goext/wmo/queryFindOne.go

package wmo

import (
	"context"
	"errors"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
	"gogs.mikescher.com/BlackForestBytes/goext/exerr"
	"gogs.mikescher.com/BlackForestBytes/goext/langext"
)

func (c *Coll[TData]) FindOne(ctx context.Context, filter bson.M) (TData, error) {
	r, err := c.findOneInternal(ctx, filter, false)
	if err != nil {
		return *new(TData), exerr.Wrap(err, "mongo-query[find-one] failed").Str("collection", c.Name()).Build()
	}

	return *r, nil
}

func (c *Coll[TData]) FindOneOpt(ctx context.Context, filter bson.M) (*TData, error) {
	r, err := c.findOneInternal(ctx, filter, true)
	if err != nil {
		return nil, exerr.Wrap(err, "mongo-query[find-one-opt] failed").Str("collection", c.Name()).Build()
	}

	return r, nil
}

func (c *Coll[TData]) FindOneByID(ctx context.Context, id EntityID) (TData, error) {
	r, err := c.findOneInternal(ctx, bson.M{"_id": id}, false)
	if err != nil {
		return *new(TData), exerr.Wrap(err, "mongo-query[find-one-by-id] failed").Id("id", id).Str("collection", c.Name()).Build()
	}

	return *r, nil
}

func (c *Coll[TData]) FindOneOptByID(ctx context.Context, id EntityID) (*TData, error) {
	r, err := c.findOneInternal(ctx, bson.M{"_id": id}, true)
	if err != nil {
		return nil, exerr.Wrap(err, "mongo-query[find-one-opt-by-id] failed").Id("id", id).Str("collection", c.Name()).Build()
	}

	return r, nil
}

func (c *Coll[TData]) findOneInternal(ctx context.Context, filter bson.M, allowNull bool) (*TData, error) {

	if len(c.extraModPipeline) == 0 {

		// simple case, use mongo FindOne

		mongoRes := c.coll.FindOne(ctx, filter)

		res, err := c.decodeSingle(ctx, mongoRes)
		if allowNull && errors.Is(err, mongo.ErrNoDocuments) {
			return nil, nil
		}
		if err != nil {
			return nil, exerr.Wrap(err, "mongo-query[find-one] failed").Any("filter", filter).Str("collection", c.Name()).Build()
		}

		return &res, nil

	} else {

		// complex case, we one ore more additional pipeline stages, convert to aggregation

		pipeline := mongo.Pipeline{}
		pipeline = append(pipeline, bson.D{{Key: "$match", Value: filter}})
		pipeline = append(pipeline, bson.D{{Key: "$limit", Value: 1}})

		pipeline = langext.ArrConcat(pipeline, c.extraModPipeline)

		cursor, err := c.coll.Aggregate(ctx, pipeline)
		if err != nil {
			return nil, exerr.Wrap(err, "mongo-aggregation [find-one] failed").Any("pipeline", pipeline).Str("collection", c.Name()).Build()
		}

		if cursor.Next(ctx) {
			v, err := c.decodeSingle(ctx, cursor)
			if err != nil {
				return nil, exerr.Wrap(err, "mongo-aggregation [find-one] failed to decode results").Any("pipeline", pipeline).Str("collection", c.Name()).Build()
			}
			return &v, nil
		} else if allowNull {
			return nil, nil
		} else {
			return nil, exerr.Wrap(mongo.ErrNoDocuments, "mongo-aggregation [find-one] returned no documents").Any("pipeline", pipeline).Str("collection", c.Name()).Build()
		}
	}
}