94 lines
2.3 KiB
Go
94 lines
2.3 KiB
Go
// Package middleware implements the TrackerLogic interface by executing
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// a series of middleware hooks.
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package middleware
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import (
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"errors"
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"sync"
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"gopkg.in/yaml.v2"
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)
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var (
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driversM sync.RWMutex
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drivers = make(map[string]Driver)
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// ErrDriverDoesNotExist is the error returned by NewMiddleware when a
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// middleware driver with that name does not exist.
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ErrDriverDoesNotExist = errors.New("middleware driver with that name does not exist")
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)
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// Driver is the interface used to initialize a new type of middleware.
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//
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// The options parameter is YAML encoded bytes that should be unmarshalled into
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// the hook's custom configuration.
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type Driver interface {
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NewHook(options []byte) (Hook, error)
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}
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// RegisterDriver makes a Driver available by the provided name.
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//
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// If called twice with the same name, the name is blank, or if the provided
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// Driver is nil, this function panics.
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func RegisterDriver(name string, d Driver) {
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if name == "" {
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panic("middleware: could not register a Driver with an empty name")
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}
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if d == nil {
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panic("middleware: could not register a nil Driver")
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}
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driversM.Lock()
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defer driversM.Unlock()
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if _, dup := drivers[name]; dup {
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panic("middleware: RegisterDriver called twice for " + name)
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}
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drivers[name] = d
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}
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// New attempts to initialize a new middleware instance from the
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// list of registered Drivers.
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//
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// If a driver does not exist, returns ErrDriverDoesNotExist.
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func New(name string, optionBytes []byte) (Hook, error) {
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driversM.RLock()
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defer driversM.RUnlock()
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var d Driver
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d, ok := drivers[name]
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if !ok {
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return nil, ErrDriverDoesNotExist
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}
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return d.NewHook(optionBytes)
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}
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// HookConfig is the generic configuration format used for all registered Hooks.
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type HookConfig struct {
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Name string `yaml:"name"`
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Options map[string]interface{} `yaml:"options"`
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}
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// HooksFromHookConfigs is a utility function for initializing Hooks in bulk.
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func HooksFromHookConfigs(cfgs []HookConfig) (hooks []Hook, err error) {
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for _, cfg := range cfgs {
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// Marshal the options back into bytes.
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var optionBytes []byte
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optionBytes, err = yaml.Marshal(cfg.Options)
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if err != nil {
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return
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}
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var h Hook
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h, err = New(cfg.Name, optionBytes)
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if err != nil {
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return
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}
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hooks = append(hooks, h)
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}
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return
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}
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