/*
Copyright 2011 Google Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package server

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"regexp"
	"strconv"
	"strings"

	"camlistore.org/pkg/blobref"
	"camlistore.org/pkg/blobserver"
	"camlistore.org/pkg/httputil"
	"camlistore.org/pkg/jsonconfig"
	"camlistore.org/pkg/search"
	uistatic "camlistore.org/server/camlistored/ui"
)

var _ = log.Printf

var (
	staticFilePattern = regexp.MustCompile(`^([a-zA-Z0-9\-\_]+\.(html|js|css|png|jpg|gif))$`)
	identPattern      = regexp.MustCompile(`^[a-zA-Z\_]+$`)

	// Download URL suffix:
	//   $1: blobref (checked in download handler)
	//   $2: optional "/filename" to be sent as recommended download name,
	//       if sane looking
	downloadPattern  = regexp.MustCompile(`^download/([^/]+)(/.*)?$`)
	thumbnailPattern = regexp.MustCompile(`^thumbnail/([^/]+)(/.*)?$`)
	treePattern      = regexp.MustCompile(`^tree/([^/]+)(/.*)?$`)
)

var uiFiles = uistatic.Files

// UIHandler handles serving the UI and discovery JSON.
type UIHandler struct {
	// URL prefixes (path or full URL) to the primary blob and
	// search root.  Only used by the UI and thus necessary if UI
	// is true.
	BlobRoot     string
	SearchRoot   string
	JSONSignRoot string

	PublishRoots map[string]*PublishHandler

	Storage blobserver.Storage // of BlobRoot
	Cache   blobserver.Storage // or nil
	Search  *search.Handler    // or nil
	sc      ScaledImage        // cache for scaled images, optional

	staticHandler http.Handler
}

func init() {
	blobserver.RegisterHandlerConstructor("ui", newUiFromConfig)
}

func newUiFromConfig(ld blobserver.Loader, conf jsonconfig.Obj) (h http.Handler, err error) {
	ui := &UIHandler{}
	ui.BlobRoot = conf.OptionalString("blobRoot", "")
	ui.SearchRoot = conf.OptionalString("searchRoot", "")
	ui.JSONSignRoot = conf.OptionalString("jsonSignRoot", "")
	pubRoots := conf.OptionalList("publishRoots")
	cachePrefix := conf.OptionalString("cache", "")
	scType := conf.OptionalString("scaledImage", "")
	if err = conf.Validate(); err != nil {
		return
	}

	ui.PublishRoots = make(map[string]*PublishHandler)
	for _, pubRoot := range pubRoots {
		h, err := ld.GetHandler(pubRoot)
		if err != nil {
			return nil, fmt.Errorf("UI handler's publishRoots references invalid %q", pubRoot)
		}
		pubh, ok := h.(*PublishHandler)
		if !ok {
			return nil, fmt.Errorf("UI handler's publishRoots references invalid %q; not a PublishHandler", pubRoot)
		}
		ui.PublishRoots[pubRoot] = pubh
	}

	checkType := func(key string, htype string) {
		v := conf.OptionalString(key, "")
		if v == "" {
			return
		}
		ct := ld.GetHandlerType(v)
		if ct == "" {
			err = fmt.Errorf("UI handler's %q references non-existant %q", key, v)
		} else if ct != htype {
			err = fmt.Errorf("UI handler's %q references %q of type %q; expected type %q", key, v,
				ct, htype)
		}
	}
	checkType("searchRoot", "search")
	checkType("jsonSignRoot", "jsonsign")
	if err != nil {
		return
	}

	if ui.BlobRoot != "" {
		bs, err := ld.GetStorage(ui.BlobRoot)
		if err != nil {
			return nil, fmt.Errorf("UI handler's blobRoot of %q error: %v", ui.BlobRoot, err)
		}
		ui.Storage = bs
	}

	if cachePrefix != "" {
		bs, err := ld.GetStorage(cachePrefix)
		if err != nil {
			return nil, fmt.Errorf("UI handler's cache of %q error: %v", cachePrefix, err)
		}
		ui.Cache = bs
		switch scType {
		case "lrucache":
			ui.sc = NewScaledImageLru()
		default:
			return nil, fmt.Errorf("unsupported ui handler's scType: %q ", scType)
		}
	}

	if ui.SearchRoot != "" {
		h, _ := ld.GetHandler(ui.SearchRoot)
		ui.Search = h.(*search.Handler)
	}

	ui.staticHandler = http.FileServer(uiFiles)

	return ui, nil
}

func camliMode(req *http.Request) string {
	return req.URL.Query().Get("camli.mode")
}

func wantsDiscovery(req *http.Request) bool {
	return req.Method == "GET" &&
		(req.Header.Get("Accept") == "text/x-camli-configuration" ||
			camliMode(req) == "config")
}

func wantsUploadHelper(req *http.Request) bool {
	return req.Method == "POST" && camliMode(req) == "uploadhelper"
}

func wantsPermanode(req *http.Request) bool {
	return req.Method == "GET" && blobref.Parse(req.FormValue("p")) != nil
}

func wantsGallery(req *http.Request) bool {
	return req.Method == "GET" && blobref.Parse(req.FormValue("g")) != nil
}

func wantsBlobInfo(req *http.Request) bool {
	return req.Method == "GET" && blobref.Parse(req.FormValue("b")) != nil
}

func wantsFileTreePage(req *http.Request) bool {
	return req.Method == "GET" && blobref.Parse(req.FormValue("d")) != nil
}

func (ui *UIHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	base := req.Header.Get("X-PrefixHandler-PathBase")
	suffix := req.Header.Get("X-PrefixHandler-PathSuffix")

	rw.Header().Set("Vary", "Accept")
	switch {
	case wantsDiscovery(req):
		ui.serveDiscovery(rw, req)
	case wantsUploadHelper(req):
		ui.serveUploadHelper(rw, req)
	case strings.HasPrefix(suffix, "download/"):
		ui.serveDownload(rw, req)
	case strings.HasPrefix(suffix, "thumbnail/"):
		ui.serveThumbnail(rw, req)
	case strings.HasPrefix(suffix, "tree/"):
		ui.serveFileTree(rw, req)
	default:
		file := ""
		if m := staticFilePattern.FindStringSubmatch(suffix); m != nil {
			file = m[1]
		} else {
			switch {
			case wantsPermanode(req):
				file = "permanode.html"
			case wantsGallery(req):
				file = "gallery.html"
			case wantsBlobInfo(req):
				file = "blobinfo.html"
			case wantsFileTreePage(req):
				file = "filetree.html"
			case req.URL.Path == base:
				file = "home.html"
			default:
				http.Error(rw, "Illegal URL.", 404)
				return
			}
		}
		req.URL.Path = "/" + file
		ui.staticHandler.ServeHTTP(rw, req)
	}
}

func discoveryHelper(rw http.ResponseWriter, req *http.Request, m map[string]interface{}) {
	rw.Header().Set("Content-Type", "text/javascript")
	inCb := false
	if cb := req.FormValue("cb"); identPattern.MatchString(cb) {
		fmt.Fprintf(rw, "%s(", cb)
		inCb = true
	}
	bytes, _ := json.MarshalIndent(m, "", "  ")
	rw.Write(bytes)
	if inCb {
		rw.Write([]byte{')'})
	}
}

func (ui *UIHandler) serveDiscovery(rw http.ResponseWriter, req *http.Request) {
	pubRoots := map[string]interface{}{}
	for key, pubh := range ui.PublishRoots {
		m := map[string]interface{}{
			"name":   pubh.RootName,
			"prefix": []string{key},
			// TODO: include gpg key id
		}
		if ui.Search != nil {
			pn, err := ui.Search.Index().PermanodeOfSignerAttrValue(ui.Search.Owner(), "camliRoot", pubh.RootName)
			if err == nil {
				m["currentPermanode"] = pn.String()
			}
		}
		pubRoots[pubh.RootName] = m
	}

	discoveryHelper(rw, req, map[string]interface{}{
		"blobRoot":        ui.BlobRoot,
		"searchRoot":      ui.SearchRoot,
		"jsonSignRoot":    ui.JSONSignRoot,
		"uploadHelper":    "?camli.mode=uploadhelper", // hack; remove with better javascript
		"downloadHelper":  "./download/",
		"directoryHelper": "./tree/",
		"publishRoots":    pubRoots,
	})
}

func (ui *UIHandler) serveDownload(rw http.ResponseWriter, req *http.Request) {
	if ui.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := req.Header.Get("X-PrefixHandler-PathSuffix")
	m := downloadPattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	fbr := blobref.Parse(m[1])
	if fbr == nil {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	dh := &DownloadHandler{
		Fetcher: ui.Storage,
		Cache:   ui.Cache,
	}
	dh.ServeHTTP(rw, req, fbr)
}

func (ui *UIHandler) serveThumbnail(rw http.ResponseWriter, req *http.Request) {
	if ui.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := req.Header.Get("X-PrefixHandler-PathSuffix")
	m := thumbnailPattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	query := req.URL.Query()
	width, err := strconv.Atoi(query.Get("mw"))
	if err != nil {
		http.Error(rw, "Invalid specified max width 'mw': "+err.Error(), 500)
		return
	}
	height, err := strconv.Atoi(query.Get("mh"))
	if err != nil {
		http.Error(rw, "Invalid specified height 'mh': "+err.Error(), 500)
		return
	}

	blobref := blobref.Parse(m[1])
	if blobref == nil {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	th := &ImageHandler{
		Fetcher:   ui.Storage,
		Cache:     ui.Cache,
		MaxWidth:  width,
		MaxHeight: height,
		sc:        ui.sc,
	}
	th.ServeHTTP(rw, req, blobref)
}

func (ui *UIHandler) serveFileTree(rw http.ResponseWriter, req *http.Request) {
	if ui.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := req.Header.Get("X-PrefixHandler-PathSuffix")
	m := treePattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	blobref := blobref.Parse(m[1])
	if blobref == nil {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	fth := &FileTreeHandler{
		Fetcher: ui.Storage,
		file:    blobref,
	}
	fth.ServeHTTP(rw, req)
}