package dashboard

import (
	"context"
	"errors"
	"time"

	"gorm.io/gorm"

	"git.apinb.com/ops/license/internal/issuance"
)

var ErrInvalidInput = errors.New("invalid dashboard input")

type Overview struct {
	SubjectCount      int64
	IssuanceCount     int64
	ExpiringSoonCount int64
	RecentIssuances   []issuance.RecordSummary
}

type Service struct {
	db *gorm.DB
}

func NewService(db *gorm.DB) (*Service, error) {
	if db == nil {
		return nil, ErrInvalidInput
	}
	return &Service{db: db}, nil
}

func (s *Service) Get(ctx context.Context) (Overview, error) {
	if s == nil || s.db == nil || ctx == nil {
		return Overview{}, ErrInvalidInput
	}

	var result Overview
	db := s.db.WithContext(ctx)
	if err := db.Raw("SELECT COUNT(*) FROM authorization_subjects").Scan(&result.SubjectCount).Error; err != nil {
		return Overview{}, err
	}
	if err := db.Raw("SELECT COUNT(*) FROM licence_issuances").Scan(&result.IssuanceCount).Error; err != nil {
		return Overview{}, err
	}

	shanghai := time.FixedZone("Asia/Shanghai", 8*60*60)
	now := time.Now().In(shanghai)
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, shanghai)
	endDate := today.AddDate(0, 0, 30)
	if err := db.Raw(`
		SELECT COUNT(*)
		FROM (
			SELECT DISTINCT ON (subject_id) subject_id, expires_on
			FROM licence_issuances
			ORDER BY subject_id, issued_at DESC, id DESC
		) AS latest
		WHERE latest.expires_on BETWEEN ? AND ?`, today, endDate).
		Scan(&result.ExpiringSoonCount).Error; err != nil {
		return Overview{}, err
	}

	if err := db.Raw(`
		SELECT issuances.id, issuances.subject_id, subjects.platform_name, subjects.workspace,
			issuances.issuance_type, issuances.previous_licence_id, issuances.valid_from,
			issuances.expires_on, issuances.issued_at
		FROM licence_issuances AS issuances
		JOIN authorization_subjects AS subjects ON subjects.id = issuances.subject_id
		ORDER BY issuances.issued_at DESC, issuances.id DESC
		LIMIT 10`).Scan(&result.RecentIssuances).Error; err != nil {
		return Overview{}, err
	}
	if result.RecentIssuances == nil {
		result.RecentIssuances = make([]issuance.RecordSummary, 0)
	}
	return result, nil
}