package httpserver

import (
	"compress/gzip"
	"crypto/rand"
	"encoding/base64"
	"html/template"
	"io"
	"io/fs"
	"mime"
	"net/http"
	"path"
	"path/filepath"
	"strings"
	"time"

	"go.uber.org/zap"

	"go.c3c.cz/cv/app/server/internal/files"
	"go.c3c.cz/cv/app/server/internal/version"
)

type handler struct {
	indexTemplate  *template.Template
	logger         *zap.Logger
	frontendConfig string
}

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	f, err := files.Public.Open(path.Join("data", "public", r.URL.Path))
	if err != nil {
		h.serveIndex(w)
		return
	}

	fi, err := f.Stat()
	if err != nil || fi.IsDir() {
		h.serveIndex(w)
		return
	}

	h.serveFile(w, r, version.CommitTime, f)
}

func (h *handler) serveFile(w http.ResponseWriter, r *http.Request, modtime time.Time, f fs.File) {
	if !modtime.IsZero() {
		ims := r.Header.Get("If-Modified-Since")
		modtime = modtime.Truncate(time.Second)
		if t, err := http.ParseTime(ims); err == nil && !modtime.After(t) {
			w.WriteHeader(http.StatusNotModified)
			return
		}
		w.Header().Set("Last-Modified", modtime.UTC().Format(http.TimeFormat))
	}

	w.Header().Set("Content-Type", mime.TypeByExtension(filepath.Ext(r.URL.Path)))

	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
		w.Header().Set("Content-Encoding", "gzip")
		gw, err := gzip.NewWriterLevel(w, gzip.DefaultCompression)
		if err != nil {
			h.logger.Warn("Could not create gzip writer", zap.Error(err))
			return
		}
		if n, _ := io.Copy(gw, f); n == 0 {
			w.Header().Del("Content-Encoding")
			gw.Reset(io.Discard)
		}
		err = gw.Close()

		if err != nil {
			h.logger.Warn("Could not close gzip writer", zap.Error(err))
			return
		}
	} else {
		_, err := io.Copy(w, f)
		if err != nil {
			h.logger.Warn("Could not write file response", zap.Error(err))
			return
		}
	}
}

type indexData struct {
	Config   string
	CspNonce string
}

func (h *handler) serveIndex(w http.ResponseWriter) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")

	if h.indexTemplate == nil {
		_, _ = w.Write([]byte("no index"))
		return
	}

	token := make([]byte, 12)
	_, err := rand.Read(token)
	if err != nil {
		h.logger.Warn("Could not create random csp token", zap.Error(err))
		return
	}

	data := indexData{
		Config:   h.frontendConfig,
		CspNonce: base64.RawStdEncoding.EncodeToString(token),
	}

	w.Header().Set("Content-Security-Policy", "script-src 'self' 'nonce-"+data.CspNonce+"' 'unsafe-eval'")
	w.Header().Set("X-Frame-Options", "DENY")
	w.Header().Set("X-XSS-Protection", "1; mode=block")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.Header().Set("Referrer-Policy", "same-origin")
	w.Header().Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
	w.Header().Set("Permissions-Policy", "accelerometer=(), camera=(), geolocation=(), microphone=(), payment=(), usb=()")

	err = h.indexTemplate.Execute(w, data)
	if err != nil {
		h.logger.Warn("Could not execute index template", zap.Error(err))
	}
}