vinegar/servlet/config.go

package servlet

import (
	"encoding/json"
	"errors"
	"fmt"
	"geniuscartel.xyz/vinegar/vinegarUtil"
	"io/ioutil"
)

type (
	// ConfigType is an enum representing the types of configuration routes.
	// There are currently 3 options:
	//
	//	Text - Used for simple text/HTML routes.
	//	Image - Used for image file routes.
	//	SingleFile - Used for serving a single file.
	//
	// These constants define the allowed values for the ConfigType
	// field used when loading route configurations from a JSON file.
	//
	//
	// So when loading a JSON config, the "ConfigType" field must be
	// set to one of these constant values like "Text" or "Image".

	ConfigType string

	// ConfigEntry defines a single route configuration entry.
	// Used to configure routes from a JSON config file.
	ConfigEntry struct {

		// ConfigType indicates the type of route - Text, Image etc.
		ConfigType ConfigType

		// UrlPattern is the URL regex pattern to match for the route.
		UrlPattern string

		// FileLocation is the file path or directory to serve files from.
		FileLocation string

		// UseBuiltinCache indicates whether to use the built-in LRU cache.
		UseBuiltinCache bool
	}

	Config struct {
		ListeningAddress string
		Routes           []ConfigEntry
	}
)

const (
	// defaultTemplateFileName is the default file name for the generated
	// blank config template.
	defaultTemplateFileName = "servlet.json.example.tmpl"

	// defaultListeningPort is the default HTTP listening port.
	// Set to ":8080" to listen on port 8080.
	defaultListeningPort = ":8080"

	// defaultUrlPattern is the default URL pattern route.
	// Set to "/*" to match all URLs.
	defaultUrlPattern = "/*"

	// defaultFileLocation is the default file location to serve static files from.
	// Set to "errors/" to serve from a directory called "errors".
	defaultFileLocation = "errors/"
)

const (
	// Text is a ConfigType constant representing a text/HTML route.
	Text ConfigType = "Text"

	// Image is a ConfigType constant representing an image file route.
	Image = "Image"

	// SingleFile is a ConfigType constant representing a route that
	// serves a single file.
	SingleFile = "SingleFile"
)

func CreateBlankConfig() *Config {
	conf := Config{
		ListeningAddress: defaultListeningPort,
		Routes:           make([]ConfigEntry, 0, 10),
	}

	dummyRoute := ConfigEntry{
		ConfigType:      Text,
		UrlPattern:      defaultUrlPattern,
		FileLocation:    defaultFileLocation,
		UseBuiltinCache: false,
	}

	conf.Routes = append(conf.Routes, dummyRoute)

	return &conf
}

func LoadConfig(pathlike string) (*VinegarHttpServlet, error) {
	contents, err := vinegarUtil.GetDiskContent(pathlike)
	if err != nil {
		CreateBlankConfig()
		return nil, err
	}

	conf := Config{}
	err = json.Unmarshal(*contents, &conf)
	if err != nil {
		return nil, err
	}
	servlet := NewServlet(conf.ListeningAddress)
	for _, v := range conf.Routes {
		constructor, err := getConstructorFunction(v.ConfigType)
		if err != nil {

			return nil, err
		}
		//we don't have to invoke servlet.AddRoute because the static routes already do that for us
		constructor(servlet, v.UrlPattern, v.FileLocation, v.UseBuiltinCache)

	}
	return servlet, nil

}

func (e ConfigEntry) toRoute(serv *VinegarHttpServlet) error {
	constructor, err := getConstructorFunction(e.ConfigType)
	if err != nil {
		return err
	}
	constructor(serv, e.UrlPattern, e.FileLocation, e.UseBuiltinCache)
	return nil
}

func getConstructorFunction(t ConfigType) (RouteConstructor, error) {
	switch t {
	case Text:
		return NewTextRoute, nil
	case Image:
		return NewImageRoute, nil
	case SingleFile:
		return NewSingleFileRoute, nil
	}
	return nil, errors.New(fmt.Sprintf("could not determine constructor for invalid ConfigType: %s", t))
}

func GenerateBlankConfig() error {
	conf := CreateBlankConfig()
	content, err := json.Marshal(&conf)
	if err != nil {
		return err
	}
	fmt.Println("Generating a blank configuration file at ")
	ioutil.WriteFile(defaultTemplateFileName, content, 0755)
	return nil
}