diamond-orm/relationship.go

package orm

import (
	"fmt"
	sb "github.com/henvic/pgq"
	"reflect"
	"strings"
)

// RelationshipType - used to distinguish a Relationship between various
// common entity relationship types
type RelationshipType int

const (
	HasOne RelationshipType = iota
	HasMany
	BelongsTo
	ManyToOne // the other side of a HasMany relationship
	ManyToMany
)

// Relationship - intermediate representation of how two types
// relate to each other. i.e., if struct A embeds struct B,
// a Relationship will be created for those two while parsing the Model for A.
type Relationship struct {
	Type         RelationshipType // the type of this relationship (see RelationshipType)
	JoinTable    string           // the name of the join table, if specified explicitly via struct tag, otherwise blank
	Model        *Model           // the primary Model which contains this relationship
	FieldName    string           // the name of the struct field with this relationship
	Idx          int              // the index of the struct field with this relationship
	RelatedType  reflect.Type     // the reflect.Type for the struct field named by FieldName
	RelatedModel *Model           // the Model representing the type of the embedded slice/struct
	Kind         reflect.Kind     // field kind (struct, slice, ...)
	m2mInverse   *Relationship    // the "inverse" side of an explicit ManyToMany relationship
	Nullable     bool             // whether the foreign key for this relationship can have a nullable column
	OriginalField reflect.StructField // the original reflect.StructField object associated with this relationship
}

// ComputeJoinTable - computes the name of the join table for ManyToMany relationships.
// will return a snake_cased autogenerated name for unidirectional ManyToMany .
// the "implicit" behavior is invoked upon one of the following conditions being met:
// - the primary Relationship.Model
func (r *Relationship) ComputeJoinTable() string {
	if r.JoinTable != "" {
		return r.JoinTable
	}
	otherSide := r.RelatedModel.TableName
	if r.Model.embeddedIsh {
		otherSide = pascalToSnakeCase(r.FieldName)
	}
	return r.Model.TableName + "_" + otherSide
}

func (r *Relationship) relatedID() *Field {
	return r.RelatedModel.Fields[r.RelatedModel.IDField]
}

func (r *Relationship) primaryID() *Field {
	return r.Model.Fields[r.Model.IDField]
}

func (r *Relationship) joinField() string {
	if r.Type == ManyToOne {
		return r.RelatedModel.Name + "ID"
	}
	if r.Type == ManyToMany && !r.Model.embeddedIsh {
		return r.RelatedModel.Name + "ID"
	}
	return r.FieldName + "ID"
}

func (r *Relationship) m2mIsh() bool {
	needsMany := false
	if !r.Model.embeddedIsh && r.RelatedModel.embeddedIsh {
		rr, ok := r.RelatedModel.Relationships[r.Model.Name]
		if ok && rr.Type != ManyToOne {
			needsMany = true
		}
	}
	return ((r.Model.embeddedIsh && !r.RelatedModel.embeddedIsh) || needsMany) &&
		r.Type == HasMany
}

func (r *Relationship) joinInsert(v reflect.Value, e *Query, pfk any) error {
	if r.Type != ManyToMany &&
		!r.m2mIsh() {
		return nil
	}
	ichild := v
	for ichild.Kind() == reflect.Ptr {
		ichild = ichild.Elem()
	}
	if ichild.Kind() == reflect.Struct {
		jtable := r.ComputeJoinTable()
		jargs := make([]any, 0)
		jcols := make([]string, 0)
		jcols = append(jcols, fmt.Sprintf("%s_id",
			r.Model.TableName,
		))
		jargs = append(jargs, pfk)

		jcols = append(jcols, r.RelatedModel.TableName+"_id")
		jargs = append(jargs, ichild.FieldByName(r.RelatedModel.IDField).Interface())
		var ecnt int
		e.tx.QueryRow(e.ctx,
			fmt.Sprintf("SELECT count(*) from %s where %s = $1 and %s = $2", r.ComputeJoinTable(), jcols[0], jcols[1]), jargs...).Scan(&ecnt)
		if ecnt > 0 {
			return nil
		}
		jsql := fmt.Sprintf("INSERT INTO %s (%s) VALUES ($1, $2)", jtable, strings.Join(jcols, ", "))
		e.engine.logQuery("insert/join", jsql, jargs)
		if !e.engine.dryRun {
			_ = e.tx.QueryRow(e.ctx, jsql, jargs...).Scan()
		}
	}
	return nil
}

func (r *Relationship) joinDelete(pk, fk any, q *Query) error {
	dq := sb.Delete(r.ComputeJoinTable()).Where(fmt.Sprintf("%s_id = ?", r.Model.TableName), pk)
	if fk != nil {
		dq = dq.Where(fmt.Sprintf("%s_id = ?", r.RelatedModel.TableName), fk)
	}
	ds, aa := dq.MustSQL()
	q.engine.logQuery("delete/join", ds, aa)
	if !q.engine.dryRun {
		_, err := q.tx.Exec(q.ctx, ds, aa...)
		return err
	}
	return nil
}

func parseRelationship(field reflect.StructField, modelMap map[string]*Model, outerType reflect.Type, idx int, settings map[string]string) *Relationship {
	rel := &Relationship{
		Model:         modelMap[outerType.Name()],
		RelatedModel:  modelMap[field.Type.Name()],
		RelatedType:   field.Type,
		Idx:           idx,
		Kind:          field.Type.Kind(),
		FieldName:     field.Name,
		OriginalField: field,
	}
	if rel.RelatedType.Kind() == reflect.Slice || rel.RelatedType.Kind() == reflect.Array {
		rel.RelatedType = rel.RelatedType.Elem()
	}
	if rel.RelatedModel == nil {
		if rel.RelatedType.Name() == "" {
			rt := rel.RelatedType
			for rt.Kind() == reflect.Ptr || rt.Kind() == reflect.Slice || rt.Kind() == reflect.Array {
				rel.Nullable = true
				rel.RelatedType = rel.RelatedType.Elem()
				rt = rel.RelatedType
			}
		}
		rel.RelatedModel = modelMap[rel.RelatedType.Name()]
		if _, ok := modelMap[rel.RelatedType.Name()]; !ok {
			rel.RelatedModel = parseModel(reflect.New(rel.RelatedType).Interface())
			modelMap[rel.RelatedType.Name()] = rel.RelatedModel
			parseModelFields(rel.RelatedModel, modelMap)
			rel.RelatedModel.embeddedIsh = true
		}
	}
	switch field.Type.Kind() {
	case reflect.Struct:
		rel.Type = HasOne
	case reflect.Slice, reflect.Array:
		rel.Type = HasMany
	}
	maybeM2m := settings["m2m"]
	if maybeM2m == "" {
		maybeM2m = settings["manytomany"]
	}
	if rel.Type == HasMany && maybeM2m != "" {
		rel.JoinTable = maybeM2m
	}
	return rel
}
func addForeignKeyFields(ref *Relationship) {
	if !ref.RelatedModel.embeddedIsh && !ref.Model.embeddedIsh {
		ref.Type = BelongsTo
	} else if !ref.Model.embeddedIsh && ref.RelatedModel.embeddedIsh {

		if ref.Type == HasMany {
			nr := &Relationship{
				RelatedModel: ref.Model,
				Model:        ref.RelatedModel,
				Kind:         ref.RelatedModel.Type.Kind(),
				Idx:          -1,
				RelatedType:  ref.Model.Type,
			}
			nr.Type = ManyToOne
			nr.FieldName = nr.RelatedModel.Name
			ref.RelatedModel.Relationships[nr.FieldName] = nr
		} else if ref.Type == HasOne {
			ref.Type = BelongsTo
		}
	} else if ref.Model.embeddedIsh && !ref.RelatedModel.embeddedIsh {

	}
}