# plugins/discourse-md5_authentication/plugin.rb

# frozen_string_literal: true

# name: discourse-md5_authentication
# about: A plugin to authenticate users with MD5 passwords from legacy systems
# version: 0.16
# authors: saint@federated.computer
# url: https://gitea.federated.computer/saint/discourse-md5_authentication.git

# require 'digest'

# enabled_site_setting :legacymd5password_auth_enabled

after_initialize do
  # Define a module to hold the legacy MD5 authentication logic
  module LegacyMd5Authentication

    # Constants
    ITOA64 = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

    # Override the create method to add our custom authentication checks
    def create
      Rails.logger.warn "MD5 -- AA -- start create"
      # Ensure required parameters are present
      params.require(:login)
      params.require(:password)

      # Validate the length of the password
      return invalid_credentials if params[:password].length > User.max_password_length

      # Find the user by username or email
      user = User.find_by_username_or_email(normalized_login_param)

      Rails.logger.warn "MD5 -- BB -- second"
      # Check if site is in staff writes-only mode and ensure user is staff if true
      raise Discourse::ReadOnly if staff_writes_only_mode? && !user&.staff?

      # Apply rate limiting for second factor authentication
      rate_limit_second_factor!(user)

      if user.present?
        Rails.logger.warn "MD5 -- CC -- user.present"
        # Retrieve the provided password and custom MD5 password hash from user custom fields
        password = params[:password]
        custom_password_md5 = user.custom_fields['custom_password_md5']

        # Log the presence of custom MD5 hash for debugging
        Rails.logger.warn "MD5 -- Check for MD5 password in custom field"
        if custom_password_md5.present?
          Rails.logger.warn "MD5 -- MD5 password is present custom_password_md5: #{custom_password_md5} password: #{password}"

          # Verify the provided password against the stored MD5 hash
          if verify_gossamer_password(password, custom_password_md5)
            # If MD5 hash matches, update the user's password and other attributes
            Rails.logger.warn "MD5 -- MD5 matches"

            # Set the user's password to the provided one and update other attributes
            user.password = password
            user.active = true
            user.approved = true
            user.approved_at = Time.now
            user.approved_by_id = 1
            user.custom_fields['custom_password_md5'] = nil # Clear the custom MD5 field
            user.save!
            Rails.logger.warn "MD5 -- DD -- user.present"

            # Generate a new token and hash it
            token = SecureRandom.hex(20)
            token_hash = EmailToken.hash_token(token)

            # Create a confirmed email token for the user
            EmailToken.create!(
              user_id: user.id,
              email: user.email,
              token_hash: token_hash,
              confirmed: true
            )
            Rails.logger.warn("MD5 -- Generated token for user #{user.username}: #{token}")

            Rails.logger.warn "MD5 -- Updated user: #{user.id}"
          else
            # If MD5 hash does not match, log the failed login attempt
            Rails.logger.warn "MD5 -- MD5 Password (hash) incorrect for user: #{user.id}"
            invalid_credentials
            return
          end

        elsif !user.confirm_password?(password)
          # If no MD5 hash is present and the provided password is incorrect
          Rails.logger.warn "MD5 -- Password incorrect for user: #{user.id}"
          invalid_credentials
          return
        end

        # If the site requires user approval and the user is not yet approved
        if login_not_approved_for?(user)
          render json: login_not_approved
          return
        end

        # Invalidate any invite link for the user
        Invite.invalidate_for_email(user.email)

        # Check if the user's password has expired
        if user.password_expired?(password)
          render json: { error: "expired", reason: "expired" }
          return
        end
      else
        # If no user is found with the provided credentials
        invalid_credentials
        return
      end

      # Check for any login errors
      if payload = login_error_check(user)
        return render json: payload
      end

      # Authenticate second factor if required
      second_factor_auth_result = authenticate_second_factor(user)
      return render(json: @second_factor_failure_payload) unless second_factor_auth_result.ok

      # If user is active and email is confirmed, proceed with login
      if user.active && user.email_confirmed?
        login(user, second_factor_auth_result)
      else
        not_activated(user)
      end
    end

    # Helper methods to handle MD5 password verification

    def to64(value, length)
      # Convert a value to a base64-like representation
      result = String.new
      length.times do
        result << ITOA64[value & 0x3f]
        value >>= 6
        Rails.logger.warn "to64 result: #{result}"
      end
      result
    end

    def gossamer_md5_crypt(password, legacy_hash)
      # Extract the salt from the legacy hash
      parts = legacy_hash.split('$')
      salt = parts[2]

      # Limit the salt to 8 characters
      salt = salt[0, 8]

      magic = "$GT$"
      Rails.logger.warn "MD5 magic: #{magic}"

      ctx = Digest::MD5.new
      ctx.update(password)
      ctx.update(magic)
      ctx.update(salt)

      final = Digest::MD5.new
      final.update(password)
      final.update(salt)
      final.update(password)
      final_digest = final.digest

      password_length = password.length

      # Process the password with various hashing operations
      while password_length > 0
        ctx.update(final_digest[0, [password_length, 16].min])
        password_length -= 16
      end

      password_length = password.length
      while password_length > 0
        if password_length & 1 != 0
          ctx.update("\x00")
        else
          ctx.update(password[0, 1])
        end
        password_length >>= 1
      end

      final_digest = ctx.digest
      Rails.logger.warn "MD6 final_digest: #{final_digest}"

      result = String.new
      Rails.logger.warn "A result: #{result}"
      result << to64((final_digest[0].ord << 16) | (final_digest[6].ord << 8) | final_digest[12].ord, 4)
      Rails.logger.warn "B result: #{result}"
      result << to64((final_digest[1].ord << 16) | (final_digest[7].ord << 8) | final_digest[13].ord, 4)
      Rails.logger.warn "C result: #{result}"
      result << to64((final_digest[2].ord << 16) | (final_digest[8].ord << 8) | final_digest[14].ord, 4)
      Rails.logger.warn "D result: #{result}"
      result << to64((final_digest[3].ord << 16) | (final_digest[9].ord << 8) | final_digest[15].ord, 4)
      Rails.logger.warn "E result: #{result}"
      result << to64((final_digest[4].ord << 16) | (final_digest[10].ord << 8) | final_digest[5].ord, 4)
      Rails.logger.warn "F result: #{result}"
      result << to64(final_digest[11].ord, 2)
      Rails.logger.warn "G result: #{result}"

      Rails.logger.warn "magic salt result   #{magic}#{salt}$#{result}"
      "#{magic}#{salt}$#{result}"
    end

    def verify_gossamer_password(password, legacy_hash)
      # Verify the provided password against the stored MD5 hash
      generated_hash = gossamer_md5_crypt(password, legacy_hash)
      generated_hash == legacy_hash
    end
  end

  # Extend the SessionController class to include the LegacyMd5Authentication module
  class ::SessionController
    prepend LegacyMd5Authentication
  end
end