package server

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"net/url"
	"os"
	"slices"
	"strconv"
	"strings"
	"time"

	"website/internal/builder"
	cfg "website/internal/config"
	"website/internal/log"
	"website/internal/vcs"
	"website/internal/website"

	"github.com/ardanlabs/conf/v3"
	"github.com/osdevisnot/sorvor/pkg/livereload"
	"github.com/pkg/errors"
	"golang.org/x/net/http2"
	"golang.org/x/net/http2/h2c"
)

var (
	CommitSHA    = "local"
	ShortSHA     = "local"
	serverHeader = fmt.Sprintf("website (%s)", ShortSHA)
)

type Config struct {
	Root          string `conf:"default:website"`
	Redirect      bool   `conf:"default:true"`
	ListenAddress string `conf:"default:localhost"`
	Port          int    `conf:"default:8080,short:p"`
	TLSPort       int    `conf:"default:8443"`
	TLS           bool   `conf:"default:false"`

	Development bool   `conf:"default:false,flag:dev"`
	ACMECA      string `conf:"env:ACME_CA"`
	ACMECACert  string `conf:"env:ACME_CA_CERT"`
	Domains     string
}

type Server struct {
	*http.Server
	redirectHandler func(http.ResponseWriter, *http.Request)
	runtimeConfig   *Config
	config          *cfg.Config
}

func applyDevModeOverrides(config *cfg.Config, runtimeConfig *Config) {
	config.CSP.ScriptSrc = slices.Insert(config.CSP.ScriptSrc, 0, "'unsafe-inline'")
	config.CSP.ConnectSrc = slices.Insert(config.CSP.ConnectSrc, 0, "'self'")
	if runtimeConfig.Domains != "" {
		config.Domains = strings.Split(runtimeConfig.Domains, ",")
	} else {
		config.Domains = []string{runtimeConfig.ListenAddress}
	}
	scheme := "http"
	port := runtimeConfig.Port
	if runtimeConfig.TLS {
		scheme = "https"
		port = runtimeConfig.TLSPort
	}
	config.BaseURL = cfg.URL{
		URL: &url.URL{
			Scheme: scheme,
			Host:   net.JoinHostPort(config.Domains[0], strconv.Itoa(port)),
		},
	}
}

func updateCSPHashes(config *cfg.Config, r *builder.Result) {
	clear(config.CSP.StyleSrc)
	for i, h := range r.Hashes {
		config.CSP.StyleSrc[i] = fmt.Sprintf("'%s'", h)
	}
}

func serverHeaderHandler(wrappedHandler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		log.Debug(
			"headers",
			"proto",
			r.Header.Get("X-Forwarded-Proto"),
			"host",
			r.Header.Get("X-Forwarded-Host"),
			"scheme",
			r.URL.Scheme,
			"secure",
			r.TLS != nil,
		)
		log.Debug("host", "request", r.Host, "header", r.Header.Get("Host"))
		if r.ProtoMajor >= 2 && r.Header.Get("Host") != "" {
			// net/http does this for HTTP/1.1, but not h2c
			// TODO: check with HTTP/2.0 (i.e. with TLS)
			log.Debug("host", "request", r.Host, "header", r.Header.Get("Host"))
			r.Host = r.Header.Get("Host")
			r.Header.Del("Host")
		}
		w.Header().Set("Server", serverHeader)
		wrappedHandler.ServeHTTP(w, r)
	})
}

func rebuild(builderConfig builder.IOConfig, config *cfg.Config) error {
	r, err := builder.BuildSite(builderConfig, config)
	if err != nil {
		return errors.WithMessage(err, "could not build site")
	}
	updateCSPHashes(config, r)

	return nil
}

func New(runtimeConfig *Config) (*Server, error) {
	if !runtimeConfig.Development {
		vcsConfig := &vcs.Config{}
		_, err := conf.Parse("", vcsConfig)
		if err != nil {
			return nil, err
		}
		_, err = vcs.CloneOrUpdate(vcsConfig)
		if err != nil {
			return nil, err
		}
		err = os.Chdir(vcsConfig.LocalPath)
		if err != nil {
			return nil, err
		}
		runtimeConfig.Root = "website"
	}

	config, err := cfg.GetConfig()
	if err != nil {
		return nil, errors.WithMessage(err, "error parsing configuration file")
	}
	if runtimeConfig.Development {
		applyDevModeOverrides(config, runtimeConfig)
	}

	listenAddress := net.JoinHostPort(runtimeConfig.ListenAddress, strconv.Itoa(runtimeConfig.Port))
	top := http.NewServeMux()

	builderConfig := builder.IOConfig{
		Source:      "content",
		Destination: runtimeConfig.Root,
		Development: runtimeConfig.Development,
	}

	err = rebuild(builderConfig, config)
	if err != nil {
		return nil, err
	}

	if runtimeConfig.Development {
		liveReload := livereload.New()
		top.Handle("/_/reload", liveReload)
		liveReload.Start()
		fw, err := NewFileWatcher()
		if err != nil {
			return nil, errors.WithMessage(err, "could not create file watcher")
		}
		for _, dir := range []string{"content", "static", "templates", "internal/builder"} {
			err := fw.AddRecursive(dir)
			if err != nil {
				return nil, errors.WithMessagef(
					err,
					"could not add directory %s to file watcher",
					dir,
				)
			}
		}
		err = fw.Add(".")
		if err != nil {
			return nil, errors.WithMessage(err, "could not add directory to file watcher")
		}
		go fw.Start(func(filename string) {
			log.Info("rebuilding site", "changed_file", filename)
			err := rebuild(builderConfig, config)
			if err != nil {
				log.Error("error rebuilding site", "error", err)
			}
		})
	}

	loggingMux := http.NewServeMux()
	mux, err := website.NewMux(config, runtimeConfig.Root)
	if err != nil {
		return nil, errors.Wrap(err, "could not create website mux")
	}

	redirectHandler := func(w http.ResponseWriter, r *http.Request) {
		path, _ := website.CanonicalisePath(r.URL.Path)
		newURL := config.BaseURL.JoinPath(path)
		http.Redirect(w, r, newURL.String(), 301)
	}
	if runtimeConfig.Redirect {
		loggingMux.Handle(config.BaseURL.Hostname()+"/", mux)
		loggingMux.HandleFunc("/", redirectHandler)
	} else {
		loggingMux.Handle("/", mux)
	}

	top.Handle("/",
		serverHeaderHandler(
			wrapHandlerWithLogging(loggingMux),
		),
	)

	top.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusNoContent)
	})

	return &Server{
		Server: &http.Server{
			Addr:              listenAddress,
			ReadHeaderTimeout: 1 * time.Minute,
			Handler: http.MaxBytesHandler(h2c.NewHandler(
				top,
				&http2.Server{
					IdleTimeout: 15 * time.Minute,
				},
			), 0),
		},
		redirectHandler: redirectHandler,
		config:          config,
		runtimeConfig:   runtimeConfig,
	}, nil
}

func (s *Server) serve(tls bool) error {
	if tls {
		return s.serveTLS()
	}

	return s.serveTCP()
}

func (s *Server) Start() error {
	if err := s.serve(s.runtimeConfig.TLS); err != http.ErrServerClosed {
		return errors.Wrap(err, "error creating/closing server")
	}

	return nil
}

func (s *Server) Stop() chan struct{} {
	log.Debug("stop called")

	idleConnsClosed := make(chan struct{})

	go func() {
		log.Debug("shutting down server")
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		err := s.Server.Shutdown(ctx)
		log.Debug("server shut down")
		if err != nil {
			// Error from closing listeners, or context timeout:
			log.Warn("HTTP server Shutdown", "error", err)
		}
		close(idleConnsClosed)
	}()

	return idleConnsClosed
}