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package main
import (
"encoding/csv"
"math"
"os"
"strconv"
"strings"
)
type ZipcodeDetails struct {
Latitude float64 `json:"latitude"`
Longitude float64 `json:"longitude"`
City string `json:"city"`
State string `json:"state"`
}
const EarthRadiusMiles float64 = 3960
const EarthRadiusKm float64 = 6373
const DegToRad float64 = math.Pi / 180
func (zip1 *ZipcodeDetails) DistanceTo(zip2 *ZipcodeDetails) (float64, float64) {
// the arc distance ψ = arccos(sin φ_1 sin φ_2 cos(θ_1-θ_2) + cos φ_1 cos φ_2)
// where
// φ_k = 90° - latitude_k
// θ_k = longitude_k
// (both in radians)
theta1 := zip1.Longitude * DegToRad
theta2 := zip2.Longitude * DegToRad
phi1 := (90 - zip1.Latitude) * DegToRad
phi2 := (90 - zip2.Latitude) * DegToRad
arc := math.Acos(math.Sin(phi1)*math.Sin(phi2)*math.Cos(theta1-theta2) + math.Cos(phi1)*math.Cos(phi2))
return arc * EarthRadiusMiles, arc * EarthRadiusKm
}
type ZipcodeDatabase struct {
Zipcodes map[string]*ZipcodeDetails
}
func NewZipcodeDatabase() *ZipcodeDatabase {
db := &ZipcodeDatabase{}
db.Zipcodes = make(map[string]*ZipcodeDetails)
return db
}
func (db *ZipcodeDatabase) Insert(zipcode string, details *ZipcodeDetails) {
db.Zipcodes[zipcode] = details
}
func (db *ZipcodeDatabase) Find(zipcode string) *ZipcodeDetails {
return db.Zipcodes[zipcode]
}
func (db *ZipcodeDatabase) LoadFromCSV(filename string) error {
zips, err := getZipsFromFile(filename)
if err != nil {
return err
}
for _, row := range zips {
db.Insert(row[0], getDetailsFromRow(row))
}
return nil
}
func getZipsFromFile(filename string) ([][]string, error) {
reader, err := os.Open(filename)
if err != nil {
return nil, err
}
defer reader.Close()
csvReader := csv.NewReader(reader)
zips, err := csvReader.ReadAll()
if err != nil {
return nil, err
}
return zips, nil
}
func getFloat(stringVal string) float64 {
floatVal, err := strconv.ParseFloat(strings.TrimSpace(stringVal), 64)
if err != nil {
return 0
} else {
return floatVal
}
}
func getDetailsFromRow(row []string) *ZipcodeDetails {
return &ZipcodeDetails{
State: row[1],
Latitude: getFloat(row[2]),
Longitude: getFloat(row[3]),
City: row[4],
}
}
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