package main

import (
	"bufio"
	"encoding/csv"
	"flag"
	"fmt"
	"io"
	"maps"
	"math/rand"
	"os"
	"regexp"
	"slices"
	"strconv"
	"strings"
	"time"

	"github.com/joho/godotenv"
)

type SMSSender interface {
	CurlString(to, text string) string
	Send(to, text string) error
}

type SMSMessage struct {
	Name     string
	Number   string
	Template string
	Vars     map[string]string
	Text     string
}

type TextMessage struct {
	Text string `json:"text"`
}

type Payload struct {
	TextMessage  TextMessage `json:"textMessage"`
	PhoneNumbers []string    `json:"phoneNumbers"`
	Priority     int         `json:"priority,omitempty"`
}

var ErrInvalidClockFormat = fmt.Errorf("invalid clock time, ex: '06:00 PM', '6pm', or '18:00' (space and case insensitive)")
var ErrInvalidClockTime = fmt.Errorf("invalid hour or minute, for example '27:63 p' would not be valid")
var ErrPhoneEmpty = fmt.Errorf("no phone number")
var ErrPhoneInvalid11 = fmt.Errorf("invalid 11-digit number (does not start with 1)")
var ErrPhoneInvalid12 = fmt.Errorf("invalid 12-digit number (does not start with +1)")
var ErrPhoneInvalidLength = fmt.Errorf("invalid number length (should be 10 digits or 12 with +1 prefix)")

type MainConfig struct {
	csvPath     string
	dryRun      bool
	printCurl   bool
	shuffle     bool
	startClock  string
	startTime   time.Time
	runTime     time.Time
	endClock    string
	endTime     time.Time
	maxDuration time.Duration
	duration    time.Duration
	minDelay    time.Duration
	maxDelay    time.Duration
	delay       time.Duration
	verbose     bool
	confirmed   bool
}

const (
	textReset  = "\033[0m"
	textBold   = "\033[1m"
	fgYellow   = "\033[33m"
	fgBlue     = "\033[34m"
	fgGreen    = "\033[32m"
	fgRed      = "\033[31m"
	textErr    = textBold + fgRed
	textWarn   = textBold + fgYellow
	textInfo   = fgYellow
	textTmpl   = fgGreen
	textPrompt = fgBlue
)

func main() {
	var err error
	cfg := MainConfig{
		maxDelay: 2 * time.Minute,
	}

	_ = godotenv.Load("./.env")

	// note: we could also use twilio, or whatever
	var sender SMSSender = &SMSGatewayForAndroid{
		baseURL:  os.Getenv("SMSGW_BASEURL"),
		username: os.Getenv("SMSGW_USERNAME"),
		password: os.Getenv("SMSGW_PASSWORD"),
	}

	// TODO add days of week
	// TODO add start time zone and end time zone for whole country (e.g. 9am ET to 8pm PT)
	now := time.Now()
	zoneName, offset := now.Zone()

	flag.BoolVar(&cfg.confirmed, "y", false, "Confirm without prompting")
	flag.BoolVar(&cfg.verbose, "verbose", false, "Show parse warnings and other debug info")
	flag.BoolVar(&cfg.dryRun, "dry-run", false, "Skip sending messages and sleeping, runs without confirmation")
	flag.BoolVar(&cfg.printCurl, "print-curl", false, "Show full curl commands instead of messages")
	flag.StringVar(&cfg.csvPath, "csv", "./messages.csv", "Path to file with newline-delimited phone numbers")
	flag.BoolVar(&cfg.shuffle, "shuffle", false, "Randomize the list")
	flag.StringVar(&cfg.startClock, "start-time", "10am", "don't send messages before this time (e.g. 10:00, 10am, 00:00)")
	flag.StringVar(&cfg.endClock, "end-time", "8:30pm", "don't send messages after this time (e.g. 4pm, 23:59)")
	flag.DurationVar(&cfg.maxDuration, "max-duration", 0, "don't send messages for more than this long (e.g. 10m, 2h30m, 6h)")
	flag.DurationVar(&cfg.minDelay, "min-delay", 0, "don't send messages closer together on average than this (e.g. 10s, 2m) (Default: 20s)")
	flag.Parse()

	fmt.Fprintf(os.Stderr, "Info: Time zone: %s, Offset: %.2fh\n", zoneName, float64(offset)/3600)
	// os.Exit(1)

	// now, startTime, and endTime checks
	{
		cfg.startTime, err = parseClock(cfg.startClock, now)
		if err != nil {
			fmt.Fprintf(os.Stderr, "\n%sError%s: could not use --start-time %q: %v\n", textErr, textReset, cfg.startClock, err)
			os.Exit(1)
		}
		cfg.endTime, err = parseClock(cfg.endClock, now)
		if err != nil {
			fmt.Fprintf(os.Stderr, "\n%sError%s: could not use --end-time %q: %v\n", textErr, textReset, cfg.endClock, err)
			os.Exit(1)
		}
		if cfg.startTime.After(cfg.endTime) || cfg.startTime.Equal(cfg.endTime) {
			fmt.Fprintf(os.Stderr,
				"\n%sError%s: no time between --start-time %q and --end-time %q\n", textErr, textReset, cfg.startTime, cfg.endTime)
			os.Exit(1)
		}
	}

	if cfg.minDelay == 0 {
		cfg.minDelay = 20 * time.Second
	}
	if cfg.maxDelay < cfg.minDelay {
		cfg.maxDelay = cfg.minDelay
	}

	fmt.Fprintf(os.Stderr, "Info: opening, reading, and parsing %q\n", cfg.csvPath)
	file, err := os.Open(cfg.csvPath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "\n%sError%s: %v\n", textErr, textReset, err)
		os.Exit(1)
	}
	defer func() {
		_ = file.Close()
	}()
	csvr := csv.NewReader(file)
	csvr.FieldsPerRecord = -1

	messages, warns, err := cfg.LaxParseCSV(csvr)
	if err != nil {
		fmt.Fprintf(os.Stderr, "\n%sError%s: %v\n", textErr, textReset, err)
		os.Exit(1)
	}
	if len(warns) > 0 {
		fmt.Fprintf(os.Stderr, "\n")
		fmt.Fprintf(os.Stderr, "%sWarning%s: skipped %d rows with missing or invalid data\n", textWarn, textReset, len(warns))
		if !cfg.verbose {
			fmt.Fprintf(os.Stderr, "         (pass --verbose for more detail)\n")
		}
		if cfg.verbose {
			for _, warn := range warns {
				fmt.Fprintf(os.Stderr, "   Skip: %s\n", warn.Message)
			}
		}
		fmt.Fprintf(os.Stderr, "\n")
	}
	fmt.Fprintf(os.Stderr, "Info: list of %d messages\n", len(messages))

	if now.After(cfg.endTime) || now.Equal(cfg.endTime) {
		fmt.Fprintf(os.Stderr, "%sWarning%s: Too late now. %sWaiting until tomorrow%s:\n", textWarn, textReset, textWarn, textReset)

		cfg.startTime = safeSetTomorrow(cfg.startTime)
		cfg.endTime = safeSetTomorrow(cfg.endTime)

		// check for issues caused by daylight savings
		if cfg.startTime.After(cfg.endTime) || cfg.startTime.Equal(cfg.endTime) {
			fmt.Fprintf(os.Stderr,
				"\n%sError%s: no time between --start-time %q and --end-time %q\n",
				textErr, textReset,
				cfg.startTime, cfg.endTime,
			)
			os.Exit(1)
		}

		fmt.Fprintf(os.Stderr, "         %s\n\n", cfg.startTime)
	}
	if now.Before(cfg.startTime) {
		fmt.Fprintf(os.Stderr, "\n%sWarning%s: It's too early now. %sWaiting until %s.%s\n\n", textWarn, textReset, textWarn, cfg.startTime.Format("3:04pm"), textReset)
	}

	cfg.runTime = now
	if cfg.startTime.After(now) {
		cfg.runTime = cfg.startTime
	}

	// duration
	{
		cfg.duration = cfg.endTime.Sub(cfg.runTime)
		if cfg.maxDuration != 0 {
			if cfg.maxDuration < cfg.duration {
				cfg.duration = cfg.maxDuration
			}
		}
		var startAgo = now.Sub(cfg.startTime)
		if startAgo >= 0 {
			fmt.Fprintf(os.Stderr, "Info: start after %s         (%s ago)\n", cfg.startTime.Format("3:04pm"), startAgo.Round(time.Second))
		} else {
			startAgo *= -1
			fmt.Fprintf(os.Stderr, "Info: start after %s         (%s from now)\n", cfg.startTime.Format("3:04pm"), startAgo.Round(time.Second))
		}
		fmt.Fprintf(os.Stderr, "Info: end around %s          (%s from now)\n", cfg.endTime.Format("3:04pm"), cfg.duration.Round(time.Second))
	}

	// delay
	{
		n := len(messages)
		// add a small buffer so we complete in the time, even with randomness
		n += 2
		cfg.delay = cfg.duration / time.Duration(n)
		if cfg.delay < cfg.minDelay {
			fmt.Fprintf(os.Stderr, "\n")
			fmt.Fprintf(os.Stderr, "%sWarning%s: cannot send all %d messages in %s (would require 1 message every %s)\n", textWarn, textReset, len(messages), cfg.duration.Round(time.Second), cfg.delay.Round(time.Millisecond))
			fmt.Fprintf(os.Stderr, "         (we'll just %ssend what we can%s for now, 1 every %s)\n", textWarn, textReset, cfg.minDelay)
			fmt.Fprintf(os.Stderr, "\n")
			cfg.delay = cfg.minDelay
		}
		if cfg.delay > cfg.maxDelay {
			cfg.delay = cfg.maxDelay
		}

		// add a small buffer to allow for a final message, with randomness
		cfg.duration = cfg.duration + cfg.delay + cfg.delay
	}

	r := rand.New(rand.NewSource(37))
	if cfg.shuffle {
		r.Shuffle(len(messages), func(i, j int) {
			messages[i], messages[j] = messages[j], messages[i]
		})
	}

	quarterDelay := cfg.delay / 4
	baseDelay := quarterDelay * 3
	jitter := int64(quarterDelay * 2)
	fmt.Fprintf(os.Stderr,
		"Info: delay %s between messages  (%s + %s jitter)\n",
		cfg.delay.Round(time.Second), baseDelay.Round(time.Millisecond), time.Duration(jitter).Round(time.Millisecond),
	)

	if len(messages) == 0 {
		fmt.Fprintf(os.Stderr, "\n%sError%s: no messages to send\n", textErr, textReset)
		os.Exit(1)
	}

	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "Info: This is what a %ssample message%s from list look like:\n", textInfo, textReset)
	fmt.Fprintf(os.Stderr, "\n")
	fmt.Fprintf(os.Stderr, "      To: %s (%s)\n", messages[0].Number, messages[0].Name)
	fmt.Fprintf(os.Stderr, "      %s%s%s\n", textTmpl, messages[0].Template, textReset)
	fmt.Fprintf(os.Stderr, "      %s%s%s\n", textInfo, messages[0].Text, textReset)
	fmt.Fprintf(os.Stderr, "\n")

	if !cfg.confirmed && !cfg.dryRun {
		if !confirmContinue() {
			fmt.Fprintf(os.Stderr, "%scanceled%s\n", textErr, textReset)
			os.Exit(1)
			return
		}
	}

	// if there was a delay
	diff := cfg.startTime.Sub(now)
	if diff > 0 {
		fmt.Fprintf(os.Stderr, "\n%sWarning%s: It's too early now. %sWaiting until %s.%s\n", textWarn, textReset, textWarn, cfg.startTime.Format("3:04pm"), textReset)
		time.Sleep(diff)
		fmt.Fprintf(os.Stderr, "\n")
	}

	deadline := now.Add(cfg.duration)
	for i, message := range messages {
		now := time.Now()
		if now.After(deadline) {
			cur := i + 1
			last := len(messages)
			left := last - cur
			if left > 0 {
				fmt.Fprintf(os.Stderr, "\n%sError%s: Oh, look at the time. Ending now. (%d messages remaining)\n", textErr, textReset, left)
				os.Exit(1)
				return
			}
		}

		var delay time.Duration
		{
			ns := int64(baseDelay) + rand.Int63n(jitter)
			delay = time.Duration(ns)
		}

		if i > 0 {
			if cfg.dryRun || cfg.printCurl {
				fmt.Printf("sleep %s\n\n", delay.Round(time.Millisecond))
			} else {
				time.Sleep(delay)
			}
		}

		fmt.Fprintf(os.Stderr, "# Send to %s (%s) %s-%s\n", message.Number[:2], message.Number[2:5], message.Number[5:8], message.Number[8:])
		if cfg.printCurl {
			curl := sender.CurlString(message.Number, message.Text)
			fmt.Println(curl)
		} else {
			fmt.Fprintf(os.Stderr, "%s\n", message.Text)
		}
		if cfg.dryRun {
			continue
		}

		if err := sender.Send(message.Number, message.Text); err != nil {
			fmt.Fprintf(os.Stderr, "%sError%s: %v\n", textErr, textReset, err)
			continue
		}
	}

	fmt.Fprintf(os.Stderr, "\nInfo: finished at %s\n", time.Now())
}

func confirmContinue() bool {
	reader := bufio.NewReader(os.Stdin)
	for {
		fmt.Printf(textPrompt + "Continue? [y/N] " + textReset)
		input, err := reader.ReadString('\n')
		if err != nil {
			return false // EOF or error → treat as no
		}

		input = strings.TrimSpace(strings.ToLower(input))

		switch input {
		case "y", "yes":
			return true
		case "", "n", "no":
			return false
		default:
			fmt.Fprintf(os.Stderr, "%sError%s: please answer y or n", textErr, textReset)
			// loop again
		}
	}
}

// set by day rather than time to account for daylight savings
func safeSetTomorrow(ref time.Time) time.Time {
	return time.Date(ref.Year(), ref.Month(), 1+ref.Day(), ref.Hour(), ref.Minute(), 0, 0, ref.Location())
}

// we're not just skipping symbols,
// we're also eliminating non-printing characters copied from HTML and such
func cleanPhoneNumber(raw string) string {
	var cleaned strings.Builder
	for i, char := range raw {
		if (i == 0 && char == '+') || (char >= '0' && char <= '9') {
			cleaned.WriteRune(char)
		}
	}
	return cleaned.String()
}

func (cfg *MainConfig) validateAndFormatNumber(number string) (string, error) {
	switch len(number) {
	case 0:
		return "", ErrPhoneEmpty
	case 10:
		return "+1" + number, nil
	case 11:
		if strings.HasPrefix(number, "1") {
			return "+" + number, nil
		}
		return "", fmt.Errorf("%w: %s", ErrPhoneInvalid11, number)
	case 12:
		if strings.HasPrefix(number, "+1") {
			return number, nil
		}
		return "", fmt.Errorf("%w: %s", ErrPhoneInvalid12, number)
	default:
		return "", fmt.Errorf("%w: %s", ErrPhoneInvalidLength, number)
	}
}

func GetFieldIndex(header []string, name string) int {
	for i, h := range header {
		if strings.EqualFold(strings.TrimSpace(h), name) {
			return i
		}
	}
	return -1
}

type CSVWarn struct {
	Index   int
	Code    string
	Message string
	Record  []string
}

func (w CSVWarn) Error() string {
	return w.Message
}

var reUnmatchedVars = regexp.MustCompile(`(\{[^}]+\})`)

func (cfg *MainConfig) LaxParseCSV(csvr *csv.Reader) (messages []SMSMessage, warns []CSVWarn, err error) {
	header, err := csvr.Read()
	if err != nil {
		return nil, nil, fmt.Errorf("header could not be parsed: %w", err)
	}

	FIELD_NAME := GetFieldIndex(header, "Name")
	FIELD_PHONE := GetFieldIndex(header, "Phone")
	FIELD_MESSAGE := GetFieldIndex(header, "Message")
	if FIELD_NAME == -1 || FIELD_PHONE == -1 || FIELD_MESSAGE == -1 {
		return nil, nil, fmt.Errorf("header is missing one or more of 'Name', 'Phone', and/or 'Message'")
	}
	FIELD_MIN := 1 + slices.Max([]int{FIELD_NAME, FIELD_PHONE, FIELD_MESSAGE})

	rowIndex := 1 // 1-index, start at header
	for {
		rowIndex++
		rec, err := csvr.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, nil, fmt.Errorf("failed to parse row %d (and all following rows): %w", rowIndex, err)
		}

		if len(rec) < FIELD_MIN {
			warns = append(warns, CSVWarn{
				Index:   rowIndex,
				Code:    "TooFewFields",
				Message: fmt.Sprintf("ignoring row %d: too few fields (want %d, have %d)", rowIndex, FIELD_MIN, len(rec)),
				Record:  rec,
			})
			continue
		}

		vars := make(map[string]string)
		n := min(len(header), len(rec))
		for i := range n {
			switch i {
			case FIELD_NAME, FIELD_PHONE, FIELD_MESSAGE:
				continue
			default:
				key := header[i]
				val := rec[i]
				vars[key] = val
			}
		}

		message := SMSMessage{
			Name:     strings.TrimSpace(rec[FIELD_NAME]),
			Number:   strings.TrimSpace(rec[FIELD_PHONE]),
			Template: strings.TrimSpace(rec[FIELD_MESSAGE]),
			Vars:     vars,
			Text:     strings.TrimSpace(rec[FIELD_MESSAGE]),
		}
		message.Text = replaceVar(message.Template, "Name", message.Name)

		keyIter := maps.Keys(message.Vars)
		keys := slices.Sorted(keyIter)
		for _, key := range keys {
			val := message.Vars[key]
			message.Text = replaceVar(message.Text, key, val)
		}

		if tmpls := reUnmatchedVars.FindAllString(message.Text, -1); len(tmpls) != 0 {
			return nil, nil, &CSVWarn{
				Index: rowIndex,
				Code:  "UnmatchedVars",
				Message: fmt.Sprintf(
					"failing due to row %d (%s): leftover template variable(s): %s",
					rowIndex, message.Name, strings.Join(tmpls, " "),
				),
				Record: rec,
			}
		}

		message.Number = cleanPhoneNumber(message.Number)
		message.Number, err = cfg.validateAndFormatNumber(message.Number)
		if err != nil {
			warns = append(warns, CSVWarn{
				Index:   rowIndex,
				Code:    "PhoneInvalid",
				Message: fmt.Sprintf("ignoring row %d (%s): %s", rowIndex, message.Name, err.Error()),
				Record:  rec,
			})
			continue
		}

		messages = append(messages, message)
	}

	return messages, warns, nil
}

func replaceVar(text, key, val string) string {
	if val != "" {
		// No special treatment:
		// "Hey {+Name}," => "Hey Doe,"
		// "Bob,{Name}" => "Bob,Doe"
		// "{Name-},Joe" => "Doe,Joe"
		// "Hi {-Name-}, Joe" => "Hi Doe, Joe"
		var reHasVar = regexp.MustCompile(fmt.Sprintf(`\{\+?%s-?\}`, regexp.QuoteMeta(key)))
		return reHasVar.ReplaceAllString(text, val)
	}

	var metaKey = regexp.QuoteMeta(key)

	// "Hey {+Name}," => "Hey ,"
	var reEatNone = regexp.MustCompile(fmt.Sprintf(`\{\+%s\}`, metaKey))
	text = reEatNone.ReplaceAllString(text, val)

	// "Bob,{Name};" => "Bob;"
	var reEatOneLeft = regexp.MustCompile(fmt.Sprintf(`.?\{%s\}`, metaKey))
	text = reEatOneLeft.ReplaceAllString(text, val)

	// ",{Name-};Joe" => ",Joe"
	var reEatOneRight = regexp.MustCompile(fmt.Sprintf(`\{%s-\}.?`, metaKey))
	text = reEatOneRight.ReplaceAllString(text, val)

	// "Hi {-Name-}, Joe" => "Hi Joe"
	var reEatOneBoth = regexp.MustCompile(fmt.Sprintf(`.?\{-%s-\}.?`, metaKey))
	text = reEatOneBoth.ReplaceAllString(text, val)

	return text
}

// parseClock parses "10am", "10:00", "22:30", etc. into today's date + that time
func parseClock(s string, ref time.Time) (t time.Time, err error) {
	// "10:05 AM" => "10:05am"
	// "10 AM" => "10am"
	// "23:05" => "23:05"
	// "00" => "00"
	s = strings.ToLower(strings.TrimSpace(s))
	s = strings.ReplaceAll(s, " ", "")

	var hour, min int
	var ampm string

	// "10:05am" => "10:05"
	// "10am" => "10"
	// "23:05" => "23:05"
	// "00" => "00"
	if strings.HasSuffix(s, "am") {
		ampm = "am"
		s = strings.TrimSuffix(s, "am")
	} else if strings.HasSuffix(s, "pm") {
		ampm = "pm"
		s = strings.TrimSuffix(s, "pm")
	}

	// "10:05" => {hour: 10, minute: 5}
	// "10" => {hour: 10, minute: 0}
	// "00" => {hour: 0, minute: 0}
	// "23:05" => "23:05"
	// "00" => "00"
	parts := strings.Split(s, ":")
	switch len(parts) {
	case 2:
		minStr := parts[1]
		minStr = strings.TrimLeft(minStr, "0")
		if len(minStr) > 0 {
			min, err = strconv.Atoi(minStr)
			if err != nil {
				return t, ErrInvalidClockFormat
			}
		}
		fallthrough
	case 1:
		hourStr := parts[0]
		hourStr = strings.TrimLeft(hourStr, "0")
		if len(hourStr) > 0 {
			hour, err = strconv.Atoi(hourStr)
			if err != nil {
				return t, ErrInvalidClockFormat
			}
		}
	default:
		return t, ErrInvalidClockFormat
	}

	if hour < 0 || hour > 23 || min < 0 || min > 59 {
		return t, ErrInvalidClockTime
	}

	switch ampm {
	case "pm":
		if hour < 12 {
			hour += 12
		}
	case "am":
		if hour == 12 {
			hour = 0
		}
	case "":
		// no change
	default:
		panic(fmt.Errorf("impossible condition: ampm set to %q", ampm))
	}

	t = time.Date(ref.Year(), ref.Month(), ref.Day(), hour, min, 0, 0, ref.Location())
	return t, nil
}