package main

import (
	"bufio"
	"bytes"
	"compress/gzip"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"
	"text/template"
	"time"
)

const b64Width = 76

var (
	webAssetsTmpl = template.Must(template.New("web_assets").Parse("" +
		"package conway\n" +
		"// WARNING: GENERATED FILE, NERDS! {{.Now}}\n" +
		"\n" +
		"const (\n" +
		"	gameOfLifeIndexHtml = `{{.IndexHTML}}`\n" +
		"	normalizeCss = `{{.NormalizeCSS}}`\n" +
		"	jqueryMinJs = `{{.JqueryMinJS}}`\n" +
		")\n"))
	normalizeCssUrl = "http://necolas.github.com/normalize.css/2.0.1/normalize.css"
	jqueryMinJsUrl  = "http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"
)

type webAssetStrings struct {
	IndexHTML    string
	NormalizeCSS string
	JqueryMinJS  string
	Now          time.Time
}

func die(err error) {
	log.Fatal("CRUD:", err)
}

func toB64(input []byte) string {
	var (
		err error
		out bytes.Buffer
	)
	encoded := base64.StdEncoding.EncodeToString(input)
	lenEncoded := len(encoded)

	outbuf := bufio.NewWriter(&out)
	inbuf := strings.NewReader(encoded)

	outbuf.WriteByte('\n')
	if err != nil {
		die(err)
	}

	nWritten := 0
	for {
		for n := 0; n < b64Width; n++ {
			c, err := inbuf.ReadByte()
			if err == io.EOF {
				break
			}

			if err != nil {
				die(err)
			}

			err = outbuf.WriteByte(c)
			if err != nil {
				die(err)
			}

			nWritten++
		}

		_, err := inbuf.ReadByte()
		if err == io.EOF {
			break
		}

		if err != nil {
			die(err)
		}

		err = inbuf.UnreadByte()
		if err != nil {
			die(err)
		}

		err = outbuf.WriteByte('\n')
		if err != nil {
			die(err)
		}
	}

	if nWritten != lenEncoded {
		die(errors.New(fmt.Sprintf("base64-encoded length = %d, but wrote %d",
			lenEncoded, nWritten)))
	}

	outbuf.Flush()
	return string(out.Bytes())
}

func toGz(input []byte) []byte {
	var buf bytes.Buffer

	zwriter, err := gzip.NewWriterLevel(&buf, gzip.BestCompression)
	if err != nil {
		die(err)
	}

	zbuf := bufio.NewWriter(zwriter)

	toWrite := len(input)
	for written := 0; written < toWrite; {
		n, err := zbuf.Write(input[written:])
		if err != nil {
			die(err)
		}
		written += n
	}

	zbuf.Flush()
	zwriter.Close()
	return buf.Bytes()
}

func fetchUrl(url string) []byte {
	resp, err := http.Get(url)
	if err != nil {
		die(err)
	}

	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		die(err)
	}

	return body
}

func fetchIndexHtml(indexHtmlPath string) []byte {
	fd, err := os.Open(indexHtmlPath)
	if err != nil {
		die(err)
	}

	body, err := ioutil.ReadAll(fd)
	if err != nil {
		die(err)
	}

	return body
}

func toB64Gz(input []byte) string {
	return string(toB64(toGz(input)))
}

func main() {
	if len(os.Args) < 2 {
		die(errors.New(fmt.Sprintf("Usage: %s <index.html-path>", os.Args[0])))
	}

	assets := &webAssetStrings{
		IndexHTML:    toB64Gz(fetchIndexHtml(os.Args[1])),
		NormalizeCSS: toB64Gz(fetchUrl(normalizeCssUrl)),
		JqueryMinJS:  toB64Gz(fetchUrl(jqueryMinJsUrl)),
		Now:          time.Now(),
	}

	webAssetsTmpl.Execute(os.Stdout, assets)
}