package user

import (
	"context"
	"fmt"
	"time"
)

type Service struct {
	repo UserRepository
}

func NewService(repo UserRepository) *Service {
	return &Service{repo: repo}
}

func (s *Service) GetProfile(ctx context.Context, userID string) (*User, error) {
	return s.repo.GetByID(ctx, userID)
}

func (s *Service) UpdateProfile(ctx context.Context, userID string, req UpdateProfileRequest) (*User, error) {
	if err := validateProfileRequest(req); err != nil {
		return nil, err
	}

	if !req.HasBodyParams() {
		updated, err := s.repo.Update(ctx, userID, req)
		if err != nil {
			return nil, fmt.Errorf("update profile: %w", err)
		}
		return updated, nil
	}

	// Need to update profile + recalculate calories in a single transaction.
	// First, get current user to merge with incoming fields for calorie calculation.
	current, err := s.repo.GetByID(ctx, userID)
	if err != nil {
		return nil, fmt.Errorf("get user: %w", err)
	}

	// Merge current values with request to compute calories
	height := current.HeightCM
	if req.HeightCM != nil {
		height = req.HeightCM
	}
	weight := current.WeightKG
	if req.WeightKG != nil {
		weight = req.WeightKG
	}
	dob := current.DateOfBirth
	if req.DateOfBirth != nil {
		dob = req.DateOfBirth
	}
	age := AgeFromDOB(dob)
	gender := current.Gender
	if req.Gender != nil {
		gender = req.Gender
	}
	activity := current.Activity
	if req.Activity != nil {
		activity = req.Activity
	}
	goal := current.Goal
	if req.Goal != nil {
		goal = req.Goal
	}

	calories := CalculateDailyCalories(height, weight, age, gender, activity, goal)

	var calReq *UpdateProfileRequest
	if calories != nil {
		calReq = &UpdateProfileRequest{DailyCalories: calories}
	}

	updated, err := s.repo.UpdateInTx(ctx, userID, req, calReq)
	if err != nil {
		return nil, fmt.Errorf("update profile: %w", err)
	}

	return updated, nil
}

func validateProfileRequest(req UpdateProfileRequest) error {
	if req.HeightCM != nil {
		if *req.HeightCM < 100 || *req.HeightCM > 250 {
			return fmt.Errorf("height_cm must be between 100 and 250")
		}
	}
	if req.WeightKG != nil {
		if *req.WeightKG < 30 || *req.WeightKG > 300 {
			return fmt.Errorf("weight_kg must be between 30 and 300")
		}
	}
	if req.DateOfBirth != nil {
		t, err := time.Parse("2006-01-02", *req.DateOfBirth)
		if err != nil {
			return fmt.Errorf("date_of_birth must be in YYYY-MM-DD format")
		}
		if t.After(time.Now()) {
			return fmt.Errorf("date_of_birth cannot be in the future")
		}
		age := AgeFromDOB(req.DateOfBirth)
		if *age < 10 || *age > 120 {
			return fmt.Errorf("date_of_birth must yield an age between 10 and 120")
		}
	}
	if req.Gender != nil {
		if *req.Gender != "male" && *req.Gender != "female" {
			return fmt.Errorf("gender must be 'male' or 'female'")
		}
	}
	if req.Activity != nil {
		switch *req.Activity {
		case "low", "moderate", "high":
		default:
			return fmt.Errorf("activity must be 'low', 'moderate', or 'high'")
		}
	}
	if req.Goal != nil {
		switch *req.Goal {
		case "lose", "maintain", "gain":
		default:
			return fmt.Errorf("goal must be 'lose', 'maintain', or 'gain'")
		}
	}
	return nil
}