78 lines
2.8 KiB
Go
78 lines
2.8 KiB
Go
// Copyright 2016 Pulumi, Inc. All rights reserved.
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package resource
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import (
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"strings"
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"github.com/pulumi/coconut/pkg/tokens"
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"github.com/pulumi/coconut/pkg/util/contract"
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)
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// URN is a friendly, but unique, URN for a resource, most often auto-assigned by Coconut. These are
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// used as unique IDs for objects, and help us to perform graph diffing and resolution of resource objects.
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//
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// In theory, we could support manually assigned URIs in the future. For the time being, however, we have opted to
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// simplify developers' lives by mostly automating the generation of them algorithmically. The one caveat where it
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// isn't truly automatic is that a developer -- or resource provider -- must provide a semi-unique name part.
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//
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// Each resource URN is of the form:
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//
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// urn:coconut:<Namespace>::<AllocModule>::<Type>::<Name>
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//
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// wherein each element is the following:
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//
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// <Namespace> The namespace being deployed into
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// <AllocModule> The module token in which the object was allocated
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// <Type> The object type's full type token
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// <Name> The human-friendly name identifier assigned by the developer or provider
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//
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// In the future, we may add elements to the URN; it is more important that it is unique than it is human-typable.
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type URN string
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const (
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URNPrefix = "urn:" + URNNamespaceID + ":" // the standard URN prefix
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URNNamespaceID = "coconut" // the URN namespace
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URNNameDelimiter = "::" // the delimiter between URN name elements
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)
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// NewURN creates a unique resource URN for the given resource object.
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func NewURN(ns tokens.QName, alloc tokens.Module, t tokens.Type, name tokens.QName) URN {
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urn := URN(
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URNPrefix +
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string(ns) +
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URNNameDelimiter + string(alloc) +
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URNNameDelimiter + string(t) +
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URNNameDelimiter + string(name),
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)
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contract.Assert(!urn.Replacement())
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return urn
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}
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// replaceURNSuffix is the suffix for URNs referring to resources that are being replaced.
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const replaceURNSuffix = URN("#<new-id(replace)>")
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// Name returns the name part of a URN.
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func (urn URN) Name() string {
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urns := string(urn)
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contract.Assert(strings.HasPrefix(urns, URNPrefix))
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return urns[len(URNPrefix):]
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}
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// Replace returns a new, modified replacement URN (used to tag resources that are meant to be replaced).
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func (urn URN) Replace() URN {
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contract.Assert(!urn.Replacement())
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return urn + replaceURNSuffix
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}
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// Unreplace returns the underlying replacement's URN.
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func (urn URN) Unreplace() URN {
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contract.Assert(urn.Replacement())
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return urn[:len(urn)-len(replaceURNSuffix)]
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}
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// Replacement returns true if this URN refers to a resource that is meant to be replaced.
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func (urn URN) Replacement() bool {
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return strings.HasSuffix(string(urn), string(replaceURNSuffix))
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}
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