better repl

go.mod

@@ -1,3 +1,10 @@
 module github.com/chirst/cdb
 
-go 1.24
+go 1.24.0
+
+toolchain go1.24.3
+
+require (
+	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/term v0.38.0
+)

go.sum

@@ -0,0 +1,4 @@
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/term v0.38.0 h1:PQ5pkm/rLO6HnxFR7N2lJHOZX6Kez5Y1gDSJla6jo7Q=
+golang.org/x/term v0.38.0/go.mod h1:bSEAKrOT1W+VSu9TSCMtoGEOUcKxOKgl3LE5QEF/xVg=

repl/repl.go

@@ -2,52 +2,78 @@
 package repl
 
 import (
-	"bufio"
+	"errors"
 	"fmt"
+	"io"
 	"os"
+	"os/signal"
+	"slices"
 	"strings"
+	"syscall"
 
 	"github.com/chirst/cdb/db"
+	"golang.org/x/term"
 )
 
 const (
 	// emptyRowValue is printed when the cell in a row is nil.
 	emptyRowValue = "NULL"
 	// emptyHeaderValue is printed when the cell in a header is the empty string
 	emptyHeaderValue = "<anonymous>"
-)
-
-// ansi are codes that will color terminal output
-const (
-	ansiWarn  = "\033[33m"
-	ansiReset = "\033[0m"
+	// prompt is the prompt.
+	prompt = "cdb> "
+	// promptContinued is the prompt when it is pending termination for example
+	// by a semi colon.
+	promptContinued = "...> "
 )
 
 type repl struct {
-	db *db.DB
+	db       *db.DB
+	terminal *term.Terminal
 }
 
 func New(db *db.DB) *repl {
-	return &repl{db: db}
+	r := &repl{
+		db:       db,
+		terminal: term.NewTerminal(os.Stdin, prompt),
+	}
+	r.loadHistory()
+	return r
 }
 
 func (r *repl) Run() {
-	fmt.Println("Welcome to cdb. Type .exit to exit")
+	r.writeLn("Welcome to cdb. Type .exit to exit")
 	if r.db.UseMemory {
-		fmt.Println(ansiWarn + "WARN database is running in memory and will not persist changes" + ansiReset)
+		r.writeWarning("WARN database is running in memory and will not persist changes")
 	}
-	reader := bufio.NewScanner(os.Stdin)
+
+	// Handling kill signals works under two methods for the REPL. When the
+	// terminal is in raw mode the signals are caught by readline as bytes. When
+	// the terminal is not in raw mode the signals are caught by the following
+	// channel.
+	//
+	// The handling keeping in mind two major considerations in that the
+	// terminal history is written to and the database always allows a long
+	// running query to be shut down.
+	c := make(chan os.Signal, 2)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+	go func() {
+		<-c
+		r.exitGracefully()
+	}()
+
 	previousInput := ""
-	for r.getInput(reader, previousInput) {
-		input := previousInput + reader.Text()
+	for {
+		line := r.readLine(previousInput)
+		input := previousInput + line
 		if len(input) == 0 {
 			continue
 		}
 		if input[0] == '.' {
 			if input == ".exit" {
-				os.Exit(0)
+				r.exitGracefully()
 			}
-			fmt.Println("Command not supported")
+			r.writeLn("Command not supported")
 			continue
 		}
 
@@ -61,27 +87,50 @@ func (r *repl) Run() {
 		for _, statement := range statements {
 			result := r.db.Execute(statement, []any{})
 			if result.Err != nil {
-				fmt.Printf("Err: %s\n", result.Err)
+				r.writeLn("Err: " + result.Err.Error())
 				continue
 			}
 			if result.Text != "" {
-				fmt.Println(result.Text)
+				r.writeLn(result.Text)
 			}
 			if len(result.ResultRows) != 0 {
-				fmt.Println(r.printRows(result.ResultHeader, result.ResultRows))
+				r.writeLn(r.printRows(result.ResultHeader, result.ResultRows))
 			}
-			fmt.Printf("Time: %s\n", result.Duration)
+			r.writeLn("Time: " + result.Duration.String())
 		}
 	}
 }
 
-func (*repl) getInput(reader *bufio.Scanner, previousInput string) bool {
+func (r *repl) readLine(previousInput string) string {
+	oldState, err := term.MakeRaw(int(os.Stdin.Fd()))
+	if err != nil {
+		panic(err)
+	}
+	defer term.Restore(int(os.Stdin.Fd()), oldState)
 	if previousInput == "" {
-		fmt.Printf("cdb> ")
+		r.terminal.SetPrompt(prompt)
 	} else {
-		fmt.Printf("...> ")
+		r.terminal.SetPrompt(promptContinued)
+	}
+	line, err := r.terminal.ReadLine()
+	if err != nil {
+		if err == io.EOF {
+			term.Restore(int(os.Stdin.Fd()), oldState)
+			r.exitGracefully()
+		}
+		panic("err reading line: " + err.Error())
 	}
-	return reader.Scan()
+	return line
+}
+
+func (r *repl) writeLn(text string) {
+	r.terminal.Write(([]byte)(text + "\n"))
+}
+
+func (r *repl) writeWarning(text string) {
+	r.terminal.Write(r.terminal.Escape.Yellow)
+	r.writeLn(text)
+	r.terminal.Write(r.terminal.Escape.Reset)
 }
 
 func (r *repl) printRows(resultHeader []string, resultRows [][]*string) string {
@@ -163,3 +212,70 @@ func (*repl) printRow(row []*string, widths []int) string {
 	}
 	return ret
 }
+
+func (r *repl) exitGracefully() {
+	r.saveHistory()
+	os.Exit(0)
+}
+
+func (r *repl) loadHistory() {
+	p, err := r.getHistoryPath()
+	if err != nil {
+		r.writeWarning("failed to get history path " + err.Error())
+		return
+	}
+	contents, err := os.ReadFile(p)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return
+		}
+		r.writeWarning("failed to load history " + err.Error())
+		return
+	}
+	lines := strings.Split((string)(contents), "\n")
+	slices.Reverse(lines)
+	for _, line := range lines {
+		if line == "" {
+			continue
+		}
+		r.terminal.History.Add(line)
+	}
+}
+
+func (r *repl) saveHistory() {
+	history := []byte{}
+	for i := range r.terminal.History.Len() {
+		str_entry := r.terminal.History.At(i)
+		byte_entry := ([]byte)(str_entry + "\n")
+		history = append(history, byte_entry...)
+	}
+	p, err := r.getHistoryPath()
+	if err != nil {
+		r.writeWarning("failed to get history path for saving " + err.Error())
+		return
+	}
+	f, err := os.OpenFile(p, os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		r.writeWarning("failed to open history file for saving " + err.Error())
+		return
+	}
+	defer f.Close()
+	err = f.Truncate(0)
+	if err != nil {
+		r.writeWarning("failed to overwrite history " + err.Error())
+		return
+	}
+	_, err = f.Write(history)
+	if err != nil {
+		r.writeWarning("failed to write history " + err.Error())
+		return
+	}
+}
+
+func (r *repl) getHistoryPath() (string, error) {
+	dir, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return dir + "/.cdb_history", nil
+}