package webcontroller

import (
	"errors"
	"fmt"
	"html/template"
	"net/http"
	"net/http/httputil"
	"net/url"
	"os"
	"strings"

	"fornaxian.tech/log"
	"fornaxian.tech/pixeldrain_api_client/pixelapi"
	"github.com/julienschmidt/httprouter"
)

type Config struct {
	APIURLExternal   string `toml:"api_url_external"`
	APIURLInternal   string `toml:"api_url_internal"`
	APISocketPath    string `toml:"api_socket_path"`
	ResourceDir      string `toml:"resource_dir"`
	DebugMode        bool   `toml:"debug_mode"`
	ProxyAPIRequests bool   `toml:"proxy_api_requests"`
}

// WebController controls how requests are handled and makes sure they have
// proper context when running
type WebController struct {
	tpl    *template.Template
	config Config

	// Server hostname, displayed in the footer of every web page
	hostname string

	// API client to use for all requests. If the user is authenticated you
	// should call Login() on this object. Calling Login will create a copy and
	// not alter the original PixelAPI, but it will use the same HTTP Transport
	api pixelapi.PixelAPI
}

// New initializes a new WebController by registering all the request handlers
// and parsing the page template
func New(r *httprouter.Router, conf Config) (wc *WebController) {
	hostname, err := os.Hostname()
	if err != nil {
		panic(fmt.Errorf("could not get hostname: %s", err))
	}

	wc = &WebController{
		config:   conf,
		hostname: hostname,
		api:      pixelapi.New(conf.APIURLInternal),
	}
	if conf.APISocketPath != "" {
		wc.api = wc.api.UnixSocketPath(conf.APISocketPath)
	}
	wc.tpl = wc.parseTemplate()

	// Serve static files
	var fs = http.FileServer(http.Dir(conf.ResourceDir + "/static"))
	var resourceHandler = func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
		// Cache resources for a year. Except the Svelte entrypoint, it keeps its
		// name when it changes. The chunks it imports have a hash in their name
		if p.ByName("filepath") == "/svelte/wrap.js" {
			w.Header().Set("Cache-Control", "no-cache")
		} else {
			w.Header().Set("Cache-Control", "public, max-age=31536000")
		}
		r.URL.Path = p.ByName("filepath")
		fs.ServeHTTP(w, r)
	}
	r.HEAD("/res/*filepath", resourceHandler)
	r.OPTIONS("/res/*filepath", resourceHandler)
	r.GET("/res/*filepath", resourceHandler)

	// Browsers and crawlers look for these in the root
	var rootFile = func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) { fs.ServeHTTP(w, r) }
	r.GET("/favicon.ico", rootFile)
	r.GET("/robots.txt", rootFile)

	if conf.ProxyAPIRequests {
		remoteURL, err := url.Parse(strings.TrimSuffix(conf.APIURLInternal, "/api"))
		if err != nil {
			panic(fmt.Errorf("failed to parse reverse proxy URL '%s': %w", conf.APIURLInternal, err))
		}

		log.Info("Starting API proxy to %s", remoteURL)
		var prox = httputil.NewSingleHostReverseProxy(remoteURL)
		var proxyHandler = func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
			log.Info("Proxying request to %s", r.URL)
			r.Host = remoteURL.Host
			r.Header.Set("Origin", remoteURL.String())
			prox.ServeHTTP(w, r)
		}
		for _, method := range []string{"OPTIONS", "GET", "POST", "PUT", "PATCH", "DELETE"} {
			r.Handle(method, "/api/*p", proxyHandler)
		}
	}

	// Every other path is a page of the app, which shows its own not found
	// message for paths it doesn't know
	var page = middleware(func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
		w.Header().Set("X-Frame-Options", "DENY")
		wc.renderPage(w, r, wc.newTemplateData(r))
	})
	r.NotFound = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { page(w, r, nil) })

	// Filesystem pages embed the requested node, for link previews
	var directory = middleware(wc.serveDirectory)
	r.GET("/d/*path", directory)
	r.HEAD("/d/*path", directory)

	return wc
}

func middleware(handle httprouter.Handle) httprouter.Handle {
	return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
		// Redirect the user to the correct domain
		if hostname, found := strings.CutPrefix(r.Host, "www."); found {
			http.Redirect(
				w, r,
				"https://"+hostname+r.URL.String(),
				http.StatusMovedPermanently,
			)
			return
		}

		w.Header().Set("Strict-Transport-Security", "max-age=31536000")
		w.Header().Set("X-Clacks-Overhead", "GNU Terry Pratchett")
		handle(w, r, p)
	}
}

func (wc *WebController) getAPIKey(r *http.Request) (key string, err error) {
	if cookie, err := r.Cookie("nova_auth_key"); err == nil {
		if len(cookie.Value) == 36 {
			return cookie.Value, nil
		}
	}
	return "", errors.New("not a valid Nova authentication cookie")
}