ampelmaennchen.git

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package db

import (
	"embed"
	"fmt"
	"log"
	"sort"
)

//go:embed migrations
var migrationsDir embed.FS

func Migrate() error {
	_, err := db.Exec("create table if not exists migrations(id text)")
	if err != nil {
		return fmt.Errorf("while creating migrations table: %w", err)
	}

	rows, err := db.Query("select id from migrations order by id")
	if err != nil {
		return fmt.Errorf("while checking if migrations exist: %w", err)
	}

	migrationEntries, err := migrationsDir.ReadDir("migrations")
	if err != nil {
		return fmt.Errorf("while reading migrations directory: %w", err)
	}

	sort.Slice(migrationEntries, func(i int, j int) bool {
		return (migrationEntries[i].Name() < migrationEntries[j].Name())
	})

	for i, migrationEntry := range migrationEntries {
		if rows.Next() {
			var nameInDB string
			err := rows.Scan(&nameInDB)
			if err != nil {
				return fmt.Errorf("while scanning migration %d: %w", i, err)
			}

			if migrationEntry.Name() != nameInDB {
				return fmt.Errorf("while checking migration %d, mismatch in names: ‘%s’ in db, ‘%s’ in file", i, nameInDB, migrationEntry.Name())
			}
		} else {
			log.Printf("performing migration %s\n", migrationEntry.Name())
			migration, err := migrationsDir.ReadFile("migrations/" + migrationEntry.Name())
			if err != nil {
				return fmt.Errorf("while reading migration %s: %w", migrationEntry.Name(), err)
			}

			_, err = db.Exec(string(migration))
			if err != nil {
				return fmt.Errorf("while performing migration %s: %w", migrationEntry.Name(), err)
			}

			_, err = db.Exec("insert into migrations values($1)", migrationEntry.Name())
			if err != nil {
				return fmt.Errorf("while adding migration %s to db: %w", migrationEntry.Name(), err)
			}
		}
	}
	return nil
}