mirror of
https://github.com/shokinn/hosts-go.git
synced 2025-08-23 08:33:02 +00:00
feat(parser): Implement hosts file parser with intelligent formatting
- Added `internal/core/parser.go` for parsing hosts files, including: - Support for standard entries (IPv4, IPv6, multiple aliases, inline comments) - Handling of comments and disabled entries - Error recovery for malformed lines with warnings - Intelligent formatting with adaptive spacing and column alignment - Backup and atomic write operations for file safety test(parser): Add comprehensive tests for hosts file parsing - Created `tests/parser_test.go` with 54 test cases covering: - Standard entries and comments - Malformed lines and whitespace variations - Round-trip parsing to ensure format preservation - Backup functionality for hosts files docs(progress): Update project progress and next steps - Mark Phase 1 as complete and outline tasks for Phase 2 (TUI implementation) - Highlight completed features and testing coverage
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parent
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10 changed files with 1303 additions and 210 deletions
417
internal/core/parser.go
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417
internal/core/parser.go
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package core
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import (
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"bufio"
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"fmt"
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"net"
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"os"
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"path/filepath"
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"regexp"
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"strings"
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"time"
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)
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// ParseWarning represents a warning encountered during parsing
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type ParseWarning struct {
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Line int // Line number (1-based)
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Message string // Warning message
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}
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// FormattingStyle represents the detected formatting style of a hosts file
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type FormattingStyle struct {
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UseTabs bool // Whether to use tabs for separation
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SpacesPerTab int // Number of spaces per tab if using spaces
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IPWidth int // Width for IP column alignment
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HostWidth int // Width for hostname column alignment
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AlignComments bool // Whether to align comments
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}
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// DetectFormattingStyle analyzes the given lines to determine the formatting style
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func DetectFormattingStyle(lines []string) FormattingStyle {
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style := FormattingStyle{
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UseTabs: true,
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SpacesPerTab: 4,
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IPWidth: 15,
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HostWidth: 30,
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AlignComments: true,
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}
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tabCount, spaceCount := 0, 0
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spaceLengths := make(map[int]int)
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for _, line := range lines {
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// Skip empty lines and comments
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line = strings.TrimSpace(line)
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if line == "" || strings.HasPrefix(line, "#") {
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continue
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}
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if strings.Contains(line, "\t") {
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tabCount++
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} else {
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// Look for sequences of spaces between non-space characters
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spaceRegex := regexp.MustCompile(`\S\s{2,}\S`)
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if spaceRegex.MatchString(line) {
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spaceCount++
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// Find all space sequences and count their lengths
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allSpaces := regexp.MustCompile(`\s{2,}`)
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matches := allSpaces.FindAllString(line, -1)
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for _, match := range matches {
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spaceLengths[len(match)]++
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}
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}
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}
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}
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// Use spaces if more space-separated lines than tab-separated
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if spaceCount > tabCount {
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style.UseTabs = false
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// Find the greatest common divisor of all space lengths to detect the base unit
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if len(spaceLengths) > 0 {
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var lengths []int
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for length := range spaceLengths {
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if length >= 2 {
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lengths = append(lengths, length)
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}
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}
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if len(lengths) > 0 {
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gcd := lengths[0]
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for i := 1; i < len(lengths); i++ {
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gcd = findGCD(gcd, lengths[i])
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}
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// Use GCD as the base spacing unit, but ensure it's at least 2 and reasonable
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if gcd >= 2 && gcd <= 8 {
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style.SpacesPerTab = gcd
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} else if len(lengths) == 1 {
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// Single space length detected, use it directly
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style.SpacesPerTab = lengths[0]
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} else {
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style.SpacesPerTab = 4 // fallback
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}
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} else {
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style.SpacesPerTab = 4 // fallback
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}
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} else {
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style.SpacesPerTab = 4 // fallback
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}
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}
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return style
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}
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// findGCD finds the greatest common divisor of two integers
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func findGCD(a, b int) int {
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for b != 0 {
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a, b = b, a%b
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}
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return a
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}
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// ParseHostsFile reads and parses a hosts file from the filesystem
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func ParseHostsFile(filepath string) (*HostsFile, []ParseWarning, error) {
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file, err := os.Open(filepath)
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if err != nil {
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return nil, nil, fmt.Errorf("failed to open hosts file: %w", err)
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}
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defer file.Close()
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var lines []string
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scanner := bufio.NewScanner(file)
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for scanner.Scan() {
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lines = append(lines, scanner.Text())
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}
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if err := scanner.Err(); err != nil {
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return nil, nil, fmt.Errorf("failed to read hosts file: %w", err)
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}
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return ParseHostsContent(lines)
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}
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// ParseHostsContent parses hosts file content from a slice of lines
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func ParseHostsContent(lines []string) (*HostsFile, []ParseWarning, error) {
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hostsFile := NewHostsFile()
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var warnings []ParseWarning
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for lineNum, line := range lines {
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lineNum++ // Convert to 1-based indexing
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// Skip empty lines
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if strings.TrimSpace(line) == "" {
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continue
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}
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// Handle comments and disabled entries
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if strings.HasPrefix(strings.TrimSpace(line), "#") {
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if entry, warning := parseCommentLine(line, lineNum); entry != nil {
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hostsFile.AddEntry(entry)
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if warning != nil {
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warnings = append(warnings, *warning)
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}
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} else if comment := parseStandaloneComment(line); comment != "" {
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hostsFile.Comments = append(hostsFile.Comments, comment)
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}
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continue
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}
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// Parse regular entry
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entry, warning := parseEntryLine(line, lineNum)
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if entry != nil {
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hostsFile.AddEntry(entry)
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}
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if warning != nil {
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warnings = append(warnings, *warning)
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}
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}
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return hostsFile, warnings, nil
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}
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// parseCommentLine parses a commented line, which might be a disabled entry
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func parseCommentLine(line string, lineNum int) (*HostEntry, *ParseWarning) {
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// Remove the leading # and any whitespace
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content := strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(line), "#"))
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// Split by comment first to handle inline comments in disabled entries
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commentParts := strings.SplitN(content, "#", 2)
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entryPart := strings.TrimSpace(commentParts[0])
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var inlineComment string
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if len(commentParts) > 1 {
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inlineComment = strings.TrimSpace(commentParts[1])
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}
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// Try to parse as a disabled entry
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parts := regexp.MustCompile(`\s+`).Split(entryPart, -1)
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if len(parts) < 2 {
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return nil, nil // This is just a standalone comment
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}
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ip := strings.TrimSpace(parts[0])
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if net.ParseIP(ip) == nil {
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return nil, nil // Not a valid IP, treat as standalone comment
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}
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hostname := strings.TrimSpace(parts[1])
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if err := validateHostname(hostname); err != nil {
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warning := &ParseWarning{
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Line: lineNum,
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Message: fmt.Sprintf("invalid hostname in disabled entry: %v", err),
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}
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return nil, warning
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}
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// Create the entry
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entry := &HostEntry{
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IP: ip,
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Hostname: hostname,
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Aliases: make([]string, 0),
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Comment: inlineComment,
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Active: false, // Commented out = inactive
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Original: line,
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}
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// Parse aliases
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for i := 2; i < len(parts); i++ {
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alias := strings.TrimSpace(parts[i])
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if alias != "" {
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if err := validateHostname(alias); err == nil {
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entry.Aliases = append(entry.Aliases, alias)
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}
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}
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}
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return entry, nil
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}
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// parseStandaloneComment extracts a standalone comment
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func parseStandaloneComment(line string) string {
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content := strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(line), "#"))
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return content
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}
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// parseEntryLine parses a regular (non-commented) entry line
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func parseEntryLine(line string, lineNum int) (*HostEntry, *ParseWarning) {
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// Split by comment first
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parts := strings.SplitN(line, "#", 2)
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entryPart := strings.TrimSpace(parts[0])
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var comment string
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if len(parts) > 1 {
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comment = strings.TrimSpace(parts[1])
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}
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// Split the entry part by whitespace
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fields := regexp.MustCompile(`\s+`).Split(entryPart, -1)
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if len(fields) < 2 {
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return nil, &ParseWarning{
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Line: lineNum,
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Message: "missing hostname",
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}
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}
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ip := strings.TrimSpace(fields[0])
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if net.ParseIP(ip) == nil {
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return nil, &ParseWarning{
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Line: lineNum,
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Message: fmt.Sprintf("invalid IP address: %s", ip),
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}
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}
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hostname := strings.TrimSpace(fields[1])
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if err := validateHostname(hostname); err != nil {
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return nil, &ParseWarning{
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Line: lineNum,
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Message: fmt.Sprintf("invalid hostname: %v", err),
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}
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}
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entry := &HostEntry{
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IP: ip,
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Hostname: hostname,
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Aliases: make([]string, 0),
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Comment: comment,
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Active: true,
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Original: line,
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}
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// Parse aliases
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for i := 2; i < len(fields); i++ {
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alias := strings.TrimSpace(fields[i])
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if alias != "" {
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if err := validateHostname(alias); err == nil {
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entry.Aliases = append(entry.Aliases, alias)
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}
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}
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}
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return entry, nil
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}
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// FormatHostsFile formats a hosts file with intelligent formatting
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func FormatHostsFile(hostsFile *HostsFile) []string {
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var lines []string
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// Add standalone comments first (treating them as header comments)
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for _, comment := range hostsFile.Comments {
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lines = append(lines, "# "+comment)
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}
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// Calculate column widths for alignment
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ipWidth, hostWidth := calculateColumnWidths(hostsFile.Entries)
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// Format entries
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for _, entry := range hostsFile.Entries {
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line := formatEntry(entry, ipWidth, hostWidth)
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lines = append(lines, line)
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}
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return lines
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}
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// calculateColumnWidths determines optimal column widths for alignment
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func calculateColumnWidths(entries []*HostEntry) (int, int) {
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maxIPWidth := 10
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maxHostWidth := 15
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for _, entry := range entries {
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if len(entry.IP) > maxIPWidth {
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maxIPWidth = len(entry.IP)
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}
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if len(entry.Hostname) > maxHostWidth {
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maxHostWidth = len(entry.Hostname)
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}
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}
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return maxIPWidth + 2, maxHostWidth + 2
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}
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// formatEntry formats a single entry with intelligent alignment
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func formatEntry(entry *HostEntry, ipWidth, hostWidth int) string {
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var parts []string
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// Format IP address with padding
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parts = append(parts, fmt.Sprintf("%-*s", ipWidth, entry.IP))
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// Format hostname with padding
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parts = append(parts, fmt.Sprintf("%-*s", hostWidth, entry.Hostname))
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// Add aliases
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for _, alias := range entry.Aliases {
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parts = append(parts, alias)
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}
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line := strings.Join(parts, "\t")
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// Add comment if present
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if entry.Comment != "" {
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line += "\t# " + entry.Comment
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}
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// Add comment prefix if inactive
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if !entry.Active {
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line = "# " + line
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}
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return line
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}
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// WriteHostsFile writes a hosts file to the filesystem with intelligent formatting
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func WriteHostsFile(filepath string, hostsFile *HostsFile) error {
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// Create backup before writing
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if _, err := BackupHostsFile(filepath); err != nil {
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return fmt.Errorf("failed to create backup: %w", err)
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}
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// Format the content
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lines := FormatHostsFile(hostsFile)
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content := strings.Join(lines, "\n") + "\n"
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// Write to temporary file first for atomic operation
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tmpPath := filepath + ".tmp"
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if err := os.WriteFile(tmpPath, []byte(content), 0644); err != nil {
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return fmt.Errorf("failed to write temporary file: %w", err)
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}
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// Atomic move
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if err := os.Rename(tmpPath, filepath); err != nil {
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os.Remove(tmpPath) // Clean up temp file
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return fmt.Errorf("failed to replace hosts file: %w", err)
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}
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return nil
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}
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// BackupHostsFile creates a backup of the hosts file
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func BackupHostsFile(hostsPath string) (string, error) {
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// Create config directory
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homeDir, err := os.UserHomeDir()
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if err != nil {
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return "", fmt.Errorf("failed to get home directory: %w", err)
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}
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configDir := filepath.Join(homeDir, ".config", "hosts-go")
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if err := os.MkdirAll(configDir, 0755); err != nil {
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return "", fmt.Errorf("failed to create config directory: %w", err)
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}
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// Create backup filename with timestamp
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timestamp := time.Now().Format("20060102-150405")
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backupPath := filepath.Join(configDir, fmt.Sprintf("hosts.backup.%s", timestamp))
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// Copy the file
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content, err := os.ReadFile(hostsPath)
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if err != nil {
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return "", fmt.Errorf("failed to read original hosts file: %w", err)
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}
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if err := os.WriteFile(backupPath, content, 0644); err != nil {
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return "", fmt.Errorf("failed to write backup file: %w", err)
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}
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return backupPath, nil
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}
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