library/cmd/serve/api.go

package main

import (
	"encoding/json"
	"io"
	"io/fs"
	"net/http"

	"git.yetaga.in/alazyreader/library/media"
	"tailscale.com/client/tailscale"
)

type Router struct {
	static fs.FS
	lib    Library
	rcol   RecordCollection
}

type AdminRouter struct {
	static fs.FS
	lib    Library
	ts     *tailscale.LocalClient
}

type handler struct {
	get    func()
	post   func()
	put    func()
	delete func()
}

func (h handler) Handle(w http.ResponseWriter, req *http.Request) {
	if req.Method == http.MethodHead && h.get != nil {
		h.get()
	} else if req.Method == http.MethodGet && h.get != nil {
		h.get()
	} else if req.Method == http.MethodPost && h.post != nil {
		h.post()
	} else if req.Method == http.MethodPut && h.put != nil {
		h.put()
	} else if req.Method == http.MethodDelete && h.delete != nil {
		h.delete()
	} else {
		badMethod(w)
	}
}

func writeError[T any](t T, err error) func(w http.ResponseWriter) (T, bool) {
	return func(w http.ResponseWriter) (T, bool) {
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
		return t, err == nil
	}
}

func writeNoBody(w http.ResponseWriter, status int) {
	w.WriteHeader(status)
}
func writeJSON(w http.ResponseWriter, b any, status int) {
	bytes, err := json.Marshal(b)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	w.Write(bytes)
	w.Write([]byte("\n"))
}

func (router *Router) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	switch r.URL.Path {
	case "/api/records":
		handler{
			get: func() { getRecords(router.rcol, w, r) },
		}.Handle(w, r)
	case "/api/books":
		handler{
			get: func() { getBooks(router.lib, w, r) },
		}.Handle(w, r)
	default:
		static(router.static).ServeHTTP(w, r)
	}
}

func (router *AdminRouter) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	switch r.URL.Path {
	case "/api/whoami":
		handler{
			get: func() { getWhoAmI(router.ts, w, r) },
		}.Handle(w, r)
	case "/api/books":
		handler{
			get:    func() { getBooks(router.lib, w, r) },
			post:   func() { addBook(router.lib, w, r) },
			delete: func() { deleteBook(router.lib, w, r) },
		}.Handle(w, r)
	default:
		static(router.static).ServeHTTP(w, r)
	}
}

func badMethod(w http.ResponseWriter) {
	writeJSON(w,
		struct{ Error string }{Error: "method not supported"},
		http.StatusMethodNotAllowed)
}

func getBooks(l Library, w http.ResponseWriter, r *http.Request) {
	books, err := l.GetAllBooks(r.Context())
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, books, http.StatusOK)
}

func addBook(l Library, w http.ResponseWriter, r *http.Request) {
	if r.Body == nil {
		http.Error(w, "no body provided", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()
	b, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "error reading body", http.StatusBadRequest)
		return
	}
	book := &media.Book{}
	err = json.Unmarshal(b, book)
	if err != nil {
		http.Error(w, "error parsing body", http.StatusBadRequest)
		return
	}
	err = l.AddBook(r.Context(), book)
	if err != nil {
		http.Error(w, "error parsing body", http.StatusBadRequest)
		return
	}
	writeNoBody(w, http.StatusAccepted)
}

func deleteBook(l Library, w http.ResponseWriter, r *http.Request) {
	if r.Body == nil {
		http.Error(w, "no body provided", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()
	b, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "error reading body", http.StatusBadRequest)
		return
	}
	book := &media.Book{}
	err = json.Unmarshal(b, book)
	if err != nil {
		http.Error(w, "error parsing body", http.StatusBadRequest)
		return
	}
	err = l.DeleteBook(r.Context(), book)
	if err != nil {
		http.Error(w, "error parsing body", http.StatusBadRequest)
		return
	}
	writeNoBody(w, http.StatusAccepted)
}

func getRecords(l RecordCollection, w http.ResponseWriter, r *http.Request) {
	records, err := l.GetAllRecords(r.Context())
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	writeJSON(w, records, http.StatusOK)
}

func getWhoAmI(ts *tailscale.LocalClient, w http.ResponseWriter, r *http.Request) {
	whois, ok := writeError(ts.WhoIs(r.Context(), r.RemoteAddr))(w)
	if !ok {
		return
	}
	writeJSON(w, struct {
		Username      string `json:"Username"`
		DisplayName   string `json:"DisplayName"`
		ProfilePicURL string `json:"ProfilePicURL"`
	}{
		Username:      whois.UserProfile.LoginName,
		DisplayName:   whois.UserProfile.DisplayName,
		ProfilePicURL: whois.UserProfile.ProfilePicURL,
	}, http.StatusOK)
}

func static(f fs.FS) http.Handler {
	return http.FileServer(http.FS(f))
}