieldIndexOne uint8
+
+	// separator is the separator used to split the fields.
+	separator string
+}
+
+// Extract extracts an IP address from the given text line.
+// It returns the IP address and a boolean indicating whether the IP address was found.
+func (d *defaultTextExtract) Extract(line string) (string, bool) {
+	fields := strings.Split(line, d.separator)
+	if len(fields) <= int(d.fieldIndexOne) {
+		return "", false
+	}
+
+	return fields[d.fieldIndexOne], true
+}
+
+// intervalTextExtract is a TextExtract implementation that extracts an IP address range from a text line.
+type intervalTextExtract struct {
+	// fieldIndexOne specifies the index of the first field to extract from the split string.
+	// From this field, the IP address range will be extracted.
+	fieldIndexOne uint8
+
+	// fieldIndexTwo specifies the index of the second field to extract from the split string.
+	// This field will be used as the end of the IP address range.
+	fieldIndexTwo uint8
+
+	// separator specifies the separator used to split the fields.
+	separator string
+}
+
+// Extract extracts an IP address range from the given text line.
+// It returns the IP address range and a boolean indicating whether the IP address range was found.
+func (d *intervalTextExtract) Extract(line string) (string, bool) {
+	fields := strings.Split(line, d.separator)
+	if len(fields) <= int(d.fieldIndexOne) || len(fields) <= int(d.fieldIndexTwo) {
+		return "", false
+	}
+
+	return fields[d.fieldIndexOne] + "-" + fields[d.fieldIndexTwo], true
+}
+
+// cidrTextExtract is a TextExtract implementation that extracts an IP address range from a text line.
+type cidrTextExtract struct {
+	// fieldIndexOne is the index of the field that contains the IP address.
+	fieldIndexOne uint8
+
+	// fieldIndexTwo is the index of the field that contains the CIDR prefix length.
+	fieldIndexTwo uint8
+
+	// separator is the separator used to split the fields.
+	separator string
+}
+
+// Extract extracts an IP address range from the given text line.
+// It returns the IP address range and a boolean indicating whether the IP address range was found.
+func (d *cidrTextExtract) Extract(line string) (string, bool) {
+	fields := strings.Split(line, d.separator)
+	if len(fields) <= int(d.fieldIndexOne) || len(fields) <= int(d.fieldIndexTwo) {
+		return "", false
+	}
+	return fields[d.fieldIndexOne] + "/" + fields[d.fieldIndexTwo], true
+}
+
+// NewDefaultTextExtract creates a new default TextExtract instance.
+func NewDefaultTextExtract(fieldIndexOne uint8, separator string) TextExtract {
+	return &defaultTextExtract{
+		fieldIndexOne: fieldIndexOne,
+		separator:     separator,
+	}
+}
+
+// NewIntervalTextExtract creates a new TextExtract instance that extracts an IP address range.
+func NewIntervalTextExtract(fieldIndexOne uint8, fieldIndexTwo uint8, separator string) TextExtract {
+	return &intervalTextExtract{
+		fieldIndexOne: fieldIndexOne,
+		fieldIndexTwo: fieldIndexTwo,
+		separator:     separator,
+	}
+}
+
+// NewCIDRTextExtract creates a new TextExtract instance that extracts an IP address range.
+func NewCIDRTextExtract(fieldIndexOne uint8, fieldIndexTwo uint8, separator string) TextExtract {
+	return &cidrTextExtract{
+		fieldIndexOne: fieldIndexOne,
+		fieldIndexTwo: fieldIndexTwo,
+		separator:     separator,
+	}
+}
+
+// textParser is a parser implementation that reads text data from an io.Reader and extracts IP addresses.
+type textParser struct {
+	textExtract TextExtract
+}
+
+// NewText creates a new TextParser instance.
+func NewText(textExtract TextExtract) (Parser, error) {
+	if textExtract == nil || textExtract.Extract == nil {
+		return nil, fmt.Errorf("text extract is nil")
+	}
+
+	return &textParser{
+		textExtract: textExtract,
+	}, nil
+}
+
+// Parse reads text data from the given io.Reader and extracts IP addresses.
+func (p *textParser) Parse(body io.Reader, validator IPValidator, limit uint) (IPs, error) {
+	scanner := bufio.NewScanner(body)
+
+	buf := make([]byte, 0, 64*1024)
+	scanner.Buffer(buf, 1024*1024)
+
+	var ips IPs
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, ";") || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		ip, isFound := p.textExtract.Extract(line)
+		if !isFound {
+			continue
+		}
+
+		ip = strings.TrimSpace(ip)
+		if !validator.IsValid(ip) {
+			continue
+		}
+
+		ips = append(ips, ip)
+		if limit > 0 && uint(len(ips)) >= limit {
+			break
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("read response: %w", err)
+	}
+
+	return ips, nil
+}