import hashlib
import random
import string
from datetime import timedelta

from odoo import fields


class OtpService:

    def __init__(self, env):
        self.env = env

    def _hash_otp(self, otp_code):
        return hashlib.sha256(otp_code.encode()).hexdigest()

    def generate(self, email):
        """Create a 6-digit OTP, store its SHA-256 hash, return plaintext."""
        otp_code = ''.join(random.choices(string.digits, k=6))
        otp_hash = self._hash_otp(otp_code)
        expires_at = fields.Datetime.now() + timedelta(minutes=15)

        self.env['encoach.otp'].sudo().create({
            'email': email,
            'otp_hash': otp_hash,
            'expires_at': expires_at,
        })
        return otp_code

    def verify(self, email, otp_code):
        """Find unexpired, unused record and check SHA-256 hash match."""
        otp_hash = self._hash_otp(otp_code)
        now = fields.Datetime.now()
        record = self.env['encoach.otp'].sudo().search([
            ('email', '=', email),
            ('otp_hash', '=', otp_hash),
            ('used', '=', False),
            ('expires_at', '>=', now),
        ], limit=1, order='created_at desc')

        if record:
            record.write({'used': True})
            return True
        return False

    def can_resend(self, email):
        """Check if resend_count < 3 for the latest OTP."""
        record = self.env['encoach.otp'].sudo().search([
            ('email', '=', email),
        ], limit=1, order='created_at desc')
        return record and record.resend_count < 3

    def mark_resend(self, email):
        """Increment resend_count on the latest OTP for this email."""
        record = self.env['encoach.otp'].sudo().search([
            ('email', '=', email),
        ], limit=1, order='created_at desc')
        if record:
            record.write({'resend_count': record.resend_count + 1})