// Package source owns Mongo connection generations and operation lifetimes.
package source

import (
	"context"

	merrors "git.sendico.io/tech/sxchnge/shared/errors"
	"go.mongodb.org/mongo-driver/v2/mongo"
)

// Source pins one database/client until release. The returned context must be
// passed to nested operations so transactions never cross client generations.
type Source interface {
	Acquire(context.Context) (*mongo.Database, context.Context, func(), error)
}

type fixed struct{ database *mongo.Database }

// Fixed adapts an externally owned database, e.g. a test fixture. It never closes it.
func Fixed(database *mongo.Database) Source { return &fixed{database: database} }

func (s *fixed) Acquire(ctx context.Context) (*mongo.Database, context.Context, func(), error) {
	if s.database == nil {
		return nil, ctx, nil, merrors.FailedPrecondition("database is not configured")
	}
	if session := mongo.SessionFromContext(ctx); session != nil && session.Client() != s.database.Client() {
		return nil, ctx, nil, merrors.FailedPrecondition("transaction belongs to another database client")
	}
	return s.database, ctx, func() {}, nil
}