Ilia Denisov
67 lines
2.4 KiB
Go
67 lines
2.4 KiB
Go
// Package engineimage resolves the Docker reference Lobby publishes on
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// `runtime:start_jobs`. The reference is built from a configurable
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// template that must contain the literal `{engine_version}` placeholder
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// and a per-game `target_engine_version`.
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//
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// The resolver intentionally performs only template substitution and a
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// non-empty-version guard. Semver validation of the engine version
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// itself lives in `lobby/internal/domain/game` and runs at game-record
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// construction time; by the time `startgame.Service.Handle` reads the
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// record the version is already validated.
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package engineimage
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import (
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"errors"
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"fmt"
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"strings"
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)
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// VersionPlaceholder is the literal token a template must contain. The
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// resolver substitutes it with the per-game engine version verbatim.
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const VersionPlaceholder = "{engine_version}"
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// Resolver substitutes a per-game engine version into a pre-validated
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// template. The template is validated once at construction so per-game
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// `Resolve` calls remain pure string substitution.
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type Resolver struct {
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template string
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}
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// NewResolver returns a Resolver that uses template for every Resolve
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// call. It returns an error if template is empty or does not contain
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// VersionPlaceholder.
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func NewResolver(template string) (*Resolver, error) {
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trimmed := strings.TrimSpace(template)
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if trimmed == "" {
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return nil, errors.New("engine image resolver: template must not be empty")
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}
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if !strings.Contains(trimmed, VersionPlaceholder) {
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return nil, fmt.Errorf(
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"engine image resolver: template %q must contain placeholder %q",
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template, VersionPlaceholder,
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)
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}
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return &Resolver{template: trimmed}, nil
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}
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// Template returns the validated template string the resolver was
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// constructed with. The accessor is intended for diagnostics and tests.
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func (resolver *Resolver) Template() string {
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if resolver == nil {
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return ""
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}
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return resolver.template
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}
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// Resolve substitutes VersionPlaceholder in the validated template with
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// version. It returns an error when version is empty or whitespace.
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func (resolver *Resolver) Resolve(version string) (string, error) {
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if resolver == nil {
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return "", errors.New("engine image resolver: nil resolver")
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}
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if strings.TrimSpace(version) == "" {
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return "", errors.New("engine image resolver: engine version must not be empty")
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}
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return strings.ReplaceAll(resolver.template, VersionPlaceholder, version), nil
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}
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