sleipnir.go

/*
* Copyright (c) 1998, Regents of the University of California
* All rights reserved.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
*     * Redistributions of source code must retain the above copyright
*       notice, this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*     * Neither the name of the University of California, Berkeley nor the
*       names of its contributors may be used to endorse or promote products
*       derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package main

import (
	"bytes"
	"encoding/csv"
	"flag"
	"fmt"
	"github.com/elazarl/goproxy"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"regexp"
)

var contents = map[string][]byte{}
var dates = map[string]int64{}

func getConfig(configFile string) [][]string {
	file, e := os.Open(configFile)
	if e != nil {
		panic(e)
	}
	defer file.Close()

	csvReader := csv.NewReader(file)
	records, e := csvReader.ReadAll()
	if e != nil {
		panic(e)
	}

	return records
}

func getFileModDate(fileName string) (int64, bool) {
	file, e := os.Open(fileName)
	if e != nil {
		fmt.Errorf("Error when reading", fileName, e.Error())
		return 0, false
	}
	fi, e := file.Stat()
	if e != nil {
		fmt.Errorf("Error when reading informations from", fileName, e.Error())
		return 0, false
	}
	return fi.ModTime().Unix(), true
}

func NewResponse(r *http.Request, contentType string, status int, contentFileName string) *http.Response {
	resp := &http.Response{}
	resp.Request = r
	resp.TransferEncoding = r.TransferEncoding
	resp.Header = make(http.Header)
	resp.Header.Add("Content-Type", contentType)
	resp.StatusCode = status

	var b []byte

	currentDate, ok := getFileModDate(contentFileName)
	if !ok {
		return nil
	}
	date, ok := dates[contentFileName]
	if !ok {
		date = 0
	}

	var e error
	if currentDate > date {
		b, e = ioutil.ReadFile(contentFileName)
		if e != nil {
			fmt.Errorf("Error when reading", contentFileName, e.Error())
			return nil
		}
		contents[contentFileName] = b
		dates[contentFileName] = currentDate
		fmt.Println("")
	} else {
		fmt.Println(" [from cache]")
		b, _ = contents[contentFileName]
	}

	reader := bytes.NewReader(b)
	resp.ContentLength = int64(reader.Len())
	resp.Body = ioutil.NopCloser(reader)
	return resp
}

func CreateDefault(listen string, configFile string, verbose bool) {
	proxy := goproxy.NewProxyHttpServer()
	proxy.Verbose = verbose

	records := getConfig(configFile)
	fmt.Println("Configuration from", configFile, ":")
	for i, config := range records {
		if i == 0 {
			// header line
			continue
		}
		defaultUrl := config[0]
		regexpUrl, e := regexp.Compile(defaultUrl)
		if e != nil {
			fmt.Errorf("Can't parse regexp", defaultUrl, e.Error())
		}
		contentType := config[1]
		newFile := config[2]
		fmt.Println("- replace", defaultUrl, "by", newFile)
		proxy.OnRequest(goproxy.UrlMatches(regexpUrl)).DoFunc(
			func(r *http.Request, ctx *goproxy.ProxyCtx) (*http.Request, *http.Response) {
				fmt.Print("Intercept ", defaultUrl, " and serve ", newFile)
				response := NewResponse(r, contentType, http.StatusOK, newFile)
				return r, response
			})
	}
	fmt.Println("")
	fmt.Println("Listen", listen)
	fmt.Println("^C to stop")
	fmt.Println("")

	log.Fatal(http.ListenAndServe(listen, proxy))
}

func main() {
	var addr string
	var configFile string
	var verbose bool
	var help bool
	flag.StringVar(&addr, "a", ":8888", "Bind to this address:port")
	flag.StringVar(&configFile, "c", "config.csv", "Config file")
	flag.BoolVar(&verbose, "v", false, "Verbose")
	flag.BoolVar(&help, "h", false, "Print this help")

	flag.Parse()
	if help {
		flag.Usage()
		return
	}

	CreateDefault(addr, configFile, verbose)
}