package contact

import (
	"errors"
	"net/mail"
	"strings"
	"unicode/utf8"

	"technical.kiwi/website/internal/contactcheck"
)

const (
	maxNameLen    = 120
	maxEmailLen   = 254
	maxMessageLen = 8000
	minMessageLen = 20
)

// Submission is validated contact form input.
type Submission struct {
	Name    string
	Email   string
	Message string
}

// Errors maps field names to user-facing messages.
type Errors map[string]string

func (e Errors) Any() bool {
	return len(e) > 0
}

// Parse reads and validates a contact form POST.
func Parse(name, email, message string) (Submission, Errors) {
	errs := make(Errors)

	name = strings.TrimSpace(name)
	email = strings.TrimSpace(email)
	message = strings.TrimSpace(message)

	if name == "" {
		errs["name"] = "Name is required."
	} else if utf8.RuneCountInString(name) > maxNameLen {
		errs["name"] = "Name is too long."
	}

	if email == "" {
		errs["email"] = "Email is required."
	} else if utf8.RuneCountInString(email) > maxEmailLen {
		errs["email"] = "Email is too long."
	} else {
		addr, err := mail.ParseAddress(email)
		if err != nil {
			errs["email"] = "Enter a valid email address."
		} else {
			email = addr.Address
		}
	}

	if message == "" {
		errs["message"] = "Message is required."
	} else if utf8.RuneCountInString(message) < minMessageLen {
		errs["message"] = "Message must be at least 20 characters."
	} else if utf8.RuneCountInString(message) > maxMessageLen {
		errs["message"] = "Message is too long."
	}

	if !errs.Any() {
		if err := contactcheck.ValidateEnglish(name, message); err != nil {
			switch {
			case errors.Is(err, contactcheck.ErrTooShort):
				errs["message"] = "Message must be at least 20 characters."
			case errors.Is(err, contactcheck.ErrTooLong):
				errs["message"] = "Message is too long."
			case errors.Is(err, contactcheck.ErrName):
				errs["name"] = "Name is too long."
			case errors.Is(err, contactcheck.ErrNotEnglish):
				errs["message"] = "This site only accepts messages written in English. If your message is in English, try adding a few more clear sentences so we can detect the language reliably."
			default:
				errs["message"] = "Could not accept this message."
			}
		}
	}

	if errs.Any() {
		return Submission{}, errs
	}

	return Submission{Name: name, Email: email, Message: message}, nil
}