package database

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"
	"time"

	"sneak.berlin/go/vaultik/internal/log"
	"sneak.berlin/go/vaultik/internal/types"
)

// FileRepository provides access to the files table, which stores file
// metadata (path, times, permissions, ownership, symlink targets).
type FileRepository struct {
	db *DB
}

// NewFileRepository creates a FileRepository backed by db.
func NewFileRepository(db *DB) *FileRepository {
	return &FileRepository{db: db}
}

// Create inserts or updates a file row (upsert on path), using tx when
// non-nil. The file's ID is generated when zero and updated from the
// database's RETURNING clause.
func (r *FileRepository) Create(ctx context.Context, tx *sql.Tx, file *File) error {
	// Generate UUID if not provided
	if file.ID.IsZero() {
		file.ID = types.NewFileID()
	}

	query := `
		INSERT INTO files (id, path, source_path, mtime, size, mode, uid, gid, link_target)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT(path) DO UPDATE SET
			source_path = excluded.source_path,
			mtime = excluded.mtime,
			size = excluded.size,
			mode = excluded.mode,
			uid = excluded.uid,
			gid = excluded.gid,
			link_target = excluded.link_target
		RETURNING id
	`

	var (
		idStr string
		err   error
	)

	if tx != nil {
		LogSQL("Execute", query,
			file.ID.String(), file.Path.String(), file.SourcePath.String(),
			file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID,
			file.LinkTarget.String())
		err = tx.QueryRowContext(ctx, query,
			file.ID.String(), file.Path.String(), file.SourcePath.String(),
			file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID,
			file.LinkTarget.String()).Scan(&idStr)
	} else {
		err = r.db.QueryRowWithLog(ctx, query,
			file.ID.String(), file.Path.String(), file.SourcePath.String(),
			file.MTime.Unix(), file.Size, file.Mode, file.UID, file.GID,
			file.LinkTarget.String()).Scan(&idStr)
	}

	if err != nil {
		return fmt.Errorf("inserting file: %w", err)
	}

	// Parse the returned ID
	file.ID, err = types.ParseFileID(idStr)
	if err != nil {
		return fmt.Errorf("parsing file ID: %w", err)
	}

	return nil
}

// GetByPath returns the file at the given path, or nil if the path is not
// in the index.
func (r *FileRepository) GetByPath(ctx context.Context, path string) (*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		WHERE path = ?
	`

	file, err := r.scanFile(r.db.conn.QueryRowContext(ctx, query, path))
	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil //nolint:nilnil // nil,nil signals not-found; callers check nil
	}

	if err != nil {
		return nil, fmt.Errorf("querying file: %w", err)
	}

	return file, nil
}

// GetByID retrieves a file by its UUID
func (r *FileRepository) GetByID(ctx context.Context, id types.FileID) (*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		WHERE id = ?
	`

	file, err := r.scanFile(r.db.conn.QueryRowContext(ctx, query, id.String()))
	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil //nolint:nilnil // nil,nil signals not-found; callers check nil
	}

	if err != nil {
		return nil, fmt.Errorf("querying file: %w", err)
	}

	return file, nil
}

// GetByPathTx returns the file at the given path within a transaction, or
// nil if the path is not in the index.
func (r *FileRepository) GetByPathTx(
	ctx context.Context, tx *sql.Tx, path string,
) (*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		WHERE path = ?
	`

	LogSQL("GetByPathTx QueryRowContext", query, path)
	file, err := r.scanFile(tx.QueryRowContext(ctx, query, path))
	LogSQL("GetByPathTx Scan complete", query, path)

	if errors.Is(err, sql.ErrNoRows) {
		return nil, nil //nolint:nilnil // nil,nil signals not-found; callers check nil
	}

	if err != nil {
		return nil, fmt.Errorf("querying file: %w", err)
	}

	return file, nil
}

// fileRowScanner abstracts *sql.Row and *sql.Rows for scanning a file row.
type fileRowScanner interface {
	Scan(dest ...any) error
}

// ListModifiedSince returns all files whose recorded mtime is at or after
// since, ordered by path.
func (r *FileRepository) ListModifiedSince(
	ctx context.Context, since time.Time,
) ([]*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		WHERE mtime >= ?
		ORDER BY path
	`

	rows, err := r.db.conn.QueryContext(ctx, query, since.Unix())
	if err != nil {
		return nil, fmt.Errorf("querying files: %w", err)
	}

	defer func() {
		err := rows.Close()
		if err != nil {
			Fatalf("failed to close rows: %v", err)
		}
	}()

	var files []*File

	for rows.Next() {
		file, err := r.scanFileRows(rows)
		if err != nil {
			return nil, fmt.Errorf("scanning file: %w", err)
		}

		files = append(files, file)
	}

	return files, rows.Err()
}

// Delete removes the file row at the given path, using tx when non-nil.
func (r *FileRepository) Delete(ctx context.Context, tx *sql.Tx, path string) error {
	query := `DELETE FROM files WHERE path = ?`

	var err error
	if tx != nil {
		_, err = tx.ExecContext(ctx, query, path)
	} else {
		_, err = r.db.ExecWithLog(ctx, query, path)
	}

	if err != nil {
		return fmt.Errorf("deleting file: %w", err)
	}

	return nil
}

// DeleteByID deletes a file by its UUID
func (r *FileRepository) DeleteByID(
	ctx context.Context, tx *sql.Tx, id types.FileID,
) error {
	query := `DELETE FROM files WHERE id = ?`

	var err error
	if tx != nil {
		_, err = tx.ExecContext(ctx, query, id.String())
	} else {
		_, err = r.db.ExecWithLog(ctx, query, id.String())
	}

	if err != nil {
		return fmt.Errorf("deleting file: %w", err)
	}

	return nil
}

// ListByPrefix returns all files whose path starts with prefix, ordered by
// path.
func (r *FileRepository) ListByPrefix(
	ctx context.Context, prefix string,
) ([]*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		WHERE path LIKE ? || '%'
		ORDER BY path
	`

	rows, err := r.db.conn.QueryContext(ctx, query, prefix)
	if err != nil {
		return nil, fmt.Errorf("querying files: %w", err)
	}

	defer func() {
		err := rows.Close()
		if err != nil {
			Fatalf("failed to close rows: %v", err)
		}
	}()

	var files []*File

	for rows.Next() {
		file, err := r.scanFileRows(rows)
		if err != nil {
			return nil, fmt.Errorf("scanning file: %w", err)
		}

		files = append(files, file)
	}

	return files, rows.Err()
}

// ListAll returns all files in the database
func (r *FileRepository) ListAll(ctx context.Context) ([]*File, error) {
	query := `
		SELECT id, path, source_path, mtime, size, mode, uid, gid, link_target
		FROM files
		ORDER BY path
	`

	rows, err := r.db.conn.QueryContext(ctx, query)
	if err != nil {
		return nil, fmt.Errorf("querying files: %w", err)
	}

	defer func() {
		err := rows.Close()
		if err != nil {
			Fatalf("failed to close rows: %v", err)
		}
	}()

	var files []*File

	for rows.Next() {
		file, err := r.scanFileRows(rows)
		if err != nil {
			return nil, fmt.Errorf("scanning file: %w", err)
		}

		files = append(files, file)
	}

	return files, rows.Err()
}

// CreateBatch inserts or updates multiple files in a single statement for efficiency.
// File IDs must be pre-generated before calling this method.
func (r *FileRepository) CreateBatch(
	ctx context.Context, tx *sql.Tx, files []*File,
) error {
	if len(files) == 0 {
		return nil
	}

	// Each files row binds this many SQL variables.
	const fileCols = 9

	// Batch at 100 rows to be safe with SQLite's variable limit.
	const batchSize = 100

	for i := 0; i < len(files); i += batchSize {
		end := min(i+batchSize, len(files))

		batch := files[i:end]

		query := `INSERT INTO files
			(id, path, source_path, mtime, size, mode, uid, gid, link_target)
			VALUES `

		args := make([]any, 0, len(batch)*fileCols)

		var querySb325 strings.Builder

		for j, f := range batch {
			if j > 0 {
				querySb325.WriteString(", ")
			}

			querySb325.WriteString("(?, ?, ?, ?, ?, ?, ?, ?, ?)")

			args = append(args,
				f.ID.String(), f.Path.String(), f.SourcePath.String(),
				f.MTime.Unix(), f.Size, f.Mode, f.UID, f.GID,
				f.LinkTarget.String())
		}

		query += querySb325.String() //nolint:gosec // G202: appends "?" placeholders only

		query += ` ON CONFLICT(path) DO UPDATE SET
			source_path = excluded.source_path,
			mtime = excluded.mtime,
			size = excluded.size,
			mode = excluded.mode,
			uid = excluded.uid,
			gid = excluded.gid,
			link_target = excluded.link_target`

		var err error
		if tx != nil {
			_, err = tx.ExecContext(ctx, query, args...)
		} else {
			_, err = r.db.ExecWithLog(ctx, query, args...)
		}

		if err != nil {
			return fmt.Errorf("batch inserting files: %w", err)
		}
	}

	return nil
}

// DeleteOrphaned deletes files that are not referenced by any snapshot
func (r *FileRepository) DeleteOrphaned(ctx context.Context) error {
	query := `
		DELETE FROM files
		WHERE NOT EXISTS (
			SELECT 1 FROM snapshot_files
			WHERE snapshot_files.file_id = files.id
		)
	`

	result, err := r.db.ExecWithLog(ctx, query)
	if err != nil {
		return fmt.Errorf("deleting orphaned files: %w", err)
	}

	rowsAffected, _ := result.RowsAffected()
	if rowsAffected > 0 {
		log.Debug("Deleted orphaned files", "count", rowsAffected)
	}

	return nil
}

// scanFile is a helper that scans a single file row
func (r *FileRepository) scanFile(row *sql.Row) (*File, error) {
	return r.scanFileFrom(row)
}

// scanFileRows is a helper that scans a file row from rows iterator
func (r *FileRepository) scanFileRows(rows *sql.Rows) (*File, error) {
	return r.scanFileFrom(rows)
}

// scanFileFrom scans one file row from any row scanner.
func (r *FileRepository) scanFileFrom(row fileRowScanner) (*File, error) {
	var (
		file                          File
		idStr, pathStr, sourcePathStr string
		mtimeUnix                     int64
		linkTarget                    sql.NullString
	)

	err := row.Scan(
		&idStr,
		&pathStr,
		&sourcePathStr,
		&mtimeUnix,
		&file.Size,
		&file.Mode,
		&file.UID,
		&file.GID,
		&linkTarget,
	)
	if err != nil {
		return nil, err
	}

	file.ID, err = types.ParseFileID(idStr)
	if err != nil {
		return nil, fmt.Errorf("parsing file ID: %w", err)
	}

	file.Path = types.FilePath(pathStr)
	file.SourcePath = types.SourcePath(sourcePathStr)

	file.MTime = time.Unix(mtimeUnix, 0).UTC()
	if linkTarget.Valid {
		file.LinkTarget = types.FilePath(linkTarget.String)
	}

	return &file, nil
}