package main

import (
	"context"
	"crypto/sha256"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/gorilla/mux"
)

// Attaches a request's IP address to the request's context
func newCtxUserIP(ctx context.Context, r *http.Request) context.Context {
	base := strings.Split(r.RemoteAddr, ":")
	uip := base[0]
	return context.WithValue(ctx, ctxKey, uip)
}

// Retrieves a request's IP address from the request's context
func getIPFromCtx(ctx context.Context) string {
	uip, ok := ctx.Value(ctxKey).(string)
	if !ok {
		log.Printf("Couldn't retrieve IP from request\n")
	}
	return uip
}

// Shim function to modify/pass context value to a handler
func ipMiddleware(hop http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx := newCtxUserIP(r.Context(), r)
		hop.ServeHTTP(w, r.WithContext(ctx))
	})
}

// handles "/"
func indexHandler(w http.ResponseWriter, r *http.Request) {
	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	// Stat the index template to get the mod time
	var etag string
	if indextmpl, err := os.Stat("assets/tmpl/index.html"); err != nil {
		log.Printf("Couldn't stat index template for ETag ... %v\n", err)
	} else {
		etag = fmt.Sprintf("%x", sha256.Sum256([]byte(indextmpl.ModTime().String())))
	}

	// Take the hex-encoded sha256 sum of the index template's mod time
	// to send as an ETag. If an error occured when grabbing the file info,
	// the ETag will be empty.
	w.Header().Set("ETag", "\""+etag+"\"")
	w.Header().Set("Content-Type", htmlutf8)

	// Pass the confObj.Instance data to the template,
	// then send it to the client.
	err := tmpls.ExecuteTemplate(w, "index.html", confObj.Instance)
	if err != nil {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

}

// handles "/api"
func apiBaseHandler(w http.ResponseWriter, r *http.Request) {
	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	timerfc3339, err := time.Now().MarshalText()
	if err != nil {
		log.Printf("Couldn't format time as RFC3339: %v\n", err)
	}
	etag := fmt.Sprintf("%x", sha256.Sum256(timerfc3339))
	w.Header().Set("ETag", etag)
	w.Header().Set("Content-Type", txtutf8)
	pathdata := []byte("\n\n" + r.URL.Path)
	timerfc3339 = append(timerfc3339, pathdata...)
	n, err := w.Write(timerfc3339)
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

// handles "/api/plain"
// maybe add json/xml support later
func apiFormatHandler(w http.ResponseWriter, r *http.Request) {
	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	vars := mux.Vars(r)
	format := vars["format"]

	w.Header().Set("Content-Type", txtutf8)
	n, err := w.Write([]byte(format + "\n"))
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

// handles "/api/plain/(users|mentions|tweets)"
func apiEndpointHandler(w http.ResponseWriter, r *http.Request) {
	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	if r.FormValue("q") != "" || r.FormValue("url") != "" {
		apiEndpointQuery(w, r)
		return
	}

	w.Header().Set("Content-Type", htmlutf8)
	n, err := w.Write([]byte(r.URL.String()))
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}

}

// handles POST for "/api/plain/users"
func apiEndpointPOSTHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	format := vars["format"]
	endpoint := vars["endpoint"]

	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	w.Header().Set("Content-Type", htmlutf8)
	n, err := w.Write([]byte(format + "/" + endpoint))
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}

}

// handles "/api/plain/tags"
func apiTagsBaseHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	format := vars["format"]

	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	w.Header().Set("Content-Type", htmlutf8)
	n, err := w.Write([]byte("api/" + format + "/tags"))
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}

}

// handles "/api/plain/tags/[a-zA-Z0-9]+"
func apiTagsHandler(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	format := vars["format"]
	tags := vars["tags"]

	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	w.Header().Set("Content-Type", htmlutf8)
	n, err := w.Write([]byte("api/" + format + "/tags/" + tags))
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}

}

// Serving the stylesheet virtually because
// files aren't served directly.
func cssHandler(w http.ResponseWriter, r *http.Request) {
	uip := getIPFromCtx(r.Context())
	log.Printf("Request from %v :: %v %v\n", uip, r.Method, r.URL)

	// read the raw bytes of the stylesheet
	css, err := ioutil.ReadFile("assets/style.css")
	if err != nil {
		if os.IsNotExist(err) {
			log.Printf("CSS file does not exist: /css request 404\n")
			http.Error(w, err.Error(), http.StatusNotFound)
			return
		}
		log.Printf("500: %v\n", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// Get the mod time for the etag header
	stat, err := os.Stat("assets/style.css")
	if err != nil {
		log.Printf("Couldn't stat CSS file to send ETag header: %v\n", err)
	}

	// Sending the sha256 sum of the modtime in hexadecimal for the ETag header
	etag := fmt.Sprintf("%x", sha256.Sum256([]byte(stat.ModTime().String())))

	w.Header().Set("ETag", "\""+etag+"\"")
	w.Header().Set("Content-Type", cssutf8)
	n, err := w.Write(css)
	if err != nil || n == 0 {
		log.Printf("500: Error writing to HTTP stream: %v, %v %v via %v\n", err, r.Method, r.URL, uip)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}