Add Phase 2 TUI improvements: disk space checks and error hints

- Created internal/checks package for disk space and error classification
- CheckDiskSpace(): Real-time disk usage detection (80% warning, 95% critical)
- CheckDiskSpaceForRestore(): 4x archive size requirement calculation
- ClassifyError(): Smart error classification (ignorable/warning/critical/fatal)
- FormatErrorWithHint(): User-friendly error messages with actionable solutions
- Integrated disk checks into backup/restore workflows with pre-flight validation
- Error hints for: lock exhaustion, disk full, syntax errors, permissions, connections
- Blocks operations at 95% disk usage, warns at 80%

internal/checks/disk_check.go

@@ -0,0 +1,161 @@
+package checks
+
+import (
+	"fmt"
+	"path/filepath"
+	"syscall"
+)
+
+// DiskSpaceCheck represents disk space information
+type DiskSpaceCheck struct {
+	Path           string
+	TotalBytes     uint64
+	AvailableBytes uint64
+	UsedBytes      uint64
+	UsedPercent    float64
+	Sufficient     bool
+	Warning        bool
+	Critical       bool
+}
+
+// CheckDiskSpace checks available disk space for a given path
+func CheckDiskSpace(path string) *DiskSpaceCheck {
+	// Get absolute path
+	absPath, err := filepath.Abs(path)
+	if err != nil {
+		absPath = path
+	}
+
+	// Get filesystem stats
+	var stat syscall.Statfs_t
+	if err := syscall.Statfs(absPath, &stat); err != nil {
+		// Return error state
+		return &DiskSpaceCheck{
+			Path:       absPath,
+			Critical:   true,
+			Sufficient: false,
+		}
+	}
+
+	// Calculate space
+	totalBytes := stat.Blocks * uint64(stat.Bsize)
+	availableBytes := stat.Bavail * uint64(stat.Bsize)
+	usedBytes := totalBytes - availableBytes
+	usedPercent := float64(usedBytes) / float64(totalBytes) * 100
+
+	check := &DiskSpaceCheck{
+		Path:           absPath,
+		TotalBytes:     totalBytes,
+		AvailableBytes: availableBytes,
+		UsedBytes:      usedBytes,
+		UsedPercent:    usedPercent,
+	}
+
+	// Determine status thresholds
+	check.Critical = usedPercent >= 95
+	check.Warning = usedPercent >= 80 && !check.Critical
+	check.Sufficient = !check.Critical && !check.Warning
+
+	return check
+}
+
+// CheckDiskSpaceForRestore checks if there's enough space for restore (needs 4x archive size)
+func CheckDiskSpaceForRestore(path string, archiveSize int64) *DiskSpaceCheck {
+	check := CheckDiskSpace(path)
+	requiredBytes := uint64(archiveSize) * 4 // Account for decompression
+	
+	// Override status based on required space
+	if check.AvailableBytes < requiredBytes {
+		check.Critical = true
+		check.Sufficient = false
+		check.Warning = false
+	} else if check.AvailableBytes < requiredBytes*2 {
+		check.Warning = true
+		check.Sufficient = false
+	}
+	
+	return check
+}
+
+// FormatDiskSpaceMessage creates a user-friendly disk space message
+func FormatDiskSpaceMessage(check *DiskSpaceCheck) string {
+	var status string
+	var icon string
+
+	if check.Critical {
+		status = "CRITICAL"
+		icon = "❌"
+	} else if check.Warning {
+		status = "WARNING"
+		icon = "⚠️ "
+	} else {
+		status = "OK"
+		icon = "✓"
+	}
+
+	msg := fmt.Sprintf(`📊 Disk Space Check (%s):
+   Path: %s
+   Total: %s
+   Available: %s (%.1f%% used)
+   %s Status: %s`,
+		status,
+		check.Path,
+		formatBytes(check.TotalBytes),
+		formatBytes(check.AvailableBytes),
+		check.UsedPercent,
+		icon,
+		status)
+
+	if check.Critical {
+		msg += "\n   \n   ⚠️  CRITICAL: Insufficient disk space!"
+		msg += "\n   Operation blocked. Free up space before continuing."
+	} else if check.Warning {
+		msg += "\n   \n   ⚠️  WARNING: Low disk space!"
+		msg += "\n   Backup may fail if database is larger than estimated."
+	} else {
+		msg += "\n   \n   ✓ Sufficient space available"
+	}
+
+	return msg
+}
+
+// EstimateBackupSize estimates backup size based on database size
+func EstimateBackupSize(databaseSize uint64, compressionLevel int) uint64 {
+	// Typical compression ratios:
+	// Level 0 (no compression): 1.0x
+	// Level 1-3 (fast): 0.4-0.6x
+	// Level 4-6 (balanced): 0.3-0.4x
+	// Level 7-9 (best): 0.2-0.3x
+
+	var compressionRatio float64
+	if compressionLevel == 0 {
+		compressionRatio = 1.0
+	} else if compressionLevel <= 3 {
+		compressionRatio = 0.5
+	} else if compressionLevel <= 6 {
+		compressionRatio = 0.35
+	} else {
+		compressionRatio = 0.25
+	}
+
+	estimated := uint64(float64(databaseSize) * compressionRatio)
+
+	// Add 10% buffer for metadata, indexes, etc.
+	return uint64(float64(estimated) * 1.1)
+}
+
+
+
+// formatBytes formats bytes to human-readable format
+func formatBytes(bytes uint64) string {
+	const unit = 1024
+	if bytes < unit {
+		return fmt.Sprintf("%d B", bytes)
+	}
+	div, exp := uint64(unit), 0
+	for n := bytes / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %ciB", float64(bytes)/float64(div), "KMGTPE"[exp])
+}