tracker/tracker/middleware.go

// Copyright 2016 The Chihaya Authors. All rights reserved.
// Use of this source code is governed by the BSD 2-Clause license,
// which can be found in the LICENSE file.

package tracker

import "github.com/chihaya/chihaya"

// AnnounceHandler is a function that operates on an AnnounceResponse before it
// has been delivered to a client.
type AnnounceHandler func(*chihaya.TrackerConfig, *chihaya.AnnounceRequest, *chihaya.AnnounceResponse) error

// AnnounceMiddleware is a higher-order function used to implement the chaining
// of AnnounceHandlers.
type AnnounceMiddleware func(AnnounceHandler) AnnounceHandler

// AnnounceMiddlewareConstructor is a function that creates a new
// AnnounceMiddleware from a MiddlewareConfig.
type AnnounceMiddlewareConstructor func(chihaya.MiddlewareConfig) (AnnounceMiddleware, error)

type announceChain struct{ mw []AnnounceMiddleware }

func (c *announceChain) Append(mw ...AnnounceMiddleware) {
	c.mw = append(c.mw, mw...)
}

func (c *announceChain) Handler() AnnounceHandler {
	final := func(cfg *chihaya.TrackerConfig, req *chihaya.AnnounceRequest, resp *chihaya.AnnounceResponse) error {
		return nil
	}

	for i := len(c.mw) - 1; i >= 0; i-- {
		final = c.mw[i](final)
	}
	return final
}

var announceMiddlewareConstructors = make(map[string]AnnounceMiddlewareConstructor)

// RegisterAnnounceMiddlewareConstructor makes a configurable middleware
// globally available under the provided name.
//
// If this function is called twice with the same name or if the constructor is
// nil, it panics.
func RegisterAnnounceMiddlewareConstructor(name string, mw AnnounceMiddlewareConstructor) {
	if mw == nil {
		panic("tracker: could not register nil AnnounceMiddlewareConstructor")
	}

	if _, dup := announceMiddlewareConstructors[name]; dup {
		panic("tracker: could not register duplicate AnnounceMiddleware: " + name)
	}

	announceMiddlewareConstructors[name] = mw
}

// RegisterAnnounceMiddleware makes a middleware globally available under the
// provided name.
//
// This function is intended to register middleware that has no configuration.
// If this function is called twice with the same name or if the middleware is
// nil, it panics.
func RegisterAnnounceMiddleware(name string, mw AnnounceMiddleware) {
	if mw == nil {
		panic("tracker: could not register nil AnnounceMiddleware")
	}

	RegisterAnnounceMiddlewareConstructor(name, func(_ chihaya.MiddlewareConfig) (AnnounceMiddleware, error) {
		return mw, nil
	})
}

// ScrapeHandler is a function that operates on a ScrapeResponse before it has
// been delivered to a client.
type ScrapeHandler func(*chihaya.TrackerConfig, *chihaya.ScrapeRequest, *chihaya.ScrapeResponse) error

// ScrapeMiddleware is higher-order function used to implement the chaining of
// ScrapeHandlers.
type ScrapeMiddleware func(ScrapeHandler) ScrapeHandler

// ScrapeMiddlewareConstructor is a function that creates a new
// ScrapeMiddleware from a MiddlewareConfig.
type ScrapeMiddlewareConstructor func(chihaya.MiddlewareConfig) (ScrapeMiddleware, error)

type scrapeChain struct{ mw []ScrapeMiddleware }

func (c *scrapeChain) Append(mw ...ScrapeMiddleware) {
	c.mw = append(c.mw, mw...)
}

func (c *scrapeChain) Handler() ScrapeHandler {
	final := func(cfg *chihaya.TrackerConfig, req *chihaya.ScrapeRequest, resp *chihaya.ScrapeResponse) error {
		return nil
	}
	for i := len(c.mw) - 1; i >= 0; i-- {
		final = c.mw[i](final)
	}
	return final
}

var scrapeMiddlewareConstructors = make(map[string]ScrapeMiddlewareConstructor)

// RegisterScrapeMiddlewareConstructor makes a configurable middleware globally
// available under the provided name.
//
// If this function is called twice with the same name or if the constructor is
// nil, it panics.
func RegisterScrapeMiddlewareConstructor(name string, mw ScrapeMiddlewareConstructor) {
	if mw == nil {
		panic("tracker: could not register nil ScrapeMiddlewareConstructor")
	}

	if _, dup := scrapeMiddlewareConstructors[name]; dup {
		panic("tracker: could not register duplicate ScrapeMiddleware: " + name)
	}

	scrapeMiddlewareConstructors[name] = mw
}

// RegisterScrapeMiddleware makes a middleware globally available under the
// provided name.
//
// This function is intended to register middleware that has no configuration.
// If this function is called twice with the same name or if the middleware is
// nil, it panics.
func RegisterScrapeMiddleware(name string, mw ScrapeMiddleware) {
	if mw == nil {
		panic("tracker: could not register nil ScrapeMiddleware")
	}

	RegisterScrapeMiddlewareConstructor(name, func(_ chihaya.MiddlewareConfig) (ScrapeMiddleware, error) {
		return mw, nil
	})
}