import { Payload } from 'payload'
import { getMailing, renderTemplate, parseAndValidateEmails } from './utils/helpers.js'
import { BaseEmailDocument } from './types/index.js'

// Options for sending emails
export interface SendEmailOptions<T extends BaseEmailDocument = BaseEmailDocument> {
  // Template-based email
  template?: {
    slug: string
    variables?: Record<string, any>
  }
  // Direct email data
  data?: Partial<T>
  // Common options
  collectionSlug?: string // defaults to 'emails'
}

/**
 * Send an email with full type safety
 *
 * @example
 * ```typescript
 * // With your generated Email type
 * import { Email } from './payload-types'
 *
 * const email = await sendEmail<Email>(payload, {
 *   template: {
 *     slug: 'welcome',
 *     variables: { name: 'John' }
 *   },
 *   data: {
 *     to: 'user@example.com',
 *     customField: 'value' // Your custom fields are type-safe!
 *   }
 * })
 * ```
 */
export const sendEmail = async <TEmail extends BaseEmailDocument = BaseEmailDocument>(
  payload: Payload,
  options: SendEmailOptions<TEmail>
): Promise<TEmail> => {
  const mailing = getMailing(payload)
  const collectionSlug = options.collectionSlug || mailing.collections.emails || 'emails'

  let emailData: Partial<TEmail> = { ...options.data } as Partial<TEmail>

  // If using a template, render it first
  if (options.template) {
    const { html, text, subject } = await renderTemplate(
      payload,
      options.template.slug,
      options.template.variables || {}
    )

    // Template values take precedence over data values
    emailData = {
      ...emailData,
      subject,
      html,
      text,
    } as Partial<TEmail>
  }

  // Validate required fields
  if (!emailData.to) {
    throw new Error('Field "to" is required for sending emails')
  }

  // Validate required fields based on whether template was used
  if (options.template) {
    // When using template, subject and html should have been set by renderTemplate
    if (!emailData.subject || !emailData.html) {
      throw new Error(`Template rendering failed: template "${options.template.slug}" did not provide required subject and html content`)
    }
  } else {
    // When not using template, user must provide subject and html directly
    if (!emailData.subject || !emailData.html) {
      throw new Error('Fields "subject" and "html" are required when sending direct emails without a template')
    }
  }

  // Process email addresses using shared validation (handle null values)
  if (emailData.to) {
    emailData.to = parseAndValidateEmails(emailData.to as string | string[])
  }
  if (emailData.cc && emailData.cc !== null) {
    emailData.cc = parseAndValidateEmails(emailData.cc as string | string[])
  }
  if (emailData.bcc && emailData.bcc !== null) {
    emailData.bcc = parseAndValidateEmails(emailData.bcc as string | string[])
  }
  if (emailData.replyTo && emailData.replyTo !== null) {
    const validated = parseAndValidateEmails(emailData.replyTo as string | string[])
    // replyTo should be a single email, so take the first one if array
    emailData.replyTo = validated && validated.length > 0 ? validated[0] : undefined
  }
  if (emailData.from && emailData.from !== null) {
    const validated = parseAndValidateEmails(emailData.from as string | string[])
    // from should be a single email, so take the first one if array
    emailData.from = validated && validated.length > 0 ? validated[0] : undefined
  }

  // Create the email in the collection with proper typing
  const email = await payload.create({
    collection: collectionSlug,
    data: emailData
  })

  // Validate that the created email has the expected structure
  if (!email || typeof email !== 'object' || !email.id) {
    throw new Error('Failed to create email: invalid response from database')
  }

  return email as TEmail
}

export default sendEmail