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

class EducationTimetableSlot(models.Model):
    _name = 'education.timetable.slot'
    _description = 'Timetable Slot'
    _order = 'date desc, start_time'

    # Academic References (Student Population)
    program_id = fields.Many2one('education.program', string='Program', required=True)
    academic_year_id = fields.Many2one('education.academic.year', string='Academic Year', required=True)
    term_id = fields.Many2one('education.academic.term', string='Term')
    batch_id = fields.Many2one('education.batch', string='Batch')
    semester_id = fields.Many2one('education.semester', string='Semester', index=True)
    section_id = fields.Many2one('education.section', string='Section', index=True)
    company_id = fields.Many2one(
        'res.company',
        string='Company',
        required=True,
        default=lambda self: self.env.company,
        index=True,
    )

    # Slot Details
    subject_id = fields.Many2one('education.subject', string='Subject', required=True)
    faculty_id = fields.Many2one('res.users', string='Faculty / Instructor', required=True)
    room_id = fields.Many2one('education.room', string='Room / Venue', required=True)

    # Schedule
    date = fields.Date(string='Date', required=True)
    start_time = fields.Float(string='Start Time', required=True)
    end_time = fields.Float(string='End Time', required=True)

    active = fields.Boolean(default=True)
    state = fields.Selection([
        ('draft', 'Draft'),
        ('confirmed', 'Confirmed'),
        ('cancelled', 'Cancelled')
    ], string='Status', default='draft')

    @api.depends('subject_id.name', 'date', 'start_time')
    def _compute_display_name(self):
        for rec in self:
            subj = rec.subject_id.name or 'Class'
            d = str(rec.date) if rec.date else ''
            rec.display_name = f"{subj} ({d})"

    def action_confirm(self):
        for rec in self:
            rec.state = 'confirmed'

    def action_cancel(self):
        for rec in self:
            rec.state = 'cancelled'

    def action_draft(self):
        for rec in self:
            rec.state = 'draft'

    @api.constrains('start_time', 'end_time')
    def _check_time(self):
        for rec in self:
            if rec.start_time < 0.0 or rec.end_time > 24.0:
                raise ValidationError("Start and end times must be within a valid 24-hour day (0:00 to 24:00).")
            if rec.start_time >= rec.end_time:
                raise ValidationError("Start time must be strictly earlier than end time.")

    @api.constrains(
        'date', 'start_time', 'end_time', 'faculty_id', 'room_id',
        'program_id', 'academic_year_id', 'term_id', 'batch_id',
        'semester_id', 'section_id', 'company_id', 'state', 'active'
    )
    def _check_overlap(self):
        for rec in self:
            if rec.state == 'cancelled' or not rec.active:
                continue

            domain_base = [
                ('id', '!=', rec.id),
                ('date', '=', rec.date),
                ('state', '!=', 'cancelled'),
                ('active', '=', True),
                # Interval logic: existing_start < new_end AND existing_end > new_start
                ('start_time', '<', rec.end_time),
                ('end_time', '>', rec.start_time),
            ]
            if rec.company_id:
                domain_base.append(('company_id', '=', rec.company_id.id))

            # 1. Check Faculty Conflict
            faculty_conflict = self.search(domain_base + [('faculty_id', '=', rec.faculty_id.id)], limit=1)
            if faculty_conflict:
                raise ValidationError(
                    f"Faculty conflict: {rec.faculty_id.name} already has an active class scheduled on {rec.date} overlapping this time."
                )

            # 2. Check Room Conflict
            room_conflict = self.search(domain_base + [('room_id', '=', rec.room_id.id)], limit=1)
            if room_conflict:
                raise ValidationError(
                    f"Room conflict: Room '{rec.room_id.name}' is already booked for an overlapping class on {rec.date}."
                )

            # 3. Check Student Population Conflict
            # Population is defined by Program + Academic Year + Term + Batch + Semester + Section
            population_domain = domain_base + [
                ('program_id', '=', rec.program_id.id),
                ('academic_year_id', '=', rec.academic_year_id.id),
            ]
            
            # OR logic for term_id: either matches exactly, or one of them is False
            if rec.term_id:
                population_domain.append('|')
                population_domain.append(('term_id', '=', False))
                population_domain.append(('term_id', '=', rec.term_id.id))
                
            # OR logic for batch_id: either matches exactly, or one of them is False
            if rec.batch_id:
                population_domain.append('|')
                population_domain.append(('batch_id', '=', False))
                population_domain.append(('batch_id', '=', rec.batch_id.id))

            # OR logic for semester_id: either matches exactly, or one of them is False
            if rec.semester_id:
                population_domain.append('|')
                population_domain.append(('semester_id', '=', False))
                population_domain.append(('semester_id', '=', rec.semester_id.id))

            # OR logic for section_id: either matches exactly, or one of them is False
            if rec.section_id:
                population_domain.append('|')
                population_domain.append(('section_id', '=', False))
                population_domain.append(('section_id', '=', rec.section_id.id))
            
            population_conflict = self.search(population_domain, limit=1)
            if population_conflict:
                raise ValidationError(
                    f"Student group conflict: The academic cohort already has an overlapping class scheduled on {rec.date}."
                )