functionExamples_test.go

// Tests and examples for package ais
package ais_test

import (
	"fmt"
	"strings"
	"time"

	"github.com/FATHOM5/ais"
)

// Example demonstrates a simple use of the Distance function.
func ExampleRecord_Distance() {
	h := strings.Split("MMSI,BaseDateTime,LAT,LON,SOG,COG,Heading,VesselName,IMO,CallSign,VesselType,Status,Length,Width,Draft,Cargo", ",")
	headers := ais.Headers{Fields: h}
	latIndex, _ := headers.Contains("LAT")
	lonIndex, _ := headers.Contains("LON")

	data1 := strings.Split("477307900,2017-12-01T00:00:03,36.90512,-76.32652,0.0,131.0,352.0,FIRST,IMO9739666,VRPJ6,1004,moored,337,,,", ",")
	data2 := strings.Split("477307902,2017-12-01T00:00:03,36.91512,-76.22652,2.3,311.0,182.0,SECOND,IMO9739800,XHYSF,,underway using engines,337,,,", ",")
	rec1 := ais.Record(data1)
	rec2 := ais.Record(data2)

	nm, err := rec1.Distance(rec2, latIndex, lonIndex)
	if err != nil {
		panic(err)
	}
	fmt.Printf("The ships are %.1fnm away from one another.\n", nm)

	// Output:
	// The ships are 4.8nm away from one another.
}

func ExampleRecord_ParseTime() {
	h := strings.Split("MMSI,BaseDateTime,LAT,LON,SOG,COG,Heading,VesselName,IMO,CallSign,VesselType,Status,Length,Width,Draft,Cargo", ",")
	data := strings.Split("477307900,2017-12-01T00:00:03,36.90512,-76.32652,0.0,131.0,352.0,FIRST,IMO9739666,VRPJ6,1004,moored,337,,,", ",")

	headers := ais.Headers{Fields: h}
	rec := ais.Record(data)

	timeIndex, _ := headers.Contains("BaseDateTime")

	t, err := rec.ParseTime(timeIndex)
	if err != nil {
		panic(err)
	}
	fmt.Printf("The record timestamp is at %s\n", t.Format(ais.TimeLayout))

	// Output:
	// The record timestamp is at 2017-12-01T00:00:03
}

type subsetOneDay struct {
	rs        *ais.RecordSet
	d1        time.Time // date we want to match
	timeIndex int       //index value of BaseDateTime in the record
}

func (sod *subsetOneDay) Match(rec *ais.Record) (bool, error) {
	d2, err := time.Parse(ais.TimeLayout, (*rec)[sod.timeIndex])
	if err != nil {
		return false, fmt.Errorf("subsetOneDay: %v", err)
	}
	d2 = d2.Truncate(24 * time.Hour)
	return sod.d1.Equal(d2), nil
}

func ExampleRecordSet_Subset() {
	rs, _ := ais.OpenRecordSet("testdata/ten.csv")
	defer rs.Close()

	// Implement a concreate type of subsetOneDay to return records
	// from 25 Dec 2017.
	timeIndex, ok := rs.Headers().Contains("BaseDateTime")
	if !ok {
		panic("recordset does not contain the header BaseDateTime")
	}
	targetDate, _ := time.Parse("2006-01-02", "2017-12-25")
	sod := &subsetOneDay{
		rs:        rs,
		d1:        targetDate,
		timeIndex: timeIndex,
	}

	matches, _ := rs.Subset(sod)
	//matches.Save("newSet.csv")
	subsetRec, _ := matches.Read()
	subsetDate := (*subsetRec)[timeIndex]
	date, _ := time.Parse(ais.TimeLayout, subsetDate)
	fmt.Printf("The first record in the subset has BaseDateTime %v\n", date.Format("2006-01-02"))

	// Output:
	// The first record in the subset has BaseDateTime 2017-12-25
}