grafana/pkg/services/ngalert/api/hooks.go

package api

import (
	"net/url"

	"github.com/grafana/grafana/pkg/api/response"
	"github.com/grafana/grafana/pkg/infra/log"
	contextmodel "github.com/grafana/grafana/pkg/services/contexthandler/model"
)

type RequestHandlerFunc func(*contextmodel.ReqContext) response.Response

type Hooks struct {
	logger log.Logger
	hooks  map[string]RequestHandlerFunc
}

// NewHooks creates an empty set of request handler hooks. Hooks can be used
// to replace handlers for specific paths.
func NewHooks(logger log.Logger) *Hooks {
	return &Hooks{
		logger: logger,
		hooks:  make(map[string]RequestHandlerFunc),
	}
}

// Add creates a new request hook for a path, causing requests to the path to
// be handled by the hook function, and not the original handler.
func (h *Hooks) Set(path string, hook RequestHandlerFunc) {
	h.logger.Info("Setting hook override for the specified route", "path", path)
	h.hooks[path] = hook
}

// Get returns a hook if one is defined for the matching URL.
// Get also returns a bool indicating whether or not a matching hook exists.
func (h *Hooks) Get(url *url.URL) (RequestHandlerFunc, bool) {
	hook, ok := h.hooks[url.Path]
	return hook, ok
}

// Wrap returns a new handler which will intercept paths with hooks configured,
// and invoke the hooked in handler instead. If no hook is configured for a path,
// then the given handler is invoked.
func (h *Hooks) Wrap(next RequestHandlerFunc) RequestHandlerFunc {
	return func(req *contextmodel.ReqContext) response.Response {
		if hook, ok := h.Get(req.Context.Req.URL); ok {
			h.logger.Debug("Hook defined - invoking new handler", "path", req.Context.Req.URL.Path)
			return hook(req)
		}
		return next(req)
	}
}