from datetime import datetime
from app.extensions import db

DOC_TYPES = [
    ('handover', 'Equipment Handover Receipt'),
    ('assignment', 'Asset Assignment Agreement'),
    ('return', 'Equipment Return Form'),
    ('offboarding', 'Off-Boarding Checklist'),
    ('custom', 'Custom Document'),
]


class Paperwork(db.Model):
    """Generated paperwork documents tied to a user and optionally an asset."""
    __tablename__ = 'paperwork'

    id = db.Column(db.Integer, primary_key=True)

    document_type = db.Column(db.String(30), nullable=False)   # see DOC_TYPES
    title = db.Column(db.String(200), nullable=False)

    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    asset_id = db.Column(db.Integer, db.ForeignKey('assets.id'), nullable=True)
    assignment_id = db.Column(db.Integer, db.ForeignKey('assignments.id'), nullable=True)

    # FK to DocumentTemplate — null for legacy ReportLab-generated docs
    template_id = db.Column(db.Integer, db.ForeignKey('document_templates.id'), nullable=True)

    # JSON snapshot of merge variables used at generation time.
    # Kept forever so the document can be re-rendered (e.g. after PII masking).
    merge_vars = db.Column(db.Text, nullable=True)

    # Legacy free-text / JSON snapshot (kept for backwards compat)
    template_data = db.Column(db.Text, nullable=True)

    # Generated output files (relative to their respective folders)
    pdf_filename = db.Column(db.String(300), nullable=True)
    docx_filename = db.Column(db.String(300), nullable=True)

    notes = db.Column(db.Text, nullable=True)

    # Signature
    signed_at = db.Column(db.DateTime, nullable=True)
    signed_by_name = db.Column(db.String(200), nullable=True)   # printed name
    signature_data = db.Column(db.Text, nullable=True)           # base64 PNG

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

    created_by = db.relationship('AdminUser', foreign_keys=[created_by_id])
    template = db.relationship('DocumentTemplate', back_populates='paperwork_docs',
                               foreign_keys=[template_id])

    @property
    def doc_type_label(self):
        return dict(DOC_TYPES).get(self.document_type, self.document_type)

    @property
    def is_signed(self):
        return self.signed_at is not None

    def get_merge_vars(self):
        if self.merge_vars:
            try:
                import json
                return json.loads(self.merge_vars)
            except (ValueError, TypeError):
                return {}
        return {}

    def __repr__(self):
        return f'<Paperwork id={self.id} type={self.document_type}>'