/*
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 serverconfig

import (
	"fmt"
	"http"
	"log"
	"os"
	"strings"

	"camli/auth"
	"camli/blobserver"
	"camli/blobserver/handlers"
	"camli/httputil"
	"camli/jsonconfig"
)

const camliPrefix = "/camli/"

var ErrCamliPath = os.NewError("Invalid Camlistore request path")

type handlerConfig struct {
	prefix string         // "/foo/"
	htype  string         // "localdisk", etc
	conf   jsonconfig.Obj // never nil

	settingUp, setupDone bool
}

type handlerLoader struct {
	installer HandlerInstaller
	baseURL string
	config  map[string]*handlerConfig // prefix -> config
	handler map[string]interface{}    // prefix -> http.Handler / func / blobserver.Storage
}

type HandlerInstaller interface {
	Handle(path string, handler http.Handler)
}

type storageAndConfig struct {
	blobserver.Storage
	config *blobserver.Config
}

func parseCamliPath(path string) (action string, err os.Error) {
	camIdx := strings.Index(path, camliPrefix)
	if camIdx == -1 {
		return "", ErrCamliPath
	}
	action = path[camIdx+len(camliPrefix):]
	return
}

func unsupportedHandler(conn http.ResponseWriter, req *http.Request) {
	httputil.BadRequestError(conn, "Unsupported camlistore path or method.")
}

func (s *storageAndConfig) Config() *blobserver.Config {
	return s.config
}

func handleCamliUsingStorage(conn http.ResponseWriter, req *http.Request, action string, storage blobserver.StorageConfiger) {
	handler := unsupportedHandler
	switch req.Method {
	case "GET":
		switch action {
		case "enumerate-blobs":
			handler = auth.RequireAuth(handlers.CreateEnumerateHandler(storage))
		case "stat":
			handler = auth.RequireAuth(handlers.CreateStatHandler(storage))
		default:
			handler = handlers.CreateGetHandler(storage)
		}
	case "POST":
		switch action {
		case "stat":
			handler = auth.RequireAuth(handlers.CreateStatHandler(storage))
		case "upload":
			handler = auth.RequireAuth(handlers.CreateUploadHandler(storage))
		case "remove":
			handler = auth.RequireAuth(handlers.CreateRemoveHandler(storage))
		}
	case "PUT": // no longer part of spec
		handler = auth.RequireAuth(handlers.CreateNonStandardPutHandler(storage))
	}
	handler(conn, req)
}

// where prefix is like "/" or "/s3/" for e.g. "/camli/" or "/s3/camli/*"
func makeCamliHandler(prefix, baseURL string, storage blobserver.Storage) http.Handler {
	if !strings.HasSuffix(prefix, "/") {
		panic("expected prefix to end in slash")
	}
	baseURL = strings.TrimRight(baseURL, "/")

	storageConfig := &storageAndConfig{
		storage,
		&blobserver.Config{
			Writable: true,
			Readable: true,
			IsQueue:  false,
			URLBase:  baseURL + prefix[:len(prefix)-1],
		},
	}
	return http.HandlerFunc(func(conn http.ResponseWriter, req *http.Request) {
		action, err := parseCamliPath(req.URL.Path[len(prefix)-1:])
		if err != nil {
			log.Printf("Invalid request for method %q, path %q",
				req.Method, req.URL.Path)
			unsupportedHandler(conn, req)
			return
		}
		handleCamliUsingStorage(conn, req, action, storageConfig)
	})
}

func (hl *handlerLoader) FindHandlerByTypeIfLoaded(htype string) (prefix string, handler interface{}, err os.Error) {
	for prefix, config := range hl.config {
		if config.htype == htype {
			return prefix, hl.handler[prefix], nil
		}
	}
	return "", nil, os.ENOENT
}

func (hl *handlerLoader) setupAll() {
	for prefix := range hl.config {
		hl.setupHandler(prefix)
	}
}

func (hl *handlerLoader) configType(prefix string) string {
	if h, ok := hl.config[prefix]; ok {
		return h.htype
	}
	return ""
}

func (hl *handlerLoader) getOrSetup(prefix string) interface{} {
	hl.setupHandler(prefix)
	return hl.handler[prefix]
}

func (hl *handlerLoader) GetStorage(prefix string) (blobserver.Storage, os.Error) {
	hl.setupHandler(prefix)
	if s, ok := hl.handler[prefix].(blobserver.Storage); ok {
		return s, nil
	}
	return nil, fmt.Errorf("bogus storage handler referenced as %q", prefix)
}

func (hl *handlerLoader) GetHandler(prefix string) (interface{}, os.Error) {
	hl.setupHandler(prefix)
	if s, ok := hl.handler[prefix].(blobserver.Storage); ok {
		return s, nil
	}
	if h, ok := hl.handler[prefix].(http.Handler); ok {
		return h, nil
	}
	return nil, fmt.Errorf("bogus http or storage handler referenced as %q", prefix)
}

func (hl *handlerLoader) GetHandlerType(prefix string) string {
	hl.setupHandler(prefix)
	return hl.configType(prefix)
}

func exitFailure(pattern string, args ...interface{}) {
	if !strings.HasSuffix(pattern, "\n") {
		pattern = pattern + "\n"
	}
	panic(fmt.Sprintf(pattern, args...))
}

func (hl *handlerLoader) setupHandler(prefix string) {
	h, ok := hl.config[prefix]
	if !ok {
		exitFailure("invalid reference to undefined handler %q", prefix)
	}
	if h.setupDone {
		// Already setup by something else reference it and forcing it to be
		// setup before the bottom loop got to it.
		return
	}
	if h.settingUp {
		exitFailure("loop in configuration graph; %q tried to load itself indirectly", prefix)
	}
	h.settingUp = true
	defer func() {
		h.setupDone = true
		if hl.handler[prefix] == nil {
			panic(fmt.Sprintf("setupHandler for %q didn't install a handler", prefix))
		}
	}()

	if strings.HasPrefix(h.htype, "storage-") {
		stype := h.htype[len("storage-"):]
		// Assume a storage interface
		pstorage, err := blobserver.CreateStorage(stype, hl, h.conf)
		if err != nil {
			exitFailure("error instantiating storage for prefix %q, type %q: %v",
				h.prefix, stype, err)
		}
		hl.handler[h.prefix] = pstorage
		hl.installer.Handle(prefix+"camli/", makeCamliHandler(prefix, hl.baseURL, pstorage))
		return
	}

	hh, err := blobserver.CreateHandler(h.htype, hl, h.conf)
	if err != nil {
		exitFailure("error instantiating handler for prefix %q, type %q: %v",
			h.prefix, h.htype, err)
	}
	hl.handler[prefix] = hh
	hl.installer.Handle(prefix, &httputil.PrefixHandler{prefix, hh})
}

type Config struct {
	jsonconfig.Obj
	UIPath string  // Not valid until after InstallHandlers
	configPath string  // Filesystem path
}

func Load(configPath string) (*Config, os.Error) {
	obj, err := jsonconfig.ReadFile(configPath)
	if err != nil {
		return nil, err
	}
	conf := &Config{
		Obj: obj,
		configPath: configPath,
	}
	return conf, nil
}

func (config *Config) InstallHandlers(hi HandlerInstaller, baseURL string) (outerr os.Error) {
	defer func() {
		err := recover()
		if err == nil {
			return
		}
		outerr = fmt.Errorf("%v", err)
	}()

	auth.AccessPassword = config.OptionalString("password", "")
	if url := config.OptionalString("baseURL", ""); url != "" {
		baseURL = url
	}
	prefixes := config.RequiredObject("prefixes")
	if err := config.Validate(); err != nil {
		return fmt.Errorf("configuration error in root object's keys: %v", err)
	}

	hl := &handlerLoader{
		installer:      hi,
		baseURL: baseURL,
		config:  make(map[string]*handlerConfig),
		handler: make(map[string]interface{}),
	}

	for prefix, vei := range prefixes {
		if !strings.HasPrefix(prefix, "/") {
			exitFailure("prefix %q doesn't start with /", prefix)
		}
		if !strings.HasSuffix(prefix, "/") {
			exitFailure("prefix %q doesn't end with /", prefix)
		}
		pmap, ok := vei.(map[string]interface{})
		if !ok {
			exitFailure("prefix %q value is a %T, not an object", prefix, vei)
		}
		pconf := jsonconfig.Obj(pmap)
		enabled := pconf.OptionalBool("enabled", true)
		if !enabled {
			continue
		}
		handlerType := pconf.RequiredString("handler")
		handlerArgs := pconf.OptionalObject("handlerArgs")
		if err := pconf.Validate(); err != nil {
			exitFailure("configuration error in prefix %s: %v", prefix, err)
		}
		h := &handlerConfig{
			prefix: prefix,
			htype:  handlerType,
			conf:   handlerArgs,
		}
		hl.config[prefix] = h

		if handlerType == "ui" {
			config.UIPath = prefix
		}
	}
	hl.setupAll()
	return nil
}