from rest_framework import serializers
from datetime import datetime

class IncomeSerializer(serializers.Serializer):
    id = serializers.CharField(read_only=True)
    title = serializers.CharField(max_length=200)
    amount = serializers.DecimalField(max_digits=10, decimal_places=2)
    category = serializers.CharField(max_length=100, required=False, allow_blank=True)
    date = serializers.DateField()
    description = serializers.CharField(required=False, allow_blank=True)
    is_recurring = serializers.BooleanField(default=False)
    recurrence_interval = serializers.ChoiceField(
        choices=['daily', 'weekly', 'monthly', 'yearly'], 
        required=False, 
        allow_null=True,
        allow_blank=True
    )

    def validate(self, data):
        if data.get('recurrence_interval') == '':
            data['recurrence_interval'] = None
            
        if data.get('is_recurring') and not data.get('recurrence_interval'):
            raise serializers.ValidationError("Recurrence interval is required for recurring income.")
        return data

class ExpenseSerializer(serializers.Serializer):
    id = serializers.CharField(read_only=True)
    title = serializers.CharField(max_length=200)
    amount = serializers.DecimalField(max_digits=10, decimal_places=2)
    category = serializers.CharField(max_length=100, required=False, allow_blank=True)
    date = serializers.DateField()
    is_recurring = serializers.BooleanField(default=False)
    recurrence_interval = serializers.ChoiceField(
        choices=['daily', 'weekly', 'monthly', 'yearly'], 
        required=False, 
        allow_null=True,
        allow_blank=True
    )
    description = serializers.CharField(required=False, allow_blank=True)

    def validate(self, data):
        if data.get('recurrence_interval') == '':
            data['recurrence_interval'] = None
            
        if data.get('is_recurring') and not data.get('recurrence_interval'):
            raise serializers.ValidationError("Recurrence interval is required for recurring expense.")
        return data

class BudgetSerializer(serializers.Serializer):
    id = serializers.CharField(read_only=True)
    category = serializers.CharField(max_length=100)
    limit_amount = serializers.FloatField()
    month = serializers.CharField(max_length=7) # Format: YYYY-MM
    
    # Read-only fields for status
    spent_amount = serializers.FloatField(read_only=True)
    remaining_amount = serializers.FloatField(read_only=True)
    is_exceeded = serializers.BooleanField(read_only=True)
    alert_message = serializers.CharField(read_only=True)

class SavingsGoalSerializer(serializers.Serializer):
    id = serializers.CharField(read_only=True)
    name = serializers.CharField(max_length=200)
    target_amount = serializers.FloatField()
    current_amount = serializers.FloatField(default=0.0)
    category = serializers.CharField(max_length=100, required=False, allow_blank=True)
    target_date = serializers.DateField(required=False, allow_null=True)
    color = serializers.CharField(max_length=20, default='#6366f1')
    
    # Read-only progress
    progress_percentage = serializers.FloatField(read_only=True)
    is_completed = serializers.BooleanField(read_only=True)

    def to_internal_value(self, data):
        # Handle empty string for target_date
        if 'target_date' in data and data['target_date'] == '':
            data = data.copy()
            data['target_date'] = None
        return super().to_internal_value(data)