import { EmailTemplate } from '../types';

// Helper functions remain synchronous as they are utility functions
export const generateTemplateKey = (name: string): string => {
  return name.trim().toLowerCase().replace(/\s+/g, '_').replace(/[^a-z0-9_]/g, '');
};

export const generateSQL = (template: EmailTemplate): string => {
  const fullHtml = `${template.header}${template.body}${template.footer}`.replace(/'/g, "''");
  const header = template.header.replace(/'/g, "''");
  const body = template.body.replace(/'/g, "''");
  const footer = template.footer.replace(/'/g, "''");
  const subject = template.subject.replace(/'/g, "''");
  const vars = JSON.stringify(template.variables).replace(/'/g, "''");
  const key = generateTemplateKey(template.name);

  return `INSERT INTO email_templates (id, template_key, name, description, subject, header_html, body_html, footer_html, full_html, required_variables)
VALUES ('${template.id}', '${key}', '${template.name.replace(/'/g, "''")}', '${template.description?.replace(/'/g, "''") || ''}', '${subject}', '${header}', '${body}', '${footer}', '${fullHtml}', '${vars}')
ON DUPLICATE KEY UPDATE 
    subject = VALUES(subject),
    header_html = VALUES(header_html),
    body_html = VALUES(body_html),
    footer_html = VALUES(footer_html),
    full_html = VALUES(full_html),
    required_variables = VALUES(required_variables);`;
};

export const generateSelectSQL = (template: EmailTemplate): string => {
  const key = generateTemplateKey(template.name);
  return `SELECT * FROM email_templates WHERE template_key = '${key}';`;
};

export const generateN8nCode = (template: EmailTemplate): string => {
  const varsMap = template.variables.map(v => `  "${v}": "REPLACE_WITH_VALUE"`).join(',\n');
  const hasVars = template.variables.length > 0;

  return `// n8n Code Node - Template Populator
// 1. Ensure the previous node (SQL) returns the template with 'full_html' column.
// 2. Adjust the 'item.json.full_html' path if your SQL node output is different.

for (const item of items) {
  const templateHtml = item.json.full_html;

  // Define your dynamic data here
  const replacements = {
${hasVars ? varsMap : '  // No variables detected in this template'}
  };

  let finalHtml = templateHtml;
  
  // Perform replacement
  for (const [key, value] of Object.entries(replacements)) {
    // Replaces {{key}} globally
    finalHtml = finalHtml.replace(new RegExp('{{' + key + '}}', 'g'), value);
  }

  // Output the processed HTML
  item.json.processed_html = finalHtml;
}

return items;`;
};

// Async API calls to replace synchronous localStorage
export const getTemplates = async (): Promise<EmailTemplate[]> => {
  try {
    const response = await fetch('/api/templates');
    if (!response.ok) throw new Error('Failed to fetch');
    return await response.json();
  } catch (e) {
    console.error("Failed to load templates", e);
    return [];
  }
};

export const saveTemplate = async (template: EmailTemplate): Promise<void> => {
  try {
    const response = await fetch('/api/templates', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(template),
    });
    
    if (!response.ok) {
      const error = await response.json();
      throw new Error(error.message || 'Failed to save');
    }
  } catch (e) {
    console.error("Failed to save template", e);
    throw e;
  }
};

export const deleteTemplate = async (id: string): Promise<void> => {
  try {
    const response = await fetch(`/api/templates/${id}`, {
      method: 'DELETE',
    });
    if (!response.ok) throw new Error('Failed to delete');
  } catch (e) {
    console.error("Failed to delete template", e);
    throw e;
  }
};