package migrations

import (
	"context"
	"database/sql"
	"fmt"
	"path/filepath"
	"strings"
	"time"

	"github.com/jmoiron/sqlx"
	"github.com/stashapp/stash/pkg/logger"
	"github.com/stashapp/stash/pkg/sqlite"
	"gopkg.in/guregu/null.v4"
)

const legacyZipSeparator = "\x00"

func post32(ctx context.Context, db *sqlx.DB) error {
	logger.Info("Running post-migration for schema version 32")

	m := schema32Migrator{
		migrator: migrator{
			db: db,
		},
		folderCache: make(map[string]folderInfo),
	}

	if err := m.migrateFolders(ctx); err != nil {
		return fmt.Errorf("migrating folders: %w", err)
	}

	if err := m.migrateFiles(ctx); err != nil {
		return fmt.Errorf("migrating files: %w", err)
	}

	if err := m.deletePlaceholderFolder(ctx); err != nil {
		return fmt.Errorf("deleting placeholder folder: %w", err)
	}

	return nil
}

type folderInfo struct {
	id    int
	zipID sql.NullInt64
}

type schema32Migrator struct {
	migrator
	folderCache map[string]folderInfo
}

func (m *schema32Migrator) migrateFolders(ctx context.Context) error {
	logger.Infof("Migrating folders")

	const (
		limit    = 1000
		logEvery = 10000
	)

	lastID := 0
	count := 0

	for {
		gotSome := false

		if err := m.withTxn(ctx, func(tx *sqlx.Tx) error {
			query := "SELECT `folders`.`id`, `folders`.`path` FROM `folders` INNER JOIN `galleries` ON `galleries`.`folder_id` = `folders`.`id`"

			if lastID != 0 {
				query += fmt.Sprintf("AND `folders`.`id` > %d ", lastID)
			}

			query += fmt.Sprintf("ORDER BY `folders`.`id` LIMIT %d", limit)

			rows, err := tx.Query(query)
			if err != nil {
				return err
			}
			defer rows.Close()

			for rows.Next() {
				var id int
				var p string

				err := rows.Scan(&id, &p)
				if err != nil {
					return err
				}

				lastID = id
				gotSome = true
				count++

				parent := filepath.Dir(p)
				parentID, zipFileID, err := m.createFolderHierarchy(tx, parent)
				if err != nil {
					return err
				}

				_, err = tx.Exec("UPDATE `folders` SET `parent_folder_id` = ?, `zip_file_id` = ? WHERE `id` = ?", parentID, zipFileID, id)
				if err != nil {
					return err
				}
			}

			return rows.Err()
		}); err != nil {
			return err
		}

		if !gotSome {
			break
		}

		if count%logEvery == 0 {
			logger.Infof("Migrated %d folders", count)
		}
	}

	return nil
}

func (m *schema32Migrator) migrateFiles(ctx context.Context) error {
	const (
		limit    = 1000
		logEvery = 10000
	)

	result := struct {
		Count int `db:"count"`
	}{0}

	if err := m.db.Get(&result, "SELECT COUNT(*) AS count FROM `files`"); err != nil {
		return err
	}

	logger.Infof("Migrating %d files...", result.Count)

	lastID := 0
	count := 0

	for {
		gotSome := false

		// using offset for this is slow. Save the last id and filter by that instead
		query := "SELECT `id`, `basename` FROM `files` "
		if lastID != 0 {
			query += fmt.Sprintf("WHERE `id` > %d ", lastID)
		}

		query += fmt.Sprintf("ORDER BY `id` LIMIT %d", limit)

		if err := m.withTxn(ctx, func(tx *sqlx.Tx) error {
			rows, err := tx.Query(query)
			if err != nil {
				return err
			}
			defer rows.Close()

			for rows.Next() {
				gotSome = true

				var id int
				var p string

				err := rows.Scan(&id, &p)
				if err != nil {
					return err
				}

				if strings.Contains(p, legacyZipSeparator) {
					// remove any null characters from the path
					p = strings.ReplaceAll(p, legacyZipSeparator, string(filepath.Separator))
				}

				parent := filepath.Dir(p)
				basename := filepath.Base(p)
				if parent != "." {
					parentID, zipFileID, err := m.createFolderHierarchy(tx, parent)
					if err != nil {
						return err
					}

					_, err = tx.Exec("UPDATE `files` SET `parent_folder_id` = ?, `zip_file_id` = ?, `basename` = ? WHERE `id` = ?", parentID, zipFileID, basename, id)
					if err != nil {
						return fmt.Errorf("migrating file %s: %w", p, err)
					}
				} else {
					// if we don't reassign from the placeholder, it will fail
					// so log a warning at least here
					logger.Warnf("Unable to migrate invalid path: %s", p)
				}

				lastID = id
				count++
			}

			return rows.Err()
		}); err != nil {
			return err
		}

		if !gotSome {
			break
		}

		if count%logEvery == 0 {
			logger.Infof("Migrated %d files", count)

			// manual checkpoint to flush wal file
			if _, err := m.db.Exec("PRAGMA wal_checkpoint(FULL)"); err != nil {
				return fmt.Errorf("running wal checkpoint: %w", err)
			}
		}
	}

	logger.Infof("Finished migrating files")

	return nil
}

func (m *schema32Migrator) deletePlaceholderFolder(ctx context.Context) error {
	// only delete the placeholder folder if no files/folders are attached to it
	result := struct {
		Count int `db:"count"`
	}{0}

	if err := m.db.Get(&result, "SELECT COUNT(*) AS count FROM `files` WHERE `parent_folder_id` = 1"); err != nil {
		return err
	}

	if result.Count > 0 {
		return fmt.Errorf("not deleting placeholder folder because it has %d files", result.Count)
	}

	result.Count = 0

	if err := m.db.Get(&result, "SELECT COUNT(*) AS count FROM `folders` WHERE `parent_folder_id` = 1"); err != nil {
		return err
	}

	if result.Count > 0 {
		return fmt.Errorf("not deleting placeholder folder because it has %d folders", result.Count)
	}

	return m.withTxn(ctx, func(tx *sqlx.Tx) error {
		_, err := tx.Exec("DELETE FROM `folders` WHERE `id` = 1")
		return err
	})
}

func (m *schema32Migrator) createFolderHierarchy(tx *sqlx.Tx, p string) (*int, sql.NullInt64, error) {
	parent := filepath.Dir(p)

	if parent == p {
		// get or create this folder
		return m.getOrCreateFolder(tx, p, nil, sql.NullInt64{})
	}

	var (
		parentID  *int
		zipFileID sql.NullInt64
		err       error
	)

	// try to find parent folder in cache first
	foundEntry, ok := m.folderCache[parent]
	if ok {
		parentID = &foundEntry.id
		zipFileID = foundEntry.zipID
	} else {
		parentID, zipFileID, err = m.createFolderHierarchy(tx, parent)
		if err != nil {
			return nil, sql.NullInt64{}, err
		}
	}

	return m.getOrCreateFolder(tx, p, parentID, zipFileID)
}

func (m *schema32Migrator) getOrCreateFolder(tx *sqlx.Tx, path string, parentID *int, zipFileID sql.NullInt64) (*int, sql.NullInt64, error) {
	foundEntry, ok := m.folderCache[path]
	if ok {
		return &foundEntry.id, foundEntry.zipID, nil
	}

	const query = "SELECT `id`, `zip_file_id` FROM `folders` WHERE `path` = ?"
	rows, err := tx.Query(query, path)
	if err != nil {
		return nil, sql.NullInt64{}, err
	}
	defer rows.Close()

	if rows.Next() {
		var id int
		var zfid sql.NullInt64
		err := rows.Scan(&id, &zfid)
		if err != nil {
			return nil, sql.NullInt64{}, err
		}

		return &id, zfid, nil
	}

	if err := rows.Err(); err != nil {
		return nil, sql.NullInt64{}, err
	}

	const insertSQL = "INSERT INTO `folders` (`path`,`parent_folder_id`,`zip_file_id`,`mod_time`,`created_at`,`updated_at`) VALUES (?,?,?,?,?,?)"

	var parentFolderID null.Int
	if parentID != nil {
		parentFolderID = null.IntFrom(int64(*parentID))
	}

	now := time.Now()
	result, err := tx.Exec(insertSQL, path, parentFolderID, zipFileID, time.Time{}, now, now)
	if err != nil {
		return nil, sql.NullInt64{}, fmt.Errorf("creating folder %s: %w", path, err)
	}

	id, err := result.LastInsertId()
	if err != nil {
		return nil, sql.NullInt64{}, fmt.Errorf("creating folder %s: %w", path, err)
	}

	idInt := int(id)

	m.folderCache[path] = folderInfo{id: idInt, zipID: zipFileID}

	return &idInt, zipFileID, nil
}

func init() {
	sqlite.RegisterPostMigration(32, post32)
}