package main

import (
	"database/sql"
	"embed"
	"fmt"
	"html/template"
	"net/http"
	"time"

	"golang.org/x/crypto/bcrypt"

	_ "github.com/mattn/go-sqlite3"
)

//go:embed templates/*
var templatesFS embed.FS

//go:embed schema.sql
var schemaSQL string

type Trainer struct {
	ID    int
	Name  string
	Email string
	Areas []TrainingArea
}

type Training struct {
	ID           int
	Title        string
	TrainingType string
	Mode         string
	Start        time.Time
	End          time.Time
	Status       string
	Trainers     []Trainer
	Area         TrainingArea
}

type TrainingArea struct {
	ID       int
	Name     string
	Trainers []Trainer
}

func (ta TrainingArea) IsTrainerAssigned(trainerID int) bool {
	if ta.Trainers == nil {
		return false
	}

	for _, trainer := range ta.Trainers {
		if trainer.ID == trainerID {
			return true
		}
	}

	return false
}

var db *sql.DB

func initDB() {
	var err error
	db, err = sql.Open("sqlite3", "training.db")
	if err != nil {
		panic(err)
	}

	_, err = db.Exec(schemaSQL)
	if err != nil {
		panic(err)
	}
}

var tmpl *template.Template

func initTemplates() {
	var err error
	tmpl, err = template.ParseFS(templatesFS, "templates/*.html")
	if err != nil {
		panic(fmt.Sprintf("Error parsing templates: %v", err))
	}
}

func homeHandler(w http.ResponseWriter, r *http.Request) {
	err := tmpl.ExecuteTemplate(w, "home.html", nil)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
	}
}

func trainingAreaListHandler(w http.ResponseWriter, r *http.Request) {
	areas, err := fetchTrainingAreasWithTrainers()
	if err != nil {
		http.Error(w, "Database error", http.StatusInternalServerError)
		return
	}

	trainers, err := fetchTrainers()
	if err != nil {
		http.Error(w, "Database error", http.StatusInternalServerError)
		return
	}

	data := struct {
		Areas    []TrainingArea
		Trainers []Trainer
	}{
		Areas:    areas,
		Trainers: trainers,
	}

	err = tmpl.ExecuteTemplate(w, "training_area_list.html", data)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
		return
	}
}

func fetchTrainingAreasWithTrainers() ([]TrainingArea, error) {
	rows, err := db.Query(`
		SELECT ta.id, ta.name, t.id, t.name, t.email 
		FROM training_areas ta
		LEFT JOIN trainer_training_areas tta ON ta.id = tta.training_area_id
		LEFT JOIN trainers t ON tta.trainer_id = t.id
		ORDER BY ta.id, t.name`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	areaMap := make(map[int]*TrainingArea)

	for rows.Next() {
		var areaID int
		var areaName string
		var trainerID sql.NullInt64
		var trainerName sql.NullString
		var trainerEmail sql.NullString

		err := rows.Scan(&areaID, &areaName, &trainerID, &trainerName, &trainerEmail)
		if err != nil {
			return nil, err
		}

		_, exists := areaMap[areaID]
		if !exists {
			area := &TrainingArea{ID: areaID, Name: areaName}
			areaMap[areaID] = area
		}

		if trainerID.Valid {
			areaMap[areaID].Trainers = append(areaMap[areaID].Trainers, Trainer{
				ID:    int(trainerID.Int64),
				Name:  trainerName.String,
				Email: trainerEmail.String,
			})
		}
	}

	var areas []TrainingArea
	for _, area := range areaMap {
		areas = append(areas, *area)
	}

	return areas, nil
}

func assignTrainerToAreaHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		trainerID := r.FormValue("trainer_id")
		areaID := r.FormValue("training_area_id")

		if trainerID == "" || areaID == "" {
			http.Error(w, "Trainer and Training Area are required", http.StatusBadRequest)
			return
		}

		_, err := db.Exec("INSERT OR IGNORE INTO trainer_training_areas (trainer_id, training_area_id) VALUES (?, ?)", trainerID, areaID)
		if err != nil {
			http.Error(w, "Database error", http.StatusInternalServerError)
			return
		}

		http.Redirect(w, r, "/training-areas", http.StatusSeeOther)
	}
}

func addTrainingAreaHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		name := r.FormValue("name")
		if name == "" {
			http.Error(w, "Name is required", http.StatusBadRequest)
			return
		}

		_, err := db.Exec("INSERT INTO training_areas (name) VALUES (?)", name)
		if err != nil {
			http.Error(w, "Database error", http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/training-areas", http.StatusSeeOther)
		return
	}

	err := tmpl.ExecuteTemplate(w, "add_training_area.html", nil)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
	}
}

func fetchTrainings() ([]Training, error) {
	rows, err := db.Query("SELECT id, title, training_type, mode, start, end, status FROM trainings")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var trainings []Training
	for rows.Next() {
		var t Training
		var start, end string
		err := rows.Scan(&t.ID, &t.Title, &t.TrainingType, &t.Mode, &start, &end, &t.Status)
		if err != nil {
			return nil, err
		}
		t.Start, _ = time.Parse("2006-01-02 15:04:05", start)
		t.End, _ = time.Parse("2006-01-02 15:04:05", end)
		trainings = append(trainings, t)
	}
	return trainings, nil
}

func trainingListHandler(w http.ResponseWriter, r *http.Request) {
	trainings, err := fetchTrainings()
	if err != nil {
		http.Error(w, "Database error", http.StatusInternalServerError)
		return
	}

	err = tmpl.ExecuteTemplate(w, "training_list.html", trainings)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
	}
}

func fetchTrainers() ([]Trainer, error) {
	rows, err := db.Query("SELECT id, name, email FROM trainers")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var trainers []Trainer
	for rows.Next() {
		var t Trainer
		err := rows.Scan(&t.ID, &t.Name, &t.Email)
		if err != nil {
			return nil, err
		}
		trainers = append(trainers, t)
	}
	return trainers, nil
}

func trainerListHandler(w http.ResponseWriter, r *http.Request) {
	trainers, err := fetchTrainers()
	if err != nil {
		http.Error(w, "Database error", http.StatusInternalServerError)
		return
	}

	err = tmpl.ExecuteTemplate(w, "trainer_list.html", trainers)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
	}
}

func addTrainerHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost {
		name := r.FormValue("name")
		email := r.FormValue("email")
		if name == "" || email == "" {
			http.Error(w, "Name and Email are required", http.StatusBadRequest)
			return
		}

		_, err := db.Exec("INSERT INTO trainers (name, email) VALUES (?, ?)", name, email)
		if err != nil {
			http.Error(w, "Database error", http.StatusInternalServerError)
			return
		}
		http.Redirect(w, r, "/trainers", http.StatusSeeOther)
		return
	}

	err := tmpl.ExecuteTemplate(w, "add_trainer.html", nil)
	if err != nil {
		http.Error(w, fmt.Sprintf("Error in templating page %v", err), http.StatusInternalServerError)
	}

}

func hashPassword(password string) (string, error) {
	bytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(bytes), err
}

func setupAdminHandler(w http.ResponseWriter, r *http.Request) {
	// Check if an admin exists
	var count int
	err := db.QueryRow("SELECT COUNT(*) FROM admins").Scan(&count)
	if err != nil {
		http.Error(w, "Database error", http.StatusInternalServerError)
		return
	}

	// If an admin exists, redirect to login
	if count > 0 {
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	// If it's a POST request, create the admin
	if r.Method == http.MethodPost {
		name := r.FormValue("name")
		email := r.FormValue("email")
		password := r.FormValue("password")

		if email == "" || password == "" || name == "" {
			http.Error(w, "Name, email and password are required", http.StatusBadRequest)
			return
		}

		// Hash the password
		hashedPassword, err := hashPassword(password)
		if err != nil {
			http.Error(w, "Error hashing password", http.StatusInternalServerError)
			return
		}

		// Insert the admin into the database
		_, err = db.Exec("INSERT INTO admins (name, email, password) VALUES (?, ?, ?)", name, email, hashedPassword)
		if err != nil {
			http.Error(w, "Error saving admin", http.StatusInternalServerError)
			return
		}

		// Redirect to login after setup
		http.Redirect(w, r, "/login", http.StatusSeeOther)
		return
	}

	// Show the admin setup page
	err = tmpl.ExecuteTemplate(w, "setup_admin.html", nil)
	if err != nil {
		http.Error(w, "Template rendering error", http.StatusInternalServerError)
	}
}

func redirectIfNoAdmin(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		var count int
		err := db.QueryRow("SELECT COUNT(*) FROM admins").Scan(&count)
		if err != nil || count == 0 {
			http.Redirect(w, r, "/setup-admin", http.StatusSeeOther)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func main() {
	initDB()
	initTemplates()
	http.Handle("/", redirectIfNoAdmin(http.HandlerFunc(homeHandler)))
	http.Handle("/trainings", redirectIfNoAdmin(http.HandlerFunc(trainingListHandler)))
	http.Handle("/trainers", redirectIfNoAdmin(http.HandlerFunc(trainerListHandler)))
	http.Handle("/trainers/add", redirectIfNoAdmin(http.HandlerFunc(addTrainerHandler)))
	http.Handle("/training-areas", redirectIfNoAdmin(http.HandlerFunc(trainingAreaListHandler)))
	http.Handle("/training-areas/add", redirectIfNoAdmin(http.HandlerFunc(addTrainingAreaHandler)))
	http.Handle("/training-areas/assign-trainer", redirectIfNoAdmin(http.HandlerFunc(assignTrainerToAreaHandler)))

	http.HandleFunc("/setup-admin", setupAdminHandler)

	fmt.Println("Server running on http://localhost:8080")
	http.ListenAndServe(":8080", nil)
}