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plugin.go
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plugin.go
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// Package plugin implements a plugin layer for gentleman components.
// Exports the required interface that must be implemented by plugins.
//
// Plugins are phase-oriented middleware function handlers encapsulated
// in a simple interface that will be consumed by the middleware layer in
// order to trigger the plugin handler.
//
// Plugin implementors can decide to build a plugin to handle a unique
// middleware phase or instead handle multiple phases: request, response, error...
package plugin
import (
"gopkg.in/h2non/gentleman.v0/context"
)
// Plugin interface that must be implemented by plugins
type Plugin interface {
// Enable enabled the plugin
Enable()
// Disable disables the plugin
Disable()
// Disabled returns true if the plugin is enabled
Disabled() bool
// Remove will remove the plugin from the middleware stack
Remove()
// Enabled returns true if the plugin was removed
Removed() bool
// Exec executes the plugin handler for a specific middleware phase.
Exec(string, *context.Context, context.Handler)
}
// Handlers represents a map to store middleware handler functions per phase.
type Handlers map[string]context.HandlerFunc
// Layer encapsulates an Error, Request and Response function handlers
type Layer struct {
// removed stores if the plugin was removed
removed bool
// disabled stores if the plugin was disabled
disabled bool
// Handlers defines the required handlers
Handlers Handlers
// DefaultHandler is an optional field used to store
// a default handler for any middleware phase.
DefaultHandler context.HandlerFunc
}
// New creates a new plugin layer.
func New() *Layer {
return &Layer{Handlers: make(Handlers)}
}
// Disable will disable the current plugin
func (p *Layer) Disable() {
p.disabled = true
}
// Enable will enable the current plugin
func (p *Layer) Enable() {
p.disabled = false
}
// Disabled returns true if the plugin is enabled
func (p *Layer) Disabled() bool {
return p.disabled
}
// Remove will remove the plugin from the middleware stack
func (p *Layer) Remove() {
p.removed = true
}
// Removed returns true if the plugin Was removed
func (p *Layer) Removed() bool {
return p.removed
}
// SetHandler uses a new handler function for the given middleware phase.
func (p *Layer) SetHandler(phase string, handler context.HandlerFunc) {
p.Handlers[phase] = handler
}
// SetHandlers uses a new map of handler functions.
func (p *Layer) SetHandlers(handlers Handlers) {
p.Handlers = handlers
}
// Exec executes the plugin handler for the given middleware phase passing the given context.
func (p *Layer) Exec(phase string, ctx *context.Context, h context.Handler) {
if p.disabled || p.removed {
h.Next(ctx)
return
}
fn := p.Handlers[phase]
if fn == nil {
fn = p.DefaultHandler
}
if fn == nil {
h.Next(ctx)
return
}
fn(ctx, h)
}
// NewPhasePlugin creates a new plugin layer
// to handle a given middleware phase.
func NewPhasePlugin(phase string, handler context.HandlerFunc) Plugin {
return &Layer{Handlers: Handlers{phase: handler}}
}
// NewResponsePlugin creates a new plugin layer
// to handle response middleware phase
func NewResponsePlugin(handler context.HandlerFunc) Plugin {
return NewPhasePlugin("response", handler)
}
// NewRequestPlugin creates a new plugin layer
// to handle request middleware phase
func NewRequestPlugin(handler context.HandlerFunc) Plugin {
return NewPhasePlugin("request", handler)
}
// NewErrorPlugin creates a new plugin layer
// to handle error middleware phase
func NewErrorPlugin(handler context.HandlerFunc) Plugin {
return NewPhasePlugin("error", handler)
}