package email

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"text/template"
)

// EmailService handles transactional email sending
type EmailService struct {
	apiKey   string
	fromAddr string
	baseURL  string
}

// NewEmailService creates a new email service using Resend API
func NewEmailService() *EmailService {
	apiKey := os.Getenv("RESEND_API_KEY")
	fromAddr := os.Getenv("EMAIL_FROM")
	if fromAddr == "" {
		fromAddr = "noreply@gohorsejobs.com"
	}

	return &EmailService{
		apiKey:   apiKey,
		fromAddr: fromAddr,
		baseURL:  "https://api.resend.com/emails",
	}
}

// IsConfigured returns true if email service is properly configured
func (s *EmailService) IsConfigured() bool {
	return s.apiKey != ""
}

// EmailPayload represents the Resend API request body
type EmailPayload struct {
	From    string   `json:"from"`
	To      []string `json:"to"`
	Subject string   `json:"subject"`
	HTML    string   `json:"html"`
	Text    string   `json:"text,omitempty"`
}

// SendEmail sends an email via Resend API
func (s *EmailService) SendEmail(to []string, subject, htmlBody, textBody string) error {
	if !s.IsConfigured() {
		return fmt.Errorf("email service not configured: RESEND_API_KEY missing")
	}

	payload := EmailPayload{
		From:    s.fromAddr,
		To:      to,
		Subject: subject,
		HTML:    htmlBody,
		Text:    textBody,
	}

	jsonBody, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal email payload: %w", err)
	}

	req, err := http.NewRequest("POST", s.baseURL, bytes.NewBuffer(jsonBody))
	if err != nil {
		return fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", s.apiKey))
	req.Header.Set("Content-Type", "application/json")

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to send email: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		return fmt.Errorf("email API error: status %d", resp.StatusCode)
	}

	return nil
}

// WelcomeEmailData contains data for welcome email template
type WelcomeEmailData struct {
	Name    string
	Email   string
	AppURL  string
	AppName string
}

// SendWelcome sends a welcome email to new users
func (s *EmailService) SendWelcome(to, name string) error {
	data := WelcomeEmailData{
		Name:    name,
		Email:   to,
		AppURL:  os.Getenv("APP_URL"),
		AppName: "GoHorse Jobs",
	}

	html, err := renderTemplate(welcomeTemplate, data)
	if err != nil {
		return err
	}

	return s.SendEmail([]string{to}, "🐴 Bem-vindo ao GoHorse Jobs!", html, "")
}

// PasswordResetData contains data for password reset email
type PasswordResetData struct {
	Name      string
	ResetLink string
	AppName   string
	ExpiresIn string
}

// SendPasswordReset sends a password reset email
func (s *EmailService) SendPasswordReset(to, name, resetToken string) error {
	appURL := os.Getenv("APP_URL")
	if appURL == "" {
		appURL = "https://gohorsejobs.com"
	}

	data := PasswordResetData{
		Name:      name,
		ResetLink: fmt.Sprintf("%s/reset-password?token=%s", appURL, resetToken),
		AppName:   "GoHorse Jobs",
		ExpiresIn: "1 hora",
	}

	html, err := renderTemplate(passwordResetTemplate, data)
	if err != nil {
		return err
	}

	return s.SendEmail([]string{to}, "🔑 Redefinição de senha - GoHorse Jobs", html, "")
}

// ApplicationReceivedData contains data for application notification
type ApplicationReceivedData struct {
	ApplicantName string
	JobTitle      string
	CompanyName   string
	JobURL        string
	AppName       string
}

// SendApplicationReceived notifies recruiter about new application
func (s *EmailService) SendApplicationReceived(to, applicantName, jobTitle, companyName, jobID string) error {
	appURL := os.Getenv("APP_URL")
	if appURL == "" {
		appURL = "https://gohorsejobs.com"
	}

	data := ApplicationReceivedData{
		ApplicantName: applicantName,
		JobTitle:      jobTitle,
		CompanyName:   companyName,
		JobURL:        fmt.Sprintf("%s/jobs/%s/applications", appURL, jobID),
		AppName:       "GoHorse Jobs",
	}

	html, err := renderTemplate(applicationReceivedTemplate, data)
	if err != nil {
		return err
	}

	subject := fmt.Sprintf("📩 Nova candidatura para %s", jobTitle)
	return s.SendEmail([]string{to}, subject, html, "")
}

// Helper function to render templates
func renderTemplate(tmplStr string, data interface{}) (string, error) {
	tmpl, err := template.New("email").Parse(tmplStr)
	if err != nil {
		return "", fmt.Errorf("failed to parse template: %w", err)
	}

	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, data); err != nil {
		return "", fmt.Errorf("failed to execute template: %w", err)
	}

	return buf.String(), nil
}

// Email templates
const welcomeTemplate = `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style>
        body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; background: #f5f5f5; padding: 20px; }
        .container { max-width: 600px; margin: 0 auto; background: white; border-radius: 12px; overflow: hidden; box-shadow: 0 4px 15px rgba(0,0,0,0.1); }
        .header { background: linear-gradient(135deg, #10b981, #059669); padding: 30px; text-align: center; }
        .header h1 { color: white; margin: 0; font-size: 24px; }
        .content { padding: 30px; }
        .btn { display: inline-block; background: #10b981; color: white; padding: 12px 24px; text-decoration: none; border-radius: 8px; margin-top: 20px; }
        .footer { background: #f8f8f8; padding: 20px; text-align: center; color: #666; font-size: 12px; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>🐴 Bem-vindo ao {{.AppName}}!</h1>
        </div>
        <div class="content">
            <p>Olá, <strong>{{.Name}}</strong>!</p>
            <p>Sua conta foi criada com sucesso. Agora você pode:</p>
            <ul>
                <li>🔍 Buscar vagas de emprego</li>
                <li>📝 Candidatar-se às melhores oportunidades</li>
                <li>💼 Gerenciar seu perfil profissional</li>
            </ul>
            <a href="{{.AppURL}}/jobs" class="btn">Ver Vagas Disponíveis</a>
        </div>
        <div class="footer">
            <p>© 2024 {{.AppName}}. Todos os direitos reservados.</p>
        </div>
    </div>
</body>
</html>
`

const passwordResetTemplate = `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style>
        body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; background: #f5f5f5; padding: 20px; }
        .container { max-width: 600px; margin: 0 auto; background: white; border-radius: 12px; overflow: hidden; box-shadow: 0 4px 15px rgba(0,0,0,0.1); }
        .header { background: linear-gradient(135deg, #f59e0b, #d97706); padding: 30px; text-align: center; }
        .header h1 { color: white; margin: 0; font-size: 24px; }
        .content { padding: 30px; }
        .btn { display: inline-block; background: #f59e0b; color: white; padding: 12px 24px; text-decoration: none; border-radius: 8px; margin-top: 20px; }
        .warning { background: #fef3cd; border: 1px solid #ffc107; padding: 15px; border-radius: 8px; margin-top: 20px; }
        .footer { background: #f8f8f8; padding: 20px; text-align: center; color: #666; font-size: 12px; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>🔑 Redefinição de Senha</h1>
        </div>
        <div class="content">
            <p>Olá, <strong>{{.Name}}</strong>!</p>
            <p>Recebemos uma solicitação para redefinir a senha da sua conta.</p>
            <a href="{{.ResetLink}}" class="btn">Redefinir Minha Senha</a>
            <div class="warning">
                <strong>⚠️ Atenção:</strong> Este link expira em <strong>{{.ExpiresIn}}</strong>.
                Se você não solicitou esta redefinição, ignore este email.
            </div>
        </div>
        <div class="footer">
            <p>© 2024 {{.AppName}}. Todos os direitos reservados.</p>
        </div>
    </div>
</body>
</html>
`

const applicationReceivedTemplate = `
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style>
        body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; background: #f5f5f5; padding: 20px; }
        .container { max-width: 600px; margin: 0 auto; background: white; border-radius: 12px; overflow: hidden; box-shadow: 0 4px 15px rgba(0,0,0,0.1); }
        .header { background: linear-gradient(135deg, #3b82f6, #1d4ed8); padding: 30px; text-align: center; }
        .header h1 { color: white; margin: 0; font-size: 24px; }
        .content { padding: 30px; }
        .job-card { background: #f0f9ff; border: 1px solid #bae6fd; padding: 20px; border-radius: 8px; margin: 20px 0; }
        .btn { display: inline-block; background: #3b82f6; color: white; padding: 12px 24px; text-decoration: none; border-radius: 8px; margin-top: 20px; }
        .footer { background: #f8f8f8; padding: 20px; text-align: center; color: #666; font-size: 12px; }
    </style>
</head>
<body>
    <div class="container">
        <div class="header">
            <h1>📩 Nova Candidatura!</h1>
        </div>
        <div class="content">
            <p>Uma nova candidatura foi recebida para a vaga em <strong>{{.CompanyName}}</strong>:</p>
            <div class="job-card">
                <h3 style="margin: 0 0 10px 0;">{{.JobTitle}}</h3>
                <p style="margin: 0;"><strong>Candidato:</strong> {{.ApplicantName}}</p>
            </div>
            <a href="{{.JobURL}}" class="btn">Ver Candidatura</a>
        </div>
        <div class="footer">
            <p>© 2024 {{.AppName}}. Todos os direitos reservados.</p>
        </div>
    </div>
</body>
</html>
`