package files

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

var ErrNotFound = errors.New("not found")
var ErrNameTaken = errors.New("name already exists in this folder")
var ErrCycle = errors.New("target is a descendant of the folder being moved")

type Store struct {
	db *pgxpool.Pool
}

func NewStore(db *pgxpool.Pool) *Store {
	return &Store{db: db}
}

const fileCols = `id, owner_id, group_id, folder_id, name, mime_type, size, checksum, storage_key, has_thumbnail, version, versioning_enabled, document_date, created_at, updated_at`

func scanFile(row interface{ Scan(...any) error }, f *File) error {
	return row.Scan(
		&f.ID, &f.OwnerID, &f.GroupID, &f.FolderID, &f.Name, &f.MimeType,
		&f.Size, &f.Checksum, &f.StorageKey, &f.HasThumbnail,
		&f.Version, &f.VersioningEnabled, &f.DocumentDate, &f.CreatedAt, &f.UpdatedAt,
	)
}

// ── Files ────────────────────────────────────────────────────────────────────

func (s *Store) CreateFile(ctx context.Context, f *File) (*File, error) {
	var out File
	err := scanFile(s.db.QueryRow(ctx,
		`INSERT INTO files (owner_id, group_id, folder_id, name, mime_type, size, checksum, storage_key,
		                    versioning_enabled)
		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
		 RETURNING `+fileCols,
		f.OwnerID, f.GroupID, f.FolderID, f.Name, f.MimeType, f.Size, f.Checksum, f.StorageKey,
		versioniertVonAnfang(f.Name),
	), &out)
	if err != nil {
		if isUniqueViolation(err) {
			return nil, ErrNameTaken
		}
		return nil, fmt.Errorf("create file: %w", err)
	}
	return &out, nil
}

// versioniertVonAnfang: Welche Dateien ihre Fassungen von der ersten Minute an
// behalten.
//
// Versionierung ist sonst bewusst abgeschaltet (Migration 000006): Jede
// Ueberschreibung hiesse eine weitere Fassung, und der Speicher liefe
// unbemerkt voll.
//
// Fuer Zeichnungen stimmt diese Rechnung nicht. Sie werden **in sich** immer
// wieder bearbeitet – das ist ihr normales Leben, anders als bei einer
// hochgeladenen Rechnung – und sie sind ein paar Kilobyte gross. Vor allem
// aber: Ohne gleichzeitiges Arbeiten kann der Zweite den Ersten
// ueberschreiben, und die Versionshistorie ist dann das Einzige, was die
// Arbeit zurueckholt. Ohne sie waere die Warnung im Editor ein Versprechen
// ohne Deckung.
func versioniertVonAnfang(name string) bool {
	return strings.HasSuffix(strings.ToLower(name), ".excalidraw")
}

// GetFileByID fetches a file without owner check (used by public share downloads).
func (s *Store) GetFileByID(ctx context.Context, id uuid.UUID) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`SELECT `+fileCols+` FROM files WHERE id = $1 AND is_deleted = false`, id,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("get file by id: %w", err)
	}
	return &f, nil
}

func (s *Store) GetFile(ctx context.Context, id, ownerID uuid.UUID) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`SELECT `+fileCols+` FROM files WHERE id = $1 AND (owner_id = $2 OR group_id = $2) AND is_deleted = false`,
		id, ownerID,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("get file: %w", err)
	}
	return &f, nil
}

func (s *Store) ListFiles(ctx context.Context, ownerID uuid.UUID, folderID *uuid.UUID) ([]*File, error) {
	var rows pgx.Rows
	var err error
	if folderID == nil {
		rows, err = s.db.Query(ctx,
			`SELECT `+fileCols+` FROM files
			 WHERE (owner_id = $1 OR group_id = $1) AND folder_id IS NULL AND is_deleted = false ORDER BY name`,
			ownerID,
		)
	} else {
		rows, err = s.db.Query(ctx,
			`SELECT `+fileCols+` FROM files
			 WHERE (owner_id = $1 OR group_id = $1) AND folder_id = $2 AND is_deleted = false ORDER BY name`,
			ownerID, folderID,
		)
	}
	if err != nil {
		return nil, fmt.Errorf("list files: %w", err)
	}
	defer rows.Close()
	return scanFiles(rows)
}

// SoftDeleteFile marks a file as deleted and updates its storage_key to the trash path.
// The caller must move the blob to trashKey before calling this.
func (s *Store) SoftDeleteFile(ctx context.Context, id, ownerID uuid.UUID, trashKey string) error {
	tag, err := s.db.Exec(ctx,
		`UPDATE files SET is_deleted = true, deleted_at = NOW(), storage_key = $3
		 WHERE id = $1 AND (owner_id = $2 OR group_id = $2) AND is_deleted = false`,
		id, ownerID, trashKey,
	)
	if err != nil {
		return fmt.Errorf("soft delete file: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// GetTrashedFile returns a soft-deleted file by ID (needed before restore/hard-delete).
func (s *Store) GetTrashedFile(ctx context.Context, id, ownerID uuid.UUID) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`SELECT `+fileCols+` FROM files WHERE id=$1 AND (owner_id = $2 OR group_id = $2) AND is_deleted=true`,
		id, ownerID,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("get trashed file: %w", err)
	}
	return &f, nil
}

func (s *Store) RenameFile(ctx context.Context, id, ownerID uuid.UUID, name, storageKey string) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`UPDATE files SET name=$3, storage_key=$4
		 WHERE id=$1 AND (owner_id = $2 OR group_id = $2) AND is_deleted=false
		 RETURNING `+fileCols,
		id, ownerID, name, storageKey,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		if isUniqueViolation(err) {
			return nil, ErrNameTaken
		}
		return nil, fmt.Errorf("rename file: %w", err)
	}
	return &f, nil
}

func (s *Store) MoveFile(ctx context.Context, id, ownerID uuid.UUID, newFolderID *uuid.UUID, storageKey string) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`UPDATE files SET folder_id=$3, storage_key=$4
		 WHERE id=$1 AND (owner_id = $2 OR group_id = $2) AND is_deleted=false
		 RETURNING `+fileCols,
		id, ownerID, newFolderID, storageKey,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("move file: %w", err)
	}
	return &f, nil
}

type TrashFile struct {
	File
	FolderPath *string `json:"folder_path"`
}

func (s *Store) ListTrash(ctx context.Context, userID uuid.UUID) ([]*TrashFile, error) {
	// Sichtbar ist der eigene Papierkorb plus der jeder Gruppe, in der man
	// Mitglied ist. Ohne den zweiten Teil verschwände eine gelöschte
	// Gruppendatei spurlos: Sie gehört keinem Konto, tauchte also in keinem
	// persönlichen Papierkorb auf und wäre nicht wiederherstellbar.
	const principal = `(f.owner_id = $1 OR f.group_id IN (
	                        SELECT group_id FROM group_members WHERE user_id = $1))`

	rows, err := s.db.Query(ctx,
		`WITH RECURSIVE folder_paths AS (
		   SELECT id, name::text AS full_path
		   FROM folders
		    WHERE parent_id IS NULL
		      AND (owner_id = $1 OR group_id IN (
		               SELECT group_id FROM group_members WHERE user_id = $1))
		   UNION ALL
		   SELECT fo.id, fp.full_path || ' / ' || fo.name
		   FROM folders fo JOIN folder_paths fp ON fo.parent_id = fp.id
		 )
		 SELECT f.id, f.owner_id, f.group_id, f.folder_id, f.name, f.mime_type, f.size, f.checksum,
		        f.storage_key, f.has_thumbnail, f.version, f.versioning_enabled,
		        f.created_at, f.updated_at,
		        fp.full_path AS folder_path
		 FROM files f
		 LEFT JOIN folder_paths fp ON fp.id = f.folder_id
		 WHERE `+principal+` AND f.is_deleted = true
		 ORDER BY f.deleted_at DESC`,
		userID,
	)
	if err != nil {
		return nil, fmt.Errorf("list trash: %w", err)
	}
	defer rows.Close()
	result := make([]*TrashFile, 0)
	for rows.Next() {
		var item TrashFile
		if err := rows.Scan(
			&item.ID, &item.OwnerID, &item.GroupID, &item.FolderID, &item.Name, &item.MimeType,
			&item.Size, &item.Checksum, &item.StorageKey, &item.HasThumbnail,
			&item.Version, &item.VersioningEnabled, &item.CreatedAt, &item.UpdatedAt,
			&item.FolderPath,
		); err != nil {
			return nil, err
		}
		result = append(result, &item)
	}
	return result, rows.Err()
}

// RestoreFile marks a file as active again and updates its storage_key to the restored path.
// The caller must move the blob from .trash/ back to newStorageKey before calling this.
func (s *Store) RestoreFile(ctx context.Context, id, ownerID uuid.UUID, newStorageKey string) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`UPDATE files SET is_deleted = false, deleted_at = NULL, storage_key = $3
		 WHERE id = $1 AND (owner_id = $2 OR group_id = $2) AND is_deleted = true
		 RETURNING `+fileCols,
		id, ownerID, newStorageKey,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("restore file: %w", err)
	}
	return &f, nil
}

// HardDeleteFile permanently removes a file and returns its storage key plus all version
// storage keys so the caller can delete the blobs. file_versions rows are removed by
// the ON DELETE CASCADE on the FK.
// EmptyTrash löscht alle Papierkorb-Einträge eines Nutzers endgültig und
// liefert sämtliche Blob-Schlüssel zurück, damit der Aufrufer die Bytes
// entfernen kann.
//
// Die IDs werden mit zurückgegeben, weil zu jeder Datei noch ein
// Vorschaubild unter "thumbs/<id>.jpg" liegen kann.
func (s *Store) EmptyTrash(ctx context.Context, ownerID uuid.UUID) (fileIDs []uuid.UUID, keys []string, err error) {
	// Erst die Versionsblobs einsammeln – die Kaskade räumt die Zeilen mit weg.
	rows, err := s.db.Query(ctx,
		`SELECT v.storage_key
		   FROM file_versions v
		   JOIN files f ON f.id = v.file_id
		  WHERE (f.owner_id = $1 OR f.group_id = $1) AND f.is_deleted = true`, ownerID)
	if err != nil {
		return nil, nil, fmt.Errorf("list trash version keys: %w", err)
	}
	for rows.Next() {
		var k string
		if err := rows.Scan(&k); err != nil {
			rows.Close()
			return nil, nil, err
		}
		keys = append(keys, k)
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return nil, nil, err
	}

	rows, err = s.db.Query(ctx,
		`DELETE FROM files WHERE (owner_id = $1 OR group_id = $1) AND is_deleted = true
		 RETURNING id, storage_key`, ownerID)
	if err != nil {
		return nil, nil, fmt.Errorf("empty trash: %w", err)
	}
	defer rows.Close()
	for rows.Next() {
		var id uuid.UUID
		var k string
		if err := rows.Scan(&id, &k); err != nil {
			return nil, nil, err
		}
		fileIDs = append(fileIDs, id)
		keys = append(keys, k)
	}
	return fileIDs, keys, rows.Err()
}

func (s *Store) HardDeleteFile(ctx context.Context, id, ownerID uuid.UUID) (storageKey string, versionKeys []string, err error) {
	// Collect version blobs before the cascade removes them.
	rows, err := s.db.Query(ctx,
		`SELECT storage_key FROM file_versions WHERE file_id = $1`, id)
	if err != nil {
		return "", nil, fmt.Errorf("list version keys: %w", err)
	}
	for rows.Next() {
		var k string
		if err := rows.Scan(&k); err != nil {
			rows.Close()
			return "", nil, err
		}
		versionKeys = append(versionKeys, k)
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return "", nil, err
	}

	err = s.db.QueryRow(ctx,
		`DELETE FROM files WHERE id = $1 AND (owner_id = $2 OR group_id = $2) AND is_deleted = true
		 RETURNING storage_key`,
		id, ownerID,
	).Scan(&storageKey)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", nil, ErrNotFound
	}
	if err != nil {
		return "", nil, fmt.Errorf("hard delete file: %w", err)
	}
	return storageKey, versionKeys, nil
}

func (s *Store) UsedBytes(ctx context.Context, ownerID uuid.UUID) (int64, error) {
	var n int64
	err := s.db.QueryRow(ctx,
		`SELECT COALESCE(SUM(size), 0) FROM files WHERE (owner_id = $1 OR group_id = $1) AND is_deleted = false`,
		ownerID,
	).Scan(&n)
	return n, err
}

// GetFolderPath resolves the full slash-separated path for a folder, e.g. "Urlaub/2024".
// Returns "" for root (nil folderID).
func (s *Store) GetFolderPath(ctx context.Context, folderID *uuid.UUID) (string, error) {
	if folderID == nil {
		return "", nil
	}
	var path string
	err := s.db.QueryRow(ctx,
		`WITH RECURSIVE p AS (
		   SELECT id, name, parent_id, name::text AS full_path
		   FROM folders WHERE id = $1
		   UNION ALL
		   SELECT f.id, f.name, f.parent_id, f.name || '/' || p.full_path
		   FROM folders f JOIN p ON f.id = p.parent_id
		 )
		 SELECT full_path FROM p WHERE parent_id IS NULL`,
		*folderID,
	).Scan(&path)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", nil
	}
	return path, err
}

// GetFileByName finds a non-deleted file by name in a folder (for versioning on re-upload).
func (s *Store) GetFileByName(ctx context.Context, ownerID uuid.UUID, folderID *uuid.UUID, name string) (*File, error) {
	var f File
	var err error
	if folderID == nil {
		err = scanFile(s.db.QueryRow(ctx,
			`SELECT `+fileCols+` FROM files
			 WHERE (owner_id = $1 OR group_id = $1) AND folder_id IS NULL AND name=$2 AND is_deleted=false`,
			ownerID, name,
		), &f)
	} else {
		err = scanFile(s.db.QueryRow(ctx,
			`SELECT `+fileCols+` FROM files
			 WHERE (owner_id = $1 OR group_id = $1) AND folder_id=$2 AND name=$3 AND is_deleted=false`,
			ownerID, *folderID, name,
		), &f)
	}
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	return &f, err
}

func (s *Store) CreateVersion(ctx context.Context, fileID uuid.UUID, version int, size int64, checksum, storageKey string) error {
	_, err := s.db.Exec(ctx,
		`INSERT INTO file_versions (file_id, version, size, checksum, storage_key)
		 VALUES ($1, $2, $3, $4, $5)`,
		fileID, version, size, checksum, storageKey,
	)
	return err
}

// UpdateFileContent replaces blob metadata and increments version. Resets has_thumbnail.
func (s *Store) UpdateFileContent(ctx context.Context, id uuid.UUID, size int64, checksum, storageKey string) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`UPDATE files SET size=$2, checksum=$3, storage_key=$4, version=version+1, has_thumbnail=false
		 WHERE id=$1 AND is_deleted=false RETURNING `+fileCols,
		id, size, checksum, storageKey,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	return &f, err
}

// DeleteVersion entfernt einen Versionseintrag. Wird beim Wiederherstellen
// gebraucht: dessen Inhalt ist danach die aktive Fassung, der Eintrag also
// gegenstandslos. Der Blob wird nicht angefasst – er wandert zur Datei.
func (s *Store) DeleteVersion(ctx context.Context, versionID, fileID uuid.UUID) error {
	_, err := s.db.Exec(ctx,
		`DELETE FROM file_versions WHERE id=$1 AND file_id=$2`, versionID, fileID)
	return err
}

// SetVersioning schaltet die Versionierung einer Datei um.
//
// Bestehende Fassungen bleiben beim Ausschalten erhalten – sie zu löschen wäre
// stiller Datenverlust. Es entstehen ab dann nur keine neuen mehr.
func (s *Store) SetVersioning(ctx context.Context, id, ownerID uuid.UUID, enabled bool) (*File, error) {
	var f File
	err := scanFile(s.db.QueryRow(ctx,
		`UPDATE files SET versioning_enabled=$3
		 WHERE id=$1 AND (owner_id = $2 OR group_id = $2) AND is_deleted=false RETURNING `+fileCols,
		id, ownerID, enabled,
	), &f)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	return &f, err
}

// PruneVersions keeps the newest maxKeep versions and deletes the rest.
// Returns storage keys of deleted versions so the caller can remove the blobs.
func (s *Store) PruneVersions(ctx context.Context, fileID uuid.UUID, maxKeep int) ([]string, error) {
	rows, err := s.db.Query(ctx,
		`DELETE FROM file_versions
		 WHERE id IN (
		   SELECT id FROM file_versions WHERE file_id=$1
		   ORDER BY version DESC OFFSET $2
		 ) RETURNING storage_key`,
		fileID, maxKeep,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var keys []string
	for rows.Next() {
		var k string
		if err := rows.Scan(&k); err == nil {
			keys = append(keys, k)
		}
	}
	return keys, rows.Err()
}

func (s *Store) ListVersions(ctx context.Context, fileID, ownerID uuid.UUID) ([]*FileVersion, error) {
	// Verify ownership via JOIN
	rows, err := s.db.Query(ctx,
		`SELECT fv.id, fv.file_id, fv.version, fv.size, fv.checksum, fv.storage_key, fv.created_at
		 FROM file_versions fv
		 JOIN files f ON f.id = fv.file_id
		 WHERE fv.file_id=$1 AND (f.owner_id = $2 OR f.group_id = $2)
		 ORDER BY fv.version DESC`,
		fileID, ownerID,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	result := make([]*FileVersion, 0)
	for rows.Next() {
		var v FileVersion
		if err := rows.Scan(&v.ID, &v.FileID, &v.Version, &v.Size, &v.Checksum, &v.StorageKey, &v.CreatedAt); err != nil {
			return nil, err
		}
		result = append(result, &v)
	}
	return result, rows.Err()
}

func (s *Store) GetVersion(ctx context.Context, versionID, fileID, ownerID uuid.UUID) (*FileVersion, error) {
	var v FileVersion
	err := s.db.QueryRow(ctx,
		`SELECT fv.id, fv.file_id, fv.version, fv.size, fv.checksum, fv.storage_key, fv.created_at
		 FROM file_versions fv
		 JOIN files f ON f.id = fv.file_id
		 WHERE fv.id=$1 AND fv.file_id=$2 AND (f.owner_id = $3 OR f.group_id = $3)`,
		versionID, fileID, ownerID,
	).Scan(&v.ID, &v.FileID, &v.Version, &v.Size, &v.Checksum, &v.StorageKey, &v.CreatedAt)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrNotFound
	}
	return &v, err
}

func (s *Store) UpdateThumbnail(ctx context.Context, id uuid.UUID, hasThumbnail bool) error {
	_, err := s.db.Exec(ctx,
		`UPDATE files SET has_thumbnail = $2 WHERE id = $1`, id, hasThumbnail)
	return err
}

// ── helpers ───────────────────────────────────────────────────────────────────

func scanFiles(rows pgx.Rows) ([]*File, error) {
	result := make([]*File, 0)
	for rows.Next() {
		var f File
		if err := scanFile(rows, &f); err != nil {
			return nil, err
		}
		result = append(result, &f)
	}
	return result, rows.Err()
}

func isUniqueViolation(err error) bool {
	if err == nil {
		return false
	}
	type sqlStater interface{ SQLState() string }
	var se sqlStater
	if errors.As(err, &se) {
		return se.SQLState() == "23505"
	}
	return false
}

// PreviewVersion sagt, aus welcher Fassung das zwischengespeicherte PDF
// entstanden ist – 0 heißt: es gibt keins.
//

// FilesWithPreview liefert die Kennungen aller Dateien, zu denen ein PDF
// abgelegt ist. Der GC braucht das: Ohne diese Liste hielte er jedes
// Vorschau-PDF für herrenlos und löschte es nach einem Tag weg.
func (s *Store) FilesWithPreview(ctx context.Context) ([]string, error) {
	rows, err := s.db.Query(ctx, `SELECT id::text FROM files WHERE preview_version > 0`)
	if err != nil {
		return nil, fmt.Errorf("files with preview: %w", err)
	}
	defer rows.Close()
	var ids []string
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		ids = append(ids, id)
	}
	return ids, rows.Err()
}