package main

import (
	"crypto/rand"
	"embed"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"io/fs"
	"net/http"
	"os"
	"path"
	"sync/atomic"
	"time"

	"log/slog"

	"go.balki.me/collage-maker/collage"
)

var (
	imagesDir      string
	collageDir     string
	localAssets    bool
	collageNameGen *nameGen
	imagesDirFs    fs.FS

	// go:embed web/*
	webFS embed.FS
)

func main() {
	flag.StringVar(&imagesDir, "images-dir", "images", "Sets the images dir")
	flag.StringVar(&collageDir, "collages-dir", "collages", "Sets the collages dir")
	flag.BoolVar(&localAssets, "local-assets", false, "Serve local assets for testing")

	flag.Parse()

	collageNameGen = NewNameGen()
	imagesDirFs = os.DirFS(imagesDir)
	imagesURLPath := "images"
	collagesPath := "collages"

	addFileServer := func(path, dir string) {

		httpFileServer := http.FileServer(http.Dir(dir))
		http.Handle("/"+path+"/", http.StripPrefix("/"+path, httpFileServer))
	}

	addFileServer(imagesURLPath, imagesDir)
	addFileServer(collagesPath, collageDir)

	if localAssets {
		httpFileServer := http.FileServer(http.Dir("web"))
		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			w.Header().Add("Cache-Control", "no-cache")
			httpFileServer.ServeHTTP(w, r)
		})
	} else {
		fs, err := fs.Sub(webFS, "web")

		if err != nil {
			panic(err)
		}

		httpFileServer := http.FileServer(http.FS(fs))
		http.Handle("/", httpFileServer)
	}

	http.HandleFunc("/make-collage", func(w http.ResponseWriter, r *http.Request) {
		collageReq := collage.Request{}
		body, err := io.ReadAll(r.Body)
		if err != nil {
			slog.Error("failed to read request body", "error", err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		if err := json.Unmarshal(body, &collageReq); err != nil {
			slog.Error("failed to unmarshal json request", "error", err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		collageFile, err := MakeCollage(&collageReq)
		if err != nil {
			slog.Error("failed to make collage", "error", err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		w.Write([]byte(collageFile))
	})
	if err := http.ListenAndServe(":8767", nil); err != nil {
		slog.Error("http ListenAndServe failed", "error", err)
	}
}

type nameGen struct {
	prefix  string
	counter atomic.Uint64
}

func NewNameGen() *nameGen {
	currentTime := time.Now().Unix()
	randBytes := make([]byte, 8)
	_, err := rand.Read(randBytes)
	if err != nil {
		panic(err)
	}
	alpha := []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
	uniqRunID := ""
	for _, b := range randBytes {
		uniqRunID += string(alpha[int(b)%len(alpha)])
	}
	return &nameGen{
		prefix:  fmt.Sprintf("%d-%s", currentTime, uniqRunID),
		counter: atomic.Uint64{},
	}
}

func (n *nameGen) Next() string {
	return fmt.Sprintf("%s-%d", n.prefix, n.counter.Add(1))
}

func MakeCollage(req *collage.Request) (string, error) {
	collageFile := fmt.Sprintf("collage-%s.jpg", collageNameGen.Next())
	out, err := os.Create(path.Join(collageDir, collageFile))
	if err != nil {
		return "", fmt.Errorf("failed to create collage output file, err: %w", err)
		// slog.Error("failed to create collage output file", "error", err)
	}
	if err := collage.Make(req, imagesDirFs, out); err != nil {
		return "", fmt.Errorf("failed to make collage, err: %w", err)
	}
	return collageFile, nil
}

// curl -D - --json @req.json http://localhost:8767/make-collage