"""Cache of AI-generated follow-up text to avoid LLM cost on repeats."""

import hashlib

from odoo import _, api, fields, models


class FusionFollowupTextCache(models.Model):
    _name = "fusion.followup.text.cache"
    _description = "Cache of AI-generated follow-up text"
    _order = "generated_at desc"

    partner_id = fields.Many2one('res.partner', required=True, ondelete='cascade')
    level_id = fields.Many2one('fusion.followup.level', ondelete='cascade')
    company_id = fields.Many2one('res.company', required=True,
                                 default=lambda self: self.env.company)

    fingerprint = fields.Char(required=True, index=True,
                              help="SHA-256 of input parameters")

    subject = fields.Char()
    body = fields.Text()
    tone_used = fields.Selection([
        ('gentle', 'Gentle'), ('firm', 'Firm'), ('legal', 'Legal'),
    ])
    key_points = fields.Json()

    generated_at = fields.Datetime(default=fields.Datetime.now, required=True)
    expires_at = fields.Datetime()
    use_count = fields.Integer(default=0)
    provider = fields.Char()

    @api.model
    def compute_fingerprint(self, *, partner_id: int, level_id: int,
                            overdue_amount: float, longest_overdue_days: int,
                            invoice_count: int, tone: str) -> str:
        """Stable hash of the inputs that determine the generated text."""
        s = f"{partner_id}|{level_id}|{round(overdue_amount, 2)}|" \
            f"{longest_overdue_days}|{invoice_count}|{tone}"
        return hashlib.sha256(s.encode('utf-8')).hexdigest()

    @api.model
    def lookup(self, *, partner_id: int, level_id: int,
               overdue_amount: float, longest_overdue_days: int,
               invoice_count: int, tone: str):
        """Find a cached entry matching these inputs, or empty recordset."""
        fp = self.compute_fingerprint(
            partner_id=partner_id, level_id=level_id,
            overdue_amount=overdue_amount,
            longest_overdue_days=longest_overdue_days,
            invoice_count=invoice_count, tone=tone,
        )
        return self.search([
            ('partner_id', '=', partner_id),
            ('fingerprint', '=', fp),
        ], limit=1)

    def action_increment_use(self):
        for rec in self:
            rec.use_count += 1