package email

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

const resendAPIURL = "https://api.resend.com/emails"

// Client handles email sending via Resend
type Client struct {
	apiKey     string
	fromEmail  string
	fromName   string
	httpClient *http.Client
}

// NewClient creates a new Resend email client
func NewClient(apiKey, fromEmail, fromName string) *Client {
	return &Client{
		apiKey:    apiKey,
		fromEmail: fromEmail,
		fromName:  fromName,
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}
}

// Email represents an email to be sent
type Email struct {
	To          []string          `json:"to"`
	From        string            `json:"from"`
	Subject     string            `json:"subject"`
	HTML        string            `json:"html,omitempty"`
	Text        string            `json:"text,omitempty"`
	Attachments []Attachment      `json:"attachments,omitempty"`
	Headers     map[string]string `json:"headers,omitempty"`
}

// Attachment represents an email attachment
type Attachment struct {
	Filename string `json:"filename"`
	Content  []byte `json:"content"`
}

// SendEmail sends an email via Resend
func (c *Client) SendEmail(to []string, subject, htmlBody, textBody string) error {
	from := c.fromEmail
	if c.fromName != "" {
		from = fmt.Sprintf("%s <%s>", c.fromName, c.fromEmail)
	}

	email := Email{
		To:      to,
		From:    from,
		Subject: subject,
		HTML:    htmlBody,
		Text:    textBody,
	}

	return c.send(email)
}

// SendEmailWithAttachment sends an email with attachments
func (c *Client) SendEmailWithAttachment(to []string, subject, htmlBody, textBody string, attachments []Attachment) error {
	from := c.fromEmail
	if c.fromName != "" {
		from = fmt.Sprintf("%s <%s>", c.fromName, c.fromEmail)
	}

	email := Email{
		To:          to,
		From:        from,
		Subject:     subject,
		HTML:        htmlBody,
		Text:        textBody,
		Attachments: attachments,
	}

	return c.send(email)
}

// SendInvoice sends an invoice email with PDF attachment
func (c *Client) SendInvoice(to []string, invoiceNumber string, pdfData []byte, htmlBody string) error {
	if htmlBody == "" {
		htmlBody = fmt.Sprintf(`
			<h2>Faktura %s</h2>
			<p>Bifogat finner du din faktura.</p>
			<p>Vid frågor, kontakta oss.</p>
		`, invoiceNumber)
	}

	attachments := []Attachment{
		{
			Filename: fmt.Sprintf("faktura-%s.pdf", invoiceNumber),
			Content:  pdfData,
		},
	}

	return c.SendEmailWithAttachment(
		to,
		fmt.Sprintf("Faktura %s", invoiceNumber),
		htmlBody,
		fmt.Sprintf("Faktura %s bifogad.", invoiceNumber),
		attachments,
	)
}

// SendQuote sends a quote email with PDF attachment
func (c *Client) SendQuote(to []string, quoteNumber string, pdfData []byte, htmlBody string) error {
	if htmlBody == "" {
		htmlBody = fmt.Sprintf(`
			<h2>Offert %s</h2>
			<p>Bifogat finner du din offert.</p>
			<p>Offerten är giltig i 30 dagar.</p>
		`, quoteNumber)
	}

	attachments := []Attachment{
		{
			Filename: fmt.Sprintf("offert-%s.pdf", quoteNumber),
			Content:  pdfData,
		},
	}

	return c.SendEmailWithAttachment(
		to,
		fmt.Sprintf("Offert %s", quoteNumber),
		htmlBody,
		fmt.Sprintf("Offert %s bifogad.", quoteNumber),
		attachments,
	)
}

// SendWelcome sends a welcome email to a new customer
func (c *Client) SendWelcome(to []string, customerName string) error {
	htmlBody := fmt.Sprintf(`
		<h2>Välkommen %s!</h2>
		<p>Tack för att du valde oss. Vi ser fram emot ett gott samarbete.</p>
		<p>Logga in på din dashboard för att se dina uppgifter och hantera dina ärenden.</p>
	`, customerName)

	return c.SendEmail(
		to,
		"Välkommen!",
		htmlBody,
		fmt.Sprintf("Välkommen %s! Tack för att du valde oss.", customerName),
	)
}

// SendPaymentReminder sends a payment reminder
func (c *Client) SendPaymentReminder(to []string, invoiceNumber string, amount float64, currency string, dueDate time.Time) error {
	htmlBody := fmt.Sprintf(`
		<h2>Påminnelse: Faktura %s</h2>
		<p>Detta är en påminnelse om att faktura %s på <strong>%.2f %s</strong> förfaller %s.</p>
		<p>Vänligen betala i tid för att undvika påminnelseavgifter.</p>
	`, invoiceNumber, invoiceNumber, amount, currency, dueDate.Format("2006-01-02"))

	return c.SendEmail(
		to,
		fmt.Sprintf("Påminnelse: Faktura %s", invoiceNumber),
		htmlBody,
		fmt.Sprintf("Påminnelse: Faktura %s på %.2f %s förfaller %s.", invoiceNumber, amount, currency, dueDate.Format("2006-01-02")),
	)
}

// SendPasswordReset sends a password reset email
func (c *Client) SendPasswordReset(to []string, resetToken string, resetURL string) error {
	htmlBody := fmt.Sprintf(`
		<h2>Återställ ditt lösenord</h2>
		<p>Du har begärt att återställa ditt lösenord.</p>
		<p><a href="%s" style="background:#C96A3A;color:white;padding:12px 24px;text-decoration:none;border-radius:6px;">Återställ lösenord</a></p>
		<p>Om du inte begärt detta, ignorera detta meddelande.</p>
	`, resetURL+"?token="+resetToken)

	return c.SendEmail(
		to,
		"Återställ ditt lösenord",
		htmlBody,
		"Klicka på länken för att återställa ditt lösenord: "+resetURL+"?token="+resetToken,
	)
}

func (c *Client) send(email Email) error {
	payload, err := json.Marshal(email)
	if err != nil {
		return fmt.Errorf("marshal email: %w", err)
	}

	req, err := http.NewRequest("POST", resendAPIURL, bytes.NewReader(payload))
	if err != nil {
		return fmt.Errorf("create request: %w", err)
	}

	req.Header.Set("Authorization", "Bearer "+c.apiKey)
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("send request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		var errResp struct {
			Error  string `json:"error"`
			Status int    `json:"status"`
		}
		if err := json.NewDecoder(resp.Body).Decode(&errResp); err != nil {
			return fmt.Errorf("resend API error (status %d)", resp.StatusCode)
		}
		return fmt.Errorf("resend API error: %s (status %d)", errResp.Error, resp.StatusCode)
	}

	return nil
}