// Package supportbundle creates bounded, redacted diagnostic archives without
// accepting arbitrary source paths from API clients.
package supportbundle

import (
	"archive/zip"
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"tera-clone/services/tera-api/internal/storage/atomicfile"
)

const (
	defaultMaxArtifacts = 4
	defaultMaxBytes     = 8 * 1024 * 1024
	defaultMaxSection   = 2 * 1024 * 1024
	maxSections         = 16
)

type Options struct {
	Directory    string
	MaxArtifacts int
	MaxBytes     int
	MaxSection   int
}

type Section struct {
	Name  string
	Value any
}

type CreateRequest struct {
	BundleID    string
	GeneratedAt time.Time
	Sections    []Section
}

type Artifact struct {
	BundleID  string
	Filename  string
	SizeBytes int
	SHA256    string
	Sections  []string
	Content   []byte
}

type Service interface {
	Create(context.Context, CreateRequest) (Artifact, error)
	Read(context.Context, string) (Artifact, error)
}

type Manager struct {
	directory    string
	maxArtifacts int
	maxBytes     int
	maxSection   int
	mu           sync.Mutex
}

func NewManager(options Options) (*Manager, error) {
	if options.Directory == "" || !filepath.IsAbs(options.Directory) {
		return nil, errors.New("support bundle directory must be an absolute path")
	}
	if options.MaxArtifacts == 0 {
		options.MaxArtifacts = defaultMaxArtifacts
	}
	if options.MaxBytes == 0 {
		options.MaxBytes = defaultMaxBytes
	}
	if options.MaxSection == 0 {
		options.MaxSection = defaultMaxSection
	}
	if options.MaxArtifacts < 1 || options.MaxArtifacts > 32 {
		return nil, errors.New("support bundle max artifacts must be between 1 and 32")
	}
	if options.MaxBytes < 64*1024 || options.MaxBytes > 64*1024*1024 {
		return nil, errors.New("support bundle max bytes must be between 65536 and 67108864")
	}
	if options.MaxSection < 1024 || options.MaxSection > options.MaxBytes {
		return nil, errors.New("support bundle max section must be between 1024 and max bytes")
	}
	return &Manager{
		directory:    filepath.Clean(options.Directory),
		maxArtifacts: options.MaxArtifacts,
		maxBytes:     options.MaxBytes,
		maxSection:   options.MaxSection,
	}, nil
}

func (m *Manager) Create(ctx context.Context, request CreateRequest) (Artifact, error) {
	if err := validateBundleID(request.BundleID); err != nil {
		return Artifact{}, err
	}
	if request.GeneratedAt.IsZero() {
		return Artifact{}, errors.New("support bundle generated time is required")
	}
	if len(request.Sections) == 0 || len(request.Sections) > maxSections {
		return Artifact{}, fmt.Errorf("support bundle must contain between 1 and %d sections", maxSections)
	}
	if err := ctx.Err(); err != nil {
		return Artifact{}, err
	}

	m.mu.Lock()
	defer m.mu.Unlock()
	if err := ensureDirectory(m.directory); err != nil {
		return Artifact{}, err
	}
	filename := request.BundleID + ".zip"
	artifactPath := filepath.Join(m.directory, filename)
	if _, err := os.Lstat(artifactPath); err == nil {
		return Artifact{}, errors.New("support bundle artifact already exists")
	} else if !os.IsNotExist(err) {
		return Artifact{}, fmt.Errorf("inspect support bundle artifact: %w", err)
	}

	content, sectionNames, err := m.build(ctx, request)
	if err != nil {
		return Artifact{}, err
	}
	if err := atomicfile.Write(artifactPath, content, 0o600); err != nil {
		return Artifact{}, fmt.Errorf("persist support bundle: %w", err)
	}
	if err := m.trimLocked(); err != nil {
		return Artifact{}, err
	}
	digest := sha256.Sum256(content)
	return Artifact{
		BundleID: request.BundleID, Filename: filename, SizeBytes: len(content),
		SHA256: hex.EncodeToString(digest[:]), Sections: sectionNames,
	}, nil
}

func (m *Manager) Read(ctx context.Context, bundleID string) (Artifact, error) {
	if err := validateBundleID(bundleID); err != nil {
		return Artifact{}, err
	}
	if err := ctx.Err(); err != nil {
		return Artifact{}, err
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if err := ensureDirectory(m.directory); err != nil {
		return Artifact{}, err
	}
	filename := bundleID + ".zip"
	file, err := os.Open(filepath.Join(m.directory, filename))
	if err != nil {
		if os.IsNotExist(err) {
			return Artifact{}, errors.New("support bundle not found")
		}
		return Artifact{}, fmt.Errorf("open support bundle: %w", err)
	}
	defer file.Close()
	info, err := file.Stat()
	if err != nil {
		return Artifact{}, fmt.Errorf("inspect support bundle: %w", err)
	}
	if !info.Mode().IsRegular() || info.Size() < 1 || info.Size() > int64(m.maxBytes) {
		return Artifact{}, errors.New("support bundle artifact is not a bounded regular file")
	}
	content, err := io.ReadAll(io.LimitReader(file, int64(m.maxBytes)+1))
	if err != nil {
		return Artifact{}, fmt.Errorf("read support bundle: %w", err)
	}
	if len(content) > m.maxBytes {
		return Artifact{}, errors.New("support bundle artifact exceeds the configured limit")
	}
	digest := sha256.Sum256(content)
	return Artifact{
		BundleID: bundleID, Filename: filename, SizeBytes: len(content),
		SHA256: hex.EncodeToString(digest[:]), Content: content,
	}, nil
}

func (m *Manager) build(ctx context.Context, request CreateRequest) ([]byte, []string, error) {
	sectionNames := make([]string, 0, len(request.Sections))
	sectionContent := make(map[string][]byte, len(request.Sections))
	seen := make(map[string]bool, len(request.Sections))
	totalSectionBytes := 0
	for _, section := range request.Sections {
		if err := ctx.Err(); err != nil {
			return nil, nil, err
		}
		if err := validateSectionName(section.Name); err != nil {
			return nil, nil, err
		}
		if seen[section.Name] {
			return nil, nil, fmt.Errorf("support bundle section %q is duplicated", section.Name)
		}
		seen[section.Name] = true
		content, err := json.MarshalIndent(section.Value, "", "  ")
		if err != nil {
			return nil, nil, fmt.Errorf("encode support bundle section %q: %w", section.Name, err)
		}
		content = append(content, '\n')
		if len(content) > m.maxSection {
			return nil, nil, fmt.Errorf("support bundle section %q exceeds the configured limit", section.Name)
		}
		totalSectionBytes += len(content)
		if totalSectionBytes > m.maxBytes {
			return nil, nil, errors.New("support bundle sections exceed the configured aggregate limit")
		}
		sectionNames = append(sectionNames, section.Name)
		sectionContent[section.Name] = content
	}
	sort.Strings(sectionNames)
	manifest := struct {
		FormatVersion int       `json:"format_version"`
		BundleID      string    `json:"bundle_id"`
		GeneratedAt   time.Time `json:"generated_at"`
		Sections      []string  `json:"sections"`
	}{FormatVersion: 1, BundleID: request.BundleID, GeneratedAt: request.GeneratedAt.UTC(), Sections: sectionNames}
	manifestContent, err := json.MarshalIndent(manifest, "", "  ")
	if err != nil {
		return nil, nil, err
	}
	manifestContent = append(manifestContent, '\n')

	var buffer bytes.Buffer
	archive := zip.NewWriter(&buffer)
	if err := writeZipEntry(archive, "manifest.json", manifestContent, request.GeneratedAt); err != nil {
		return nil, nil, err
	}
	for _, name := range sectionNames {
		if err := writeZipEntry(archive, name, sectionContent[name], request.GeneratedAt); err != nil {
			return nil, nil, err
		}
		if buffer.Len() > m.maxBytes {
			_ = archive.Close()
			return nil, nil, errors.New("support bundle artifact exceeds the configured limit")
		}
	}
	if err := archive.Close(); err != nil {
		return nil, nil, fmt.Errorf("finalize support bundle: %w", err)
	}
	if buffer.Len() > m.maxBytes {
		return nil, nil, errors.New("support bundle artifact exceeds the configured limit")
	}
	return buffer.Bytes(), sectionNames, nil
}

func writeZipEntry(archive *zip.Writer, name string, content []byte, modified time.Time) error {
	header := &zip.FileHeader{Name: name, Method: zip.Deflate}
	header.SetMode(0o600)
	header.SetModTime(modified.UTC())
	entry, err := archive.CreateHeader(header)
	if err != nil {
		return fmt.Errorf("create support bundle entry %q: %w", name, err)
	}
	if _, err := entry.Write(content); err != nil {
		return fmt.Errorf("write support bundle entry %q: %w", name, err)
	}
	return nil
}

func (m *Manager) trimLocked() error {
	entries, err := os.ReadDir(m.directory)
	if err != nil {
		return fmt.Errorf("list support bundles: %w", err)
	}
	names := make([]string, 0, len(entries))
	for _, entry := range entries {
		name := entry.Name()
		if entry.Type().IsRegular() && strings.HasPrefix(name, "support_bundle_") && strings.HasSuffix(name, ".zip") {
			names = append(names, name)
		}
	}
	sort.Strings(names)
	for len(names) > m.maxArtifacts {
		if err := os.Remove(filepath.Join(m.directory, names[0])); err != nil {
			return fmt.Errorf("remove expired support bundle: %w", err)
		}
		names = names[1:]
	}
	return nil
}

func ensureDirectory(directory string) error {
	if info, err := os.Lstat(directory); err == nil {
		if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
			return errors.New("support bundle directory must be a real directory")
		}
	} else if os.IsNotExist(err) {
		if err := os.MkdirAll(directory, 0o700); err != nil {
			return fmt.Errorf("create support bundle directory: %w", err)
		}
	} else {
		return fmt.Errorf("inspect support bundle directory: %w", err)
	}
	if err := os.Chmod(directory, 0o700); err != nil {
		return fmt.Errorf("protect support bundle directory: %w", err)
	}
	return nil
}

func validateBundleID(value string) error {
	if len(value) != len("support_bundle_20060102_000000") || !strings.HasPrefix(value, "support_bundle_") {
		return errors.New("support bundle id is invalid")
	}
	date := value[len("support_bundle_") : len("support_bundle_")+8]
	if _, err := time.Parse("20060102", date); err != nil {
		return errors.New("support bundle id is invalid")
	}
	if value[len("support_bundle_")+8] != '_' {
		return errors.New("support bundle id is invalid")
	}
	for _, char := range value[len(value)-6:] {
		if char < '0' || char > '9' {
			return errors.New("support bundle id is invalid")
		}
	}
	return nil
}

func validateSectionName(value string) error {
	if len(value) < 6 || len(value) > 64 || !strings.HasSuffix(value, ".json") || strings.ContainsAny(value, `/\\`) {
		return errors.New("support bundle section name is invalid")
	}
	for _, char := range strings.TrimSuffix(value, ".json") {
		if (char >= 'a' && char <= 'z') || (char >= '0' && char <= '9') || char == '-' {
			continue
		}
		return errors.New("support bundle section name is invalid")
	}
	return nil
}