import json
from datetime import datetime
from app.extensions import db


class DocumentTemplate(db.Model):
    """
    Uploaded Word (.docx) templates with Jinja2-style placeholders.

    Template authors write {{ variable_name }} in their .docx file.
    When a document is generated the placeholders are replaced with actual
    context values (user, asset, assignment data).

    PII variables (those prefixed user_name, user_email, user_phone) are
    re-rendered with masked values when a user's record is masked.
    """
    __tablename__ = 'document_templates'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(200), nullable=False)
    description = db.Column(db.Text, nullable=True)

    # Category maps to Paperwork.document_type so the UI can pre-filter
    category = db.Column(db.String(30), nullable=True)  # handover|assignment|return|offboarding|custom

    # Stored filename relative to TEMPLATE_FOLDER
    filename = db.Column(db.String(300), nullable=False)

    # JSON list of placeholder names detected at upload time, e.g. ["user_name","asset_serial"]
    variables_json = db.Column(db.Text, nullable=True)

    created_by_id = db.Column(db.Integer, db.ForeignKey('admin_users.id'), nullable=True)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    created_by = db.relationship('AdminUser', foreign_keys=[created_by_id])
    paperwork_docs = db.relationship('Paperwork', back_populates='template', lazy='dynamic')

    @property
    def variables(self):
        if self.variables_json:
            try:
                return json.loads(self.variables_json)
            except (json.JSONDecodeError, TypeError):
                return []
        return []

    @variables.setter
    def variables(self, val):
        self.variables_json = json.dumps(val)

    def __repr__(self):
        return f'<DocumentTemplate id={self.id} name={self.name!r}>'