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

class EducationGradingSystem(models.Model):
    _name = 'education.grading.system'
    _description = 'Grading System'

    name = fields.Char(string='Name', required=True)
    code = fields.Char(string='Code', required=True)
    scale_type = fields.Selection([
        ('percentage', 'Percentage'),
        ('gpa_4', 'GPA 4.0'),
        ('gpa_10', 'GPA 10.0')
    ], string='Scale Type', required=True, default='percentage')
    active = fields.Boolean(default=True)
    grade_ids = fields.One2many('education.grade', 'grading_system_id', string='Grades')

    def get_grade(self, percentage):
        self.ensure_one()
        grade = self.grade_ids.filtered(lambda g: g.min_percentage <= percentage <= g.max_percentage)
        if grade:
            # If multiple match due to floating point edge cases, take the highest grade point
            return grade.sorted('grade_point', reverse=True)[0]
        return self.env['education.grade']

class EducationGrade(models.Model):
    _name = 'education.grade'
    _description = 'Education Grade'
    _order = 'sequence, id'

    grading_system_id = fields.Many2one('education.grading.system', string='Grading System', required=True, ondelete='cascade')
    name = fields.Char(string='Name', required=True)
    code = fields.Char(string='Code')
    min_percentage = fields.Float(string='Minimum Percentage', required=True)
    max_percentage = fields.Float(string='Maximum Percentage', required=True)
    grade_point = fields.Float(string='Grade Point', required=True)
    result_status = fields.Selection([
        ('pass', 'Pass'),
        ('fail', 'Fail')
    ], string='Result Status', required=True, default='pass')
    sequence = fields.Integer(string='Sequence', default=10)
    active = fields.Boolean(default=True)

    @api.constrains('min_percentage', 'max_percentage')
    def _check_percentages(self):
        for record in self:
            if record.min_percentage < 0 or record.max_percentage > 100:
                raise ValidationError("Percentages must be between 0 and 100.")
            if record.min_percentage > record.max_percentage:
                raise ValidationError("Minimum percentage cannot be greater than maximum percentage.")
            
            # Check overlaps
            domain = [
                ('grading_system_id', '=', record.grading_system_id.id),
                ('id', '!=', record.id),
                '|', '|',
                '&', ('min_percentage', '<=', record.min_percentage), ('max_percentage', '>=', record.min_percentage),
                '&', ('min_percentage', '<=', record.max_percentage), ('max_percentage', '>=', record.max_percentage),
                '&', ('min_percentage', '>=', record.min_percentage), ('max_percentage', '<=', record.max_percentage),
            ]
            if self.search_count(domain) > 0:
                raise ValidationError("Grade percentage ranges cannot overlap within the same grading system.")

    @api.constrains('grade_point')
    def _check_grade_point(self):
        for record in self:
            if record.grade_point < 0:
                raise ValidationError("Grade point cannot be negative.")