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package sqlite3
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import (
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	"embed"
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	"fmt"
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	"io/fs"
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	"path"
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	"sort"
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	"strconv"
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	"strings"
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)
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//go:embed migrations/*.sql
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var migrationFiles embed.FS
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type migration struct {
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	version int
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	name    string
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	sql     string
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}
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func loadMigrations() ([]migration, error) {
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	entries, err := fs.ReadDir(migrationFiles, "migrations")
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	if err != nil {
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		return nil, err
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	}
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	migrations := make([]migration, 0, len(entries))
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	for _, entry := range entries {
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		if entry.IsDir() {
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			continue
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		}
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		name := entry.Name()
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		version, err := parseMigrationVersion(name)
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		if err != nil {
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			return nil, err
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		}
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		body, err := fs.ReadFile(migrationFiles, path.Join("migrations", name))
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		if err != nil {
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			return nil, err
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		}
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		migrations = append(migrations, migration{
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			version: version,
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			name:    name,
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			sql:     string(body),
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		})
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	}
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	sort.Slice(migrations, func(i, j int) bool {
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		return migrations[i].version < migrations[j].version
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	})
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	if err := validateMigrationSequence(migrations); err != nil {
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		return nil, err
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	}
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	return migrations, nil
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}
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func validateMigrationSequence(migrations []migration) error {
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	for i, migration := range migrations {
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		expected := i + 1
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		if migration.version != expected {
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			return fmt.Errorf("expected migration version %04d, got %04d (%s)", expected, migration.version, migration.name)
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		}
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	}
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	return nil
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}
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func parseMigrationVersion(name string) (int, error) {
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	base := path.Base(name)
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	if !strings.HasSuffix(base, ".sql") {
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		return 0, fmt.Errorf("invalid migration name %q", name)
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	}
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	trimmed := strings.TrimSuffix(base, ".sql")
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	prefix, _, ok := strings.Cut(trimmed, "-")
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	if !ok || prefix == "" {
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		return 0, fmt.Errorf("invalid migration name %q", name)
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	}
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	version, err := strconv.Atoi(prefix)
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	if err != nil || version <= 0 {
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		return 0, fmt.Errorf("invalid migration version in %q", name)
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	}
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	return version, nil
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}