package notes

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"verstak/internal/core/files"
	"verstak/internal/core/nodes"
	"verstak/internal/core/storage"
	"verstak/internal/core/templates"
	"verstak/internal/core/util"
)

// NotesFolder is the canonical name for the notes subdirectory inside a case/project.
const NotesFolder = "Notes"

// noteFileRoot returns the absolute path to the notes subdirectory for a given parent.
// For parentless notes it returns <vaultRoot>/Notes.
func noteFileRoot(vaultRoot, parentFsPath string) string {
	if parentFsPath != "" {
		return filepath.Join(vaultRoot, parentFsPath, NotesFolder)
	}
	return filepath.Join(vaultRoot, NotesFolder)
}

// assertContained verifies that targetPath is strictly under rootDir.
// It resolves symlinks in the target path to prevent symlink-based escapes.
// Returns an error if targetPath escapes rootDir via .. or symlinks.
func assertContained(rootDir, targetPath string) error {
	cleanRoot := filepath.Clean(rootDir)
	cleanTarget := filepath.Clean(targetPath)

	// Resolve symlinks in the target path to get the real path.
	// If the path doesn't exist yet (e.g. for Create), we resolve as much
	// as possible and check the unresolved remainder separately.
	resolvedTarget, err := filepath.EvalSymlinks(cleanTarget)
	if err != nil {
		// Path doesn't exist — resolve the parent directory instead.
		dir := filepath.Dir(cleanTarget)
		resolvedDir, dirErr := filepath.EvalSymlinks(dir)
		if dirErr != nil {
			// Parent doesn't exist either — fall back to Clean-based check.
			rel, relErr := filepath.Rel(cleanRoot, cleanTarget)
			if relErr != nil {
				return fmt.Errorf("path containment check failed: %w", relErr)
			}
			if strings.HasPrefix(rel, "..") {
				return fmt.Errorf("path %q escapes root %q", cleanTarget, cleanRoot)
			}
			return nil
		}
		// Reconstruct target with resolved parent + original base name.
		resolvedTarget = filepath.Join(resolvedDir, filepath.Base(cleanTarget))
	}

	rel, err := filepath.Rel(cleanRoot, resolvedTarget)
	if err != nil {
		return fmt.Errorf("path containment check failed: %w", err)
	}
	if strings.HasPrefix(rel, "..") {
		return fmt.Errorf("path %q (resolved: %q) escapes root %q", cleanTarget, resolvedTarget, cleanRoot)
	}
	return nil
}

// Record represents a note entry (links a node to a file).
type Record struct {
	NodeID    string `json:"node_id"`
	FileID    string `json:"file_id"`
	Format    string `json:"format"`
	Encrypted bool   `json:"encrypted"`
}

// Service handles markdown notes.
type Service struct {
	db        *storage.DB
	vaultRoot string
	nodes     *nodes.Repository
	files     *files.Service
}

// NewService creates a note service.
func NewService(db *storage.DB, vaultRoot string, nodeRepo *nodes.Repository, fileSvc *files.Service) *Service {
	return &Service{db: db, vaultRoot: vaultRoot, nodes: nodeRepo, files: fileSvc}
}

// Create makes a new note node, an empty .md file, and links them.
func (s *Service) Create(parentID, title, section string) (*nodes.Node, *files.Record, error) {
	node, err := s.nodes.Create(strPtr(parentID), nodes.TypeNote, title, 0, "", "")
	if err != nil {
		return nil, nil, fmt.Errorf("create node: %w", err)
	}

	seg := templates.SafeDisplayNameToPathSegment(title)
	if seg == "" {
		seg = "note"
	}
	filename := seg + ".md"

	// Determine the canonical notes directory
	var parentFsPath string
	if parentID != "" {
		parent, err := s.nodes.GetActive(parentID)
		if err == nil && parent.FsPath != "" {
			parentFsPath = parent.FsPath
		}
	}
	destDir := noteFileRoot(s.vaultRoot, parentFsPath)

	if err := os.MkdirAll(destDir, 0o750); err != nil {
		return nil, nil, fmt.Errorf("mkdir: %w", err)
	}

	dest := filepath.Join(destDir, filename)

	// Path containment check: the resolved file must stay under destDir
	if err := assertContained(destDir, dest); err != nil {
		return nil, nil, err
	}

	if _, err := os.Stat(dest); err == nil {
		filename = fmt.Sprintf("%s_%s.md", seg, node.ID[:8])
		dest = filepath.Join(destDir, filename)
		// Re-check containment after rename
		if err := assertContained(destDir, dest); err != nil {
			return nil, nil, err
		}
	}

	if err := os.WriteFile(dest, []byte("# "+title+"\n\n"), 0o640); err != nil {
		return nil, nil, fmt.Errorf("write: %w", err)
	}

	relPath, _ := filepath.Rel(s.vaultRoot, dest)
	fileRec, err := insertFileRecord(s.db, node.ID, filename, relPath, "vault", 0)
	if err != nil {
		return nil, nil, fmt.Errorf("insert file: %w", err)
	}

	_, err = s.db.Exec(
		`INSERT INTO notes (node_id, file_id, format) VALUES (?,?,?)`,
		node.ID, fileRec.ID, "markdown")
	if err != nil {
		return nil, nil, fmt.Errorf("link note: %w", err)
	}
	return node, fileRec, nil
}

// Read returns the content of a note.
func (s *Service) Read(nodeID string) (string, error) {
	var filePath, storageMode string
	err := s.db.QueryRow(
		`SELECT f.path, f.storage_mode
		 FROM notes n JOIN files f ON n.file_id = f.id
		 WHERE n.node_id = ?`, nodeID).Scan(&filePath, &storageMode)
	if err != nil {
		return "", fmt.Errorf("query note: %w", err)
	}

	var abs string
	if storageMode == "vault" {
		abs = filepath.Join(s.vaultRoot, filePath)
	} else {
		abs = filePath
	}
	data, err := os.ReadFile(abs)
	if err != nil {
		return "", fmt.Errorf("read: %w", err)
	}
	return string(data), nil
}

// Save writes new content, backing up the old version.
func (s *Service) Save(nodeID, content string) error {
	var filePath, storageMode string
	err := s.db.QueryRow(
		`SELECT f.path, f.storage_mode
		 FROM notes n JOIN files f ON n.file_id = f.id
		 WHERE n.node_id = ?`, nodeID).Scan(&filePath, &storageMode)
	if err != nil {
		return fmt.Errorf("query: %w", err)
	}

	var abs string
	if storageMode == "vault" {
		abs = filepath.Join(s.vaultRoot, filePath)
	} else {
		abs = filePath
	}

	// Backup old version.
	if info, err := os.Stat(abs); err == nil && info.Size() > 0 {
		histDir := filepath.Join(s.vaultRoot, ".verstak", "history")
		os.MkdirAll(histDir, 0o750)
		name := filepath.Base(abs)
		backup := filepath.Join(histDir,
			fmt.Sprintf("%s_%d.bak", name, time.Now().Unix()))
		os.WriteFile(backup, mustRead(abs), 0o640)
	}

	if err := os.WriteFile(abs, []byte(content), 0o640); err != nil {
		return fmt.Errorf("write: %w", err)
	}

	// Update file size.
	info, _ := os.Stat(abs)
	size := int64(0)
	if info != nil {
		size = info.Size()
	}
	_, err = s.db.Exec(
		`UPDATE files SET size=?, updated_at=? WHERE path=? AND storage_mode=?`,
		size, utcNow(), filePath, storageMode)
	return err
}

// Delete soft-deletes the note node and moves the backing .md file to the
// shared vault trash directory (<vault>/.verstak/trash/) using the same
// trashRecord mechanism as files.DeleteNodeAndChildren. This ensures the
// deleted note appears in the unified Trash UI and can be restored/permanently
// deleted through the existing trash workflow.
func (s *Service) Delete(nodeID string) error {
	// Load the note record to find the file.
	rec, err := s.Load(nodeID)
	if err != nil {
		return fmt.Errorf("load note: %w", err)
	}

	// Get the full file record for trashRecord.
	fileRec, err := s.files.Get(rec.FileID)
	if err != nil {
		return fmt.Errorf("get file record: %w", err)
	}

	// Soft-delete the node first.
	if err := s.nodes.SoftDelete(nodeID); err != nil {
		return fmt.Errorf("soft-delete node: %w", err)
	}

	// Move the .md file to the shared trash using the existing trashRecord.
	// This places the file in <vault>/.verstak/trash/<fileID>_<filename>
	// and marks the file record as missing=1 so it can be restored later.
	if err := s.files.TrashFile(fileRec); err != nil {
		return fmt.Errorf("trash file: %w", err)
	}

	return nil
}

// Rename changes the note title and renames the backing .md file on disk.
// If a file with the target name already exists, the operation is rejected.
func (s *Service) Rename(nodeID, newTitle string) error {
	if err := s.nodes.UpdateTitle(nodeID, newTitle); err != nil {
		return fmt.Errorf("update title: %w", err)
	}

	// Load the note record to find the file.
	rec, err := s.Load(nodeID)
	if err != nil {
		return fmt.Errorf("load note: %w", err)
	}

	// Get the current file record.
	var oldPath, oldFilename, storageMode string
	err = s.db.QueryRow(
		`SELECT path, filename, storage_mode FROM files WHERE id = ?`, rec.FileID,
	).Scan(&oldPath, &oldFilename, &storageMode)
	if err != nil {
		return fmt.Errorf("query file: %w", err)
	}

	// Build old and new absolute paths.
	var oldAbs string
	if storageMode == "vault" {
		oldAbs = filepath.Join(s.vaultRoot, oldPath)
	} else {
		oldAbs = oldPath
	}
	oldDir := filepath.Dir(oldAbs)

	seg := templates.SafeDisplayNameToPathSegment(newTitle)
	if seg == "" {
		seg = "note"
	}
	newFilename := seg + ".md"
	newAbs := filepath.Join(oldDir, newFilename)

	// Collision check: reject if target exists and is different from source.
	if newAbs != oldAbs {
		if _, err := os.Stat(newAbs); err == nil {
			return fmt.Errorf("file %q already exists", newFilename)
		}
		if err := os.Rename(oldAbs, newAbs); err != nil {
			return fmt.Errorf("rename file: %w", err)
		}
		// Update file record.
		newRel, _ := filepath.Rel(s.vaultRoot, newAbs)
		_, err = s.db.Exec(
			`UPDATE files SET filename=?, path=?, updated_at=? WHERE id=?`,
			newFilename, newRel, utcNow(), rec.FileID,
		)
		if err != nil {
			return fmt.Errorf("update file record: %w", err)
		}
	}

	return nil
}

// Load looks up the note record for a node.
func (s *Service) Load(nodeID string) (*Record, error) {
	var rec Record
	var enc int
	err := s.db.QueryRow(
		`SELECT node_id, file_id, format, encrypted FROM notes WHERE node_id=?`, nodeID,
	).Scan(&rec.NodeID, &rec.FileID, &rec.Format, &enc)
	if err != nil {
		return nil, err
	}
	rec.Encrypted = enc == 1
	return &rec, nil
}

// --- helpers ---

func insertFileRecord(db *storage.DB, nodeID, filename, relPath, mode string, size int64) (*files.Record, error) {
	rec := &files.Record{
		ID:          util.UUID7(),
		NodeID:      nodeID,
		Filename:    filename,
		Path:        relPath,
		StorageMode: mode,
		Size:        size,
		MIME:        "text/plain",
		CreatedAt:   time.Now().UTC(),
		UpdatedAt:   time.Now().UTC(),
	}
	_, err := db.Exec(
		`INSERT INTO files (id,node_id,filename,path,storage_mode,size,mime,
			created_at,updated_at,missing)
		 VALUES (?,?,?,?,?,?,?,?,?,0)`,
		rec.ID, rec.NodeID, rec.Filename, rec.Path, rec.StorageMode,
		rec.Size, rec.MIME,
		rec.CreatedAt.Format(time.RFC3339), rec.UpdatedAt.Format(time.RFC3339))
	if err != nil {
		return nil, err
	}
	return rec, nil
}

func mustRead(path string) []byte {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil
	}
	return data
}

func utcNow() string {
	return time.Now().UTC().Format(time.RFC3339)
}

func strPtr(s string) *string {
	if s == "" {
		return nil
	}
	return &s
}