package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

var readingsFilename string

func init() {
	// Get user's homeDir directory
	homeDir, err := os.UserHomeDir()
	if err != nil {
		fmt.Println("Error fetching user's home directory:", err)
		os.Exit(1)
	}

	// Define the path to the application data directory
	ketotrackDir := filepath.Join(homeDir, ".ketotrack")

	// Create the directory if it does not exist
	err = os.MkdirAll(ketotrackDir, 0770)
	if err != nil {
		fmt.Println("Error creating .ketotrack directory:", err)
		os.Exit(1)
	}

	// Set data file path for readings
	readingsFilename = filepath.Join(ketotrackDir, "readings.json")
}

// Reading holds the glucose and ketone level measurements along with the time the measurements were taken.
type Reading struct {
	Time    time.Time `json:"time"`
	Glucose float64   `json:"glucose"`
	Ketone  float64   `json:"ketone"`
	GKI     float64   `json:"GKI"`
}

// NewReading creates and returns a new Reading instance with the provided glucose and ketone levels, and records
// the current time. The glucose value should be provided in mg/dL, while the ketone level should be in mmol/L.
func NewReading(glucose, ketone float64) Reading {
	var gki float64
	if ketone == 0 {
		gki = 0
	} else {
		gki = (glucose / 18) / ketone
	}

	return Reading{
		Time:    time.Now(),
		Glucose: glucose,
		Ketone:  ketone,
		GKI:     gki,
	}
}

/*
// GKI calculates and returns the Glucose Ketone Index of the reading.
// The Glucose Ketone Index helps determine the efficiency of glucose and ketone levels within the body. It is
// calculated as (glucose level in mg/dL / 18) divided by the ketone level.
func (r Reading) GKI() (float64, error) {
	if r.Ketone == 0 {
		return 0, errors.New("ketone level must not be zero to calculate GKI")
	}
	return (r.Glucose / 18) / r.Ketone, nil
}*/

func main() {
	// Take a new reading from the user
	reading, err := getReading()
	if err != nil {
		fmt.Println(err.Error())
		return
	}

	// Calculate GKI
	//gki, err := reading.GKI()
	//if err != nil {
	//	fmt.Println(err.Error())
	//	fmt.Println("You are not in ketosis.")
	//	return
	//}

	// Display GKI and level of ketosis
	fmt.Printf("\nYour GKI is: %0.2f\n", reading.GKI)
	switch {
	case reading.GKI <= 1:
		fmt.Println("You're in the highest level of ketosis.")
	case reading.GKI < 3:
		fmt.Println("You're in a high therapeutic level of ketosis.")
	case reading.GKI < 6:
		fmt.Println("You're in a moderate level of ketosis.")
	case reading.GKI <= 9:
		fmt.Println("You're in a low level of ketosis.")
	default:
		fmt.Println("You are not in ketosis.")
	}

	// Save latest reading to readings file
	readings, _ := loadReadingsFromFile(readingsFilename)
	readings = append(readings, reading)
	err = saveReadingsToFile(readingsFilename, readings)
	if err != nil {
		fmt.Printf("error saving data: %s\n", err.Error())
	}
}

func saveReadingsToFile(filename string, data []Reading) error {
	jsonData, err := json.Marshal(data)
	if err != nil {
		return err
	}
	return os.WriteFile(filename, jsonData, 0660)
}

func loadReadingsFromFile(filename string) ([]Reading, error) {
	data, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}

	var readings []Reading
	err = json.Unmarshal(data, &readings)
	if err != nil {
		return nil, err
	}

	return readings, nil
}

func getReading() (Reading, error) {
	// Get glucose reading
	glucose, err := getUserFloat("Enter glucose reading (mg/dL)")
	if err != nil {
		return Reading{}, fmt.Errorf("error getting glucose reading: %w", err)
	}

	// Validate glucose reading
	if glucose <= 0 {
		return Reading{}, errors.New("glucose reading cannot be less than or equal to 0")
	}

	// Get ketone reading
	ketone, err := getUserFloat("Enter ketone reading (mmol/L)")
	if err != nil {
		return Reading{}, fmt.Errorf("error getting ketone reading: %w", err)
	}

	// Validate ketone reading
	if ketone < 0 {
		fmt.Println("")
		return Reading{}, errors.New("ketone reading cannot be less than 0")
	}

	return NewReading(glucose, ketone), nil
}

func getUserInput(prompt string) (string, error) {
	fmt.Printf("%s: ", prompt)
	reader := bufio.NewReader(os.Stdin)
	input, err := reader.ReadString('\n')
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(input), nil
}

func getUserFloat(prompt string) (float64, error) {
	// Get input as a string
	s, err := getUserInput(prompt)
	if err != nil {
		return 0, err
	}

	// Convert string to float
	f, err := strconv.ParseFloat(s, 64)
	if err != nil {
		return 0, err
	}
	return f, nil
}