airline_stats.go

package main

import (
	"database/sql"
	"sort"
	"strings"

	"github.com/graphql-go/graphql"
)

func resolveFlightStatsByAirline(db *sql.DB) graphql.FieldResolveFn {
	return graphQLMetrics("flightstats_by_airline",
		func(p graphql.ResolveParams) (interface{}, error) {
			origin, _ := p.Args["origin"].(string)
			origin = strings.ToUpper(origin)

			dest, _ := p.Args["destination"].(string)
			dest = strings.ToUpper(dest)

			if !isAirportCode(origin) || !isAirportCode(dest) {
				return nil, nil
			}

			rows, err := db.QueryContext(p.Context,
				`SELECT
					carriers.name AS carrier_name, total_flights, delays_flights, last_flight
				FROM
					(
						SELECT
							carrier AS carrier_code,
							SUM(total_flights) AS total_flights,
							SUM(delayed_flights) AS delays_flights,
							MAX(date) AS last_flight
						FROM
							flights_day
						WHERE origin=? AND destination=?
						GROUP BY carrier_code
					) AS stats
				INNER JOIN carriers ON carrier_code=carriers.code
				`,
				origin, dest)
			if err != nil {
				return nil, err
			}
			defer rows.Close()

			stats := []*airlineStats{}

			for rows.Next() {
				var (
					row            airlineStats
					delayedFlights int
				)
				err := rows.Scan(&row.Airline, &row.TotalFlights, &delayedFlights, &row.LastFlight)
				if err != nil {
					return nil, err
				}

				row.OnTimePercentage = (1.0 - float64(delayedFlights)/float64(row.TotalFlights)) * 100

				stats = append(stats, &row)
			}

			sort.Slice(stats, func(i, j int) bool {
				return stats[j].OnTimePercentage < stats[i].OnTimePercentage
			})

			return stats, nil
		},
	)
}