package analytics

import (
	"context"
	"errors"
	"fmt"
)

var ErrUnknownTerminal = errors.New("analytics: unknown terminal")

type Terminal struct {
	TerminalID   string `json:"terminalId"`
	DisplayName  string `json:"displayName"`
	SessionCount int64  `json:"sessionCount"`
	IsDefault    bool   `json:"isDefault"`
}

func (s *Service) Terminals(ctx context.Context, merchantID int64) ([]Terminal, error) {
	rows, err := s.pool.Query(ctx, `SELECT t.source_key,count(ps.id) FROM terminals t
		LEFT JOIN payment_sessions ps ON ps.terminal_id=t.id
		WHERE t.merchant_id=$1 GROUP BY t.id ORDER BY count(ps.id) DESC,t.source_key`, merchantID)
	if err != nil {
		return nil, fmt.Errorf("querying merchant terminals: %w", err)
	}
	defer rows.Close()
	terminals := make([]Terminal, 0, 8)
	for rows.Next() {
		var terminal Terminal
		if err := rows.Scan(&terminal.TerminalID, &terminal.SessionCount); err != nil {
			return nil, fmt.Errorf("scanning merchant terminal: %w", err)
		}
		terminal.DisplayName = terminalDisplayName(terminal.TerminalID)
		terminal.IsDefault = len(terminals) == 0
		terminals = append(terminals, terminal)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterating merchant terminals: %w", err)
	}
	return terminals, nil
}

func (s *Service) validateTerminal(ctx context.Context, merchantID int64, terminalID string) error {
	if terminalID == "" {
		return nil
	}
	var exists bool
	if err := s.pool.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM terminals WHERE merchant_id=$1 AND source_key=$2)`, merchantID, terminalID).Scan(&exists); err != nil {
		return fmt.Errorf("validating merchant terminal: %w", err)
	}
	if !exists {
		return ErrUnknownTerminal
	}
	return nil
}