from odoo import fields, models


class MailTemplate(models.Model):
    _inherit = "mail.template"

    event_attachment_name_prefix = fields.Char(
        "Attachment name prefix",
        help="If there is an attachment in event registration, or in event, with a name that starts with this name, it will be attached to the mail.",
    )

    def generate_email(self, res_ids, fields):
        res = super().generate_email(res_ids, fields)

        self.ensure_one()
        multi_mode = True
        if isinstance(res_ids, int):
            res_ids = [res_ids]
            multi_mode = False

        for lang, (template, template_res_ids) in self._classify_per_lang(
            res_ids
        ).items():
            # add reports attached to event.registration or event.event from attachment name
            if template.event_attachment_name_prefix:
                for res_id in template_res_ids:
                    event_registration = self.env["event.registration"].browse(res_id)
                    attachments = self.env["ir.attachment"]
                    for (
                        event_attachment_name_prefix
                    ) in template.event_attachment_name_prefix.split(","):
                        attachments |= self.env["ir.attachment"].search(
                            [
                                ("res_model", "=", "event.registration"),
                                ("res_id", "=", res_id),
                                ("name", "like", event_attachment_name_prefix),
                            ]
                        )
                        attachments |= self.env["ir.attachment"].search(
                            [
                                ("res_model", "=", "event.event"),
                                ("res_id", "=", event_registration.event_id.id),
                                ("name", "like", event_attachment_name_prefix),
                            ]
                        )

                    attachments_res = [
                        (attachment.name, attachment.datas)
                        for attachment in attachments
                    ]

                    if multi_mode:
                        if res_id in res:
                            if "attachments" not in res[res_id]:
                                res[res_id]["attachments"] = attachments_res
                            else:
                                res[res_id]["attachments"].extend(attachments_res)
                    else:
                        if "attachments" not in res:
                            res["attachments"] = attachments_res
                        else:
                            res["attachments"].extend(attachments_res)

        return res