package server

import (
	`encoding/json`
	`encoding/xml`
	"errors"
	"fmt"
	"net"
	"net/http"
	`net/http/fcgi`
	"net/netip"
	"net/url"
	"os"
	"os/signal"
	"strings"
	"sync"
	`syscall`

	sysd "github.com/coreos/go-systemd/daemon"
	"github.com/davecgh/go-spew/spew"
	`github.com/goccy/go-yaml`
	`r00t2.io/clientinfo/version`
	"r00t2.io/goutils/multierr"
)

// Close cleanly closes any remnants of a Server. Stop should be used instead to cleanly shut down; this is a little more aggressive.
func (s *Server) Close() (err error) {

	s.log.Debug("server.Server.Close: Closing sockets.")

	if err = s.cleanup(false); err != nil {
		s.log.Err("server.Server.Close: Received error closing sockets: %v", err)
	}

	s.log.Debug("server.Server.Close: Sockets closed.")

	return
}

/*
	Run starts and runs the server. This process blocks and will shutdown on a systemd notify signal or kill signal.
	Non-HTML requests will be of type R00tInfo serialized to the requested MIME type.
*/
func (s *Server) Run() (err error) {

	var wg sync.WaitGroup
	var errChan chan error
	var mErr *multierr.MultiError = multierr.NewMultiError(nil)
	var numJobs int = 2 // sigs, listener

	s.log.Debug("server.Server.Run: Starting server.")

	signal.Notify(s.reloadChan, reloadSigs...)
	signal.Notify(s.stopChan, stopSigs...)
	s.doneChan = make(chan bool, 1)

	errChan = make(chan error, numJobs)
	wg.Add(numJobs)

	// sigs
	go func() {
		var sigErr error
		var sig os.Signal
		var smErr *multierr.MultiError = multierr.NewMultiError(nil)

		defer wg.Done()

	sigtrap:
		for !s.isStopping {
			if s.isStopping {
				break sigtrap
			}
			sig = <-s.reloadChan
			s.log.Debug("server.Server.Run: Recived signal %v (%#v): %v", sig, sig, sig.String())
			switch sig {
			case syscall.SIGHUP:
				s.log.Debug("server.Server.Run: Recived reload signal.")
				if s.isStopping {
					s.log.Debug("server.Server.Run: Server is stopping; abandoning reload.")
					if sigErr = s.Stop(); sigErr != nil {
						s.log.Err("server.Server.Run: Received error while stopping the server: %v", sigErr)
						sigErr = nil
					}
				} else {
					if sigErr = s.Reload(); sigErr != nil {
						s.log.Err("server.Server.Run: Received error while reloading the server: %v", sigErr)
						smErr.AddError(sigErr)
						sigErr = nil
					}
					break sigtrap
				}
			default:
				// Stop signal.
				s.log.Debug("server.Server.Run: Recived stop signal.")
				if sigErr = s.Stop(); sigErr != nil {
					s.log.Err("server.Server.Run: Received error while stopping the server: %v", sigErr)
					smErr.AddError(sigErr)
					sigErr = nil
				}
			}
		}

		if !smErr.IsEmpty() {
			errChan <- smErr
			return
		}
	}()

	// listener
	go func() {
		var lErr error

		defer wg.Done()

		if isSystemd {
			var supported bool

			// https://www.freedesktop.org/software/systemd/man/sd_notify.html
			if supported, lErr = sysd.SdNotify(false, sysd.SdNotifyReady); lErr != nil {
				s.log.Err(
					"server.Server.Run: Error encountered when notifying systemd of changestate to READY (supported: %v): %v",
					supported, lErr,
				)
				err = nil
			}
		}

		switch s.listenUri.Scheme {
		case "unix", "tcp":
			if lErr = fcgi.Serve(s.sock, s.mux); lErr != nil {
				if errors.Is(lErr, net.ErrClosed) {
					lErr = nil
				} else {
					errChan <- lErr
				}
				return
			}
		case "http":
			if lErr = http.Serve(s.sock, s.mux); lErr != nil {
				if errors.Is(lErr, http.ErrServerClosed) || errors.Is(lErr, net.ErrClosed) {
					lErr = nil
				} else {
					errChan <- lErr
				}
				return
			}
		}
	}()

	go func() {
		wg.Wait()
		close(errChan)
		s.doneChan <- true
	}()

	<-s.doneChan

	for i := 0; i < numJobs; i++ {
		if err = <-errChan; err != nil {
			mErr.AddError(err)
			err = nil
		}
	}

	if !mErr.IsEmpty() {
		err = mErr
		return
	}

	s.log.Debug("server.Server.Run: Server shut down.")

	return
}

// Stop stops the server.
func (s *Server) Stop() (err error) {

	s.log.Debug("server.Server.Stop: Stopping server.")

	s.isStopping = true

	if isSystemd {
		// https://www.freedesktop.org/software/systemd/man/sd_notify.html
		if _, err = sysd.SdNotify(false, sysd.SdNotifyStopping); err != nil {
			s.log.Err("server.Server.stop: Received error notifying systemd of stop: %v", err)
			err = nil
		}
	}

	if err = s.Close(); err != nil {
		s.log.Err("server.Server.stop: Received error closing server connections: %v", err)
		err = nil
	}

	s.log.Debug("server.Server.Stop: Server stopped.")

	return
}

// cleanup cleans up remaining sockets, closes channels, etc.
func (s *Server) cleanup(init bool) (err error) {

	var mErr *multierr.MultiError = multierr.NewMultiError(nil)

	s.log.Debug("server.Server.cleanup: Cleaning up sockets, etc.")

	if s.sock != nil && !init {
		if err = s.sock.Close(); err != nil {
			s.log.Err("server.Server.cleanup: Received error closing socket: %v", err)
			mErr.AddError(err)
			err = nil
		}
	}
	if s.listenUri.Scheme == "unix" {
		if err = os.Remove(s.listenUri.Path); err != nil {
			if !errors.Is(err, os.ErrNotExist) {
				s.log.Err("server.Server.cleanup: Failed to remove UDS '%s': %v", s.listenUri.Path, err)
				mErr.AddError(err)
			}
			err = nil
		}
	}

	if !mErr.IsEmpty() {
		err = mErr
		return
	}

	s.log.Debug("server.Server.cleanup: Completed cleanup.")

	return
}

func (s *Server) Reload() (err error) {

	s.log.Debug("server.Server.Reload: Reload called, but nothing was done; this is a placeholder as there are no reload-associated operations assigned.")
	if isSystemd {
		// https://www.freedesktop.org/software/systemd/man/sd_notify.html
		if _, err = sysd.SdNotify(false, sysd.SdNotifyReloading); err != nil {
			s.log.Err("server.Server.Reload: Received error notifying systemd of reload: %v", err)
			return
		}
	}

	// TODO?

	if isSystemd {
		var supported bool

		// https://www.freedesktop.org/software/systemd/man/sd_notify.html
		if supported, err = sysd.SdNotify(false, sysd.SdNotifyReady); err != nil {
			s.log.Err(
				"server.Server.Reload: Error encountered when notifying systemd of changestate to READY (supported: %v): %v",
				supported, err,
			)
			err = nil
		}
	}

	return
}

func (s *Server) explicit404(resp http.ResponseWriter, req *http.Request) {
	resp.WriteHeader(http.StatusNotFound)
}

func (s *Server) handleDefault(resp http.ResponseWriter, req *http.Request) {

	var err error
	var page *Page
	var uas []string
	var reqdMimes []string
	var parsedUA *R00tClient
	var nAP netip.AddrPort
	var remAddrPort string
	var parsedFmts []*parsedMIME
	var renderer outerRenderer
	var includeFmt string
	var params url.Values = make(url.Values)
	var outerFmt string = mediaJSON

	s.log.Debug("server.Server.handleDefault: Handling request:\n%s", spew.Sdump(req))

	resp.Header().Set("ClientInfo-Version", version.Ver.Short())

	page = &Page{
		Info: &R00tInfo{
			Client:  nil,
			IP:      nil,
			Port:    0,
			Headers: XmlHeaders(req.Header),
			Req:     req,
		},
		PageType: "index",
		Raw:      nil,
		RawFmt:   nil,
		Indent:   "",
		DoIndent: false,
	}

	// First the client info.
	remAddrPort = req.RemoteAddr
	if s.isHttp && req.Header.Get(httpRealHdr) != "" {
		// TODO: WHitelist explicit reverse proxy addr(s)?
		remAddrPort = req.Header.Get(httpRealHdr)
		req.Header.Del(httpRealHdr)
	}
	if remAddrPort != "" {
		if nAP, err = netip.ParseAddrPort(remAddrPort); err != nil {
			s.log.Warning("server.Server.handleDefault: Failed to parse remote address '%s': %v", remAddrPort, err)
			// Don't return an error in case we're doing weird things like direct socket clients.
			/*
				http.Error(resp, "ERROR: Failed to parse client address", http.StatusInternalServerError)
				return
			*/
			err = nil
		}
		page.Info.IP = net.ParseIP(nAP.Addr().String())
		page.Info.Port = nAP.Port()
	}
	if req.URL != nil {
		params = req.URL.Query()
	}
	uas = req.Header.Values("User-Agent")
	if uas != nil && len(uas) > 0 {
		page.Info.Client = make([]*R00tClient, 0, len(uas))
		for _, ua := range uas {
			if parsedUA, err = NewClient(ua); err != nil {
				s.log.Err("server.Server.handleDefault: Failed to create client for '%s': %v", ua, err)
				http.Error(resp, fmt.Sprintf("ERROR: Failed to parse 'User-Agent' '%s'", ua), http.StatusInternalServerError)
				return
			}
			if parsedUA.Name != nil && htmlOverride[*parsedUA.Name] {
				parsedUA.IsDesktop = true
			}
			page.Info.Client = append(page.Info.Client, parsedUA)
		}
	}
	if page.Info.Client != nil && len(page.Info.Client) > 0 {
		// Check the passed UAs for a browser. We then change the "default" format if so.
		for _, ua := range page.Info.Client {
			if ua.IsMobile || ua.IsDesktop {
				outerFmt = mediaHTML
				break
			}
		}
	}

	/*
		At this point, the outer format *default*, client IP, client port, and client version (UA) is set.
		From here, we handle explicit content requests/overrides.
	*/
	// `Accept` request header...
	reqdMimes = req.Header.Values("Accept")
	if reqdMimes != nil && len(reqdMimes) > 0 {
		if parsedFmts, err = parseAccept(strings.Join(reqdMimes, ",")); err != nil {
			s.log.Err("server.Server.handleDefault: Failed to parse Accept header '%#v' for '%s': %v", reqdMimes, remAddrPort, err)
			resp.Header()["Accept"] = okAcceptMime
			http.Error(
				resp,
				"ERROR: Invalid 'Accept' header value; see RFC 9110 § 12.5.1, https://www.iana.org/assignments/media-types/media-types.xhtml, and this response's 'Accept' header.",
				http.StatusBadRequest,
			)
			return
		}
		if outerFmt, err = decideParseAccept(parsedFmts, outerFmt); err != nil {
			if errors.Is(err, ErrUnsupportedMIME) {
				s.log.Err("server.Server.handleDefault: No supported MIME type found for '%s' via '%#v'.", remAddrPort, reqdMimes)
				resp.Header()["Accept"] = okAcceptMime
				http.Error(resp, "ERROR: No supported MIME type specified via request 'Accept'; see 'Accept' header in response for valid types.", http.StatusNotAcceptable)
				return
			} else {
				s.log.Err("server.Server.handleDefault: Received unknown error choosing from Accept header for '%s': %v", remAddrPort, err)
				http.Error(resp, "ERROR: Unknown error occurred when negotiating MIME type.", http.StatusInternalServerError)
				return
			}
		}
	}
	// `mime` URL query parameter.
	if params.Has("mime") {
		if parsedFmts, err = parseAccept(strings.Join(params["mime"], ",")); err != nil {
			s.log.Err("server.Server.handleDefault: Failed to parse 'mime' URL parameter '%#v' for '%s': %v", params["mime"], remAddrPort, err)
			resp.Header()["Accept"] = okAcceptMime
			http.Error(
				resp,
				"ERROR: Invalid 'mime' URL parameter value; see RFC 9110 § 12.5.1, https://www.iana.org/assignments/media-types/media-types.xhtml, and this response's 'Accept' header.",
				http.StatusBadRequest,
			)
			return
		}
		if outerFmt, err = decideParseAccept(parsedFmts, outerFmt); err != nil {
			if errors.Is(err, ErrUnsupportedMIME) {
				s.log.Err("server.Server.handleDefault: No supported MIME type found for '%s' via '%#v'.", remAddrPort, params["mime"])
				resp.Header()["Accept"] = okAcceptMime
				http.Error(resp, "ERROR: No supported MIME type specified via URL parameter 'mime'; see 'Accept' header in response for valid types.", http.StatusNotAcceptable)
				return
			} else {
				s.log.Err("server.Server.handleDefault: Received unknown error choosing from 'mime' URL parameter for '%s': %v", remAddrPort, err)
				http.Error(resp, "ERROR: Unknown error occurred when negotiating MIME type.", http.StatusInternalServerError)
				return
			}
		}
	}
	// 'include' URL query parameter (only for text/html).
	if outerFmt == mediaHTML && params.Has("include") {
		if parsedFmts, err = parseAccept(strings.Join(params["include"], ",")); err != nil {
			s.log.Err("server.Server.handleDefault: Failed to parse 'include' URL parameter '%#v' for '%s': %v", params["include"], remAddrPort, err)
			resp.Header()["Accept"] = okAcceptMime
			http.Error(
				resp,
				"ERROR: Invalid 'include' URL parameter value; see RFC 9110 § 12.5.1, https://www.iana.org/assignments/media-types/media-types.xhtml, and this response's 'Accept' header.",
				http.StatusBadRequest,
			)
			return
		}
		if includeFmt, err = decideParseAccept(parsedFmts, includeFmt); err != nil {
			if errors.Is(err, ErrUnsupportedMIME) {
				s.log.Err("server.Server.handleDefault: No supported MIME type found for '%s' via '%#v'.", remAddrPort, params["include"])
				resp.Header()["Accept"] = okAcceptMime
				http.Error(resp, "ERROR: No supported MIME type specified via URL parameter 'include'; see 'Accept' header in response for valid types.", http.StatusNotAcceptable)
				return
			} else {
				s.log.Err("server.Server.handleDefault: Received unknown error choosing from 'include' URL parameter for '%s': %v", remAddrPort, err)
				http.Error(resp, "ERROR: Unknown error occurred when negotiating MIME type.", http.StatusInternalServerError)
				return
			}
		}
		if includeFmt != "" {
			page.RawFmt = new(string)
			*page.RawFmt = includeFmt
		}
	}
	// 'indent' URL query parameter.
	if params.Has("indent") {
		page.DoIndent = true
		if params.Get("indent") != "" {
			page.Indent = params.Get("indent")
		} else {
			page.Indent = dfltIndent
		}
	}

	switch outerFmt {
	case mediaJSON:
		renderer = s.renderJSON
	case mediaHTML:
		renderer = s.renderHTML
	case mediaXML:
		renderer = s.renderXML
	case mediaYAML:
		renderer = s.renderYML
	default:
		s.log.Err("server.Server.handleDefault: Unknown output format '%s'", outerFmt)
		http.Error(resp, "ERROR: Unable to determine default renderer.", http.StatusInternalServerError)
		return
	}

	if err = renderer(page, resp); err != nil {
		s.log.Err("server.Server.handleDefault: Failed to render request from '%s' as '%s': %v", remAddrPort, outerFmt, err)
		// The renderer handles the error-handling with the client.
		return
	}

	return
}

func (s *Server) handleAbout(resp http.ResponseWriter, req *http.Request) {

	var err error
	var renderPage *Page = &Page{
		Info: &R00tInfo{
			Req: req,
		},
		PageType: "about",
	}

	s.log.Debug("server.Server.handleAbout: Handling request:\n%s", spew.Sdump(req))

	resp.Header().Set("ClientInfo-Version", version.Ver.Short())
	resp.Header().Set("Content-Type", "text/html; charset=utf-8")

	if err = tpl.ExecuteTemplate(resp, "about", renderPage); err != nil {
		s.log.Err("server.Server.handleAbout: Failed to execute template for '%s': %v", req.RemoteAddr, err)
		http.Error(resp, "ERROR: Failed to render HTML", http.StatusInternalServerError)
		return
	}

	s.log.Debug("server.Server.handleAbout: Handled request:\n%s", spew.Sdump(req))

	return
}

func (s *Server) handleUsage(resp http.ResponseWriter, req *http.Request) {

	var err error
	var renderPage *Page = &Page{
		Info: &R00tInfo{
			Req: req,
		},
		PageType: "usage",
	}

	s.log.Debug("server.Server.handleUsage: Handling request:\n%s", spew.Sdump(req))

	resp.Header().Set("ClientInfo-Version", version.Ver.Short())
	resp.Header().Set("Content-Type", "text/html; charset=utf-8")

	if err = tpl.ExecuteTemplate(resp, "usage", renderPage); err != nil {
		s.log.Err("server.Server.handleAbout: Failed to execute template for '%s': %v", req.RemoteAddr, err)
		http.Error(resp, "ERROR: Failed to render HTML", http.StatusInternalServerError)
		return
	}

	s.log.Debug("server.Server.handleUsage: Handled request:\n%s", spew.Sdump(req))

	return
}

func (s *Server) renderJSON(page *Page, resp http.ResponseWriter) (err error) {

	var b []byte

	resp.Header().Set("Content-Type", "application/json")

	if page.DoIndent {
		if b, err = json.MarshalIndent(page.Info, "", page.Indent); err != nil {
			s.log.Err("server.Server.renderJSON: Failed to render to indented JSON: %v", err)
			http.Error(resp, "ERROR: Failed to render JSON", http.StatusInternalServerError)
			return
		}
	} else {
		if b, err = json.Marshal(page.Info); err != nil {
			s.log.Err("server.Server.renderJSON: Failed to render to JSON: %v", err)
			http.Error(resp, "ERROR: Failed to render JSON", http.StatusInternalServerError)
			return
		}
	}
	if _, err = resp.Write(b); err != nil {
		s.log.Err("server.Server.renderJSON: Failed to send JSON: %v", err)
		return
	}

	return
}

func (s *Server) renderHTML(page *Page, resp http.ResponseWriter) (err error) {

	var b []byte

	if page.RawFmt != nil {
		switch *page.RawFmt {
		case mediaHTML:
			_ = "" // Explicit no-op; we're *serving* HTML.
		// Indentable
		case mediaJSON, mediaXML:
			if page.DoIndent {
				if b, err = mediaIndent[*page.RawFmt](page.Info, "", page.Indent); err != nil {
					s.log.Err("server.Server.renderHTML: Failed to render to indented include '%s': %v", *page.RawFmt, err)
					http.Error(resp, "ERROR: Failed to render include format", http.StatusInternalServerError)
					return
				}
			} else {
				if b, err = mediaNoIndent[*page.RawFmt](page.Info); err != nil {
					s.log.Err("server.Server.renderHTML: Failed to render to include '%s': %v", *page.RawFmt, err)
					http.Error(resp, "ERROR: Failed to render include format", http.StatusInternalServerError)
					return
				}
			}
		// Non-indentable
		case mediaYAML:
			if b, err = mediaNoIndent[*page.RawFmt](page.Info); err != nil {
				s.log.Err("server.Server.renderHTML: Failed to render to '%s': %v", *page.RawFmt, err)
			}
		}
		if b != nil {
			page.Raw = new(string)
			*page.Raw = string(b)
		}
	}

	resp.Header().Set("Content-Type", "text/html; charset=utf-8")

	if err = tpl.ExecuteTemplate(resp, "index", page); err != nil {
		s.log.Err("server.Server.renderHTML: Failed to render template: %v", err)
		http.Error(resp, "ERROR: Failed to render HTML", http.StatusInternalServerError)
		return
	}

	return
}

func (s *Server) renderXML(page *Page, resp http.ResponseWriter) (err error) {

	var b []byte

	if page.DoIndent {
		if b, err = xml.MarshalIndent(page.Info, "", page.Indent); err != nil {
			s.log.Err("server.Server.renderXML: Failed to render to indented XML: %v", err)
			http.Error(resp, "ERROR: Failed to render XML", http.StatusInternalServerError)
			return
		}
	} else {
		if b, err = xml.Marshal(page.Info); err != nil {
			s.log.Err("server.Server.renderXML: Failed to render to XML: %v", err)
			http.Error(resp, "ERROR: Failed to render XML", http.StatusInternalServerError)
			return
		}
	}

	resp.Header().Set("Content-Type", "application/xml; charset=utf-8")

	if _, err = resp.Write(b); err != nil {
		s.log.Err("server.Server.renderXML: Failed to send XML: %v", err)
		return
	}

	return
}

func (s *Server) renderYML(page *Page, resp http.ResponseWriter) (err error) {

	var b []byte

	if b, err = yaml.Marshal(page.Info); err != nil {
		s.log.Err("server.Server.renderJSON: Failed to render to JSON: %v", err)
		http.Error(resp, "ERROR: Failed to render JSON", http.StatusInternalServerError)
		return
	}

	resp.Header().Set("Content-Type", "application/yaml")

	if _, err = resp.Write(b); err != nil {
		s.log.Err("server.Server.renderJSON: Failed to send JSON: %v", err)
		return
	}

	return
}