// Copyright 2014 beego Author. All Rights Reserved.
//
// 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 beego

import (
	"bytes"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strconv"
	"strings"
	"sync"

	"errors"

	"time"

	"github.com/astaxie/beego/context"
)

var notStaticRequestErr = errors.New("request not a static file request")

func serverStaticRouter(ctx *context.Context) {
	if ctx.Input.Method() != "GET" && ctx.Input.Method() != "HEAD" {
		return
	}

	forbidden, filePath, fileInfo, err := lookupFile(ctx)
	if err == notStaticRequestErr {
		return
	}

	if forbidden {
		exception("403", ctx)
		return
	}

	if filePath == "" || fileInfo == nil {
		if RunMode == "dev" {
			Warn("Can't find/open the file:", filePath, err)
		}
		http.NotFound(ctx.ResponseWriter, ctx.Request)
		return
	}
	if fileInfo.IsDir() {
		//serveFile will list dir
		http.ServeFile(ctx.ResponseWriter, ctx.Request, filePath)
		return
	}

	var enableCompress = EnableGzip && isStaticCompress(filePath)
	var acceptEncoding string
	if enableCompress {
		acceptEncoding = context.ParseEncoding(ctx.Request)
	}
	b, n, sch, err := openFile(filePath, fileInfo, acceptEncoding)
	if err != nil {
		if RunMode == "dev" {
			Warn("Can't compress the file:", filePath, err)
		}
		http.NotFound(ctx.ResponseWriter, ctx.Request)
		return
	}

	if b {
		ctx.Output.Header("Content-Encoding", n)
	} else {
		ctx.Output.Header("Content-Length", strconv.FormatInt(sch.size, 10))
	}

	http.ServeContent(ctx.ResponseWriter, ctx.Request, filePath, sch.modTime, sch)
	return

}

type serveContentHolder struct {
	*strings.Reader
	modTime  time.Time
	size     int64
	encoding string
}

var (
	staticFileMap = make(map[string]*serveContentHolder)
	mapLock       sync.Mutex
)

func openFile(filePath string, fi os.FileInfo, acceptEncoding string) (bool, string, *serveContentHolder, error) {
	mapKey := acceptEncoding + ":" + filePath
	mapFile, ok := staticFileMap[mapKey]
	if ok {
		if mapFile.modTime == fi.ModTime() && mapFile.size == fi.Size() {
			return mapFile.encoding != "", mapFile.encoding, mapFile, nil
		}
	}
	mapLock.Lock()
	delete(staticFileMap, mapKey)
	defer mapLock.Unlock()
	if mapFile, ok = staticFileMap[mapKey]; !ok {
		file, err := os.Open(filePath)
		if err != nil {
			return false, "", nil, err
		}
		defer file.Close()
		var bufferWriter bytes.Buffer
		_, n, err := context.WriteFile(acceptEncoding, &bufferWriter, file)
		if err != nil {
			return false, "", nil, err
		}
		mapFile = &serveContentHolder{Reader: strings.NewReader(string(bufferWriter.Bytes())), modTime: fi.ModTime(), size: int64(bufferWriter.Len()), encoding: n}
		staticFileMap[mapKey] = mapFile
	}

	return mapFile.encoding != "", mapFile.encoding, mapFile, nil
}

func isStaticCompress(filePath string) bool {
	for _, statExtension := range StaticExtensionsToGzip {
		if strings.HasSuffix(strings.ToLower(filePath), strings.ToLower(statExtension)) {
			return true
		}
	}
	return false
}

func searchFile(ctx *context.Context) (string, os.FileInfo, error) {
	requestPath := filepath.Clean(ctx.Input.Request.URL.Path)
	// special processing : favicon.ico/robots.txt  can be in any static dir
	if requestPath == "/favicon.ico" || requestPath == "/robots.txt" {
		file := path.Join(".", requestPath)
		if fi, _ := os.Stat(file); fi != nil {
			return file, fi, nil
		}
		for _, staticDir := range StaticDir {
			filePath := path.Join(staticDir, requestPath)
			if fi, _ := os.Stat(filePath); fi != nil {
				return filePath, fi, nil
			}
		}
		return "", nil, errors.New(requestPath + " file not find")
	}

	for prefix, staticDir := range StaticDir {
		if len(prefix) == 0 {
			continue
		}
		if !strings.Contains(requestPath, prefix) {
			continue
		}
		if len(requestPath) > len(prefix) && requestPath[len(prefix)] != '/' {
			continue
		}
		filePath := path.Join(staticDir, requestPath[len(prefix):])
		if fi, err := os.Stat(filePath); fi != nil {
			return filePath, fi, err
		}
	}
	return "", nil, notStaticRequestErr
}

func lookupFile(ctx *context.Context) (bool, string, os.FileInfo, error) {
	fp, fi, err := searchFile(ctx)
	if fp == "" || fi == nil {
		return false, "", nil, err
	}
	if !fi.IsDir() {
		return false, fp, fi, err
	}
	ifp := filepath.Join(fp, "index.html")
	if ifi, _ := os.Stat(ifp); ifi != nil && ifi.Mode().IsRegular() {
		return false, ifp, ifi, err
	}
	return !DirectoryIndex, fp, fi, err
}