/*
Vulnerability Scanner — Scan container rootfs and CAS references for known
vulnerabilities using the OSV (Open Source Vulnerabilities) API.

Supports:
  - Debian/Ubuntu (dpkg status file)
  - Alpine (apk installed db)
  - RHEL/Fedora/Rocky (rpm query via librpm or rpm binary)

Copyright (c) Armored Gates LLC. All rights reserved.
*/
package security

import (
	"bufio"
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/armoredgate/volt/pkg/storage"
)

// ── Types ────────────────────────────────────────────────────────────────────

// Package represents an installed package detected in a rootfs.
type Package struct {
	Name    string
	Version string
	Source  string // "dpkg", "apk", "rpm"
}

// VulnResult represents a single vulnerability finding.
type VulnResult struct {
	ID         string   // CVE ID or OSV ID (e.g., "CVE-2024-1234" or "GHSA-xxxx")
	Package    string   // Affected package name
	Version    string   // Installed version
	FixedIn    string   // Version that fixes it, or "" if no fix available
	Severity   string   // CRITICAL, HIGH, MEDIUM, LOW, UNKNOWN
	Summary    string   // Short description
	References []string // URLs for more info
}

// ScanReport is the result of scanning a rootfs for vulnerabilities.
type ScanReport struct {
	Target       string        // Image or container name
	OS           string        // Detected OS (e.g., "Alpine Linux 3.19")
	Ecosystem    string        // OSV ecosystem (e.g., "Alpine", "Debian")
	PackageCount int           // Total packages scanned
	Vulns        []VulnResult  // Found vulnerabilities
	ScanTime     time.Duration // Wall-clock time for the scan
}

// ── Severity Helpers ─────────────────────────────────────────────────────────

// severityRank maps severity strings to an integer for sorting/filtering.
var severityRank = map[string]int{
	"CRITICAL": 4,
	"HIGH":     3,
	"MEDIUM":   2,
	"LOW":      1,
	"UNKNOWN":  0,
}

// SeverityAtLeast returns true if sev is at or above the given threshold.
func SeverityAtLeast(sev, threshold string) bool {
	return severityRank[strings.ToUpper(sev)] >= severityRank[strings.ToUpper(threshold)]
}

// ── Counts ───────────────────────────────────────────────────────────────────

// VulnCounts holds per-severity counts.
type VulnCounts struct {
	Critical int
	High     int
	Medium   int
	Low      int
	Unknown  int
	Total    int
}

// CountBySeverity tallies vulnerabilities by severity level.
func (r *ScanReport) CountBySeverity() VulnCounts {
	var c VulnCounts
	for _, v := range r.Vulns {
		switch strings.ToUpper(v.Severity) {
		case "CRITICAL":
			c.Critical++
		case "HIGH":
			c.High++
		case "MEDIUM":
			c.Medium++
		case "LOW":
			c.Low++
		default:
			c.Unknown++
		}
	}
	c.Total = len(r.Vulns)
	return c
}

// ── OS Detection ─────────────────────────────────────────────────────────────

// DetectOS reads /etc/os-release from rootfsPath and returns (prettyName, ecosystem, error).
// The ecosystem is mapped to the OSV ecosystem name.
func DetectOS(rootfsPath string) (string, string, error) {
	osRelPath := filepath.Join(rootfsPath, "etc", "os-release")
	f, err := os.Open(osRelPath)
	if err != nil {
		return "", "", fmt.Errorf("detect OS: %w", err)
	}
	defer f.Close()
	return parseOSRelease(f)
}

// parseOSRelease parses an os-release formatted reader.
func parseOSRelease(r io.Reader) (string, string, error) {
	var prettyName, id, versionID string

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		parts := strings.SplitN(line, "=", 2)
		if len(parts) != 2 {
			continue
		}

		key := parts[0]
		val := strings.Trim(parts[1], `"'`)

		switch key {
		case "PRETTY_NAME":
			prettyName = val
		case "ID":
			id = val
		case "VERSION_ID":
			versionID = val
		}
	}

	if err := scanner.Err(); err != nil {
		return "", "", fmt.Errorf("parse os-release: %w", err)
	}

	if prettyName == "" {
		if id != "" {
			prettyName = id
			if versionID != "" {
				prettyName += " " + versionID
			}
		} else {
			return "", "", fmt.Errorf("detect OS: no PRETTY_NAME or ID found in os-release")
		}
	}

	ecosystem := mapIDToEcosystem(id, versionID)
	return prettyName, ecosystem, nil
}

// mapIDToEcosystem maps /etc/os-release ID to OSV ecosystem.
func mapIDToEcosystem(id, versionID string) string {
	switch strings.ToLower(id) {
	case "alpine":
		return "Alpine"
	case "debian":
		return "Debian"
	case "ubuntu":
		return "Ubuntu"
	case "rocky":
		return "Rocky Linux"
	case "rhel", "centos", "fedora":
		return "Rocky Linux" // best-effort mapping
	case "sles", "opensuse-leap", "opensuse-tumbleweed", "suse":
		return "SUSE"
	default:
		return "Linux" // fallback
	}
}

// ── Package Listing ──────────────────────────────────────────────────────────

// ListPackages detects the package manager and extracts installed packages
// from the rootfs at rootfsPath.
func ListPackages(rootfsPath string) ([]Package, error) {
	var pkgs []Package
	var err error

	// Try dpkg (Debian/Ubuntu)
	dpkgStatus := filepath.Join(rootfsPath, "var", "lib", "dpkg", "status")
	if fileExists(dpkgStatus) {
		pkgs, err = parseDpkgStatus(dpkgStatus)
		if err != nil {
			return nil, fmt.Errorf("list packages (dpkg): %w", err)
		}
		return pkgs, nil
	}

	// Try apk (Alpine)
	apkInstalled := filepath.Join(rootfsPath, "lib", "apk", "db", "installed")
	if fileExists(apkInstalled) {
		pkgs, err = parseApkInstalled(apkInstalled)
		if err != nil {
			return nil, fmt.Errorf("list packages (apk): %w", err)
		}
		return pkgs, nil
	}

	// Try rpm (RHEL/Rocky/Fedora)
	rpmDB := filepath.Join(rootfsPath, "var", "lib", "rpm")
	if dirExists(rpmDB) {
		pkgs, err = parseRpmDB(rootfsPath)
		if err != nil {
			return nil, fmt.Errorf("list packages (rpm): %w", err)
		}
		return pkgs, nil
	}

	return nil, fmt.Errorf("no supported package manager found in rootfs (checked dpkg, apk, rpm)")
}

// ── dpkg parser ──────────────────────────────────────────────────────────────

// parseDpkgStatus parses /var/lib/dpkg/status to extract installed packages.
func parseDpkgStatus(path string) ([]Package, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return parseDpkgStatusReader(f)
}

// parseDpkgStatusReader parses a dpkg status file from a reader.
func parseDpkgStatusReader(r io.Reader) ([]Package, error) {
	var pkgs []Package
	var current Package
	inPackage := false

	scanner := bufio.NewScanner(r)
	// Increase buffer for potentially long Description fields
	scanner.Buffer(make([]byte, 0, 1024*1024), 1024*1024)

	for scanner.Scan() {
		line := scanner.Text()

		// Empty line separates package entries
		if strings.TrimSpace(line) == "" {
			if inPackage && current.Name != "" && current.Version != "" {
				current.Source = "dpkg"
				pkgs = append(pkgs, current)
			}
			current = Package{}
			inPackage = false
			continue
		}

		// Skip continuation lines (start with space/tab)
		if len(line) > 0 && (line[0] == ' ' || line[0] == '\t') {
			continue
		}

		parts := strings.SplitN(line, ": ", 2)
		if len(parts) != 2 {
			continue
		}

		key := parts[0]
		val := parts[1]

		switch key {
		case "Package":
			current.Name = val
			inPackage = true
		case "Version":
			current.Version = val
		case "Status":
			// Only include installed packages
			if !strings.Contains(val, "installed") || strings.Contains(val, "not-installed") {
				inPackage = false
			}
		}
	}

	// Don't forget the last entry if file doesn't end with blank line
	if inPackage && current.Name != "" && current.Version != "" {
		current.Source = "dpkg"
		pkgs = append(pkgs, current)
	}

	return pkgs, scanner.Err()
}

// ── apk parser ───────────────────────────────────────────────────────────────

// parseApkInstalled parses /lib/apk/db/installed to extract installed packages.
func parseApkInstalled(path string) ([]Package, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return parseApkInstalledReader(f)
}

// parseApkInstalledReader parses an Alpine apk installed DB from a reader.
// Format: blocks separated by blank lines. P = package name, V = version.
func parseApkInstalledReader(r io.Reader) ([]Package, error) {
	var pkgs []Package
	var current Package

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()

		if strings.TrimSpace(line) == "" {
			if current.Name != "" && current.Version != "" {
				current.Source = "apk"
				pkgs = append(pkgs, current)
			}
			current = Package{}
			continue
		}

		if len(line) < 2 || line[1] != ':' {
			continue
		}

		key := line[0]
		val := line[2:]

		switch key {
		case 'P':
			current.Name = val
		case 'V':
			current.Version = val
		}
	}

	// Last entry
	if current.Name != "" && current.Version != "" {
		current.Source = "apk"
		pkgs = append(pkgs, current)
	}

	return pkgs, scanner.Err()
}

// ── rpm parser ───────────────────────────────────────────────────────────────

// parseRpmDB queries the RPM database in the rootfs using the rpm binary.
func parseRpmDB(rootfsPath string) ([]Package, error) {
	// Try using rpm command with --root
	rpmBin, err := exec.LookPath("rpm")
	if err != nil {
		return nil, fmt.Errorf("rpm binary not found (needed to query RPM database): %w", err)
	}

	cmd := exec.Command(rpmBin, "--root", rootfsPath, "-qa", "--queryformat", "%{NAME}\\t%{VERSION}-%{RELEASE}\\n")
	out, err := cmd.Output()
	if err != nil {
		return nil, fmt.Errorf("rpm query failed: %w", err)
	}

	return parseRpmOutput(out)
}

// parseRpmOutput parses tab-separated name\tversion output from rpm -qa.
func parseRpmOutput(data []byte) ([]Package, error) {
	var pkgs []Package
	scanner := bufio.NewScanner(bytes.NewReader(data))
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" {
			continue
		}
		parts := strings.SplitN(line, "\t", 2)
		if len(parts) != 2 {
			continue
		}
		pkgs = append(pkgs, Package{
			Name:    parts[0],
			Version: parts[1],
			Source:  "rpm",
		})
	}
	return pkgs, scanner.Err()
}

// ── OSV API ──────────────────────────────────────────────────────────────────

const (
	osvQueryURL      = "https://api.osv.dev/v1/query"
	osvQueryBatchURL = "https://api.osv.dev/v1/querybatch"
	osvBatchLimit    = 1000 // max queries per batch
	osvHTTPTimeout   = 30 * time.Second
)

// osvQueryRequest is a single OSV query.
type osvQueryRequest struct {
	Package *osvPackage `json:"package"`
	Version string      `json:"version"`
}

type osvPackage struct {
	Name      string `json:"name"`
	Ecosystem string `json:"ecosystem"`
}

// osvBatchRequest wraps multiple queries.
type osvBatchRequest struct {
	Queries []osvQueryRequest `json:"queries"`
}

// osvBatchResponse contains results for a batch query.
type osvBatchResponse struct {
	Results []osvQueryResponse `json:"results"`
}

// osvQueryResponse is the response for a single query.
type osvQueryResponse struct {
	Vulns []osvVuln `json:"vulns"`
}

// osvVuln represents a vulnerability from the OSV API.
type osvVuln struct {
	ID       string `json:"id"`
	Summary  string `json:"summary"`
	Details  string `json:"details"`
	Severity []struct {
		Type  string `json:"type"`
		Score string `json:"score"`
	} `json:"severity"`
	DatabaseSpecific json.RawMessage `json:"database_specific"`
	Affected         []struct {
		Package struct {
			Name      string `json:"name"`
			Ecosystem string `json:"ecosystem"`
		} `json:"package"`
		Ranges []struct {
			Type   string `json:"type"`
			Events []struct {
				Introduced string `json:"introduced,omitempty"`
				Fixed      string `json:"fixed,omitempty"`
			} `json:"events"`
		} `json:"ranges"`
	} `json:"affected"`
	References []struct {
		Type string `json:"type"`
		URL  string `json:"url"`
	} `json:"references"`
}

// QueryOSV queries the OSV API for vulnerabilities affecting the given package.
func QueryOSV(ecosystem, pkg, version string) ([]VulnResult, error) {
	return queryOSVWithClient(http.DefaultClient, ecosystem, pkg, version)
}

func queryOSVWithClient(client *http.Client, ecosystem, pkg, version string) ([]VulnResult, error) {
	reqBody := osvQueryRequest{
		Package: &osvPackage{
			Name:      pkg,
			Ecosystem: ecosystem,
		},
		Version: version,
	}

	data, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("osv query marshal: %w", err)
	}

	req, err := http.NewRequest("POST", osvQueryURL, bytes.NewReader(data))
	if err != nil {
		return nil, fmt.Errorf("osv query: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("osv query: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("osv query: HTTP %d: %s", resp.StatusCode, string(body))
	}

	var osvResp osvQueryResponse
	if err := json.NewDecoder(resp.Body).Decode(&osvResp); err != nil {
		return nil, fmt.Errorf("osv query decode: %w", err)
	}

	return convertOSVVulns(osvResp.Vulns, pkg, version), nil
}

// QueryOSVBatch queries the OSV batch endpoint for multiple packages at once.
func QueryOSVBatch(ecosystem string, pkgs []Package) (map[string][]VulnResult, error) {
	return queryOSVBatchWithClient(&http.Client{Timeout: osvHTTPTimeout}, ecosystem, pkgs)
}

func queryOSVBatchWithClient(client *http.Client, ecosystem string, pkgs []Package) (map[string][]VulnResult, error) {
	return queryOSVBatchWithURL(client, ecosystem, pkgs, osvQueryBatchURL)
}

// queryOSVBatchWithURL is the internal implementation that accepts a custom URL (for testing).
func queryOSVBatchWithURL(client *http.Client, ecosystem string, pkgs []Package, batchURL string) (map[string][]VulnResult, error) {
	results := make(map[string][]VulnResult)

	// Process in batches of osvBatchLimit
	for i := 0; i < len(pkgs); i += osvBatchLimit {
		end := i + osvBatchLimit
		if end > len(pkgs) {
			end = len(pkgs)
		}
		batch := pkgs[i:end]

		var queries []osvQueryRequest
		for _, p := range batch {
			queries = append(queries, osvQueryRequest{
				Package: &osvPackage{
					Name:      p.Name,
					Ecosystem: ecosystem,
				},
				Version: p.Version,
			})
		}

		batchReq := osvBatchRequest{Queries: queries}
		data, err := json.Marshal(batchReq)
		if err != nil {
			return nil, fmt.Errorf("osv batch marshal: %w", err)
		}

		req, err := http.NewRequest("POST", batchURL, bytes.NewReader(data))
		if err != nil {
			return nil, fmt.Errorf("osv batch: %w", err)
		}
		req.Header.Set("Content-Type", "application/json")

		resp, err := client.Do(req)
		if err != nil {
			return nil, fmt.Errorf("osv batch: %w", err)
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			body, _ := io.ReadAll(resp.Body)
			return nil, fmt.Errorf("osv batch: HTTP %d: %s", resp.StatusCode, string(body))
		}

		var batchResp osvBatchResponse
		if err := json.NewDecoder(resp.Body).Decode(&batchResp); err != nil {
			return nil, fmt.Errorf("osv batch decode: %w", err)
		}

		// Map results back to packages
		for j, qr := range batchResp.Results {
			if j >= len(batch) {
				break
			}
			pkg := batch[j]
			vulns := convertOSVVulns(qr.Vulns, pkg.Name, pkg.Version)
			if len(vulns) > 0 {
				key := pkg.Name + "@" + pkg.Version
				results[key] = append(results[key], vulns...)
			}
		}
	}

	return results, nil
}

// convertOSVVulns converts OSV API vulnerability objects to our VulnResult type.
func convertOSVVulns(vulns []osvVuln, pkgName, pkgVersion string) []VulnResult {
	var results []VulnResult
	seen := make(map[string]bool)

	for _, v := range vulns {
		if seen[v.ID] {
			continue
		}
		seen[v.ID] = true

		result := VulnResult{
			ID:      v.ID,
			Package: pkgName,
			Version: pkgVersion,
			Summary: v.Summary,
		}

		// Extract severity
		result.Severity = extractSeverity(v)

		// Extract fixed version
		result.FixedIn = extractFixedVersion(v, pkgName)

		// Extract references
		for _, ref := range v.References {
			result.References = append(result.References, ref.URL)
		}

		results = append(results, result)
	}

	return results
}

// extractSeverity tries to determine severity from OSV data.
func extractSeverity(v osvVuln) string {
	// Try CVSS score from severity array
	for _, s := range v.Severity {
		if s.Type == "CVSS_V3" || s.Type == "CVSS_V2" {
			return cvssToSeverity(s.Score)
		}
	}

	// Try database_specific.severity
	if len(v.DatabaseSpecific) > 0 {
		var dbSpec map[string]interface{}
		if json.Unmarshal(v.DatabaseSpecific, &dbSpec) == nil {
			if sev, ok := dbSpec["severity"].(string); ok {
				return normalizeSeverity(sev)
			}
		}
	}

	// Heuristic from ID prefix
	id := strings.ToUpper(v.ID)
	if strings.HasPrefix(id, "CVE-") {
		return "UNKNOWN" // Can't determine from ID alone
	}

	return "UNKNOWN"
}

// cvssToSeverity converts a CVSS vector string to a severity category.
// It extracts the base score from CVSS v3 vectors.
func cvssToSeverity(cvss string) string {
	// CVSS v3 vectors look like: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
	// We need to parse the actual score, but the vector alone doesn't contain it.
	// For CVSS_V3 type, the score field might be the vector string or a numeric score.

	// Try parsing as a float (some APIs return the numeric score)
	var score float64
	if _, err := fmt.Sscanf(cvss, "%f", &score); err == nil {
		switch {
		case score >= 9.0:
			return "CRITICAL"
		case score >= 7.0:
			return "HIGH"
		case score >= 4.0:
			return "MEDIUM"
		case score > 0:
			return "LOW"
		}
	}

	// If it's a vector string, use heuristics
	upper := strings.ToUpper(cvss)
	if strings.Contains(upper, "AV:N") && strings.Contains(upper, "AC:L") {
		// Network accessible, low complexity — likely at least HIGH
		if strings.Contains(upper, "/C:H/I:H/A:H") {
			return "CRITICAL"
		}
		return "HIGH"
	}

	return "UNKNOWN"
}

// normalizeSeverity normalizes various severity labels to our standard set.
func normalizeSeverity(sev string) string {
	switch strings.ToUpper(strings.TrimSpace(sev)) {
	case "CRITICAL":
		return "CRITICAL"
	case "HIGH", "IMPORTANT":
		return "HIGH"
	case "MEDIUM", "MODERATE":
		return "MEDIUM"
	case "LOW", "NEGLIGIBLE", "UNIMPORTANT":
		return "LOW"
	default:
		return "UNKNOWN"
	}
}

// extractFixedVersion finds the fixed version from affected ranges.
func extractFixedVersion(v osvVuln, pkgName string) string {
	for _, affected := range v.Affected {
		if affected.Package.Name != pkgName {
			continue
		}
		for _, r := range affected.Ranges {
			for _, event := range r.Events {
				if event.Fixed != "" {
					return event.Fixed
				}
			}
		}
	}
	// Try any affected entry if package name didn't match exactly
	for _, affected := range v.Affected {
		for _, r := range affected.Ranges {
			for _, event := range r.Events {
				if event.Fixed != "" {
					return event.Fixed
				}
			}
		}
	}
	return ""
}

// ── Main Scan Functions ──────────────────────────────────────────────────────

// ScanRootfs scans a rootfs directory for vulnerabilities by detecting the OS,
// listing installed packages, and querying the OSV API.
func ScanRootfs(rootfsPath string) (*ScanReport, error) {
	return ScanRootfsWithTarget(rootfsPath, filepath.Base(rootfsPath))
}

// ScanRootfsWithTarget scans a rootfs with a custom target name for the report.
func ScanRootfsWithTarget(rootfsPath, targetName string) (*ScanReport, error) {
	start := time.Now()

	report := &ScanReport{
		Target: targetName,
	}

	// Verify rootfs exists
	if !dirExists(rootfsPath) {
		return nil, fmt.Errorf("rootfs path does not exist: %s", rootfsPath)
	}

	// Detect OS
	osName, ecosystem, err := DetectOS(rootfsPath)
	if err != nil {
		return nil, fmt.Errorf("scan: %w", err)
	}
	report.OS = osName
	report.Ecosystem = ecosystem

	// List installed packages
	pkgs, err := ListPackages(rootfsPath)
	if err != nil {
		return nil, fmt.Errorf("scan: %w", err)
	}
	report.PackageCount = len(pkgs)

	if len(pkgs) == 0 {
		report.ScanTime = time.Since(start)
		return report, nil
	}

	// Query OSV batch API
	vulnMap, err := QueryOSVBatch(ecosystem, pkgs)
	if err != nil {
		return nil, fmt.Errorf("scan: osv query failed: %w", err)
	}

	// Collect all vulnerabilities
	for _, vulns := range vulnMap {
		report.Vulns = append(report.Vulns, vulns...)
	}

	// Sort by severity (critical first)
	sort.Slice(report.Vulns, func(i, j int) bool {
		ri := severityRank[report.Vulns[i].Severity]
		rj := severityRank[report.Vulns[j].Severity]
		if ri != rj {
			return ri > rj
		}
		return report.Vulns[i].ID < report.Vulns[j].ID
	})

	report.ScanTime = time.Since(start)
	return report, nil
}

// ScanCASRef scans a CAS reference by assembling it to a temporary directory,
// scanning, and cleaning up.
func ScanCASRef(casStore *storage.CASStore, ref string) (*ScanReport, error) {
	tv := storage.NewTinyVol(casStore, "")

	// Load the manifest
	bm, err := casStore.LoadManifest(ref)
	if err != nil {
		return nil, fmt.Errorf("scan cas ref: %w", err)
	}

	// Assemble to a temp directory
	tmpDir, err := os.MkdirTemp("", "volt-scan-*")
	if err != nil {
		return nil, fmt.Errorf("scan cas ref: create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	_, err = tv.Assemble(bm, tmpDir)
	if err != nil {
		return nil, fmt.Errorf("scan cas ref: assemble: %w", err)
	}

	// Scan the assembled rootfs
	report, err := ScanRootfsWithTarget(tmpDir, ref)
	if err != nil {
		return nil, err
	}

	return report, nil
}

// ── Formatting ───────────────────────────────────────────────────────────────

// FormatReport formats a ScanReport as a human-readable string.
func FormatReport(r *ScanReport, minSeverity string) string {
	var b strings.Builder

	fmt.Fprintf(&b, "🔍 Scanning: %s\n", r.Target)
	fmt.Fprintf(&b, "  OS: %s\n", r.OS)
	fmt.Fprintf(&b, "  Packages: %d detected\n", r.PackageCount)
	fmt.Fprintln(&b)

	filtered := r.Vulns
	if minSeverity != "" {
		filtered = nil
		for _, v := range r.Vulns {
			if SeverityAtLeast(v.Severity, minSeverity) {
				filtered = append(filtered, v)
			}
		}
	}

	if len(filtered) == 0 {
		if minSeverity != "" {
			fmt.Fprintf(&b, "  No vulnerabilities found at %s severity or above.\n", strings.ToUpper(minSeverity))
		} else {
			fmt.Fprintln(&b, "  ✅ No vulnerabilities found.")
		}
	} else {
		for _, v := range filtered {
			fixInfo := fmt.Sprintf("(fixed in %s)", v.FixedIn)
			if v.FixedIn == "" {
				fixInfo = "(no fix available)"
			}
			fmt.Fprintf(&b, "  %-10s %-20s %s %s  %s\n",
				v.Severity, v.ID, v.Package, v.Version, fixInfo)
		}
	}

	fmt.Fprintln(&b)
	counts := r.CountBySeverity()
	fmt.Fprintf(&b, "  Summary: %d critical, %d high, %d medium, %d low (%d total)\n",
		counts.Critical, counts.High, counts.Medium, counts.Low, counts.Total)
	fmt.Fprintf(&b, "  Scan time: %.1fs\n", r.ScanTime.Seconds())

	return b.String()
}

// FormatReportJSON formats a ScanReport as JSON.
func FormatReportJSON(r *ScanReport) (string, error) {
	data, err := json.MarshalIndent(r, "", "  ")
	if err != nil {
		return "", err
	}
	return string(data), nil
}

// ── Helpers ──────────────────────────────────────────────────────────────────

func fileExists(path string) bool {
	_, err := os.Stat(path)
	return err == nil
}

func dirExists(path string) bool {
	info, err := os.Stat(path)
	return err == nil && info.IsDir()
}