package main

// Ideez instance code.

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

const (
	SERVER_ID_BYTES = 8
)

// This is the Object that should be paired to the Ideas.
type Ideez struct {
	Id   string
	Name string
}

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

// Data passed to the ideas_html template
type IdeasPageData struct {
	Name        string
	Ideas       []Idea
	Error       string
	RoutePrefix string
}

var (
	//go:embed templates/ideas.html
	ideas_html string
	//go:embed templates/edit.html
	idea_edit_html string
	// layout for how the date should be output in html
	DateLayout string = "02/01/2006 on 15:04"
)

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

// This function intializes a server for use it
// 1. Imports the data file for its ID, or creates one if it does not exist
// 2. Creates a SIGINT handler to save the data
// 3. Creates the html templates
// 4. Registers the routes to mux passed
// Returns a new server so that the manager can add it to the list of servers
func NewIdeez(mux *http.ServeMux, name, id string) Ideez {
	var logger = log.New(os.Stdout, "NewIdeez: ", log.Ldate)
	logger.Printf("New server %s[%s]\n", name, id)

	// Ideas for this server
	var Ideas []Idea
	// version number used for debugging compatibility with the .data file
	version := GetVersion()
	// Prefix that should be prepended before each route
	routePrefix := "/server/" + id
	// File for persistent storage
	dataFilename := DataDir + "/" + id + ".data"
	// Counter that goes up each time a new idea is created
	idCounter := 0

	// If the .data file does not exist, create it in the cache directory
	{
		f, err := os.Open(dataFilename)
		if errors.Is(err, os.ErrNotExist) {
			// The file does not exist, so create one with only Version encoded
			logger.Println("Datafile does not exist.  Creating", dataFilename)
			f, err = os.Create(dataFilename)
			if err != nil {
				logger.Fatalln("Error while creating data file:", err)
			}

			enc := gob.NewEncoder(f)
			if err := enc.Encode(version); err != nil {
				logger.Fatalln("Error while encoding Version:", err)
			}
		} else if err != nil {
			logger.Fatalln("Error while opening data file:", err)
		} else {
			dec := gob.NewDecoder(f)

			// Check the version
			var v string
			if err := dec.Decode(&v); err != io.EOF && err != nil {
				logger.Fatalln("Error while decoding version:", err)
			}
			if v != version {
				logger.Fatalf("Version mismatch for datafile@%s != package@%s\n", v, version)
			}

			// Decode the data and import it into Ideas
			if err := dec.Decode(&name); err != nil && err != io.EOF {
				logger.Fatalln("Error while decoding name:", err)
			}
			if err := dec.Decode(&Ideas); err != nil && err != io.EOF {
				logger.Fatalln("Error while decoding ideas:", err)
			}
			logger.Printf("Imported @%s: %d ideas\n", v, len(Ideas))
			if err := f.Close(); err != nil {
				logger.Fatalln("Error while closing file:", err)
			}
		}

	}

	// Data was succesfully imported
	logger.SetPrefix("Ideez(" + name + ") ")

	// Handle SIGINT
	// Save all Ideas into the data file
	// NOTE (Luca): This system might seem dumb, but it only adds overhead at startup
	// and exit of the program which is fine.
	go func() {
		c := make(chan os.Signal, 1)
		signal.Notify(c, os.Interrupt)
		<-c

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

		enc := gob.NewEncoder(f)
		if err := enc.Encode(version); err != nil {
			logger.Fatalln(err)
		}
		if err := enc.Encode(name); err != nil {
			logger.Fatalln(err)
		}
		if err := enc.Encode(Ideas); err != nil {
			logger.Fatalln("Error while saving ideas:", err)
		}

		logger.Println("data saved.")
		os.Exit(0)
	}()

	// Creating templates
	tmpl, err := template.New("ideas").Parse(ideas_html)
	if err != nil {
		logger.Fatalln(err)
	}
	_, err = tmpl.New("edit").Parse(idea_edit_html)
	if err != nil {
		logger.Fatalln(err)
	}

	// Register http handlers
	{
		mux.HandleFunc("GET "+routePrefix+"/{$}", func(w http.ResponseWriter, r *http.Request) {
			tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "", routePrefix})
		})

		mux.HandleFunc("POST "+routePrefix+"/idea/create/", func(w http.ResponseWriter, r *http.Request) {
			i := Idea{
				Title:       r.FormValue("title"),
				Author:      r.FormValue("author"),
				LastUpdated: time.Now().Format(DateLayout),
				Text:        r.FormValue("text"),
				Id:          idCounter,
			}
			if i.Title == "" || i.Author == "" || i.Text == "" {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "All fields are required", routePrefix})
				return
			}

			Ideas = append(Ideas, i)
			idCounter++

			logger.Printf("Added new idea: %#v\n", i)
			http.Redirect(w, r, routePrefix+"/", http.StatusMovedPermanently)
		})

		// A page to edit the idea, this page should lead to POST /idea/edit for confirming the edit. If
		// the user cancels they should be redirected to the start page.  This is done in the html.
		mux.HandleFunc("GET "+routePrefix+"/idea/edit/", func(w http.ResponseWriter, r *http.Request) {
			id := r.URL.Query().Get("id")
			if id == "" {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "You must provide an Idea ID.", routePrefix})
				return
			}
			idInt, err := strconv.Atoi(id)
			if err != nil {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, id + " is not a valid Idea ID.", routePrefix})
				return
			}

			for _, i := range Ideas {
				if i.Id == idInt {
					tmpl.ExecuteTemplate(w, "edit", struct {
						Idea        Idea
						RoutePrefix string
					}{i, routePrefix})
					return
				}
			}
			tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "No idea with id '" + id + "'.", routePrefix})
		})

		// Perform the edit action on the idea
		mux.HandleFunc("POST "+routePrefix+"/idea/edit/", func(w http.ResponseWriter, r *http.Request) {
			id := r.FormValue("id")
			if id == "" {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "You must provide an Idea ID.", routePrefix})
				return
			}

			idInt, err := strconv.Atoi(id)
			if err != nil {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, id + " is not a valid Idea ID.", routePrefix})
				return
			}

			var i *Idea
			for j := range Ideas {
				if Ideas[j].Id == idInt {
					i = &Ideas[j]
					break
				}
			}

			if i == nil {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "No idea with id '" + id + "'.", routePrefix})
				return
			}

			i.Title = r.FormValue("title")
			i.Text = r.FormValue("text")
			i.LastUpdated = time.Now().Format(DateLayout) + " (edit)"

			logger.Printf("Edited %#v\n", i)

			http.Redirect(w, r, routePrefix+"/", http.StatusMovedPermanently)
		})

		mux.HandleFunc("POST "+routePrefix+"/idea/delete/", func(w http.ResponseWriter, r *http.Request) {
			id := r.FormValue("id")
			if id == "" {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "You must provide an Idea ID.", routePrefix})
				return
			}

			idInt, err := strconv.Atoi(id)
			if err != nil {
				tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, id + " is not a valid Idea ID.", routePrefix})
				return
			}

			for i, v := range Ideas {
				if idInt == v.Id {
					Ideas = append(Ideas[:i], Ideas[i+1:]...)
					logger.Printf("Deleted: %#v\n", v)
					http.Redirect(w, r, routePrefix+"/", http.StatusMovedPermanently)
					return
				}
			}
			tmpl.ExecuteTemplate(w, "ideas", IdeasPageData{name, Ideas, "No idea with id '" + id + "'.", routePrefix})
		})
	}

	return Ideez{Name: name, Id: id}
}