ent/entc/gen/template/privacy/privacy.tmpl

{{/*
Copyright 2019-present Facebook Inc. All rights reserved.
This source code is licensed under the Apache 2.0 license found
in the LICENSE file in the root directory of this source tree.
*/}}

{{ define "privacy" }}

{{- with extend $ "Package" "privacy" -}}
	{{ template "header" . }}
{{ end }}

import "{{ $.Config.Package }}"

{{ $pkg := base $.Config.Package }}

var (
	// Allow may be returned by rules to indicate that the policy
	// evaluation should terminate with an allow decision.
	Allow = errors.New("ent/privacy: allow rule")

	// Deny may be returned by rules to indicate that the policy
	// evaluation should terminate with an deny decision.
	Deny = errors.New("ent/privacy: deny rule")

	// Skip may be returned by rules to indicate that the policy
	// evaluation should continue to the next rule.
	Skip = errors.New("ent/privacy: skip rule")
)

{{- range $decision := list "Allow" "Deny" "Skip" }}
	// {{ $decision }}f returns an formatted wrapped {{ $decision }} decision.
	func {{ $decision }}f(format string, a ...interface{}) error {
		return fmt.Errorf(format+": %w", append(a, {{ $decision }})...)
	}
{{- end }}

type decisionCtxKey struct {}

// DecisionContext creates a decision context.
func DecisionContext(parent context.Context, decision error) context.Context {
	if decision == nil || errors.Is(decision, Skip) {
		return parent
	}
	return context.WithValue(parent, decisionCtxKey{}, decision)
}

func decisionFromContext(ctx context.Context) (error, bool) {
	decision, ok := ctx.Value(decisionCtxKey{}).(error)
	if ok && errors.Is(decision, Allow) {
		decision = nil
	}
	return decision, ok
}

type (
	// QueryPolicy combines multiple query rules into a single policy.
	QueryPolicy []QueryRule

	// QueryRule defines the interface deciding whether a
	// query is allowed and optionally modify it.
	QueryRule interface {
		EvalQuery(context.Context, {{ $pkg }}.Query) error
	}
)

// EvalQuery evaluates a query against a query policy.
func (policy QueryPolicy) EvalQuery(ctx context.Context, q {{ $pkg }}.Query) error {
	if decision, ok := decisionFromContext(ctx); ok {
		return decision
	}
	for _, rule := range policy {
		switch decision := rule.EvalQuery(ctx, q); {
		case decision == nil || errors.Is(decision, Skip):
		case errors.Is(decision, Allow):
			return nil
		default:
			return decision
		}
	}
	return nil
}

// QueryRuleFunc type is an adapter to allow the use of
// ordinary functions as query rules.
type QueryRuleFunc func(context.Context, {{ $pkg }}.Query) error

// Eval returns f(ctx, q).
func (f QueryRuleFunc) EvalQuery(ctx context.Context, q {{ $pkg }}.Query) error {
	return f(ctx, q)
}

type (
	// MutationPolicy combines multiple mutation rules into a single policy.
	MutationPolicy []MutationRule

	// MutationRule defines the interface deciding whether a
	// mutation is allowed and optionally modify it.
	MutationRule interface {
		EvalMutation(context.Context, {{ $pkg }}.Mutation) error
	}
)

// EvalMutation evaluates a mutation against a mutation policy.
func (policy MutationPolicy) EvalMutation(ctx context.Context, m {{ $pkg }}.Mutation) error {
	if decision, ok := decisionFromContext(ctx); ok {
		return decision
	}
	for _, rule := range policy {
		switch decision := rule.EvalMutation(ctx, m); {
		case decision == nil || errors.Is(decision, Skip):
		case errors.Is(decision, Allow):
			return nil
		default:
			return decision
		}
	}
	return nil
}

// MutationRuleFunc type is an adapter to allow the use of
// ordinary functions as mutation rules.
type MutationRuleFunc func(context.Context, {{ $pkg }}.Mutation) error

// EvalMutation returns f(ctx, m).
func (f MutationRuleFunc) EvalMutation(ctx context.Context, m {{ $pkg }}.Mutation) error {
	return f(ctx, m)
}

// Policy groups query and mutation policies.
type Policy struct {
	Query QueryPolicy
	Mutation MutationPolicy
}

// EvalQuery forwards evaluation to query policy.
func (policy Policy) EvalQuery(ctx context.Context, q {{ $pkg }}.Query) error {
	return policy.Query.EvalQuery(ctx, q)
}

// EvalMutation forwards evaluation to mutation policy.
func (policy Policy) EvalMutation(ctx context.Context, m {{ $pkg }}.Mutation) error {
	return policy.Mutation.EvalMutation(ctx, m)
}

// QueryMutationRule is the interface that groups query and mutation rules.
type QueryMutationRule interface {
	QueryRule
	MutationRule
}

// AlwaysAllowRule returns a rule that returns an allow decision.
func AlwaysAllowRule() QueryMutationRule {
	return fixedDecision{Allow}
}

// AlwaysDenyRule returns a rule that returns a deny decision.
func AlwaysDenyRule() QueryMutationRule {
	return fixedDecision{Deny}
}

type fixedDecision struct {
	decision error
}

func (f fixedDecision) EvalQuery(context.Context, {{ $pkg }}.Query) error {
	return f.decision
}

func (f fixedDecision) EvalMutation(context.Context, {{ $pkg }}.Mutation) error {
	return f.decision
}

type contextDecision struct {
	eval func(context.Context) error
}

// ContextQueryMutationRule creates a query/mutation rule from a context eval func.
func ContextQueryMutationRule(eval func(context.Context) error) QueryMutationRule {
	return contextDecision{eval}
}

func (c contextDecision) EvalQuery(ctx context.Context, _ {{ $pkg }}.Query) error {
	return c.eval(ctx)
}

func (c contextDecision) EvalMutation(ctx context.Context, _ {{ $pkg }}.Mutation) error {
	return c.eval(ctx)
}

// OnMutationOperation evaluates the given rule only on a given mutation operation.
func OnMutationOperation(rule MutationRule, op {{ $pkg }}.Op) MutationRule {
	return MutationRuleFunc(func(ctx context.Context, m {{ $pkg }}.Mutation) error {
		if m.Op().Is(op) {
			return rule.EvalMutation(ctx, m)
		}
		return Skip
	})
}

// DenyMutationOperationRule returns a rule denying specified mutation operation.
func DenyMutationOperationRule(op {{ $pkg }}.Op) MutationRule {
	rule := MutationRuleFunc(func(_ context.Context, m {{ $pkg }}.Mutation) error {
		return Denyf("ent/privacy: operation %s is not allowed", m.Op())
	})
	return OnMutationOperation(rule, op)
}

{{- range $n := $.Nodes }}
	{{ $name := print $n.Name "QueryRuleFunc" }}
	{{ $type := printf "*%s.%s" $pkg $n.QueryName }}
	// The {{ $name }} type is an adapter to allow the use of ordinary
	// functions as a query rule.
	type {{ $name }} func(context.Context, {{ $type }}) error

	// EvalQuery return f(ctx, q).
	func (f {{ $name }}) EvalQuery(ctx context.Context, q {{ $pkg }}.Query) error {
		if q, ok := q.({{ $type }}); ok {
			return f(ctx, q)
		}
		return Denyf("ent/privacy: unexpected query type %T, expect {{ $type }}", q)
	}

	{{ $name = print $n.Name "MutationRuleFunc" }}
	{{ $type = printf "*%s.%s" $pkg $n.MutationName }}
	// The {{ $name }} type is an adapter to allow the use of ordinary
	// functions as a mutation rule.
	type {{ $name }} func(context.Context, {{ $type }}) error

	// EvalMutation calls f(ctx, m).
	func (f {{ $name }}) EvalMutation(ctx context.Context, m {{ $pkg }}.Mutation) error {
		if m, ok := m.({{ $type }}); ok {
			return f(ctx, m)
		}
		return Denyf("ent/privacy: unexpected mutation type %T, expect {{ $type }}", m)
	}
{{- end }}

{{ end }}