{{ define "base" }}

{{ $pkg := base $.Config.Package }}
{{ template "header" $pkg }}

{{ template "import" $ }}

// Predicate is an alias to ent.Predicate.
type Predicate = ent.Predicate

// Or groups list of predicates with the or operator between them.
func Or(predicates ...ent.Predicate) ent.Predicate {
	return ent.Predicate{
		SQL: func(s *sql.Selector) {
			for i, p := range predicates {
				if i > 0 {
					s.Or()
				}
				p.SQL(s)
			}
		},
		Gremlin: func(tr *dsl.Traversal) {
			trs := make([]interface{}, 0, len(predicates))
			for _, p := range predicates {
				t := __.New()
				p.Gremlin(t)
				trs = append(trs, t)
			}
			tr.Where(__.Or(trs...))
		},
	}
}

// Not applies the not operator on the given predicate.
func Not(p ent.Predicate) ent.Predicate {
	return ent.Predicate{
		SQL: func(s *sql.Selector) {
			p.SQL(s.Not())
		},
		Gremlin: func(tr *dsl.Traversal) {
			t := __.New()
			p.Gremlin(t)
			tr.Where(__.Not(t))
		},
	}
}

// Order applies an ordering on the traversal.
type Order ent.Predicate

{{ range $f, $order := order }}
	{{ $f = pascal $f }}
	// {{ $f }} applies the given fields in {{ upper $f }} order.
	func {{ $f }}(fields ...string) Order {
		return Order{
			SQL: func(s *sql.Selector) {
				for _, f := range fields {
					s.OrderBy(sql.{{ $f }}(f))
				}
			},
			Gremlin: func(tr *dsl.Traversal) {
				for _, f := range fields {
					tr.By(f, dsl.{{ pascal $order }})
				}
			},
		}
	}
{{ end }}

// Aggregate applies an aggregation step on the group-by traversal/selector.
type Aggregate struct {
	// SQL the column wrapped with the aggregation function.
	SQL     func(*sql.Selector) string
	// Gremlin gets two labels as parameters. The first used in the `As` step for the predicate,
	// and the second is an optional name for the next predicates (or for later usage).
	Gremlin func(string, string) (string, *dsl.Traversal)
}


// As is a pseudo aggregation function for renaming another other functions with custom names. For example:
//
//	GroupBy(field1, field2).
//	Aggregate({{ $pkg }}.As({{ $pkg }}.Sum(field1), "sum_field1"), ({{ $pkg }}.As({{ $pkg }}.Sum(field2), "sum_field2")).
//	Scan(ctx, &v)
//
func As(fn Aggregate, end string) Aggregate {
	return Aggregate{
		SQL: func(s *sql.Selector) string {
			return sql.As(fn.SQL(s), end)
		},
		Gremlin: func(start, _ string) (string, *dsl.Traversal) {
			return fn.Gremlin(start, end)
		},
	}
}

{{ range $name, $withField := aggregate }}
	{{ $fn := pascal $name }}
	// Default{{ $fn }}Label is the default label name for the {{ $fn }} aggregation function.
	// It should be used as the struct-tag for decoding, or a map key for interaction with the returned response.
	// In order to {{ quote $name }} 2 or more fields and avoid conflicting, use the `{{ $pkg }}.As({{ $pkg }}.{{ $fn }}(field), "custom_name")`
	// function with custom name in order to override it.
	const Default{{ $fn }}Label = {{ quote $name }}

	// {{ $fn }} applies the {{ quote $name }} aggregation function on {{ if $withField }}the given field of {{ end }}each group.
	func {{ $fn }}({{ if $withField }}field string{{ end }}) Aggregate {
		return Aggregate {
			SQL: func(s *sql.Selector) string {
				return sql.{{ if eq $fn "Mean" }}Avg{{ else }}{{ $fn }}{{ end }}({{ if $withField }}s.C(field){{ else }}"*"{{ end }})
			},
			Gremlin: func(start, end string) (string, *dsl.Traversal) {
				if end == "" {
					end = Default{{ $fn }}Label
				}
				return end, __.As(start).{{ if $withField }}Unfold().Values(field).{{ $fn }}(){{ else }}{{ $fn }}(dsl.Local){{ end }}.As(end)
			},
		}
	}
{{ end }}

// ErrNotFound returns when trying to fetch a specific entity and it was not found in the database.
type ErrNotFound struct {
	label string
}

// Error implements the error interface.
func (e *ErrNotFound) Error() string {
	return fmt.Sprintf("{{ $pkg }}: %s not found", e.label)
}

// IsNotFound returns a boolean indicating whether the error is a not found error.
func IsNotFound(err error) bool {
	_, ok := err.(*ErrNotFound)
	return ok
}

// ErrNotSingular returns when trying to fetch a singular entity and more then one was found in the database.
type ErrNotSingular struct {
	label string
}

// Error implements the error interface.
func (e *ErrNotSingular) Error() string {
	return fmt.Sprintf("{{ $pkg }}: %s not singular", e.label)
}

// IsNotSingular returns a boolean indicating whether the error is a not singular error.
func IsNotSingular(err error) bool {
	_, ok := err.(*ErrNotSingular)
	return ok
}


// ErrConstraintFailed returns when trying to create/update one or more entities and
// one or more of their constraints failed. For example, violation of edge or field uniqueness.
type ErrConstraintFailed struct {
	msg string
	wrap error
}

// Error implements the error interface.
func (e ErrConstraintFailed) Error() string {
	return fmt.Sprintf("{{ $pkg }}: unique constraint failed: %s", e.msg)
}

// Unwrap implements the errors.Wrapper interface.
func (e *ErrConstraintFailed) Unwrap() error {
	return e.wrap
}

// Code implements the dsl.Node interface.
func (e ErrConstraintFailed) Code() (string, []interface{}) {
	return strconv.Quote(e.prefix() + e.msg), nil
}

func (e *ErrConstraintFailed) UnmarshalGraphson(b []byte) error {
	var v [1]*string
	if err := graphson.Unmarshal(b, &v); err != nil {
		return err
	}
	if v[0] == nil {
		return fmt.Errorf("{{ $pkg }}: missing string value")
	}
	if !strings.HasPrefix(*v[0], e.prefix()) {
		return fmt.Errorf("{{ $pkg }}: invalid string for error: %s", *v[0])
	}
	e.msg = strings.TrimPrefix(*v[0], e.prefix())
	return nil
}

// prefix returns the prefix used for gremlin constants.
func (ErrConstraintFailed) prefix() string { return "Error: " }

// NewErrUniqueField creates a constraint error for unique fields.
func NewErrUniqueField(label, field string, v interface{}) *ErrConstraintFailed {
	return &ErrConstraintFailed{msg: fmt.Sprintf("field %s.%s with value: %#v", label, field, v)}
}

// NewErrUniqueEdge creates a constraint error for unique edges.
func NewErrUniqueEdge(label, edge, id string) *ErrConstraintFailed {
	return &ErrConstraintFailed{msg: fmt.Sprintf("edge %s.%s with id: %#v", label, edge, id)}
}

// IsConstraintFailure returns a boolean indicating whether the error is a constraint failure.
func IsConstraintFailure(err error) bool {
	_, ok := err.(*ErrConstraintFailed)
	return ok
}

// isConstantError indicates if the given response holds a gremlin constant containing an error.
func isConstantError(r *gremlin.Response) (*ErrConstraintFailed, bool) {
	e := &ErrConstraintFailed{}
	if err := graphson.Unmarshal(r.Result.Data, e); err != nil {
		return nil, false
	}
	return e, true
}

func isSQLConstraintError(err error) (*ErrConstraintFailed, bool) {
	// Error number 1062 is ER_DUP_ENTRY in mysql, and "UNIQUE constraint failed" is SQLite prefix.
	if msg := err.Error(); strings.HasPrefix(msg, "Error 1062") || strings.HasPrefix(msg, "UNIQUE constraint failed") {
		return &ErrConstraintFailed{msg, err}, true
	}
	return nil, false
}

// rollback calls to tx.Rollback and wraps the given error with the rollback error if occurred.
func rollback(tx dialect.Tx, err error) error {
	if rerr := tx.Rollback(); rerr != nil {
		err = fmt.Errorf("%s: %v", err.Error(), rerr)
	}
	if err, ok := isSQLConstraintError(err); ok {
		return err
	}
	return err
}

{{ $id := (index $.Nodes 0).ID.Type }}
// keys returns the keys/ids from the edge map.
func keys(m map[{{ $id }}]struct{}) []{{ $id }} {
	s := make([]{{ $id }}, 0, len(m))
	for id, _ := range m {
		s = append(s, id)
	}
	return s
}
{{ end }}