package main

import (
	"bytes"
	"encoding/base64"
	"errors"
	"fmt"
	"image"
	"log"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"
)

type httpHandler struct{}

func parsePath(r *http.Request) (string, processingOptions, error) {
	var po processingOptions
	var err error

	path := r.URL.Path
	parts := strings.Split(strings.TrimPrefix(path, "/"), "/")

	if len(parts) < 7 {
		return "", po, errors.New("Invalid path")
	}

	token := parts[0]

	if err = validatePath(token, strings.TrimPrefix(path, fmt.Sprintf("/%s", token))); err != nil {
		return "", po, err
	}

	po.resize = parts[1]

	if po.width, err = strconv.Atoi(parts[2]); err != nil {
		return "", po, fmt.Errorf("Invalid width: %s", parts[2])
	}

	if po.height, err = strconv.Atoi(parts[3]); err != nil {
		return "", po, fmt.Errorf("Invalid height: %s", parts[3])
	}

	if g, ok := gravityTypes[parts[4]]; ok {
		po.gravity = g
	} else {
		return "", po, fmt.Errorf("Invalid gravity: %s", parts[4])
	}

	po.enlarge = parts[5] != "0"

	filenameParts := strings.Split(strings.Join(parts[6:], ""), ".")

	if len(filenameParts) < 2 {
		po.format = imageTypes["jpg"]
	} else if f, ok := imageTypes[filenameParts[1]]; ok {
		po.format = f
	} else {
		return "", po, fmt.Errorf("Invalid image format: %s", filenameParts[1])
	}

	filename, err := base64.RawURLEncoding.DecodeString(filenameParts[0])
	if err != nil {
		return "", po, errors.New("Invalid filename encoding")
	}

	return string(filename), po, nil
}

func imageContentType(b []byte) string {
	_, imgtype, _ := image.DecodeConfig(bytes.NewReader(b))
	return fmt.Sprintf("image/%s", imgtype)
}

func logResponse(status int, msg string) {
	var color int

	if status > 500 {
		color = 31
	} else if status > 400 {
		color = 33
	} else {
		color = 32
	}

	log.Printf("|\033[7;%dm %d \033[0m| %s\n", color, status, msg)
}

func respondWithImage(rw http.ResponseWriter, data []byte, imgURL string, po processingOptions) {
	logResponse(200, fmt.Sprintf("Processed: %s; %+v", imgURL, po))

	rw.WriteHeader(200)
	rw.Header().Set("Content-Type", imageContentType(data))
	rw.Write(data)
}

func respondWithError(rw http.ResponseWriter, status int, err error, msg string) {
	logResponse(status, err.Error())

	rw.WriteHeader(status)
	rw.Write([]byte(msg))
}

func (h httpHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
	log.Printf("GET: %s\n", r.URL.RequestURI())

	imgURL, procOpt, err := parsePath(r)
	if err != nil {
		respondWithError(rw, 404, err, "Invalid image url")
		return
	}

	if _, err = url.ParseRequestURI(imgURL); err != nil {
		respondWithError(rw, 404, err, "Invalid image url")
		return
	}

	b, err := downloadImage(imgURL)
	if err != nil {
		respondWithError(rw, 404, err, "Image is unreacable")
		return
	}

	b, err = processImage(b, procOpt)
	if err != nil {
		respondWithError(rw, 500, err, "Error occured while processing image")
		return
	}

	respondWithImage(rw, b, imgURL, procOpt)
}

func main() {
	s := &http.Server{
		Addr:           conf.Bind,
		Handler:        httpHandler{},
		ReadTimeout:    time.Duration(conf.ReadTimeout) * time.Second,
		WriteTimeout:   time.Duration(conf.WriteTimeout) * time.Second,
		MaxHeaderBytes: 1 << 20,
	}

	log.Printf("Starting server at %s\n", conf.Bind)

	log.Fatal(s.ListenAndServe())
}