from odoo import api, fields, models
from odoo.exceptions import ValidationError


class AcademicTerm(models.Model):
    _name = 'education.academic.term'
    _description = 'Academic Term'
    _order = 'sequence, start_date'

    name = fields.Char(required=True, string='Term Name')
    code = fields.Char(string='Code', required=True, index=True)
    academic_year_id = fields.Many2one(
        'education.academic.year',
        string='Academic Year',
        required=True,
        ondelete='restrict',
        index=True,
    )
    start_date = fields.Date(string='Start Date', required=True)
    end_date = fields.Date(string='End Date', required=True)
    sequence = fields.Integer(default=1, required=True)
    active = fields.Boolean(default=True)
    state = fields.Selection([
        ('draft', 'Draft'),
        ('active', 'Active'),
        ('closed', 'Closed'),
    ], default='draft', required=True)
    company_id = fields.Many2one(
        'res.company',
        related='academic_year_id.company_id',
        store=True,
        readonly=True,
        index=True,
    )

    _sql_constraints = [
        ('uniq_term_code_year', 'unique(code, academic_year_id)', 'Term code must be unique within the academic year.'),
        ('uniq_term_sequence_year', 'unique(sequence, academic_year_id)', 'Term sequence must be unique within the academic year.'),
    ]

    @api.constrains('start_date', 'end_date')
    def _check_term_dates(self):
        for rec in self:
            if rec.start_date and rec.end_date and rec.start_date > rec.end_date:
                raise ValidationError('End date must be greater than start date.')

    @api.constrains('academic_year_id', 'start_date', 'end_date')
    def _check_term_overlap(self):
        for rec in self:
            if not rec.academic_year_id:
                continue
            overlapping = self.search([
                ('id', '!=', rec.id),
                ('academic_year_id', '=', rec.academic_year_id.id),
                ('start_date', '<=', rec.end_date),
                ('end_date', '>=', rec.start_date),
            ])
            if overlapping:
                raise ValidationError('Academic terms within the same year cannot overlap.')

    def action_activate(self):
        self.write({'state': 'active'})

    def action_close(self):
        self.write({'state': 'closed'})