package main

import (
	_ "embed"
	"encoding/gob"
	"html/template"
	"io"
	"log"
	"net/http"
	"os"
	"os/signal"
	"runtime/debug"
)

// File for persistent storage
var DataFilename = "ideas.data"

// Version number used for debugging compatibility with the .data file
var Version string

// layout for how the date should be output in html
var DateLayout string = "02/01/2006 on 15:04"

// template for listing out the ideas, should be bundled inside the executable
//
//go:embed ideas.html
var ideas_html string

var data Store

// ToDo's
// - [ ] Add a post
// - [ ] Remove a post
// - [ ] work with funcmaps in templates
// - [ ] Put a reaction on a post
// - [x] Store ideas to a file (encoder/gob)
// - [x] Change the date format printing

// Represents an idea
// CreatedAt is a formatted date string
// out of 5 rating of the idea
// formatted time string with DateLayout
type Idea struct {
	Title       string
	Description string
	Author      string
	CreatedAt   string
}

// Data needed through the programm, this data is written to DataFilename for persistent storage
// Is also the format for the Data file
type Store struct {
	Version string
	Ideas   []Idea
}

func GetVersion() string {
	buildinfo, ok := debug.ReadBuildInfo()
	if !ok {
		log.Fatalln("Could not read buildinfo to know package version.")
	}
	return buildinfo.Main.Version
}

func main() {
	Version = GetVersion()

	// Create a .data file  in the cache directory and decode eventual ideas from it
	{
		p := os.Getenv("XDG_CACHE_HOME")
		// TODO: remove for testing
		p = ""
		if p == "" {
			p = "."
		}
		DataFilename = p + "/" + DataFilename

		f, err := os.OpenFile(DataFilename, os.O_RDONLY|os.O_CREATE, 0666)
		if err != nil {
			log.Fatalln("Error while opening data file:", err)
		}

		dec := gob.NewDecoder(f)
		if err := dec.Decode(&data); err != io.EOF && err != nil {
			log.Fatalln("Error while decoding ideas:", err)
		}
		log.Println(data)

		if data.Version != Version {
			log.Fatalf("Version mismatch for datafile@%s != package@%s\n", data.Version, Version)
		}

		log.Printf("Imported @%s: %d ideas\n", data.Version, len(data.Ideas))
		if err := f.Close(); err != nil {
			log.Fatalln("Error while closing file:", err)
		}
	}

	// Handle SIGINT
	// On program exit it should write all its data to the datafile
	// TODO: Instead of recreating the file the new ideas should be appended, a way to achieve this would be that every time a new idea is added it is appended to the file, this way there is no need to ensure this.
	go func() {
		c := make(chan os.Signal, 1)
		signal.Notify(c, os.Interrupt)
		<-c

		f, err := os.Create(DataFilename)
		if err != nil {
			log.Fatalln(err)
		}
		defer f.Close()

		enc := gob.NewEncoder(f)
		if err := enc.Encode(data); err != nil {
			log.Fatalln(err)
		}
		log.Println("data saved.")
		os.Exit(0)
	}()

	tmpl, err := template.New("ideas_html").Parse(ideas_html)
	if err != nil {
		log.Fatalln(err)
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		tmpl.Execute(w, data)
	})

	log.Println("Listening on http://localhost:8080")
	err = http.ListenAndServe(":8080", nil)
	if err != nil {
		log.Fatalln(err)
	}
}