package httputils

import (
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"text/template"
	"time"
)

type Handler = func(http.ResponseWriter, *http.Request)

const templateFolder = "templates"

var templatePaths, templateModTimes, _ = getTemplates()
var templates *template.Template = template.Must(template.ParseFiles(templatePaths...))

func getTemplates() ([]string, map[string]time.Time, error) {
	var modTimes map[string]time.Time = make(map[string]time.Time)
	err := filepath.Walk(templateFolder, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if !info.IsDir() && strings.HasSuffix(path, ".html") {
			modTimes[path] = info.ModTime()
		}
		return nil
	})
	paths := make([]string, len(modTimes))
	i := 0
	for path := range modTimes {
		paths[i] = path
		i++
	}
	return paths, modTimes, err
}

func reloadTemplateIfModified(path string) {
	fileInfo, _ := os.Stat(path)
	modTime := fileInfo.ModTime()
	if modTime.After(templateModTimes[path]) {
		fmt.Printf("Reloading template %s...\n", path)
		templates.ParseFiles(path)
		templateModTimes[path] = modTime
	}
}

func reloadTemplatesIfModified() {
	for _, path := range templatePaths {
		reloadTemplateIfModified(path)
	}
}

const reloadTemplates = true

func GenerateHandler(
	file string,
	handler func(http.ResponseWriter, *http.Request) bool,
	data func(http.ResponseWriter, *http.Request) any,
	methods []string,
) Handler {
	return func(w http.ResponseWriter, r *http.Request) {
		// All templates must be reloaded in case of dependencies
		if reloadTemplates {
			reloadTemplatesIfModified()
		}
		for _, method := range methods {
			if method == r.Method {
				goto ok
			}
		}
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	ok:
		renderTemplate := handler(w, r)
		if renderTemplate && file != "" {
			w.Header().Set("Content-Type", "text/html; charset=utf-8")
			templates.ExecuteTemplate(w, file, data(w, r))
		}
	}
}

func GenerateSseHandler(handler Handler) Handler {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			w.WriteHeader(http.StatusMethodNotAllowed)
			return
		}
		w.Header().Set("Content-Type", "text/event-stream")
		w.Header().Set("Cache-Control", "no-cache")
		w.Header().Set("Connection", "keep-alive")
		w.WriteHeader(http.StatusOK)
		handler(w, r)
	}
}