fix runtime error when -n is larger than number of rows in query

README.md

@@ -1,39 +0,0 @@
-# xbit
-`xbit` (xkcd backward in time) is a program for outputting historical events
-while completing a task, inspired by [xkcd](https://xkcd.com/1017). The program
-reads a SQLite database that stores event descriptions and timestamps, allowing
-you to easily add your own events of interest.
-
-The provided SQL file will pre-populate the database with thousands of events
-scraped from
-[Wikipedia](https://en.wikipedia.org/wiki/Detailed_logarithmic_timeline). Of
-these events, over 300 were manually given timestamps.
-
-## How to use
-First create the database:
-```
-sqlite3 timeline.db < timeline.sql
-```
-
-Then set the `XBIT_DB` environment variable to the database file.
-```
-export XBIT_DB=./timeline.db
-```
-
-Call the program with `xbit -p <percentage>`, like `xbit -p 0.25`. This will
-calculate a timestamp using the formula from the xkcd comic, then output
-information about the event in the database closest to that timestamp. See
-`xbit -h` for more args.
-
-## Database details
-* Due to the time-consuming nature of manually assigning timestamps, there are
-  many events that were scraped from Wikipedia but not given timestamps. You
-may wish to skim through these and add timestamps to events you personally find
-interesting.
-* For an event to be output by `xbit`, it must have an entry in the database
-  with a unix timestamp of when the event occured. You can optionally set bools
-in the "known" columns to indicate how precise your timestamp is. These may be
-used to modify how the event is output.
-* There are a few other columns that mainly exist as artifacts from the
-  scraping process. These are not used by `xbit` and do not need to be
-populated.

go.mod

@@ -1,4 +1,4 @@
-module scm.dairydemon.net/filifa/xbit
+module dairydemon.net/xbit
 
 go 1.19
 

main.go

@@ -2,13 +2,11 @@ package main
 
 import (
 	"database/sql"
-	"errors"
 	"flag"
 	"fmt"
 	_ "github.com/mattn/go-sqlite3"
 	"log"
 	"math"
-	"os"
 	"strconv"
 	"time"
 )
@@ -35,22 +33,28 @@ func formula(p float64) int64 {
 	return int64(yearsAgo * 31556926)
 }
 
-func (db *TimelineDB) closestEvents(t int64, n uint, llimit int64, ulimit int64) ([]EventsRow, error) {
+func (db *TimelineDB) closestEvents(t int64, n int) ([]EventsRow, error) {
 	query := `
 	select description, timestamp, yearknown, monthknown, dayknown, hourknown, minuteknown, secondknown
 	from events
-	where timestamp between ? and ?
+	where timestamp is not null
 	order by abs(? - timestamp) asc
 	limit ?
 	`
 
-	rows, err := db.Query(query, llimit, ulimit, t, n)
+	events := make([]EventsRow, n)
+	stmt, err := db.Prepare(query)
 	if err != nil {
-		return nil, err
+		return events, err
+	}
+	defer stmt.Close()
+
+	rows, err := stmt.Query(t, n)
+	if err != nil {
+		return events, err
 	}
 	defer rows.Close()
 
-	events := make([]EventsRow, n)
 	i := 0
 	for ; rows.Next(); i++ {
 		var event EventsRow
@@ -66,33 +70,36 @@ func (db *TimelineDB) closestEvents(t int64, n uint, llimit int64, ulimit int64)
 }
 
 func (event *EventsRow) Output() (int64, string, string, error) {
-	if !event.timestamp.Valid {
-		return 0, "", "", errors.New("null timestamp")
-	} else if !event.description.Valid {
-		return 0, "", "", errors.New("null description")
+	timestamp, err := event.timestamp.Value()
+	if err != nil {
+		return 0, "", "", err
 	}
 
-	timestamp := event.timestamp.Int64
-	desc := event.description.String
-	yearknown := event.yearknown.Valid && event.yearknown.Bool
+	desc, err := event.description.Value()
+	if err != nil {
+		return 0, "", "", err
+	}
+
+	yearknown, err := event.yearknown.Value()
+	if err != nil {
+		return 0, "", "", err
+	}
 
 	var ago string
-	date := time.Unix(timestamp, 0)
-	if !yearknown {
+	date := time.Unix(timestamp.(int64), 0)
+	if yearknown == nil || !yearknown.(bool) {
 		yeardiff := time.Now().Year() - date.Year()
 		ago = strconv.Itoa(yeardiff) + " years ago"
 	} else {
 		ago = date.String()
 	}
 
-	return timestamp, ago, desc, nil
+	return timestamp.(int64), ago, desc.(string), nil
 }
 
 func main() {
 	percent := flag.Float64("p", -1, "percentage")
-	nevents := flag.Uint("n", 1, "number of events")
-	after := flag.Bool("a", false, "only return events occurring after computed timestamp")
-	before := flag.Bool("b", false, "only return events occurring before computed timestamp")
+	nevents := flag.Int("n", 1, "number of events")
 	flag.Parse()
 
 	if *percent < 0 || *percent > 1 {
@@ -101,30 +108,15 @@ func main() {
 
 	t := time.Now().Unix() - formula(*percent)
 
-	llimit := int64(math.MinInt64)
-	ulimit := int64(math.MaxInt64)
-	if *after && *before {
-		log.Fatal("cannot pass both -a and -b")
-	} else if *after {
-		llimit = t
-	} else if *before {
-		ulimit = t
-	}
-
-	dbpath := os.Getenv("XBIT_DB")
-	if dbpath == "" {
-		log.Fatal("XBIT_DB not set")
-	}
-
 	var db TimelineDB
 	var err error
-	db.DB, err = sql.Open("sqlite3", dbpath)
+	db.DB, err = sql.Open("sqlite3", "./timeline.db")
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer db.Close()
 
-	events, err := db.closestEvents(t, *nevents, llimit, ulimit)
+	events, err := db.closestEvents(t, *nevents)
 	if err != nil {
 		log.Fatal(err)
 	}