package stonesql

import (
	"context"
	"embed"
	"io/fs"
	"path/filepath"

	"gitstormr.dev/stone-utils/stoneerror"
)

// SQLFileExtension represents the file extension for SQL migration files.
const (
	SQLFileExtension = ".sql"
)

// ErrWalkDirFailed represents an error for failed directory traversal.
// ErrReadMigrationFailed represents an error for reading migration files.
// ErrExecuteMigrationFailed represents an error during migration execution.
// ErrMigrationProcessFailed represents a general migration process failure.
var (
	ErrWalkDirFailed = stoneerror.New(
		2001,
		"failed to walk migration directory",
	)
	ErrReadMigrationFailed = stoneerror.New(
		2002,
		"failed to read migration file",
	)
	ErrExecuteMigrationFailed = stoneerror.New(
		2003,
		"failed to execute migration",
	)
	ErrMigrationProcessFailed = stoneerror.New(
		2004,
		"migration process failed",
	)
)

// Migrator defines the interface for executing SQL migrations.
// ExecuteMigration runs a migration given its name and SQL content.
type Migrator interface {
	ExecuteMigration(ctx context.Context, name string, sqlContent string) error
}

// RunMigrations performs a series of database migrations from embedded files.
// It traverses the provided filesystem path, reads SQL files, and executes them.
// If an error occurs during traversal, reading, or execution, it wraps and returns it.
// Context to be used for execution is passed via the ctx parameter.
// The migrator parameter executes individual SQL content for migrations.
// The migrationsFS parameter provides an embedded filesystem for the SQL files.
// The path parameter specifies the directory within the embedded FS to search in.
// Returns an error if any step in the migration process fails.
func RunMigrations(
	ctx context.Context,
	migrator Migrator,
	migrationsFS embed.FS,
	path string,
) error {
	walkErr := fs.WalkDir(
		migrationsFS,
		path,
		func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				return stoneerror.Wrap(
					err, ErrWalkDirFailed.Code,
					ErrWalkDirFailed.Message,
				).
					WithMetadata("path", path)
			}

			if !d.IsDir() && filepath.Ext(path) == SQLFileExtension {
				sqlContent, readErr := migrationsFS.ReadFile(path)
				if readErr != nil {
					return stoneerror.Wrap(
						readErr, ErrReadMigrationFailed.Code,
						ErrReadMigrationFailed.Message,
					).
						WithMetadata("file", path)
				}

				if err = migrator.ExecuteMigration(
					ctx, path, string(sqlContent),
				); err != nil {
					return stoneerror.Wrap(
						err, ErrExecuteMigrationFailed.Code,
						ErrExecuteMigrationFailed.Message,
					).
						WithMetadata("migration", path)
				}
			}

			return nil
		},
	)

	if walkErr != nil {
		return stoneerror.Wrap(
			walkErr, ErrMigrationProcessFailed.Code,
			ErrMigrationProcessFailed.Message,
		).
			WithMetadata("rootPath", path)
	}

	return nil
}