package main

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

var recordsFilename 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
	recordsFilename = filepath.Join(ketotrackDir, "records.json")
}

// Record holds a pointer to a Reading or Note.
type Record struct {
	Reading *Reading `json:"reading,omitempty"`
	Note    *Note    `json:"note,omitempty"`
}

// Note holds a text note along with the time the note was taken.
type Note struct {
	Time time.Time `json:"time"`
	Text string    `json:"text"`
}

// NewNote returns a new Note
func NewNote(text string) Note {
	return Note{
		Time: time.Now(),
		Text: text,
	}
}

// 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,
	}
}

// AppContext is the application data store that holds Records
type AppContext struct {
	Records []Record
}

// LoadRecords will load records from file
func (ctx *AppContext) LoadRecords(filename string) error {
	data, err := os.ReadFile(filename)
	if err != nil {
		return err
	}
	return json.Unmarshal(data, &ctx.Records)
}

// SaveRecords will save records to a file
func (ctx *AppContext) SaveRecords(filename string) error {
	jsonData, err := json.Marshal(ctx.Records)
	if err != nil {
		return err
	}
	return os.WriteFile(filename, jsonData, 0660)
}

// AddReading will add a Reading to the AppContext
func (ctx *AppContext) AddReading(reading Reading) {
	ctx.Records = append(ctx.Records, Record{Reading: &reading})
}

// AddNote will a add a Note to the AppContext
func (ctx *AppContext) AddNote(note Note) {
	ctx.Records = append(ctx.Records, Record{Note: &note})
}

func main() {
	var appCtx AppContext

	err := appCtx.LoadRecords(recordsFilename)
	if err != nil {
		fmt.Printf("Error loading records: %s\n", err)
	}

	// Display menu
	choice, err := getUserInput("1. Enter new reading\n2. Enter new note\n3. Exit\nYour choice")
	switch choice {
	case "1":
		// Take a new reading from the user
		reading, err := getReading()
		if err != nil {
			fmt.Printf("Error getting reading: %s\n", err)
		} else {
			// 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.")
			}
			appCtx.AddReading(reading)
		}
	case "2":
		noteText, err := getUserInput("Enter your note text: ")
		if err != nil {
			fmt.Println("Error getting note: %s\n", err)
		} else {
			note := NewNote(noteText)
			appCtx.AddNote(note)
		}
	default:
		fmt.Println("Quitting...")
	}

	// Save Records before exiting
	err = appCtx.SaveRecords(recordsFilename)
	if err != nil {
		fmt.Printf("Error saving records to file: %s\n", err)
	}
}

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
}