from odoo import models
import mimetypes
import base64
import io
import zipfile


class IrAttachment(models.Model):
    _inherit = "ir.attachment"

    def _detect_mimetype(self, datas):
        # direct copy of the above function
        try:
            raw = base64.b64decode(datas)
        except:
            return "application/octet-stream"


        # office zip check
        if raw.startswith(b"PK"):
            try:
                z = zipfile.ZipFile(io.BytesIO(raw))
                names = z.namelist()

                if "ppt/presentation.xml" in names:
                    return "application/vnd.openxmlformats-officedocument.presentationml.presentation"
                if "word/document.xml" in names:
                    return "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
                if "xl/workbook.xml" in names:
                    return "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                return "application/zip"
            except:
                pass

        if raw.startswith(b"%PDF-"):
            return "application/pdf"

        return "application/octet-stream"

    def _get_extension_from_mimetype(self, mimetype):
        mapping = {
            "application/vnd.openxmlformats-officedocument.wordprocessingml.document": ".docx",
            "application/vnd.openxmlformats-officedocument.presentationml.presentation": ".pptx",
            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet": ".xlsx",
            "application/pdf": ".pdf",
            "application/zip": ".zip",
        }
        return mapping.get(mimetype, False)

    def write(self, vals):
        res = super().write(vals)

        # ----------------------------------------------------
        # 1) Fix incorrect mimetype (ex: .pptx → zip)
        # ----------------------------------------------------
        if "datas" in vals or "mimetype" in vals:
            for rec in self:
                datas = vals.get("datas", rec.datas)
                mimetype = self._detect_mimetype(datas)

                # Update mimetype if wrong
                if mimetype != rec.mimetype:
                    rec.sudo().write({"mimetype": mimetype})

                # ----------------------------------------------------
                # 2) Fix the filename extension based on correct mimetype
                # ----------------------------------------------------
                # Detect extension from mimetype
                correct_ext = self._get_extension_from_mimetype(mimetype) or ".bin"

                filename = rec.name or ""
                current_ext = ""
                if "." in filename:
                    current_ext = "." + filename.split(".")[-1].lower()

                # CASE 1: No filename or no extension
                if not filename or "." not in filename:
                    new_name = f"{rec.res_field or 'file'}_{rec.id}{correct_ext}"
                    rec.sudo().write({"name": new_name})

                # CASE 2: Wrong extension → Replace it
                elif current_ext != correct_ext:
                    base = filename.rsplit(".", 1)[0]
                    new_name = f"{base}{correct_ext}"
                    rec.sudo().write({"name": new_name})

        return res