package contented

import (
	"embed"
	"encoding/json"
	"io/fs"
	"log"
	"net/http"
	"os"
	"regexp"
	"strings"
	"time"

	"github.com/mxk/go-flowrate/flowrate"
	bolt "go.etcd.io/bbolt"
)

//go:embed static
var staticAssets embed.FS

var SERVER_HEADER string = `contented/0.0.0-dev`

const DEFAULT_MAX_CONCURRENT_THUMBS = 16

type ServerPublicProperties struct {
	AppTitle         string
	MaxUploadBytes   int64
	CanonicalBaseURL string
}

type ServerOptions struct {
	DataDirectory          string
	DBPath                 string
	DiskFilesWorldReadable bool
	BandwidthLimit         int64
	TrustXForwardedFor     bool
	EnableHomepage         bool
	MaxConcurrentThumbs    int
	ServerPublicProperties
}

func (this *ServerOptions) FileMode() os.FileMode {
	if this.DiskFilesWorldReadable {
		return 0644
	} else {
		return 0600
	}
}

type Server struct {
	opts           ServerOptions
	db             *bolt.DB
	startTime      time.Time
	thumbnailSem   chan struct{}
	metadataBucket []byte
	staticDir      fs.FS // interface
}

func NewServer(opts *ServerOptions) (*Server, error) {
	s := &Server{
		opts:           *opts,
		metadataBucket: []byte(`METADATA`),
		startTime:      time.Now(),
	}

	if s.opts.MaxConcurrentThumbs <= 0 {
		s.opts.MaxConcurrentThumbs = DEFAULT_MAX_CONCURRENT_THUMBS // default
		log.Printf("Allowing %d concurrent thumbnails", s.opts.MaxConcurrentThumbs)
	}

	s.staticDir, _ = fs.Sub(staticAssets, `static`) // can't fail

	// "fill" the thumbnailer semaphore
	s.thumbnailSem = make(chan struct{}, s.opts.MaxConcurrentThumbs)
	for i := 0; i < s.opts.MaxConcurrentThumbs; i += 1 {
		s.thumbnailSem <- struct{}{}
	}

	b, err := bolt.Open(opts.DBPath, 0644, bolt.DefaultOptions)
	if err != nil {
		return nil, err
	}

	err = b.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucketIfNotExists(s.metadataBucket)
		return err
	})
	if err != nil {
		return nil, err
	}

	s.db = b

	return s, nil
}

func (this *Server) serveJsonObject(w http.ResponseWriter, o interface{}) {
	jb, err := json.Marshal(o)
	if err != nil {
		log.Println(err.Error())
		http.Error(w, "Internal error", 500)
		return
	}

	w.Header().Set(`Content-Type`, `application/json`)
	w.WriteHeader(200)
	w.Write(jb)
}

func (this *Server) handleAbout(w http.ResponseWriter) {
	this.serveJsonObject(w, this.opts.ServerPublicProperties)
}

func (this *Server) remoteIP(r *http.Request) string {
	if this.opts.TrustXForwardedFor {
		if xff := r.Header.Get("X-Forwarded-For"); len(xff) > 0 {
			return xff
		}
	}

	return strings.TrimRight(strings.TrimRight(r.RemoteAddr, "0123456789"), ":")
}

const (
	downloadUrlPrefix = `/get/`
	metadataUrlPrefix = `/info/`
	previewUrlPrefix  = `/p/`
)

var rxThumbUrl = regexp.MustCompile(`^/thumb/(.)/(.*)$`)

func (this *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set(`Server`, SERVER_HEADER)
	w.Header().Set(`Access-Control-Allow-Origin`, `*`) // Blanket allow CORS
	if this.opts.MaxUploadBytes > 0 {
		r.Body = http.MaxBytesReader(w, r.Body, this.opts.MaxUploadBytes)
	}
	if this.opts.BandwidthLimit > 0 {
		r.Body = flowrate.NewReader(r.Body, this.opts.BandwidthLimit)
	}

	//

	if r.Method == "GET" && strings.HasPrefix(r.URL.Path, downloadUrlPrefix) {
		this.handleView(w, r, r.URL.Path[len(downloadUrlPrefix):])

	} else if r.Method == "GET" && strings.HasPrefix(r.URL.Path, metadataUrlPrefix) {
		this.handleInformation(w, r.URL.Path[len(metadataUrlPrefix):])

	} else if r.Method == "GET" && strings.HasPrefix(r.URL.Path, previewUrlPrefix) {
		this.handlePreview(w, r.URL.Path[len(previewUrlPrefix):])

	} else if r.Method == "GET" && rxThumbUrl.MatchString(r.URL.Path) {
		parts := rxThumbUrl.FindStringSubmatch(r.URL.Path)
		this.handleThumb(w, r, parts[1][0], parts[2])

	} else if r.Method == "GET" && r.URL.Path == `/about` {
		this.handleAbout(w)

	} else if r.Method == "POST" && r.URL.Path == `/upload` {
		this.handleUpload(w, r)

	} else if r.Method == "OPTIONS" {
		// Blanket allow (headers already set)
		w.WriteHeader(200)

	} else if r.Method == "GET" {

		// Conditionally block homepage access
		if !this.opts.EnableHomepage && (r.URL.Path == `/index.html` || r.URL.Path == `/`) {
			http.Error(w, "Not found", 404)
			return
		}

		// Serve static html/css/js assets
		// http.FileServer transparently redirects index.html->/ internally
		http.FileServer(http.FS(this.staticDir)).ServeHTTP(w, r)

	} else {
		http.Error(w, "Not found", 404)
	}
}