path: root/src/http/http.go

// Package http implements the HTTP-based api for the mediocre-blog.
package http

import (
	"context"
	"embed"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"net"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"dev.mediocregopher.com/mediocre-blog.git/src/cache"
	"dev.mediocregopher.com/mediocre-blog.git/src/cfg"
	"dev.mediocregopher.com/mediocre-blog.git/src/http/apiutil"
	"dev.mediocregopher.com/mediocre-blog.git/src/post"
	"dev.mediocregopher.com/mediocre-blog.git/src/post/asset"
	"dev.mediocregopher.com/mediocre-blog.git/src/render"
	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
)

//go:embed static
var staticFS embed.FS

// Params are used to instantiate a new API instance. All fields are required
// unless otherwise noted.
type Params struct {
	Logger *mlog.Logger
	Cache  cache.Cache

	PostStore       post.Store
	PostAssetStore  asset.Store
	PostAssetLoader asset.Loader
	PostDraftStore  post.DraftStore

	// PublicURL is the base URL which site visitors can navigate to.
	PublicURL *url.URL

	// GeminiPublicURL is the base URL which gemini site visitors can navigate
	// to.
	GeminiPublicURL *url.URL

	// ListenProto and ListenAddr are passed into net.Listen to create the
	// API's listener. Both "tcp" and "unix" protocols are explicitly
	// supported.
	ListenProto, ListenAddr string

	// AuthUsers keys are usernames which are allowed to edit server-side data,
	// and the values are the password hash which accompanies those users. The
	// password hash must have been produced by NewPasswordHash.
	AuthUsers map[string]string

	// AuthRatelimit indicates how much time must pass between subsequent auth
	// attempts.
	AuthRatelimit time.Duration

	// GeminiGatewayURL will be used to translate links for `gemini://` into
	// `http(s)://`. See gmi.GemtextToMarkdown.
	GeminiGatewayURL *url.URL
}

// SetupCfg implement the cfg.Cfger interface.
func (p *Params) SetupCfg(cfg *cfg.Cfg) {

	publicURLStr := cfg.String("http-public-url", "http://localhost:4000", "URL this service is accessible at")
	geminiGatewayURLStr := cfg.String("http-gemini-gateway-url", "", "Optional URL to prefix to all gemini:// links, to make them accessible over https")

	cfg.StringVar(&p.ListenProto, "http-listen-proto", "tcp", "Protocol to listen for HTTP requests with")
	cfg.StringVar(&p.ListenAddr, "http-listen-addr", ":4000", "Address/unix socket path to listen for HTTP requests on")

	httpAuthUsersStr := cfg.String("http-auth-users", "{}", "JSON object with usernames as values and password hashes (produced by the hash-password binary) as values. Denotes users which are able to edit server-side data")

	httpAuthRatelimitStr := cfg.String("http-auth-ratelimit", "5s", "Minimum duration which must be waited between subsequent auth attempts")

	cfg.OnInit(func(context.Context) error {

		err := json.Unmarshal([]byte(*httpAuthUsersStr), &p.AuthUsers)

		if err != nil {
			return fmt.Errorf("unmarshaling -http-auth-users: %w", err)
		}

		if p.AuthRatelimit, err = time.ParseDuration(*httpAuthRatelimitStr); err != nil {
			return fmt.Errorf("unmarshaling -http-auth-ratelimit: %w", err)
		}

		if !strings.HasSuffix(*publicURLStr, "/") {
			*publicURLStr += "/"
		}

		if p.PublicURL, err = url.Parse(*publicURLStr); err != nil {
			return fmt.Errorf("parsing -http-public-url: %w", err)
		}

		if *geminiGatewayURLStr != "" {
			if p.GeminiGatewayURL, err = url.Parse(*geminiGatewayURLStr); err != nil {
				return fmt.Errorf("parsing -http-gemini-gateway-url: %w", err)
			}
		}

		return nil
	})
}

// Annotate implements mctx.Annotator interface.
func (p *Params) Annotate(a mctx.Annotations) {
	a["httpPublicURL"] = p.PublicURL
	a["httpListenProto"] = p.ListenProto
	a["httpListenAddr"] = p.ListenAddr
	a["httpAuthRatelimit"] = p.AuthRatelimit
}

// API will listen on the port configured for it, and serve HTTP requests for
// the mediocre-blog.
type API interface {
	Shutdown(ctx context.Context) error
}

type api struct {
	params Params
	srv    *http.Server

	redirectTpl         *template.Template
	auther              Auther
	urlBuilder          render.URLBuilder
	postPreprocessFuncs postPreprocessFuncs
}

// New initializes and returns a new API instance, including setting up all
// listening ports.
func New(params Params) (API, error) {

	l, err := net.Listen(params.ListenProto, params.ListenAddr)
	if err != nil {
		return nil, fmt.Errorf("creating listen socket: %w", err)
	}

	if params.ListenProto == "unix" {
		if err := os.Chmod(params.ListenAddr, 0777); err != nil {
			return nil, fmt.Errorf("chmod-ing unix socket: %w", err)
		}
	}

	a := &api{
		params: params,
		auther: NewAuther(params.AuthUsers, params.AuthRatelimit),
		urlBuilder: render.NewURLBuilder(
			params.PublicURL,
			params.PublicURL, // httpURL
			params.GeminiPublicURL,
		),
	}

	a.postPreprocessFuncs = newPostPreprocessFuncs(a.urlBuilder)
	a.redirectTpl = mustParseTpl(template.New(""), "redirect.html")

	a.srv = &http.Server{Handler: a.handler()}

	go func() {
		err := a.srv.Serve(l)
		if err != nil && !errors.Is(err, http.ErrServerClosed) {
			ctx := mctx.WithAnnotator(context.Background(), &a.params)
			params.Logger.Fatal(ctx, "serving http server", err)
		}
	}()

	return a, nil
}

func (a *api) Shutdown(ctx context.Context) error {
	defer a.auther.Close()
	if err := a.srv.Shutdown(ctx); err != nil {
		return err
	}

	return nil
}

func (a *api) blogHandler() http.Handler {

	mux := http.NewServeMux()

	mux.Handle("/posts/", http.StripPrefix("/posts",
		apiutil.MethodMux(map[string]http.Handler{
			"GET":     a.getPostsHandler(),
			"EDIT":    a.editPostHandler(false),
			"MANAGE":  a.managePostsHandler(),
			"POST":    a.postPostHandler(),
			"DELETE":  a.deletePostHandler(false),
			"PREVIEW": a.previewPostHandler(),
		}),
	))

	mux.Handle("/assets/", http.StripPrefix("/assets",
		apiutil.MethodMux(map[string]http.Handler{
			"GET":    a.getPostAssetHandler(),
			"MANAGE": a.managePostAssetsHandler(),
			"POST":   a.postPostAssetHandler(),
			"DELETE": a.deletePostAssetHandler(),
		}),
	))

	mux.Handle("/drafts/", http.StripPrefix("/drafts",

		// everything to do with drafts is protected
		authMiddleware(
			a.params.Logger.WithNamespace("drafts-auther"), a.auther,
		)(
			apiutil.MethodMux(map[string]http.Handler{
				"EDIT":    a.editPostHandler(true),
				"MANAGE":  a.manageDraftPostsHandler(),
				"POST":    a.postDraftPostHandler(),
				"DELETE":  a.deletePostHandler(true),
				"PREVIEW": a.previewPostHandler(),
			}),
		),
	))

	mux.Handle("/static/", http.FileServer(http.FS(staticFS)))
	mux.Handle("/follow", a.renderDumbTplHandler("follow.html"))
	mux.Handle("/admin", a.renderDumbTplHandler("admin.html"))
	mux.Handle("/feed.xml", a.renderFeedHandler())
	mux.Handle("/", a.renderIndexHandler())

	readOnlyMiddlewares := []middleware{
		logReqMiddleware(a.params.Logger), // only log GETs on cache miss
		cacheMiddleware(a.params.Cache, a.params.PublicURL),
	}

	readWriteMiddlewares := []middleware{
		purgeCacheOnOKMiddleware(a.params.Logger, a.params.Cache),
		authMiddleware(a.params.Logger.WithNamespace("rw-auther"), a.auther),
	}

	h := apiutil.MethodMux(map[string]http.Handler{
		"GET":    applyMiddlewares(mux, readOnlyMiddlewares...),
		"MANAGE": applyMiddlewares(mux, readOnlyMiddlewares...),
		"EDIT":   applyMiddlewares(mux, readOnlyMiddlewares...),
		"*":      applyMiddlewares(mux, readWriteMiddlewares...),
	})

	return h
}

func (a *api) handler() http.Handler {

	mux := http.NewServeMux()

	mux.Handle("/", a.blogHandler())

	noCacheMiddleware := addResponseHeadersMiddleware(map[string]string{
		"Cache-Control": "no-store, max-age=0",
		"Pragma":        "no-cache",
		"Expires":       "0",
	})

	h := applyMiddlewares(
		apiutil.MethodMux(map[string]http.Handler{
			"GET":    applyMiddlewares(mux),
			"MANAGE": applyMiddlewares(mux, noCacheMiddleware),
			"EDIT":   applyMiddlewares(mux, noCacheMiddleware),
			"*": applyMiddlewares(
				mux,
				a.checkCSRFMiddleware,
				noCacheMiddleware,
			),
		}),
		setLogCtxMiddleware(),
	)

	return h
}